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Constitutively active melatonin MT1 receptors in male rat caudal arteries

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Abstract

This study assessed the state of melatonin MT1 receptor coupling in sections of male rat caudal arteries by [35S]GTPγS binding autoradiography. The melatonin MT1 receptor inverse agonist 4-phenyl-2-propionamidotetraline (4P-PDOT) (0.1–1 μM) significantly decreased [35S]GTPγS binding compared to basal, strongly suggesting the presence of constitutively active receptors. Formation of constitutively active receptors during subjective day, when the levels of melatonin are low, may be a physiological mechanism by which the organism maintains vascular tone.

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Acknowledgments

This research was supported by grants USPHS RO1 MH 42922 (M.L.D.) and T32 AG00260 (Ç.E.).

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