Nonadrenergic, noncholinergic inhibitory innervation in the longitudinal muscle of the rabbit portal vein.
1. We examined whether nitric oxide (NO) and ATP take part in inhibitory nonadrenergic, noncholinergic (NANC) neurotransmission in the portal vein of Japanese White rabbits. Longitudinal strips of the vein were suspended in organ baths containing Krebs bicarbonate solution. Preparations relaxed in response to electrical field stimulation (EFS) (25 V, 0.5 msec in duration, 1-50 Hz) and exogenous ATP (1-300 microM) after contraction was induced with 10 microM ergotamine in the presence of 3 microM guanethidine and 0.1 microM atropine. 2. The relaxation response to EFS was abolished by addition of 100 microM NG-nitro-L-arginine, an NO synthase inhibitor. This abolition was partly reversed by 10 mM L-arginine, a substrate for NO synthase. 3. The relaxation response to exogenous ATP was significantly inhibited by 1 mM suramin, a P2X- and P2Y-purinoceptor antagonist, whereas relaxation response to EFS was not inhibited by 1 mM suramin. 4. From the results of this study, we conclude that the inhibitory NANC neurotransmission is mediated by NO alone and does not involve ATP in the portal vein of Japanese White rabbits under our experimental conditions.
Mutsukado
Y
Y
Second Department of Internal Medicine, Hiroshima University School of Medicine, Japan.
Tsuru
H
H
Sasa
M
M
Kambe
M
M
Yamakido
M
M
D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D004558:Electric Stimulation; D004730:Endothelium, Vascular / Q000187:drug effects / Q000294:innervation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000294:innervation* / Q000502:physiology; D018377:Neurotransmitter Agents / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D011169:Portal Vein / Q000294:innervation* / Q000502:physiology; D058919:Purinergic P2 Receptor Antagonists; D011817:Rabbits; D013498:Suramin / Q000494:pharmacology
D004791:Enzyme Inhibitors; D018377:Neurotransmitter Agents; D058919:Purinergic P2 Receptor Antagonists; D019335:Nitroarginine; D009569:Nitric Oxide; D013498:Suramin; D000255:Adenosine Triphosphate; D019001:Nitric Oxide Synthase