Dopamine Inhibits Melatonin Synthesis in Photoreceptor Cells Through a D2‐Like Receptor Subtype in the Rat Retina: Biochemical and Histochemical Evidence
- 1 December 1996
- journal article
- research article
- Published by Wiley in Journal of Neurochemistry
- Vol. 67 (6) , 2514-2520
- https://doi.org/10.1046/j.1471-4159.1996.67062514.x
Abstract
An intrinsic oscillator, using dopamine and melatonin as antagonist signals, controls rhythmic events in the retina of nonmammals. The purpose of the present work was to localize and characterize a dopamine receptor responsible for the nocturnal inhibition of melatonin synthesis in photoreceptor cells in a mammalian retina. An antibody against the D2 receptor stained photoreceptor cell inner segments of the rat retina. α‐Methyl‐p‐tyrosine, a competitive inhibitor of tyrosine hydroxylase, enhanced the nocturnal content of melatonin, suggesting the dopamine control of melatonin synthesis as in non‐mammals. Clozapine, a D2C/D4 antagonist, also enhanced the nocturnal level of melatonin, whereas raclopride, a D2A antagonist, did not. Taken together, these results support the control of melatonin levels by dopamine through a D2C/D4 receptor in photoreceptor cells of the rat retina. The presence of D4 receptors in the rat retina was confirmed by reverse transcription‐PCR.Keywords
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