Hindawi Publishing Corporation
BioMed Research International
Volume 2015, Article ID 397943, 15 pages
http://dx.doi.org/10.1155/2015/397943
Research Article
Antidepressant-Like Effect of the Leaves of
Pseudospondias microcarpa in Mice: Evidence for
the Involvement of the Serotoninergic System,
NMDA Receptor Complex, and Nitric Oxide Pathway
DonatusWewura Adongo,1 Kennedy Kwami Edem Kukuia,2 Priscilla Kolibea Mante,1
Elvis Ofori Ameyaw,3 and Eric Woode1
1Department of Pharmacology, Faculty of Pharmacy & Pharmaceutical Sciences, College of Health Sciences,
Kwame Nkrumah University of Science & Technology, Kumasi, Ghana
2Department of Pharmacology, Medical School, University of Ghana, Accra, Ghana
3Department of Biomedical and Forensic Sciences, School of Biological Science, University of Cape Coast, Cape Coast, Ghana
Correspondence should be addressed to Donatus Wewura Adongo; donatusadongo@yahoo.com
Received 22 June 2015; Revised 5 September 2015; Accepted 14 September 2015
Academic Editor: Luigia Trabace
Copyright © 2015 Donatus Wewura Adongo et al. This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
Depression continues to be a major global health problem. Although antidepressants are used for its treatment, efficacy is
often inconsistent. Thus, the search for alternative therapeutic medicines for its treatment is still important. In this study, the
antidepressant-like effect of Pseudospondias microcarpa extract (30–300mg kg−1, p.o.) was investigated in two predictive models of
depression—forced swimming test and tail suspension test inmice.Additionally, themechanism(s) of action involvedwere assessed.
Acute treatment with the extract dose dependently reduced immobility of mice in bothmodels.The antidepressant-like effect of the
extract (100mg kg−1, p.o.) was blocked by 𝑝-chlorophenylalanine and cyproheptadine but not prazosin, propranolol, or yohimbine.
Concomitant administration of d-cycloserine and the extract potentiated the anti-immobility effect. In contrast, d-serine, a full
agonist of glycine/NMDA receptors, abolished the effects. Anti-immobility effects of PME were prevented by pretreatment of mice
with L-arginine (750mg kg−1, i.p.) and sildenafil (5mg kg−1, i.p.). On the contrary, pretreatment of mice with L-NAME (30mg kg−1,
i.p.) or methylene blue (10mg kg−1, i.p.) potentiated its effects. The extract produces an antidepressant-like effect in the FST and
TST that is dependent on the serotoninergic system, NMDA receptor complex, and the nitric oxide pathway.
1. Introduction There are several antidepressant drugs available, most
of them affecting directly or indirectly the monoaminergic
Major depression is one of the most common psychiatric system [6].These classical antidepressant agents are designed
disorders and is characterized by change in mood and lack to increase monoamine transmission, either by inhibiting
of interest in the surroundings as well as psychosocial and neuronal reuptake (imipramine, fluoxetine, or desipramine)
physical impairment [1, 2]. Depression is an important global or by inhibiting degradation (iproniazid) [7, 8]. However,
public health issue, because of the relatively high lifetime a major limitation of these antidepressants is side effects
prevalence ranging from 2% to 15% and also because it is such as sedation, blurred vision, constipation, seizures, sexual
associated with substantial disability [3]. The World Health dysfunction, and weight gain [3, 9]. Furthermore, although
Organization estimates that, by 2020, major depression will these are effective in treating most depressive episodes, a
become the second largest cause of global disease problems significant proportion of depressed patients do not display
in the world, only behind ischemic heart disease [4, 5]. signs of mood improvement until 2-3 weeks after the start of
2 BioMed Research International
the treatment [10]. Accordingly, natural plants may be free access to tap water and food (commercial pellet diet,
important sources of new antidepressant drugs and the GAFCO, Tema, Ghana). A period of at least one week for
safety of such plant extracts may be better than that of adaptation to the laboratory facilitieswas allowed.The studies
synthetic antidepressants [11, 12]. It is therefore desirable were conducted in accordance with accepted principles for
to research and develop more effective antidepressants with laboratory animal use and care (NRC, 2010). Approval for this
fewer adverse effects. Plant extracts are some of the most study was obtained from the faculty Ethics Committee.
attractive sources of new drugs and have been shown to pro-
duce promising results for the treatment of depression. For 2.4. Drugs and Chemicals. Desipramine hydrochloride, para-
instance, the excellent patient acceptance of St. John’s Wort chlorophenylalanine (pCPA), 𝛼-methyl-para-tyrosine meth-
(Hypericum perforatum L., Hypericaceae) and its extensive yl ester (AMPT), d-cycloserine (DCS, D-4-amino-3-isoxa-
use in Europe and USA for the treatment of mood disorders, zolidine), d-serine (DS), 5-hydroxy-L-tryptophan (5-HTP),
especially conditions of mild to moderate depression, has N-nitro-L-arginine methyl ester (L-NAME), L-arginine,
drawn attention to plant extracts as potential sources of norepinephrine, yohimbine, and methylene blue were pur-
highly desirable, new, and innovative antidepressant agents chased from Sigma-Aldrich Inc., St. Louis, MO, USA. Cypro-
[13, 14]. Pseudospondias microcarpa is also one of such plants heptadine was purchased from LETAP Pharmaceuticals Ltd.,
used for managing various diseases including CNS disorders Accra, Ghana. Sildenafil and prazosin hydrochloride were
[15]. However, despite the wide use of the plant, there is no from Pfizer, USA. Propranolol hydrochloride was fromWat-
data in literature on its probable antidepressant activity. son Pharma Private Ltd., India, and fluoxetine hydrochloride
Therefore, the present study evaluated the antidepressant- was from Prozac, Eli Lilly and Company Ltd., Basingstoke,
like effect of the hydroethanolic extract obtained from the England.
leaves of Pseudospondias microcarpa (PME) in two predictive
models of depression: forced swimming test (FST) and tail
suspension test (TST) in mice. Moreover, the mechanisms 2.5. Forced Swimming Test. This experiment was performed
throughwhich PME elicits its antidepressant-like actionwere according to the procedure of Porsolt et al. [16] with modifi-
investigated in the TST. cations. Briefly,micewere pretreatedwith vehicle (10mL kg
−1
of 0.9% NaCl, i.p.), PME (30, 100 and 300mg kg−1, p.o.),
fluoxetine (3, 10, and 30mg kg−1, p.o.), or desipramine (3,
2. Materials and Methods 10, and 30mg kg−1, i.p.) 60min (p.o.) or 30min (i.p.) before
2.1. Collection of Plant Material. Fresh leaves of Pseudospon- being placed individually in polypropylene cylinders (height
dias microcarpa were collected from the campus of Kwame 25 cm, diameter 10 cm) containing 10 cmofwater,maintained
Nkrumah University of Science and Technology (KNUST), at 25
∘C. With a public domain software JWatcher, version 1.0
Kumasi, near the Department of Agricultural Engineering (University of California, Los Angeles, USA, and Macquarie
(6 40.626 N, 1 34.041 W), during the month of August 2010, University, Sydney, Australia), behavioural assessment was∘ 󸀠 ∘ 󸀠
and authenticated at the Department of Herbal Medicine, measured during the last 4min of the 6-minute test period
Faculty of Pharmacy and Pharmaceutical Sciences, College of according to Detke et al. [17].Three different behaviours were
Health Sciences, KNUST, Kumasi, Ghana. A voucher speci- rated: (1) immobility: mice were judged to be immobile when
men (KNUST/HM1/2013/L005) was kept at the herbarium of they remained floating passively in the water, (2) swimming:
the faculty. mice were judged to be swimming if they were making activeswimming motions, more than necessary, to solely maintain
their head above water, and (3) climbing: mice were judged to
2.2. Plant Extraction. Leaves of the plantwere room-dried for be climbingwhen theyweremaking activemovements in and
seven days and pulverized into fine powder. The powder was out of the water with their forepaws, usually directed against
extracted by cold percolation with 70% (v/v) ethanol in water the walls. Duration of immobility, swimming, and climbing
over a period of 72 h and the resulting extract concentrated was measured.
into a syrupymass under reduced pressure at 60∘C in a rotary
evaporator. It was further dried in a hot air oven at 50∘C 2.6. Tail Suspension Test. The tail suspension test (TST) was
for a week and kept in a refrigerator for use. The yield was conducted as initially described by Steru et al. [18] with
20.5% (w/w). In this study, the crude extract is subsequently modifications [19, 20]. Animals were similarly grouped as
referred to as PME or extract. in the FST. One hour after oral administration and 30min
after intraperitoneal injection of test compounds, mice were
2.3. Animals. Male ICRmice (20–25 g) were purchased from individually suspended by the tail from a horizontal ring-
the Noguchi Memorial Institute for Medical Research, Accra, stand bar raised 30 cm above the floor using adhesive tape
Ghana, and kept in the animal house of the Department placed 1 cm from the tip of tail and positioned such that the
of Pharmacology, Kwame Nkrumah University of Science base of their tail was aligned with the horizontal plane. Test
and Technology, Kumasi, Ghana. The animals were housed sessions lasted for 6min and were videotaped. Behaviours for
in groups of 5 in stainless steel cages (34 cm × 47 cm × the last 4 min of the 6-minute period were then analysed.
