title: Mechanism of action of nicotine in isolated iris sphincter preparations of rabbit.
abstract: 1. Nicotine produced a transient contraction of rabbit isolated iris sphincter muscle, a parasympathetic ganglion-free tissue. The response to nicotine was antagonized by hexamethonium, but was insensitive to tetrodotoxin (TTX). While single treatments with atropine, capsaicin or [D-Arg1, D-Pro2, D-Trp7,9, Leu11]-substance P (rpwwL-SP) partially blocked the response, combined treatment abolished it. 2. Chronic treatment of animals with nicotine added to the drinking water (about 12 mg kg-1 per day) had no effect on the responsiveness to nicotine or the pharmacological properties of nicotine-induced contraction. 3. These results suggest that acetylcholine and tachykinin(s) released via sodium channel-independent mechanisms from nerve terminals of parasympathetic and primary sensory nerves, respectively, are involved in the nicotine-induced contractile response.
authors.affiliation: Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Hisayama
authors.forename: M
authors.initials: M
authors.lastname: Shinkai
authors.forename: I
authors.initials: I
authors.lastname: Takayanagi
authors.forename: S
authors.initials: S
authors.lastname: Morimoto
authors.forename: K
authors.initials: K
authors.lastname: Ishida
mesh_terms: D000818:Animals; D004347:Drug Interactions; D066298:In Vitro Techniques; D007498:Iris / Q000187:drug effects*; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects; D009538:Nicotine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011817:Rabbits
chemical_list: D009538:Nicotine