Inhibition of cholinergic contractions of rat ileum by tropane-type alkaloids present in Schizanthus hookeri

Abstract

The relative lack of specificity of atropine as a competitive antagonist of muscarinic receptors is a frequent cause of undesirable parasympathetic side effects. Consequently, new tropane alkaloids with potentially greater selectivity are usually seen with real interest. The cholinergic antagonistic effects of a purified mixture of tropane alkaloids extracted from Schizanthus hookeri were evaluated in rat ileum. For this purpose, ileal segments were obtained from randomly selected male Sprague-Dawley rats, and the effect of 1 · 10-4, 1 · 10-3, and 1 · 10-2 mg/mL of the purified mixture of alkaloids on the contractile response of the ileum induced with increasing doses of carbachol (5 · 10-8 - 8 · 10-4 M) was determined. The results were compared with those obtained in the presence of 3.46 · 10-7, 3.46 · 10-6, and 3.46 · 10-5 mg/mL atropine as an agonist. Tropane alkaloids extracted from Schizanthus hookeri competitively antagonized acetylcholine muscarinic receptors. © 2013 Verlag der Zeitschrift für Naturforschung, Tübingen.