Inhibition of Cholinergic Contractions of Rat Ileum by Tropane-Type Alkaloids Present in Schizanthus hookeri

The relative lack of specifi city 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 purifi ed 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 purifi ed 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.

Kimelfe