Expression of melatonin receptors in arteries involved in thermoregulation

Journal Article · Wed Aug 01 00:00:00 EDT 1990 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.87.16.6200· OSTI ID:6445729

Viswanathan, M; Laitinen, J T; Saavedra, J M ^[1]

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1. National Institute of Mental Health, Bethesda, MD (USA)

Melatonin binding sites were localized and characterized in the vasculature of the rat by using the melatonin analogue 2-(125I)iodomelatonin (125I-melatonin) and quantitative in vitro autoradiography. The expression of these sites was restricted to the caudal artery and to the arteries that form the circle of Willis at the base of the brain. The arterial 125I-melatonin binding was stable, saturable, and reversible. Saturation studies revealed that the binding represented a single class of high-affinity binding sites with a dissociation constant (Kd) of 3.4 x 10(-11) M in the anterior cerebral artery and 1.05 x 10(-10) M in the caudal artery. The binding capacities (Bmax) in these arteries were 19 and 15 fmol/mg of protein, respectively. The relative order of potency of indoles for inhibition of 125I-melatonin binding at these sites was typical of a melatonin receptor: 2-iodomelatonin greater than melatonin greater than N-acetylserotonin much much greater than 5-hydroxytryptamine. Norepinephrine-induced contraction of the caudal artery in vitro was significantly prolonged and potentiated by melatonin in a concentration-dependent manner, suggesting that these arterial binding sites are functional melatonin receptors. Neither primary steps in smooth muscle contraction (inositol phospholipid hydrolysis) nor relaxation (adenylate cyclase activation) were affected by melatonin. Melatonin, through its action on the tone of these arteries, may cause circulatory adjustments in these arteries, which are believed to be involved in thermoregulation.

• OSTI ID: 6445729
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Vol. 87:16; ISSN 0027-8424
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
MELATONIN
RECEPTORS
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL LOCALIZATION
BODY TEMPERATURE
CEREBRAL ARTERIES
CPB
DOSE-RESPONSE RELATIONSHIPS
IODINE 125
MUSCLES
NORADRENALINE
THERMOREGULATION
ADRENAL HORMONES
AMINES
AROMATICS
ARTERIES
AUTONOMIC NERVOUS SYSTEM AGENTS
AZAARENES
AZOLES
BETA DECAY RADIOISOTOPES
BLOOD VESSELS
BODY
CARDIOTONICS
CARDIOVASCULAR AGENTS
CARDIOVASCULAR SYSTEM
CONTROL
DAYS LIVING RADIOISOTOPES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
HETEROCYCLIC COMPOUNDS
INDOLES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
KINETICS
MEMBRANE PROTEINS
NEUROREGULATORS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PROTEINS
PYRROLES
RADIOISOTOPES
REACTION KINETICS
SYMPATHOMIMETICS
TEMPERATURE CONTROL
TRYPTAMINES
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