18 cm) with soft wood shavings as bedding and housing Behaviours rated were as follows: (1) immobility: a mouse
conditions controlled—temperature maintained at 24-25∘C, was judged to be immobile when it hung by its tail without
relative humidity 60–70%, and 12 h light-dark cycle.They had engaging in any active behaviour, (2) swinging: a mouse was
BioMed Research International 3
judged to be swinging when it continuously moved its paws cages with free access to food and water, and mortality rate
in the vertical position while keeping its body straight and/or was assessed 48 hours after dosing.
it moved its body from side to side, (3) curling: a mouse
was judged to be curling when it engaged in active twisting
movements of the entire body, and (4) pedalling: it is defined 2.7.5. N-Methyl-d-aspartate (NMDA) Interaction. To evalu-
as when the animal moved its paws continuously without ate the effects of d-cycloserine (DCS) and d-serine (DS)
moving its body. in the mouse TST, the drugs were administered 30minbefore the test to different experimental groups of animals.
Immobility timewas comparedwith a control group in which
2.7. Mechanism(s) of Action. The TST presents some advan- saline was injected 30min before the test. For the present
tages over the FST in allowing an objective measure of report, the doses of these drugs were chosen based on a pilot
immobility and does not induce hypothermia by immersion study and in accordance with previous studies [10, 27].
in water [21, 22].Thus, thismodel was therefore used to assess To evaluate the possible involvement of the activation
the possible mechanism of action. of the NMDA receptor system in the antidepressant effect
of PME in the TST, subeffective doses of d-cycloserine
2.7.1. Serotoninergic Depletion. In order to investigate the (2.5mg kg−1, i.p.) and d-serine (600mg kg−1, i.p.) were sep-
possible contribution of the serotoninergic system on the arately administered 15min before administration of PME
effect of PME in the TST, mice were pretreated with para- (100mg kg−1, p.o.), FLX (10mg kg−1, p.o.), DES (10mg kg−1,
chlorophenylalanine (pCPA). pCPA is known to reduce the i.p.), or saline. Forty-five minutes after administration, the
concentration of brain serotonin by inhibiting its biosynthesis mice were assessed in the TST for duration of immobility.
[23]. In the present experiment, mice were injected i.p.
either with saline (control group) or with pCPA. pCPA was 2.7.6. Involvement of L-Arginine-NO-cGMP Pathway. An
administered at the dose of 300mg kg−1 once daily for 3 appreciable number of studies have attributed a significant
consecutive days. On the fourth day (24 h after the last pCPA role to the L-arginine-NO-cGMP pathway in the pathophys-
administration), mice received PME (100mg kg−1, p.o.), FLX iology of depression [28, 29]. Therefore, the possible partic-
(10mg kg−1, p.o.), DES (10mg kg−1, i.p.), or saline 60min ipation of this pathway in the antidepressant effect of PME
(p.o.) or 30min (i.p.) before the test. was investigated. Mice were pretreated with a subeffective
dose of L-arginine [750mg kg−1, i.p., a precursor of nitric
2.7.2. 5-HTP-Induced Head-Twitch Response. PME (100mg oxide (NO)] or vehicle 15min before PME (100mg kg−1,
kg−1, p.o.), FLX (10mg kg−1, p.o.), DES (10mg kg−1, i.p.), or p.o.) administration and assessed 45min later for immobility
saline were administered 60min (p.o.) or 30min (i.p.) before time. In separate experiments, the enhanced anti-immobility
intraperitoneal administration of 5-HTP (200mg kg−1).Mice effect of PME with L-NAME [30mg kg−1, i.p., a nonselective
were then placed into plastic cages and the number of head- nitric oxide synthase (NOS) inhibitor] or methylene blue
twitches (rapid movements of the head with little or no [10mg kg−1, i.p., an inhibitor of nitric oxide synthase and an
involvement of the trunk) was counted for 8min (from 15 to inhibitor of soluble guanylate cyclase (sGC)]was investigated.
23min) after the injection of 5-HTP [24, 25]. Mice were administered with these inhibitors 15min before
PME or vehicle and assessed 45min later for immobility time
2.7.3. Effects of Some Antagonists on PME Actions in the in the TST.
TST. Appropriate doses for antagonists were selected from To observe the role of cyclic guanosine monophosphate
literature [26] as well as pilot experiments, and doses that do (cGMP) in the antidepressant action of PME, mice received
−1
not modify immobility were used. Groups of mice received an injection of sildenafil [5mg kg , i.p., a phosphodi-
saline or antagonists (cyproheptadine, 8mg kg , p.o., a 5- esterase 5 inhibitor (PDE5)] or vehicle 15min before PME−1
HT receptor antagonist; prazosin, 3mg kg , p.o., a selec- (100mg kg
−1, p.o.). Forty-five minutes after PME administra-
−1
2 tion, the mice were subjected to TST to evaluate immobility
tive 𝛼 -receptor antagonist; propranolol, 3mg kg−1, p.o., 𝛽-
1 duration.
receptor antagonist; or yohimbine 3mg kg−1, p.o.,𝛼 -receptor
2
antagonist) 30min before vehicle or PME (100mg kg−1, p.o.)
andwere assessed 45min later for immobility time in theTST. 2.8. Rotarod Test. In FST and TST, false-positive results can
be obtained with certain drugs, in particular, psychomotor
stimulants, which decrease immobility time by stimulating
2.7.4. Potentiation of Norepinephrine Toxicity. This was done locomotor activity [30, 31]. Therefore, the effect of PME on
to assess the possible involvement of the noradrenergic motor coordination was assessed using a rotarod apparatus
system in the antidepressant-like effect of PME. Mice were (UgoBasile,model 7600,Cormerio,Milan, Italy).The rotarod
randomly assigned to test groups of 10 subjects. Mice were consisted of a rotating rod (diameter of 3 cm) and individual
pretreated with vehicle (10mL kg−1 of 0.9% NaCl, i.p.), PME compartments for each mouse. Mice were trained for 3 days
(30, 100, and 300mg kg−1, p.o.), fluoxetine (30mg kg−1, p.o.), before the test to stay on the rotating rod (speed 20 rpm) for
or desipramine (30mg kg−1, i.p.) 60min (p.o.) or 30min at least 5min. On the test day, mice were randomly divided
(i.p.) prior to the s.c. injection of the sublethal dose of into seven groups: saline-treated control group, diazepam
noradrenaline (3mg kg−1). Mice were then placed in plastic group (0.1, 0.3, and 1mg kg−1, i.p.), and PME group (30, 100,
4 BioMed Research International
and 300mg kg−1, p.o.). One hour (p.o.) or 30 (i.p.) min after effects of PME at doses of 100–300mg kg−1 (𝑃 < 0.01 at 100
administration of test compounds, mice were put on the and 300mg kg−1). Results in Figure 3 show that PME did not
rotating rod and latency until fall during the 5min session significantly affect pedalling but caused an increase in time
was recorded. Animals that stayed on the bar for more than spent swinging (𝐹 = 6.951, 𝑃 = 0.0033) and curling
3,16
5min were given the maximum score of 5min. (𝐹 = 7.580,𝑃 = 0.0022). Fluoxetine significantly increased
3,16
anti-immobility effects by a maximum of 62.21 ± 25.07%.
2.9. Statistical Analysis. In all experiments, a sample size of Swinging time was also significantly increased (𝐹 = 11.59,3,16
−1
5–10 animals was utilized. All data are presented as mean ± 𝑃 = 0.0003) reaching statistical significance at 10mg kg
SEM. To compare differences between groups, one-way (𝑃 < 0.05) and 30mg kg−1 (𝑃 < 0.01). However, ANOVA did
ANOVA was performed with Newman-Keuls test as post not indicate any significant effect of fluoxetine on pedaling
hoc. In some instances, behavioural data were analysed using (𝐹 = 2.039, 𝑃 > 0.05) or curling (𝐹 = 1.246, 𝑃 = 0.326)
3,16 3,16
two-way ANOVA followed by Bonferroni’s test as post hoc. times. Administration of desipramine significantly reduced
GraphPad Prism for Windows 5 (GraphPad Software, San immobility time in a dose dependent manner by a maximum
Diego, CA, USA) was used for all statistical analysis. 𝑃 < of 80.10 ± 17.38%. Swinging time was also significantly
0.05 (Newman-Keuls test or Bonferroni’s test) was considered increased (𝐹 = 6.248, 𝑃 = 0.0052). Just like fluoxetine,
3,16
statistically significant. ANOVA did not reveal any significant effect of desipramine
on pedaling and curling times.
