Nitric oxide pathway in cat esophagus: localization of nitric oxide synthase and functional effects.
In the cat lower esophageal sphincter (LES) and esophageal body, nitric oxide synthase (NOS) immunoreactive nerves were abundant in the circular smooth muscle layer, especially in the LES region. NADPH diaphorase staining showed an identical pattern. The ability to form L-citrulline from L-arginine corresponded roughly to the distribution of NOS. Confocal microscopic analysis indicated colocalization within neurons of vasoactive intestinal peptide (VIP) in 65% of NOS-positive nerves. In LES circular smooth muscle preparations, electrically induced relaxations (single train stimuli) were generally abolished by NG-nitro-L-arginine (L-NNA). Continuous electrical stimulation for 2 min evoked a relaxation in the presence of L-NNA. This relaxation was inhibited by VIP antiserum and followed by a decrease in guanosine 3',5'-cyclic monophosphate, but not by any consistent change in adenosine 3',5'-cyclic monophosphate levels. K+ (124 mM) induced a biphasic relaxation, with L-NNA inhibiting the first phase but not the second. We conclude that nitric oxide (NO) has a major role as the mediator responsible for relaxation in the cat esophagus. NO seems also to initiate the release and enhance the effect of another transmitter.
Ny
L
L
Department of Clinical Pharmacology, Lund University, Sweden.
Alm
P
P
Larsson
B
B
Ekström
P
P
Andersson
K E
KE
D000594:Amino Acid Oxidoreductases / Q000378:metabolism*; D000818:Animals; D002415:Cats; D002956:Citrulline / Q000096:biosynthesis; D004943:Esophagogastric Junction / Q000378:metabolism; D004947:Esophagus / Q000294:innervation / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D018613:Microscopy, Confocal; D009252:NADPH Dehydrogenase / Q000378:metabolism; D009412:Nerve Fibers / Q000648:ultrastructure; D009569:Nitric Oxide / Q000378:metabolism* / Q000502:physiology*; D019001:Nitric Oxide Synthase; D009712:Nucleotides, Cyclic / Q000378:metabolism; D013194:Staining and Labeling; D014018:Tissue Distribution; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
D009712:Nucleotides, Cyclic; D002956:Citrulline; D009569:Nitric Oxide; D014660:Vasoactive Intestinal Peptide; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D009252:NADPH Dehydrogenase