Halothane inhibition of acetylcholine-induced relaxation in rat mesenteric artery and aorta.
OBJECTIVE
The effect of halothane was compared on acetylcholine (ACh)-induced relaxation of the mesenteric artery and the aorta in rats.


METHODS
The responses of isolated rat aortic and mesenteric arterial ring segments precontracted with phenylephrine to ACh (10(-8)-10(-5) M), in the presence of halothane 0-3%, were compared using isometric force tension recordings. Effects of NG-nitro-l-arginine (L-NOARG, 3 x 10(-5), methylene blue (MB, 5 x 10(-6) M), oxyhaemoglobin in (OxyHB, 10(-7) M), and various potassium channel inhibitors; tetraethylammonium (TEA, 10(-5) M, 10(-3) M), apamin (AP, 10(-7) M), charybdotoxin (ChTx, 10(-7) M) and glibenclamide (GC, 10(-5) M) on ACh-induced relaxation in mesenteric artery were tested. Using radioimmunoassay, ACh (10(-6) M)-induced guanosine 3':5'-cyclic monophosphate (cGMP) accumulation of mesenteric arterial rings pretreated with L-NAORG were also measured.


RESULTS
L-NOARG partially inhibited ACh-induced relaxation in mesenteric arterial rings (P < 0.05, maximum relaxation reduced by approximately 50%), whereas it abolished them in aortic rings. The remaining relaxation resistant to L-NOARG in mesenteric arterial rings was insensitive to additional MB or OxyHB, and was not accompanied by increases in cGMP contents of rings. Halothane inhibited endothelium-dependent relaxation in aorta and mesenteric arterial rings. This inhibitory effect was larger in aorta. Halothane also inhibited NO independent EDHF-dependent relaxation in the mesenteric arterial rings,


CONCLUSIONS
Despite a similar inhibitory effect on the EDHF relaxing pathway, halothane has a larger effect on endothelium-dependent relaxation in the aorta (NO dependent mainly) than in the mesenteric rings (NO and EDHF dependent).
Iranami
H
H
Department of Anesthesia, Wakayama Medical College, Japan.
Hatano
Y
Y
Tsukiyama
Y
Y
Yamamoto
M
M
Maeda
H
H
Mizumoto
K
K
D000109:Acetylcholine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects*; D004730:Endothelium, Vascular / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006221:Halothane / Q000494:pharmacology*; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D018685:Anesthetics, Inhalation; D004791:Enzyme Inhibitors; D019335:Nitroarginine; D019001:Nitric Oxide Synthase; D000109:Acetylcholine; D006221:Halothane