3. Results
3.3. Mechanism(s) of Antidepressant Action of PME
3.1. Forced Swimming Test. Figure 1 depicts the effect of
acute administration of PME (30–300mg kg−1, p.o.) and the 3.3.1. Pretreatment with pCPA. The results in Figure 4 show
classical antidepressant drugs fluoxetine (3–30mg kg−1, p.o.) that pCPA alone (300mg kg−1 for 3 consecutive days) did
and desipramine (3–30mg kg−1, i.p.) on mice behaviours in not modify the immobility time, while pretreatment of
the FST. mice with pCPA significantly blocked the reduction in the
In this test, ANOVA revealed that all doses of PME immobility time elicited by PME (100mg kg−1, p.o.) in the
significantly decreased the immobility time (𝐹 = 7.995, TST (𝐹 = 40.45, 𝑃 = 0.0002). Fluoxetine, the selective
1,24
3,16
𝑃 = 0.0018) and increased swimming time (𝐹 = 8.462, serotonin reuptake inhibitor (SSRI), reduced immobility in
3,16
𝑃 = 0.0013) of mice in the FST by a maximum of 62.83 ± saline-pretreated mice. However, it significantly increased
9.98%and 94.53±17.31%, respectively (Figure 1(a)). ANOVA immobility in pCPA-pretreated animals when comparedwith
revealed that PME did not significantly affect latency to the corresponding group given saline. Prior administration of
immobility (𝐹 = 3.062, 𝑃 = 0.0583). However, post hoc pCPA did not alter the response of desipramine.
3,16
analysis showed statistical significance at 300mg kg−1 (𝑃 <
0.05). Climbing timewas not affected. In Figure 1(d), ANOVA 3.3.2. 5-HTP-Induced Head-Twitch Response in Mice. As
analysis revealed that fluoxetine significantly decreased the shown in Figure 5, PME and fluoxetine potentiated the
immobility time (𝐹 = 7.995, 𝑃 = 0.0043) and increased
3,16 number of head-twitch responses by maximum of 54.08%
swimming time (𝐹 = 8.462, 𝑃 = 0.0060) of mice in FST
3,16 and 80.88% as compared to the control, respectively. Unlike
reaching statistical significance at 10 and 30mg kg−1 (both PME and fluoxetine, desipramine significantly decreased
𝑃 < 0.01). Latency to immobility (𝐹 = 4.490, 𝑃 =
3,16 the number of head-twitch responses in comparison to the
0.0181) was significantly affected but not climbing behaviour. control group (𝑃 < 0.05).
In Figure 1(e), swimming behaviour of desipramine was not
significantly affected (𝐹 = 3.350, 𝑃 = 0.669). However,
3,16
ANOVA revealed a significant reduction of immobility time 3.3.3. Effects of Antagonists on PME Actions in the TST.
(𝐹 = 11.95, 𝑃 = 0.0002) and significant increase in Cyproheptadine (8mg kg−1, p.o.), prazosin (3mg kg−1, p.o.),
3,16
immobility latency (𝐹 = 6.785, 𝑃 = 0.0037) (Figure 1(e)). propranolol (3mg kg−1, p.o.), and yohimbine (3mg kg−1, p.o.)
3,16
Climbing time was also significantly increased (𝐹 = 6.850, were administered 30min before PME and the tail suspen-
3,16
𝑃 = 0.0035). sion test was performed 45min after PME administration.
The anti-immobility effect caused by PME (100mg kg−1,
3.2. Tail Suspension Test. Figures 2 and 3 represent the p.o.) was significantly prevented by pretreatment of mice
effect of acute administration of PME (30–300mg kg , with cyproheptadine (Figure 6(a)). Prazosin (Figure 6(b)),−1
p.o.) and the classical antidepressant drugs fluoxetine (3– propranolol (Figure 6(c)), and yohimbine (Figure 6(d)) hadno effect on the anti-immobility effect of the extract.
30mg kg−1, p.o.) and desipramine (3–30mg kg−1, i.p.) on
mice behaviours in the TST. Administration of PME (30–
300mg kg−1, p.o.) 1 h before the test period significantly 3.3.4. Potentiation of Norepinephrine Toxicity. As shown in
decreased the immobility periods of mice by maximum of Table 1, injection of the sublethal dose of noradrenaline
80.98 ± 18.75% when compared to control group, indicating (3mg kg−1, s.c.) caused no mortality in PME and FLX
significant antidepressant-like activity. Newman-Keuls post treated mice. However, desipramine pretreatment potenti-
hoc test indicated statistically significant anti-immobility ated markedly and significantly NE toxicity in mice.
BioMed Research International 5
250 250 25
††† †††
200 200 ∗ 20
∗∗ ∗∗
150 150 15
∗
∗
100 ∗∗ 100 10
∗∗
50 50 5
0 0 0
Ctrl 30 100 300 Ctrl 30 100 300 Ctrl 30 100 300
PME (mg kg−1) PME (mg kg−1) PME (mg kg−1)
Immobility
Swimming
(a) (b) (c)
250 240 40
†
∗
200 † 200∗∗ ∗ 30
∗∗
160
150
120 20
100 ∗∗ ∗∗
80
10
50 40
0 0 0
Ctrl 3 10 30 Ctrl 3 10 30 Ctrl 3 10 30
FLX (mg kg−1) FLX (mg kg−1) FLX (mg kg−1)
Immobility
Swimming
(d) (e) (f)
200 240 140
∗ ∗∗
∗∗ 120
160 200
†
160 100 ∗ ∗
120
∗∗ 80120
80 ∗∗∗ 60
∗∗∗ 80 40
40 40 20
0 0 0
Ctrl 3 10 30 Ctrl 3 10 30 Ctrl 3 10 30
DES (mg kg−1) DES (mg kg−1) DES (mg kg−1)
Immobility
Swimming
(g) (h) (i)
Figure 1: Performance of mice in the FST: behavioural assessment including immobility and swimming duration (a, d, and g), immobility
latency (b, e, and h), and climbing duration (c, f, and i) after acute treatment of mice with PME, fluoxetine, and desipramine. PME (30–
300mg kg−1) and FLX (3–30mg kg−1) were p.o. administered 60min before behavioural assessment. DES (3–30mg kg−1) was i.p. injected
30min before the test. Data are expressed as group mean ± SEM (𝑛 = 5). The lower and upper margins of the boxes represent the 25th and
75th percentiles, with the extended arms representing the 10th and 90th percentiles, respectively. The median is shown as the horizontal line
within the box and symbols represent outliers. Significantly different from control: ∗𝑃 < 0.05; ∗∗ ∗∗∗𝑃 < 0.01; 𝑃 < 0.001 (one-way ANOVA
followed by Newman-Keuls post hoc test) and significant difference when immobility and swimming were compared to each other. †𝑃 < 0.05;
†††
𝑃 < 0.001 (two-way repeated measures ANOVA followed by Bonferroni’s post hoc).
Duration (s) Duration (s) Duration (s)
Latency to immobility (s) Latency to immobility (s) Latency to immobility (s)
Climbing duration (s) Climbing duration (s) Climbing duration (s)
6 BioMed Research International
200 200
160 160
120 120 ∗
80 80 ∗∗ ∗∗
∗∗ ∗∗
40 40
0 0
Ctrl 30 100 300 Ctrl 3 10 30
PME (mg kg−1) FLX (mg kg−1)
(a) (b)
200
160
120
80 ∗
∗ ∗∗
40
0
Ctrl 3 10 30
DES (mg kg−1)
(c)
Figure 2: Effects of PME (30–300mg kg−1), fluoxetine (3–30mg kg−1), and desipramine (3–30mg kg−1) on the total duration of immobility
in the TST. The values represent mean ± SEM (𝑛 = 5). The lower and upper margins of the boxes represent the 25th and 75th percentiles,
with the extended arms representing the 10th and 90th percentiles, respectively. The median is shown as the horizontal line within the box.
Significantly different from control: ∗ ∗∗𝑃 < 0.05; 𝑃 < 0.01 (one-way ANOVA followed by Newman-Keuls post hoc test).
