Abstract
Effects of pituitary adenylate cyclase activating peptide (PACAP-(1-27)) and vasoactive intestinal polypeptide (VIP) on the guinea-pig taenia caeci were studied in the presence of guanethidine and scopolamine. Both peptides (1 nmol/1-1 mumol/l) concentration-dependently relaxed the smooth muscle of the taenia. PACAP-(1-27) and VIP were nearly equipotent. Apamin (30 nmol/l), a selective blocker of calcium-activated potassium channels, abolished the relaxation induced by PACAP-(1-27) whereas the effect of VIP remained unaffected. PACAP-(1-27) may be a candidate for the noncholinergic, non-adrenergic inhibitory neurotransmitter which induces apamin-sensitive relaxation in the intestinal tract.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Apamin / pharmacology*
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Cecum / drug effects
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Guanethidine / pharmacology
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Guinea Pigs
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Hexamethonium Compounds / pharmacology
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In Vitro Techniques
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Male
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Muscle Relaxation / drug effects
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Muscle, Smooth / drug effects*
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Neuropeptides / pharmacology*
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Pituitary Adenylate Cyclase-Activating Polypeptide
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Potassium Channels / drug effects*
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Scopolamine / pharmacology
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Tetrodotoxin / pharmacology
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Vasoactive Intestinal Peptide / pharmacology
Substances
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Hexamethonium Compounds
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Neuropeptides
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Pituitary Adenylate Cyclase-Activating Polypeptide
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Potassium Channels
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Apamin
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Vasoactive Intestinal Peptide
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Tetrodotoxin
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Scopolamine
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Guanethidine