Investigating the Site of Action of an Aqueous Extract of Heliotropium indicum Linn (Boraginaceae) on Smooth Muscles

Heliotropium indicum has various traditional medicinal uses such as treating abdominal pains, dysmenorrhoea, hypertension, convulsion, post-partum inflammatory disorders, wounds and infections and skin rashes. The aim of this study therefore is to find receptors that possibly mediate the activity of H. indicum as a means of finding explanation to some of its reported traditional uses. The effect of various concentrations of agonist drugs and an aqueous extract from the plant as well as the effects of these agonist drugs and the extract in the presence of specific reference antagonist drugs were established on isolated guinea-pig ileum, rabbit jejunum, rat uterus and rat anococcygeus preparations. Data obtained was analyzed using GraphPad Prism Version 5.0 for Windows. The extract caused dose-dependent contractions similar to the acetylcholine, methylcholine, carbamylcholine, nicotine, histamine and oxytocin used on the smooth muscle preparations studied. The contractions were significantly inhibited by atropine and hexamethonium, suggesting muscarinic and nicotinic activity, adrenaline and salbutamol, suggesting adrenoceptor activity and diclofenac sodium, suggesting the inhibition of synthesis and/or effect of products of COX such as prostaglandin. The extract was significantly stable to plasma cholinesterase. The receptor activity of H. indicum explains some of its traditional medicinal uses such as relieving abdominal pain, hypertension and impotence and sexual weakness.