3.3.5. Effect of Joint Administration of d-Serine or DCS and Table 1: Effect of PME, fluoxetine, and desipramine on NE induced
PME, FLX, or DES in the TST. The effects of a combined toxicity in mice.
administration of DCS and PME, FLX, or DES on total
−1
duration of immobility in mice are shown in Figure 7(b). Group Dose (mg kg ) Number of deaths % mortality
Administration of DCS at a dose of 2.5mg kg−1 had no effect Control 0 0
on the immobility time inmice. Concomitant administration 30 0 0
of DCS (2.5mg kg−1) with PME (100mg kg−1) significantly PME 100 0 0
reduced the immobility time in mice (𝐹 = 16.42, 300 0 0
1,24
𝑃 = 0.0037) with Bonferroni’s post hoc analysis showing FLX 30 0 0
significance of 𝑃 < 0.01. Similar effects were observed for DES 30 5 50
fluoxetine (𝑃 < 0.01) but not desipramine. Data indicates the number and percentage of mice (𝑛 = 10) that died.
The effects of a combined administration of PME, FLX, or
DES and d-serine on total duration of immobility in mice are
shown in Figure 7(a). PME (100mg kg−1), FLX (10mg kg−1), 𝑃 = 0.0177). d-Serine however did not completely abolish the
and DES (10mg kg−1) significantly reduced the immobility anti-immobility of DES (𝑃 > 0.05).
time in mice as revealed by ANOVA (𝐹 = 4.483, 𝑃 =
3,16
−1
0.0182). d-Serine given alone at a dose of 600mg kg had no 3.3.6. Involvement of L-Arginine-NO-cGMP Pathway.
effect on immobility time but when combined with PME or Figure 8 shows the involvement of the nitric oxide pathway
FLX abolished their antidepressant-like effects ( −1𝐹 = 8.849, on the effects of PME in the TST. PME (100mg kg , p.o.)
1,24
Immobility time (s)
Immobility time (s)
Immobility time (s)
BioMed Research International 7
80 80 80
∗∗
60 60 60
40 40 40
20 20 20
0 0 0
Ctrl 30 100 300 Ctrl 3 10 30 Ctrl 3 10 30
PME (mg kg−1) FLX (mg kg−1) DES (mg kg−1)
(a) (b) (c)
250 250 250
200 200 200
150 150 150
100 100 100
50 50 50
0 0 0
Ctrl 30 100 300 Ctrl 3 10 30 Ctrl 3 10 30
PME (mg kg−1) FLX (mg kg−1) DES (mg kg−1)
(d) (e) (f)
80 80 80
∗∗ ∗∗∗ ∗∗
70 70 70
∗
60 60 60
∗
50 ∗ ∗ 50 50
40 40 40
30 30 30
20 20 20
10 10 10
0 0 0
Ctrl 30 100 300 Ctrl 3 10 30 Ctrl 3 10 30
−1 FLX (mg kg−1PME (mg kg ) ) DES (mg kg−1)
(g) (h) (i)
Figure 3: Performance of mice in the TST: behavioural assessment including curling (a, b, and c), pedaling (e, f, and g), and swinging (g,
h, and i) after acute treatment of mice with PME, fluoxetine, and desipramine. PME (30–300mg kg−1) and FLX (3–30mg kg−1) were p.o.
administered 60min before behavioural assessment. DES (3–30mg kg−1) was i.p. injected before the test. Data are expressed as groupmean ±
SEM (𝑛 = 5).The lower and upper margins of the boxes represent the 25th and 75th percentiles, with the extended arms representing the 10th
and 90th percentiles, respectively. The median is shown as the horizontal line within the box. Significantly different from control: ∗𝑃 < 0.05;
∗∗ ∗∗∗
𝑃 < 0.01; 𝑃 < 0.001 (one-way ANOVA followed by Newman-Keuls post hoc test).
Swinging time (s) Pedalling time (s) Curling time (s)
Swinging time (s) Pedalling time (s) Curling time (s)
Swinging time (s) Pedalling time (s) Curling time (s)
8 BioMed Research International
240 of 𝑃 < 0.01. L-NAME (30mg kg−1, i.p., a nonselective nitric
oxide synthase inhibitor) enhanced the antidepressant effect
of an effective dose of PME (100mg kg−1, p.o.) (𝐹 = 7.786,
200 1,20
−1
𝑃 = 0.0113). Methylene blue (10mg kg , i.p., an inhibitor
of NO synthase and an inhibitor of sGC) did not affect
160 ††† the immobility time in mice. However, methylene blue
significantly enhanced the antidepressant effect of PME
†† (𝐹 = 9.357, 𝑃 = 0.0062). Figure 8(d) shows that the
1,20
120 pretreatment of animals with sildenafil (5mg kg−1, i.p.,
a phosphodiesterase 5 inhibitor) significantly inhibited
the reduction in immobility time elicited by PME in TST
80 (𝑃 < 0.05).
∗
40 ∗ ∗∗ 3.4. Effect of PME on Rotarod Performance. Figure 9 shows
the effect of PME on the performance of mice in the rotarod
test.The extract caused no significant effect on the time taken
0 by mice to fall off the rotarod compared to the control at all
Ctrl PME FLX DES the doses used ( at 30–300mg kg−1𝑃 > 0.05 ). Diazepam at the
dose of 1.0mg kg−1 caused significant decrease in the latency
Saline-treated
pCPA-treated to fall off the rotating rod (𝑃 < 0.01).
Figure 4: Effects of pCPA (300mg kg−1, i.p. for 3 consecutive days)
pretreatment on the behavioural response of PME (100mg kg , 4. Discussion−1
p.o.), fluoxetine (10mg kg−1, p.o.), and desipramine (10mg kg−1, i.p.) The present study provides convincing evidence that PME,
in the tail suspension test. Data are presented as group mean ± SEM
( ). ; versus vehicle-treated animals when administered orally, produces an antidepressant-like∗ ∗∗𝑛 = 5 𝑃 < 0.05 𝑃 < 0.01
(one-way ANOVA followed by Newman-Keuls’ test). Significant effect in both the FST and TST and also elicits its action to
difference between treatments: †† ; ††† (two-way a similar extent as the selective serotonin reuptake inhibitor𝑃 < 0.01 𝑃 < 0.001
ANOVA followed by Bonferroni’s test). fluoxetine.
The FST and TST are widely used for screening poten-
tial antidepressant agents and are sensitive and relatively
100 specific to all major classes of antidepressants including
∗∗ tricyclic antidepressants (TCAs), selective serotonin reuptake
80 ∗ inhibitors (SSRIs), monoamine oxidase inhibitors (MAOIs),
60 and atypical antidepressants [16–18]. These tests are based
on the observation that rodents, after initial escape-oriented
40 movements, develop an immobile posture when placed in an
∗ inescapable stressful situation. If antidepressant treatments
20 are given prior to the test, the subjects will actively persist
0 in engaging in escape-directed behaviour for longer periods
Ctrl PME FLX DES of time than after vehicle treatment [16, 22]. There is,
indeed, a significant correlation between clinical potency and
Figure 5: Effects of PME (100mg kg−1), FLX (10mg kg−1), and DES effectiveness of antidepressants in both models [32, 33].
(10mg kg−1) on the number of 5-HTP-induced head twitches in In this study, the modified version of the FST, originally
mice. Data are expressed as mean ± SEM (𝑛 = 5). The lower and
upper margins of the boxes represent the 25th and 75th percentiles, introduced by Detke et al. [17], was used, in which three
with the extended arms representing the 10th and 90th percentiles, specific types of behaviour, that is, immobility, climbing, and
respectively. The median is shown as the horizontal line within the swimming, were measured. The modified FST distinguishes
box. ∗ ∗∗< 0.05; < 0.01 compared with the saline-treated control between passive responses (immobility) and active responses𝑃 𝑃
(one-way ANOVA followed by Newman-Keuls post hoc test). (increases in swimming or climbing) to stress [34].Moreover,
it widely measures the effects of SSRIs in mice [17]. Antide-
pressants acting through the serotoninergic system, including
the SSRIs fluoxetine, sertraline, paroxetine, and citalopram,
significantly decreased the immobility time of mice in the selectively increase swimming behaviour. In addition, the
TST (𝑃 < 0.05). Administration of L-arginine (750mg kg−1, modified FST differentiates between antidepressants that
i.p., a precursor of nitric oxide) had no anti-immobility effects work through serotoninergic mechanisms or noradrener-
on mice in the TST compared with saline- (vehicle-) treated gic mechanisms, as noradrenergic compounds selectively
animals. However, pretreatment with L-arginine prevented increased climbing behaviour [17, 35] and drugs with dual
the antidepressant-like effect of PME (100mg kg−1, p.o.) with effects increased both swimming and climbing [36, 37]. In
a Bonferroni post hoc analysis showing statistical significance this study, PME in a similar fashion as fluoxetine induced
Immobility time (s)
Frequency of head twitches
BioMed Research International 9
200
200 †
160
160
120
120
∗
∗
80
80
40 40
0 0
Veh PME Veh PME
Saline Saline
Cyproheptadine Prazosin
(a) (b)
200 160
140
160
120
120 100
∗
∗ 80
80 60
40
40
20
0 0
Veh PME Veh PME
Saline Saline
Propranolol Yohimbine
(c) (d)
Figure 6: Effect of pretreatment of mice with cyproheptadine (8mg kg−1, p.o., a 5-HT receptor antagonist, panel (a)), prazosin (3mg kg−1,
2
p.o., a selective 𝛼 -receptor antagonist, panel (b)), propranolol (3mg kg−1, p.o., 𝛽-receptor antagonist, panel (c)), and yohimbine (3mg kg−1,
1
p.o., 𝛼 -receptor antagonist, panel (d)) on PME- (100mg kg−1, p.o.) induced reduction in immobility time in the TST. Each column represents
2
the mean ± SEM ( ∗𝑛 = 6). 𝑃 < 0.05 as compared with the vehicle-treated control. †𝑃 < 0.05 as compared with the group pretreated with
vehicle and PME.
