Abstract:
This study presents the effect of an ethanolic extract of the whole plant of Synedrella nodiflora, a plant used in Ghana for the treatment of epilepsy and pain, in formalin-induced pain and acetic acid-induced writhing assay and the possible mode(s) of action of its analgesic action. For comparison, morphine and diclofenac were used as standard opioid and NSAID respectively. The ethanolic extract (100-1000 mg kg-1; p.o.) and morphine (1-10 mg kg-1; i.p.) dose-dependently decreased both phases of the formalin-induced nociceptive behavior. The antinociceptive effect of S. nodiflora (300 mg kg-1 p.o.) on the first and second phases of formalin induced pain was significantly blocked by caffeine but not by naloxone. In the acetic acid- induced writhing test, diclofenac and S. nodiflora significantly reduced the number of writhes dose dependently. Also, the effect of S. nodiflora (300 mg kg-1 p.o.) was blocked by caffeine (3 mg kg-1 i.p.) but the analgesic effect of diclofenac was enhanced significantly. The observed effects of caffeine on the central and peripheral analgesic effects of S. nodiflora in the formalin and acetic acid induced writhing suggest the possible involvement of adenosinergic mechanism(s).