Abstract
The pineal hormone melatonin was found to produce two distinct contractile responses in vascular smooth muscle. In isolated rat caudal artery segments, denuded of endothelium, melatonin (10(-10)-10(-7) M) potentiated phenylephrine-induced contractions in a concentration-dependent manner. At higher melatonin concentrations (10(-7)-10(-5) M), however, the potentiating effect was attenuated. In the presence of the melatonin MT2 receptor antagonist, 4-phenyl-2-acetamidotetraline (4P-ADOT), the attenuated constrictor responses were selectively enhanced. These results are consistent with the hypothesis that melatonin activates two receptor subtypes in vascular smooth muscle; MT2 receptors may induce relaxation, while a second receptor subtype mediates vasoconstriction.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adrenergic alpha-Agonists / pharmacology
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Animals
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Drug Synergism
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In Vitro Techniques
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Male
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Melatonin / pharmacology*
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Muscle Contraction / drug effects
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Muscle Relaxation / drug effects
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Muscle, Smooth, Vascular / drug effects*
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Phenylephrine / pharmacology
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Rats
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Rats, Inbred F344
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Receptors, Cell Surface / antagonists & inhibitors
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Receptors, Cell Surface / metabolism
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Receptors, Cytoplasmic and Nuclear / antagonists & inhibitors
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Receptors, Cytoplasmic and Nuclear / metabolism
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Receptors, Melatonin
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Tetrahydronaphthalenes / pharmacology
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Vasoconstriction / drug effects
Substances
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4-phenyl-2-acetamidotetralin
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Adrenergic alpha-Agonists
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Receptors, Cell Surface
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Receptors, Cytoplasmic and Nuclear
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Receptors, Melatonin
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Tetrahydronaphthalenes
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Phenylephrine
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Melatonin