a dose dependent reduction in the immobility time and an desipramine had no effect on swimming behaviour but
increase in the swimming behaviour, whereas no changes instead increased climbing behaviour.
were observed in the climbing behaviour. This profile of Modifications have been made in terms of the measure-
actionmay suggest that themechanism of the antidepressant- ment of specific behavioural components of active behaviours
like activity of PME is related to the modulation of the in the TST to help differentiate between classical antidepres-
serotoninergic system. In contrast to PME and fluoxetine, sants and other compounds with antidepressant-like effects
Immobility time (s) Immobility time (s)
Immobility time (s) Immobility time (s)
10 BioMed Research International
240 240
200 † † 200
160 160 †† ††
120 ∗ ∗ 120∗ ∗ ∗ ∗
∗∗∗
80 80
∗∗∗ ∗∗∗
40 40
0 0
Ctrl PME FLX DES Ctrl PME FLX DES
Saline-treated Saline-treated
d-Serine-treated d-Cycloserine-treated
(a) (b)
Figure 7: Effect of joint administration of d-serine (DS) or d-cycloserine (DCS) and PME, fluoxetine (FLX), or desipramine (DES) on the
total duration of immobility in the TST in mice. The values represent means ± SEM of 5 mice. ∗ ∗∗∗𝑃 < 0.05; 𝑃 < 0.001 versus vehicle-treated
animals (one-way ANOVA followed by Newman-Keuls’ test). Significant difference between treatments: † ††𝑃 < 0.05; 𝑃 < 0.01 (two-way
ANOVA followed by Bonferroni’s test).
but with different mechanisms of actions, such as opiates Several reports have suggested the involvement of sero-
[19, 20]. While traditional antidepressants that inhibit sero- toninergic and noradrenergic receptors in the mechanism of
tonin and/or noradrenaline reuptake decrease immobility action of several classes of antidepressant drugs, including
and increase swinging behaviour, opioids, having decreased TCAs, SSRIs, and MAOIs, as well as in the pathophysiology
immobility, increase curling behaviour [20]. It was observed of depression. The monoamine hypothesis of depression
that administration of PME, fluoxetine, and desipramine proposes that there is depletion in the levels of serotonin
showed significant antidepressant-like effects by decreasing and noradrenaline in the central nervous system [38, 39]
immobility. PME did not significantly affect pedalling but Therefore, the current effective treatments for depression are
caused an increase in time spent swinging and curling. Thus, considered to elevate brain serotonin and/or noradrenaline
PME in addition to its antidepressant-like activities could neurotransmission [40, 41]. Thus, in this study, the possible
possibly have opioidergic properties. The TST has many involvement of these systems in the antidepressant-like effect
advantages over the FST including the lack of hypothermic of PME administered orally was investigated.
effects of cold water, the ability to test strains that may have To confirm a possible contribution of the serotonin
motor deficits that make swimming difficult, and increased transmission in the antidepressant effect of PME, mice were
sensitivity to a wider range of antidepressant compounds pretreated with pCPA, an inhibitor of serotonin synthesis
[21, 37]. For this reason, the TST was used to assess the [23, 42]. Even though the depletion of 5-HT does not always
mechanisms by which PME elicits its antidepressant-like produce behavioural depression, depletion of 5-HT with
activity. pCPA blocks the effects of fluoxetine in the FST and TST,
In FST and TST, false-positive results can be obtained while the effects of desipramine, which acts primarily as a
with certain drugs, in particular, psychomotor stimulants, norepinephrine reuptake inhibitor, are unaffected by 5-HT
which decrease immobility time by stimulating locomotor depletion [23, 35]. According to previous reports, pCPA at
activity [30, 31]. Anti-immobility effect of PME seems not to the present dose administered for three consecutive days was
be associated with any motor deficits, since mice treated with able to deplete the endogenous store of serotonin successfully
PME did not impair motor coordination in the rotarod test. without affecting the noradrenergic or dopaminergic levels
This indicates that the reduction of immobility time elicited [1, 23]. In this study, the antidepressant-like effect of PME
by PME treatment in the TST and FST is unlikely due to a was abolished by pCPA administration, suggesting that 5-HT
psychomotor-stimulant effect but rather an antidepressant- in the brain is essential for its action in the TST. This effect
like effect of PME. demonstrates that the serotoninergic mechanism underlies
Immobility time (s)
Immobility time (s)
BioMed Research International 11
200 200
††
160 160
†
120 120
∗ ∗
80 80
40 40
∗∗
0 0
Veh PME Veh PME
Saline Saline
L-Arginine L-NAME
(a) (b)
200 200
†
160
150
†
120
100
∗ ∗
80
50
40 ∗∗
0 0
Veh PME Veh PME
Saline Saline
Methylene blue Sildenafil
(c) (d)
Figure 8: Effects of pretreatment of mice with L-arginine (750mg kg−1, i.p., a precursor of nitric oxide, panel (a)), L-NAME (30mg kg−1, i.p.,
a nonselective nitric oxide synthase inhibitor, panel (b)), methylene blue (10mg kg−1, i.p., an inhibitor of NO synthase and an inhibitor of
sGC, panel (c)), and sildenafil (5mg kg−1, i.p., a phosphodiesterase 5 inhibitor, panel (d)) on PME- (100 mg kg−1, p.o.) induced reduction in
immobility time in the TST. Each column represents the mean SEM ( ∗ ∗∗± 𝑛 = 6). 𝑃 < 0.05; 𝑃 < 0.01 versus vehicle-treated animals (one-way
ANOVA followed by Newman-Keuls’ test). Significant difference between treatments: † ; ††𝑃 < 0.05 𝑃 < 0.01 (two-way ANOVA followed by
Bonferroni’s test).
the acute behavioural effects of PME on tests of depressive Head-twitch response (HTR), induced by 5-HTP in mice,
behaviour. provides a simple method of determining specific activities
Administration of large doses of 5-HTP, a precursor of potentiators and antagonists for 5-HT in the central
of 5-HT, induces head twitches that occur spontaneously nervous system [43]. Administration of PME and fluoxetine
and irregularly, probably through a central action of 5-HT. potentiated 5-HTP-induced HTR in mice. This potentiation
Immobility time (s) Immobility time (s)
Immobility time (s) Immobility time (s)
12 BioMed Research International
400 400
300 300
∗∗
200 200
100 100
0 0
Control 30 100 300 0.1 0.3 1.0
PME (mg kg−1 Diazepam (mg kg−1) )
Figure 9: Behavioural effects of PME and DZP on muscle relaxant activity in the rotarod test in mice. Data are expressed as group mean ±
SEM (𝑛 = 5). ∗∗𝑃 < 0.01 compared to control group (one-way ANOVA followed by Newman-Keuls test).
of HTR may be due to the PME or fluoxetine-mediated TST [49].Thus, this study further assessed the involvement of
inhibition of the 5-HT reuptake and resulting increase of NMDA receptors in the antidepressant-like effect of PME. d-
the content of 5-HT in synapses. This finding is consistent Cycloserine is a partial agonist of glycineB site of the NMDA
with the fact that pCPA pretreatment attenuated the anti- receptor complex [10, 50]. At low doses, d-cycloserine (DCS)
immobility activity of PME and fluoxetine in the TST. In exerts an agonist profile as itmimics the action of endogenous
contrast, desipramine significantly decreased the number of glycine at its site and at higher doses competitively antago-
5-HTP-induced head-twitch responses. nizes the glycine site [10, 51]. In this study,DCSdid not change
A role for 5-HT receptors in the action of some antide- the behaviour of animals in the TST; however, a potentiating
2
pressants has been shown. Preclinical data has shown that effect was seen when DCS was given jointly with PME or
5-HT2A/2C antagonism has a significant role in the mech- fluoxetine. This apparent potentiation was manifested as a
anism underlying the antidepressant-like effect of several reduction of immobility time, which suggests a participation
antidepressants [42, 44]. Furthermore, a significant hyper- of the glycine site of the NMDA receptor complex in the
sensitivity of 5-HT receptors in the brain of depressed antidepressant-like activity of PME. In another study, the
2
suicide victims has been observed in addition to elevated influence of d-serine (a full agonist on glycine/NMDA
densities of 5-HT2A receptors in depressed patients which receptors) on the activity of PME in the TST was evaluated.
