Abstract
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.
MeSH terms
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Animals
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Apamin / pharmacology
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Autonomic Fibers, Postganglionic / metabolism*
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Carbachol / pharmacology
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Dexamethasone / pharmacology
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Endotoxemia / metabolism*
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Endotoxemia / physiopathology
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Gastric Fundus / physiopathology
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Gastrointestinal Motility / drug effects
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Gastrointestinal Motility / physiology*
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Guanylate Cyclase / antagonists & inhibitors
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Guanylate Cyclase / physiology
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Microscopy, Confocal
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Nerve Tissue Proteins / metabolism
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Nicotine / pharmacology
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Nitric Oxide / biosynthesis*
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Nitric Oxide Donors / pharmacology
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Nitric Oxide Synthase / metabolism
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Nitric Oxide Synthase Type II
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Nitroarginine / pharmacology
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Nitroso Compounds / pharmacology
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Peptide Fragments / pharmacology
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Potassium Channels, Calcium-Activated / antagonists & inhibitors
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Potassium Channels, Calcium-Activated / physiology
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Pyrazoles / pharmacology
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Pyridines / pharmacology
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Pyridoxal Phosphate / analogs & derivatives*
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Pyridoxal Phosphate / pharmacology
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Rats
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Suramin / pharmacology
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Tetrodotoxin / pharmacology
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Vasoactive Intestinal Peptide / pharmacology
Substances
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3-(4-Amino-5-cyclopropylpyrimidine-2-yl)-1-(2-fluorobenzyl)-1H-pyrazolo(3,4-b)pyridine
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Nerve Tissue Proteins
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Nitric Oxide Donors
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Nitroso Compounds
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Peptide Fragments
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Potassium Channels, Calcium-Activated
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Pyrazoles
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Pyridines
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2,2'-(hydroxynitrosohydrazono)bis-ethanamine
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pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid
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Nitroarginine
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Apamin
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Nitric Oxide
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Vasoactive Intestinal Peptide
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Tetrodotoxin
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Pyridoxal Phosphate
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Suramin
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vasoactive intestinal peptide (10-28)
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Nicotine
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Dexamethasone
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Carbachol
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Nitric Oxide Synthase
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Nitric Oxide Synthase Type II
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Nos2 protein, rat
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Guanylate Cyclase