Abstract

The effects of the aqueous extract of Khaya senegalenis (Desr) A. Juss. (Meliaceae) (EAKS) were evaluated on the contractile activity of the guinea-pig Taenia coli. EAKS in a range of concentrations from 10-8mg/ml to 10-2mg/ml induced an increase of the spontaneous rhythmic contractions and of basal muscular tone, in a concentration-dependent manner (EC50: 6.10-4 mg/ml). With 10- 2mg/ml of the extract, maximal stimulation was obtained. The effects of EAKS were comparable to those induced by acetylcholine (ACh). Moreover, the cholinoceptor antagonist, atropine, applied at a concentration of 10-6 mg/ml inhibited the stimulating effects of ACh. However, atropine did not inhibit the myostimulant action induced by EAKS. In calcium-free solution containing EDTA, a bivalent chelator, at a concentration of 10-3 mM, EAKS had no effect on the guinea-pig isolated Taenia coli. In the same conditions, ACh induced an increase of basal muscular tone. In conclusion, EAKS exerted a stimulating effect in the intestinal smooth muscle. Cholinergic mechanisms may not be involved. The myostimulating action of EAKS could be due to a mobilization of bivalent, mainly calcium flux.

Keywords: Acetylcholine, Contractions, Khaya senegalensis, Smooth muscle, Taenia caeci