Inhibition of cholinergic contractions of rat ileum by tkopane-type alkaloids present in Schizanthus hookeri.
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 x 10(-4), 1 x 10(-3), and 1 x 10(-2) mg/mL of the purified mixture of alkaloids on the contractile response of the ileum induced with increasing doses of carbachol (5 x 10(-8) - 10(-4) M) was determined. The results were compared with those obtained in the presence of 3.46 x 10(-7), 3.46 x 10(-6), and 3.46 x 10(-5) mg/mL atropine as an agonist. Tropane alkaloids extracted from Schizanthus hookeri competitively antagonized acetylcholine muscarinic receptors.
Universidad de Chile, Programa de Farmacología, ICBM, Facultad de Medicina, Casilla 70000, Santiago, Chile.
Miguel A
MA
Morales
Frederick
F
Ahumada
Erick
E
Castillo
Rafael
R
Burgos
Philippe
P
Christen
Viviana
V
Bustos
Orlando
O
Muñoz
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008401:Gas Chromatography-Mass Spectrometry; D007082:Ileum / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley
D002217:Carbachol