Inhibition of drug-induced contractions of guinea-pig ileum by Annona crassiflora seed extract.

A hydro-alcoholic extract of dried Annona crassiflora seeds (AR.1) showed a non-specific inhibitory effect on drug-induced contractions of guinea-pig ileum. Maximum responses to histamine, acetylcholine and bradykinin were reduced increasingly with increasing doses of AR.1. Affinities of the gut to the above agonists, expressed as respective pD2 values were not changed by AR.1. Dose-response curves of calcium-induced contractions in depolarized preparations were shifted to the right but maximum responses were not changed by AR.1. It is suggested that the inhibitory effect of AR.1 is due to a decrease in membrane permeability to calcium. This inhibitory effect may be responsible for the effect of Annona crassiflora as a remedy against snake venom.