Nitric oxide mediating NANC inhibition in opossum lower esophageal sphincter.
Strips from opossum lower esophageal sphincter were prepared and mounted in organ baths for recording of isometric tension. Nonadrenergic, non-cholinergic (NANC) inhibitory responses were evoked by transmural field stimulation. The relaxant responses to field stimulation were inhibited in a concentration-dependent manner by N omega-nitro-L-arginine (L-NNA), a substance known to inhibit the formation of nitric oxide (NO). At a concentration at 10(-4) M of L-NNA, most preparations contracted during field stimulation, and this response was abolished by atropine (10(-6) M). L-Arginine (10(-5) M) shifted the concentration-response curve for L-NNA to the right. Relaxant responses to VIP (10(-9) to 10(-6)M) and sodium nitroprusside (10(-9) to 10(-5) M) were unaffected by preincubation with L-NNA (10(-5) to 10(-4) M) or L-arginine (10(-5) M). The inhibition of NANC-relaxation was apparently not due to an influence on release of a NANC transmitter different from NO, since L-NNA had no preserving effects on responses to field stimulation in preparations treated with scorpion venom. We conclude that involvement of a NO-generating process from L-arginine seems mandatory for NANC responses in the isolated lower esophageal sphincter.
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Department of Surgical Gastroenterology L, Aarhus Kommunehospital, Denmark.
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Forman
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D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D004558:Electric Stimulation; D004947:Esophagus / Q000187:drug effects / Q000502:physiology*; D005260:Female; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism*; D019335:Nitroarginine; D009599:Nitroprusside / Q000494:pharmacology; D009893:Opossums; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D009599:Nitroprusside; D019335:Nitroarginine; D009569:Nitric Oxide; D014660:Vasoactive Intestinal Peptide; D002217:Carbachol; D001120:Arginine