Synthesis of nitric oxide in postganglionic myenteric neurons during endotoxemia: implications for gastric motor function in rats.
We have investigated the mechanisms underlying acute changes in gastric motor function triggered by endotoxemia. In fundal strips from rats pre-treated with endotoxin (40 microg/kg, i.p. 30 min), mechanical activity was analyzed and the source of nitric oxide (NO) was visualized by confocal microscopy of tissue loaded with the fluorescent dye DAF-FM. NOS expression was determined by quantitative RT-PCR and Western blot, and enzyme activity by the citrulline assay. Strips from endotoxin-treated rats were hypo-contractile. This was prevented by pre-incubation with the neurotoxin tetrodotoxin, the gangliar blocker hexamethonium, or non-selective and neuronal-specific NOS inhibitors (L-NOARG and TRIM, respectively). The soluble guanylyl cyclase (sGC) inhibitor ODQ and the inhibitor of small conductance Ca2+-activated K+ channels apamin prevented relaxation induced by endotoxin, nicotine, exogenous NO (DETA-NONOate), and the NO-independent sGC activator BAY 41-2272. NO synthesis was observed in neuronal soma, axons, and nerve endings of the myenteric plexus in the fundus of endotoxin-treated rats and was prevented by L-NAME, tetrodotoxin, and hexamethonium. nNOS and iNOS mRNA and protein contents were unchanged. Our findings demonstrate synthesis of NO in post-ganglionic myenteric neurons during early endotoxemia that mediates gastric hypo-contractility. The effect of NO is mediated via sGC and small conductance Ca2+-activated K+channels.
Quintana
Elsa
E
Departamento de Farmacología, Facultad de Medicina, Universidad de Valencia, Valencia, Spain.
Hernández
Carlos
C
Alvarez-Barrientos
Alberto
A
Esplugues
Juan V
JV
Barrachina
María D
MD
D000818:Animals; D001030:Apamin / Q000494:pharmacology; D001338:Autonomic Fibers, Postganglionic / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D019446:Endotoxemia / Q000378:metabolism* / Q000503:physiopathology; D005748:Gastric Fundus / Q000503:physiopathology; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology*; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors / Q000502:physiology; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009538:Nicotine / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D019335:Nitroarginine / Q000494:pharmacology; D009603:Nitroso Compounds / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000037:antagonists & inhibitors / Q000502:physiology; D011720:Pyrazoles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D013498:Suramin / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
C423582:3-(4-Amino-5-cyclopropylpyrimidine-2-yl)-1-(2-fluorobenzyl)-1H-pyrazolo(3,4-b)pyridine; D009419:Nerve Tissue Proteins; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; D010446:Peptide Fragments; D024681:Potassium Channels, Calcium-Activated; D011720:Pyrazoles; D011725:Pyridines; C094210:2,2'-(hydroxynitrosohydrazono)bis-ethanamine; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D019335:Nitroarginine; D001030:Apamin; D009569:Nitric Oxide; D014660:Vasoactive Intestinal Peptide; D013779:Tetrodotoxin; D011732:Pyridoxal Phosphate; D013498:Suramin; C047945:vasoactive intestinal peptide (10-28); D009538:Nicotine; D003907:Dexamethasone; D002217:Carbachol; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D006162:Guanylate Cyclase