showed significant reduction with a clinical recovery [1, d-Serine did not change the immobility time in the TST;
45]. In the present study, the anti-immobility effect elicited however, concomitant administration with PME, fluoxetine,
by PME in the TST was blocked by the pretreatment of and desipramine blocked their anti-immobility actions. It
mice with cyproheptadine (a 5-HT receptor antagonist), has been reported that d-serine blocked the antidepressant
2
whereas prazosin, propranolol, and yohimbine had no effects. effects of imipramine, fluoxetine, and reboxetine, suggest-
This further confirms the role of the 5-HT system in the ing that activation of the glycine/NMDA receptor complex
mechanism of the antidepressant-like activity of PME. abolishes the antidepressant effects of both serotonin and
The norepinephrine (NE) potentiation toxicity in mice noradrenaline-based compounds [10, 27, 52]. Interaction
reveals an adrenergic component of the pharmacological between NMDA receptor and serotoninergic pathway is
activity of antidepressants. Results of the present study more obvious than NMDA receptor and noradrenergic one.
showed that PME did not potentiate NE toxicity indi- This is evident by the fact that NMDA receptor antagonists
cating noninvolvement of the noradrenergic system in its release/increase the concentration of serotonin and increase
antidepressant-like effects.This further confirms the previous its turnover in the brain [53, 54]. Thus, it can be suggested
report in which the anti-immobility effect of PME was not that the antidepressant-like activity of PME (which acts via
reversed by prazosin (selective 𝛼 -receptor antagonist) and serotoninergic pathway) may occur via an effect on the
1
yohimbine (𝛼 -receptor antagonist). glycine site of NMDA receptor.
2
Several studies have implicated the NMDA class of Nitric oxide (NO) is a signalling molecule in the brain
glutamate receptors in the pathophysiology of depression and and has been implicated in neurotransmission, synaptic plas-
the mechanism of action of antidepressant treatment [27, 46, ticity, learning, perception of pain, aggression, anxiety, and
47]. In addition, studies have reported antidepressant-like depression [55–57]. It has been reported that suicidal patients
effects of a variety of NMDA receptor antagonists in animal showed significantly higher levels of plasma nitric oxide
models of depression such as the mouse FST [27, 48] and metabolites than in nonsuicidal psychiatric patients or in
Time on rod (s)
Time on rod (s)
BioMed Research International 13
normal control subjects [58, 59]. Similarly, depressed patients a putative alternative therapeutic tool that could help the
showed significantly higher plasma nitrate concentrations, conventional pharmacotherapy of depression.
suggesting that NO production is increased in depression
[51, 60]. An appreciable number of studies have attributed
a significant role to the L-arginine-NO-cGMP pathway in Conflict of Interests
the pathophysiology of depression. Therefore, the possible The authors declare that there is no conflict of interests
participation of this pathway in the antidepressant effect of regarding the publication of this paper.
PME was investigated.
Results of the present study showed that pretreatment of
mice with L-arginine, a NOS substrate, significantly inhibited Acknowledgments
the anti-immobility effect of the extract. Furthermore, a syn- The authors are grateful to Messrs Thomas Ansah, Gordon
ergistic antidepressant-like effect was observed when PME
was administered with NG
Darku, Prosper Akortia, Edmond Dery, and Prince Okyere
nitro-L-arginine-methyl ester of the Department of Pharmacology for their technical
(L-NAME), a nonselective nitric oxide synthase inhibitor, assistance.
or methylene blue, an inhibitor of both NOS and sGC.
Several studies have demonstrated that NOS inhibitors exert
antidepressant-like effects in animal models predictive of References
antidepressant activity [61, 62]. Thus, these results indicate [1] C. Girish, V. Raj, J. Arya, and S. Balakrishnan, “Evidence for the
that the inhibition of NO synthesis may be involved in involvement of the monoaminergic system, but not the opioid
the antidepressant-like effect of PME in the TST. Sev- system in the antidepressant-like activity of ellagic acid inmice,”
eral reports have shown that NOS inhibitors augment the European Journal of Pharmacology, vol. 682, no. 1–3, pp. 118–125,
behavioural effect of tricyclic antidepressants and selective 2012.
serotonin reuptake inhibitors, but not noradrenaline reup- [2] S. Nakajima, T. Suzuki, K. Watanabe, H. Kashima, and H.
take inhibitors in the FST [51, 63, 64]. Therefore, the admin- Uchida, “Accelerating response to antidepressant treatment
istration of NOS inhibitors could cause an enhanced effect in depression: a review and clinical suggestions,” Progress in
of SSRIs in antidepressant therapy. It has been shown that Neuro-Psychopharmacology and Biological Psychiatry, vol. 34,
PME elicits its anti-immobility effect via the 5-HT pathway no. 2, pp. 259–264, 2010.
devoid of the noradrenergic system. Therefore, the possible [3] D. Dhingra, P. Joshi, A. Gupta, and R. Chhillar, “Possible
involvement of the nitric oxide system in the antidepressant- involvement of monoaminergic neurotransmission in antide-
like effect of PME could be attributed to its interaction with pressant-like activity of emblica officinalis fruits in mice,” CNS
the 5-HT system. Neuroscience andTherapeutics, vol. 18, no. 5, pp. 419–425, 2012.
Heiberg et al. [61] demonstrated that excessive cGMP [4] C. J. L. Murray and A. D. Lopez, The Global Burden of Disease,
levels may produce a depression-like state and reducing its World Health Organisation, Geneva, Switzerland, 2001.
levels may produce antidepressant-like actions. The levels [5] Q. Mao, Z. Huang, S. Ip, and C. Che, “Antidepressant-like effect
of cGMP can be decreased by either inhibiting the soluble of ethanol extract from Paeonia lactiflora inmice,” Phytotherapy
guanylate cyclase (by methylene blue) or by decreasing the Research, vol. 22, no. 11, pp. 1496–1499, 2008.
function of nitric oxide (by inhibiting NOS enzyme). In [6] A. S. Elhwuegi, “Central monoamines and their role in major
addition, cGMP is degraded into guanosine monophosphate depression,” Progress in Neuro-Psychopharmacology and Biolog-
(GMP) with the help of phosphodiesterase enzyme (PDE). ical Psychiatry, vol. 28, no. 3, pp. 435–451, 2004.
Thus, inhibiting phosphodiesterase enzyme by using its [7] D. Zhou, H. Jin, H.-B. Lin et al., “Antidepressant effect of the
inhibitors may increase the levels of cGMP and therefore extracts fromFructusAkebiae,”Pharmacology Biochemistry and
produce a depression-like state [59]. Sildenafil is a selective Behavior, vol. 94, no. 3, pp. 488–495, 2010.
PDE5 inhibitor that increases the cGMP level in target tissues [8] J. M. Dwyer, B. J. Platt, S. J. Sukoff Rizzo et al., “Preclinical char-
[56, 65]. In the present study, the antidepressant-like effect of acterization of BRL 44408: antidepressant- and analgesic-like
PMEwas reversed by pretreatment with sildenafil (a selective activity through selective alpha2A-adrenoceptor antagonism,”
PDE5 inhibitor), indicating that the extract probably exerts its International Journal of Neuropsychopharmacology, vol. 13, no.
effect in the TST by decreasing cGMP levels.This is consistent 9, pp. 1193–1205, 2010.
with several reports in which sildenafil blocked the anti- [9] J. T. Andreasen, G. M. Olsen, O. Wiborg, and J. P. Redrobe,
immobility effects of compounds with antidepressant activity “Antidepressant-like effects of nicotinic acetylcholine receptor
[66–68]. antagonists, but not agonists, in the mouse forced swim and
mouse tail suspension tests,” Journal of Psychopharmacology,
vol. 23, no. 7, pp. 797–804, 2009.
5. Conclusion [10] E. Poleszak, P. Wlaź, B. Szewczyk et al., “A complex interaction
between glycine/NMDA receptors and serotonergic/noradre-
Results indicate that Pseudospondias extract produces an nergic antidepressants in the forced swim test in mice,” Journal
antidepressant-like effect in the FST and TST that is depen- of Neural Transmission, vol. 118, no. 11, pp. 1535–1546, 2011.
dent on the serotoninergic system, NMDA receptor complex, [11] V. Schulz, “Safety of St. John’s Wort extract compared to
and the L-arginine-NO-cGMP pathway. This suggests that synthetic antidepressants,”Phytomedicine, vol. 13, no. 3, pp. 199–
Pseudospondias microcarpa could be of potential interest as 204, 2006.
