Effect of methanol extract of Anacardium occidentale stem bark on agonist-induced contraction in rat uterine muscle

Anacardium occidentale (Ao) is widely used in ethnomedicine and the effect on contractility of the gut and heart muscles of laboratory rodents have been established however, its effect on the contractility of uterine muscle has been rarely researched. The present study investigated the effect of stem bark methanolic extract of Anacardium occidentale (AoME) on Isolated Rat Uterus Strips (IRUS). The Anacardium occidentale methanol extract (AoME) was obtained by solvent extraction. The IRUS were suspended in a bath containing 15 ml of De Jalon's solution through a silk connected to a force transducer. A tension of 1.0 g was applied. The strips were allowed to equilibrate for a period of 60–90 min before the commencement of the experiment. The extract (0.025- 0.3mg/ml) added cumulatively did not modify the normal tonus in most of the IRUS used except in one where it feebly contracted it. However, the contractile responses induced by acetylcholine (10-9 -10-5 M) and oxytocin (10-9 -10-5 M) on the IRUS were almost completely blocked by pre-incubated AoME at a concentration of 0.2 mg/ml. Stem bark methanol extract of Anacardium occidentale shifted the log concentration curve of both agonists to the right. The present results report the antagonistic effects of stem bark methanol extract of Anacardium occidentale on oxytocin and acetylcholine-induced contraction in rat uterus strips. Keywords: Anacardium occidentale, Oxytocin, Acetylcholine, Uterus, Smooth muscle