title: Does D4 dopamine receptor mediate the inhibitory effect of light on melatonin biosynthesis in chick retina?
abstract: The dopamine (DA) receptor mediating the inhibitory effect of light on melatonin formation in the chick retina was characterized pharmacologically. Nighttime serotonin N-acetyltransferase (NAT) activity was significantly decreased by either light exposure or by intraocular (i.oc.) administration of DA and quinpirole (a predominant D3/D4 DA receptor agonist). Several D2-like DA receptor antagonists, i.e. clozapine, haloperidol, spiroperidol, sulpiride, (+)-UH-232 and YM-09151-2, given i.oc. to light-adapted chicks markedly elevated retinal NAT activity. In contrast, raclopride (a D2/D3 DA receptor antagonist) and remoxipride (a D2-selective DA receptor antagonist) were ineffective. Spiroperidol, clozapine, haloperidol and sulpiride significantly increased melatonin content in the light-exposed retina, but had no effect on the activity of hydroxyindole-O-methyltransferase. None of D2-like DA receptor blockers tested modified the nighttime NAT activity in the chick retina. Our results indicate that the light-evoked inhibition of the nocturnal increase in melatonin biosynthesis in chick retina may involve stimulation of the D4 subtype DA receptor.
authors.affiliation: Department of Biogenic Amines, Polish Academy of Sciences, Lodz.
authors.forename: J B
authors.initials: JB
authors.lastname: Zawilska
authors.forename: J Z
authors.initials: JZ
authors.lastname: Nowak
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D000121:Acetylserotonin O-Methyltransferase / Q000378:metabolism; D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism; D002645:Chickens; D015259:Dopamine Agents / Q000494:pharmacology; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D004873:Ergolines / Q000494:pharmacology; D008027:Light; D008297:Male; D008550:Melatonin / Q000096:biosynthesis*; D019257:Quinpirole; D011954:Receptors, Dopamine / Q000502:physiology*; D050638:Receptors, Dopamine D4; D012160:Retina / Q000201:enzymology / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D014150:Antipsychotic Agents; D015259:Dopamine Agents; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D004873:Ergolines; D011954:Receptors, Dopamine; D050638:Receptors, Dopamine D4; D019257:Quinpirole; D000105:Acetyl Coenzyme A; D000121:Acetylserotonin O-Methyltransferase; D001191:Arylamine N-Acetyltransferase; D008550:Melatonin