14 BioMed Research International
[12] Y. Wang, T. Han, Y. Zhu et al., “Antidepressant properties of [27] P. Wlaź, R. Kasperek, A. Wlaź et al., “NMDA and AMPA
bioactive fractions from the extract of Crocus sativus L,” Journal receptors are involved in the antidepressant-like activity of
of Natural Medicines, vol. 64, no. 1, pp. 24–30, 2010. tianeptine in the forced swim test in mice,” Pharmacological
[13] B. Isacchi, N. Galeotti, M. C. Bergonzi, C. Ghelardini, A. Reports, vol. 63, no. 6, pp. 1526–1532, 2011.
R. Bilia, and F. F. Vincieri, “Pharmacological in vivo test to [28] A. Dhir and S. K. Kulkarni, “Involvement of l-arginine–
evaluate the bioavailability of some St John’s wort innovative nitric oxide–cyclic guanosine monophosphate pathway in the
oral preparations,” Phytotherapy Research, vol. 23, no. 2, pp. 197– antidepressant-like effect of venlafaxine in mice,” Progress in
205, 2009. Neuro-Psychopharmacology and Biological Psychiatry, vol. 31,
[14] Ǎ. L. Piato, L. P. Rizon, B. S. Martins, D. S. Nunes, and E. no. 4, pp. 921–925, 2007.
Elisabetsky, “Antidepressant profile of Ptychopetalum olacoides [29] M. Ghasemi, H. Sadeghipour, G. Poorheidari, and A. R.
Bentham (Marapuama) inmice,” Phytotherapy Research, vol. 23, Dehpour, “A role for nitrergic system in the antidepressant-
no. 4, pp. 519–524, 2009. like effects of chronic lithium treatment in the mouse forced
[15] H. M. Burkill, The Useful Plants of West Tropical Africa, Royal swimming test,” Behavioural Brain Research, vol. 200, no. 1, pp.
Botanic Gardens, 1985. 76–82, 2009.
[16] R. D. Porsolt, A. Bertin, and M. Jalfre, “Behavioral despair in [30] M. Bourin, A. J. Fiocco, and F. Clenet, “How valuable are
mice: a primary screening test for antidepressants,” Archives animal models in defining antidepressant activity?” Human
Internationales de Pharmacodynamie et deTherapie, vol. 229, no. Psychopharmacology, vol. 16, no. 1, pp. 9–21, 2001.
2, pp. 327–336, 1977. [31] A. D. E. Zomkowski, A. R. S. Santos, and A. L. S. Rodrigues,
[17] M. J. Detke, M. Rickels, and I. Lucki, “Active behaviors in the rat “Putrescine produces antidepressant-like effects in the forced
forced swimming test differentially produced by serotonergic swimming test and in the tail suspension test in mice,” Progress
and noradrenergic antidepressants,” Psychopharmacology, vol. in Neuro-Psychopharmacology and Biological Psychiatry, vol. 30,
121, no. 1, pp. 66–72, 1995. no. 8, pp. 1419–1425, 2006.
[18] L. Steru, R. Chermat, B. Thierry, and P. Simon, “The tail [32] C. P. L. Teixeira, C. T. V. de Melo, F. L. O. de Araújo et
suspension test: a new method for screening antidepressants in al., “Antidepressant-like effect of riparin II from Aniba riparia
mice,” Psychopharmacology, vol. 85, no. 3, pp. 367–370, 1985. in mice: evidence for the involvement of the monoaminergic
[19] E. Berrocoso, J. Gibert-Rahola, M. De Benito, and J. Micó, system,” Fundamental & Clinical Pharmacology, vol. 27, no. 2,
“P.2.d.022 The modified Tail Suspension Test (mTST): a new pp. 129–137, 2013.
paradigm to categorize antidepressants. Effects of classical and [33] C. T. V.Melo, A.M. R. deCarvalho, B. A.Moura et al., “Evidence
atypical opiates,” European Neuropsychopharmacology, vol. 16, for the involvement of the serotonergic, noradrenergic, and
pp. S344–S345, 2006. dopaminergic systems in the antidepressant-like action of
[20] E. Berrocoso, K. Ikeda, I. Sora, G. R. Uhl, P. Sánchez-Blázquez, riparin III obtained fromAniba riparia (Nees)Mez (Lauraceae)
and J. A. Mico, “Active behaviours produced by antidepressants in mice,” Fundamental & Clinical Pharmacology, vol. 27, no. 1,
and opioids in the mouse tail suspension test,” International pp. 104–112, 2013.
Journal of Neuropsychopharmacology, vol. 16, no. 1, pp. 151–162, [34] J. F. Cryan, R. J. Valentino, and I. Lucki, “Assessing substrates
2013. underlying the behavioral effects of antidepressants using the
[21] N. Ripoll, D. J. P. David, E. Dailly, M. Hascoët, and M. Bourin, modified rat forced swimming test,”Neuroscience andBiobehav-
“Antidepressant-like effects in various mice strains in the tail ioral Reviews, vol. 29, no. 4-5, pp. 547–569, 2005.
suspension test,” Behavioural Brain Research, vol. 143, no. 2, pp. [35] M. E. Page, M. J. Detke, A. Dalvi, L. G. Kirby, and I. Lucki,
193–200, 2003. “Serotonergic mediation of the effects of fluoxetine, but not
[22] J. F. Cryan, C.Mombereau, andA. Vassout, “The tail suspension desipramine, in the rat forced swimming test,” Psychopharma-
test as a model for assessing antidepressant activity: review of cology, vol. 147, no. 2, pp. 162–167, 1999.
pharmacological and genetic studies in mice,”Neuroscience and [36] J.-P. Rénéric and I. Lucki, “Antidepressant behavioral effects
Biobehavioral Reviews, vol. 29, no. 4-5, pp. 571–625, 2005. by dual inhibition of monoamine reuptake in the rat forced
[23] O. F. O’Leary, A. J. Bechtholt, J. J. Crowley, T. E. Hill, M. E. swimming test,” Psychopharmacology, vol. 136, no. 2, pp. 190–
Page, and I. Lucki, “Depletion of serotonin and catecholamines 197, 1998.
block the acute behavioral response to different classes of [37] G. V. Carr and I. Lucki, “The role of serotonin receptor
antidepressant drugs in the mouse tail suspension test,” Psy- subtypes in treating depression: a review of animal studies,”
chopharmacology, vol. 192, no. 3, pp. 357–371, 2007. Psychopharmacology, vol. 213, no. 2-3, pp. 265–287, 2011.
[24] E. L. Shelkunov, “Effect of imipramine-like antidepressants [38] P. L. Delgado, “Depression: the case for a monoamine defi-
on head twitching in mice induced by 5-hydroxytryptophan,” ciency,” Journal of Clinical Psychiatry, vol. 61, supplement 6, pp.
Bulletin of Experimental Biology andMedicine, vol. 86, no. 3, pp. 7–11, 2000.
1171–1173, 1978. [39] L.-T. Yi, C.-F. Li, X. Zhan et al., “Involvement of monoamin-
[25] R. Mahesh, A. Jindal, B. Gautam, S. Bhatt, and D. Pandey, ergic system in the antidepressant-like effect of the flavonoid
“Evaluation of anti-depressant-like activity of linezolid, an naringenin inmice,”Progress inNeuro-Psychopharmacology and
oxazolidinone class derivative—an investigation using behav- Biological Psychiatry, vol. 34, no. 7, pp. 1223–1228, 2010.
ioral tests battery of depression,” Biochemical and Biophysical [40] P. Delgado and F. Moreno, “Antidepressants and the brain,”
Research Communications, vol. 409, no. 4, pp. 723–726, 2011. International Clinical Psychopharmacology, vol. 14, supplement
[26] G. P. Luscombe, K. F. Martin, L. J. Hutchins, J. Gosden, and D. 1, pp. S9–S16, 1999.
J. Heal, “Mediation of the antidepressant-like effect of 8-OH- [41] B. E. Leonard, “Stress, norepinephrine and depression,” Journal
DPAT inmice by postsynaptic 5-HT1A receptors,”British Journal of Psychiatry and Neuroscience, vol. 26, supplement, pp. S11–S16,
of Pharmacology, vol. 108, no. 3, pp. 669–677, 1993. 2001.
