title: Dopamine inhibits melatonin synthesis in photoreceptor cells through a D2-like receptor subtype in the rat retina: biochemical and histochemical evidence.
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. alpha-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.
authors.affiliation: Laboratoire de NeuroCytologie Oculaire, INSERM U. 86, Paris, France.
authors.forename: J
authors.initials: J
authors.lastname: Nguyen-Legros
authors.forename: E
authors.initials: E
authors.lastname: Chanut
authors.forename: C
authors.initials: C
authors.lastname: Versaux-Botteri
authors.forename: A
authors.initials: A
authors.lastname: Simon
authors.forename: J H
authors.initials: JH
authors.lastname: Trouvin
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology; D003024:Clozapine / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D018492:Dopamine Antagonists / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007150:Immunohistochemistry; D008297:Male; D008550:Melatonin / Q000096:biosynthesis*; D008781:Methyltyrosines / Q000494:pharmacology; D010786:Photoreceptor Cells / Q000737:chemistry* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D020891:Raclopride; D051381:Rats; D017208:Rats, Wistar; D017448:Receptors, Dopamine D2 / Q000235:genetics / Q000502:physiology*; D050638:Receptors, Dopamine D4; D012160:Retina / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism; D012457:Salicylamides / Q000494:pharmacology; D019805:alpha-Methyltyrosine
chemical_list: D014150:Antipsychotic Agents; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; C493601:Drd4 protein, rat; D004791:Enzyme Inhibitors; D008781:Methyltyrosines; D017448:Receptors, Dopamine D2; D012457:Salicylamides; D015102:3,4-Dihydroxyphenylacetic Acid; D050638:Receptors, Dopamine D4; D020891:Raclopride; D019805:alpha-Methyltyrosine; D003024:Clozapine; D008550:Melatonin; D004298:Dopamine