Melatonin mediates two distinct responses in vascular smooth muscle.
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.
Doolen
S
S
Department of Pharmacology, College of Medicine, University of California, Irvine 92697-4625, USA.
Krause
D N
DN
Dubocovich
M L
ML
Duckles
S P
SP
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D004357:Drug Synergism; D066298:In Vitro Techniques; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors / Q000378:metabolism; D044094:Receptors, Melatonin; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects
C112803:4-phenyl-2-acetamidotetralin; D000316:Adrenergic alpha-Agonists; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D044094:Receptors, Melatonin; D013764:Tetrahydronaphthalenes; D010656:Phenylephrine; D008550:Melatonin