BioMed Research International 15
[42] C. C. Cardoso, K. R. Lobato, R. W. Binfare et al., “Evidence cyclase pathway in its antidepressant-like action,”Pharmacology
for the involvement of the monoaminergic system in the Biochemistry and Behavior, vol. 88, no. 4, pp. 418–426, 2008.
antidepressant-like effect of magnesium,” Progress in Neuro- [57] S. P. Sah, C. S. Mathela, and K. Chopra, “Involvement of
Psychopharmacology and Biological Psychiatry, vol. 33, no. 2, pp. nitric oxide (NO) signalling pathway in the antidepressant
235–242, 2009. activity of essential oil of Valeriana wallichii Patchouli alcohol
[43] K. Nishizawa, K. Torii, A. Kawasaki et al., “Antidepressant-like chemotype,” Phytomedicine, vol. 18, no. 14, pp. 1269–1275, 2011.
effect of Cordyceps sinensis in the mouse tail suspension test,” [58] B.-H. Lee, S.-W. Lee, D. Yoon et al., “Increased plasma nitric
Biological and Pharmaceutical Bulletin, vol. 30, no. 9, pp. 1758– oxide metabolites in suicide attempters,” Neuropsychobiology,
1762, 2007. vol. 53, no. 3, pp. 127–132, 2006.
[44] J. F. Cryan and I. Lucki, “Antidepressant-like behavioral effects [59] A. Dhir and S. K. Kulkarni, “Nitric oxide andmajor depression,”
mediated by 5-hydroxytryptamine(2C) receptors,” Journal of Nitric Oxide, vol. 24, no. 3, pp. 125–131, 2011.
Pharmacology andExperimentalTherapeutics, vol. 295, no. 3, pp. [60] E. Suzuki, G. Yagi, T. Nakaki, S. Kanba, and M. Asai, “Elevated
1120–1126, 2000. plasma nitrate levels in depressive states,” Journal of Affective
[45] J. Maj, V. Klimek, and G. Nowak, “Antidepressant drugs given Disorders, vol. 63, no. 1–3, pp. 221–224, 2001.
repeatedly increase binding to 𝛼1-adrenoceptors in the rat [61] I. L. Heiberg, G. Wegener, and R. Rosenberg, “Reduction of
cortex,” European Journal of Pharmacology, vol. 119, no. 1-2, pp. cGMP and nitric oxide has antidepressant-like effects in the
113–116, 1985. forced swimming test in rats,” Behavioural Brain Research, vol.
[46] K. Hashimoto, “The role of glutamate on the action of antide- 134, no. 1-2, pp. 479–484, 2002.
pressants,” Progress in Neuro-Psychopharmacology and Biologi- [62] O. Mutlu, G. Ulak, A. Laugeray, and C. Belzung, “Effects of
cal Psychiatry, vol. 35, no. 7, pp. 1558–1568, 2011. neuronal and inducible NOS inhibitor 1-[2-(trifluoromethyl)
[47] M. Ghasemi, M. Raza, and A. R. Dehpour, “NMDA receptor phenyl] imidazole (TRIM) in unpredictable chronic mild stress
antagonists augment antidepressant-like effects of lithium in the procedure in mice,” Pharmacology Biochemistry and Behavior,
mouse forced swimming test,” Journal of Psychopharmacology, vol. 92, no. 1, pp. 82–87, 2009.
vol. 24, no. 4, pp. 585–594, 2010. [63] A. Harkin, T. J. Connor, M. P. Burns, and J. P. Kelly, “Nitric
[48] E. Poleszak, P. Wlaź, E. Kedzierska et al., “NMDA/glutamate oxide synthase inhibitors augment the effects of serotonin
mechanism of antidepressant-like action of magnesium in re-uptake inhibitors in the forced swimming test,” European
forced swim test in mice,” Pharmacology Biochemistry and Neuropsychopharmacology, vol. 14, no. 4, pp. 274–281, 2004.
Behavior, vol. 88, no. 2, pp. 158–164, 2007. [64] G. Ulak, O. Mutlu, F. Y. Akar, F. I. Komsuoğlu, P. Tanyeri,
[49] T. Kos and P. Popik, “A comparison of the predictive therapeutic and B. F. Erden, “Neuronal NOS inhibitor 1-(2-trifluoromethyl-
and undesired side-effects of the NMDA receptor antagonist, phenyl)-imidazole augment the effects of antidepressants acting
memantine, in mice,” Behavioural Pharmacology, vol. 16, no. 3, via serotonergic system in the forced swimming test in rats,”
pp. 155–161, 2005. Pharmacology Biochemistry and Behavior, vol. 90, no. 4, pp.
[50] W. F. Hood, R. P. Compton, and J. B. Monahan, “D-cycloserine: 563–568, 2008.
a ligand for the N-methyl-d-aspartate coupled glycine receptor [65] J. A. Beavo, “Cyclic nucleotide phosphodiesterases: functional
has partial agonist characteristics,”Neuroscience Letters, vol. 98, implications of multiple isoforms,” Physiological Reviews, vol.
no. 1, pp. 91–95, 1989. 75, no. 4, pp. 725–748, 1995.
[51] A. D. E. Zomkowski, D. Engel, N. H. Gabilan, and A. L. S. [66] R. C. Almeida, C. S. Felisbino, M. G. López, A. L. S. Rodrigues,
Rodrigues, “Involvement of NMDA receptors and l-arginine- andN.H.Gabilan, “Evidence for the involvement of L-arginine-
nitric oxide-cyclic guanosine monophosphate pathway in the nitric oxide-cyclic guanosine monophosphate pathway in the
antidepressant-like effects of escitalopram in the forced swim- antidepressant-like effect of memantine in mice,” Behavioural
ming test,” European Neuropsychopharmacology, vol. 20, no. 11, Brain Research, vol. 168, no. 2, pp. 318–322, 2006.
pp. 793–801, 2010. [67] M. Moretti, A. E. D. Freitas, J. Budni, S. C. P. Fernandes, G. D.
[52] E. Poleszak, B. Szewczyk, A. Wlaź et al., “D-serine, a selective O. Balen, and A. L. S. Rodrigues, “Involvement of nitric oxide-
glycine/N-methyl-D-aspartate receptor agonist, antagonizes cGMP pathway in the antidepressant-like effect of ascorbic acid
the antidepressant-like effects of magnesium and zinc in mice,” in the tail suspension test,” Behavioural Brain Research, vol. 225,
Pharmacological Reports, vol. 60, no. 6, pp. 996–1000, 2008. no. 1, pp. 328–333, 2011.
[53] Q.-S. Yan, M. E. A. Reith, P. C. Jobe, and J. W. Dailey, [68] L. E. B. Bettio, M. P. Cunha, J. Budni et al., “Guanosine
“Dizocilpine (MK-801) increases not only dopamine but also produces an antidepressant-like effect through the modulation
serotonin and norepinephrine transmissions in the nucleus of NMDA receptors, nitric oxide-cGMP and PI3K/mTOR
accumbens as measured bymicrodialysis in freely moving rats,” pathways,” Behavioural Brain Research, vol. 234, no. 2, pp. 137–
Brain Research, vol. 765, no. 1, pp. 149–158, 1997. 148, 2012.
[54] B. Szewczyk, E. Poleszak, P. Wlaź et al., “The involvement of
serotonergic system in the antidepressant effect of zinc in the
forced swim test,” Progress in Neuro-Psychopharmacology and
Biological Psychiatry, vol. 33, no. 2, pp. 323–329, 2009.
[55] J. V. Esplugues, “NO as a signalling molecule in the nervous
system,” British Journal of Pharmacology, vol. 135, no. 5, pp.
1079–1095, 2002.
[56] L. Savegnago, C. R. Jesse, L. G. Pinto et al., “Diphenyl dise-
lenide exerts antidepressant-like and anxiolytic-like effects in
mice: involvement of l-arginine-nitric oxide-soluble guanylate
Journal of The Scientific  Autoimmune International Journal of
Tropical Medicine Scientifica World Journal Diseases Antibiotics
Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation
http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014
Journal of
Toxins  Anesthesiology 
Research and Practice
Hindawi Publishing Corporation Volume 2014 Hindawi Publishing Corporation
http://www.hindawi.com http://www.hindawi.com Volume 2014
Submit your manuscripts at
http://www.hindawi.com
Advances in 
Pharmacological Journal of
Sciences Toxicology
Hindawi Publishing Corporation Hindawi Publishing Corporation
http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014
MEDIATORS
of
INFLAMMATION
Emergency Medicine Pain Journal of Stroke
International Research and Treatment Addiction Research and Treatment
Hindawi Publishing Corporation
Hindawi Publishing Corporation Hindawi Publishing Corporation http://www.hindawi.com Volume 2014 Hindawi Publishing Corporation Hindawi Publishing Corporation
http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014
Journal of
Vaccines
BioMed Journal of International Journal of Journal of
Research International Pharmaceutics Medicinal Chemistry Drug Delivery
Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation Hindawi Publishing Corporation
http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014 http://www.hindawi.com Volume 2014