Mechanism of action of nicotine in isolated iris sphincter preparations of rabbit.
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.
Hisayama
T
T
Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan.
Shinkai
M
M
Takayanagi
I
I
Morimoto
S
S
Ishida
K
K
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
D009538:Nicotine