title: The relationship between melatonin and dopamine rhythms in the duck retina.
abstract: In the retina of duck, levels of dopamine (DA) and its main metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), fluctuate throughout the day, with high values during the light phase. The rhythmic changes in DA content and metabolism are out of phase with the daily oscillations in melatonin (MEL) and serotonin N-acetyltransferase (AA-NAT; the penultimate and key regulatory enzyme in MEL biosynthesis) activity. Acute exposure of ducks to light at night potently increased levels of DA and DOPAC, and decreased AA-NAT activity and MEL content in the retina. Intraocular administration of MEL to light-adapted ducks produced a significant decline in retinal DA and DOPAC concentrations. On the other hand, quinpirole, a D(2)/D(4)-DA receptor agonist, administered intraocularly, markedly suppressed the night-time retinal AA-NAT activity and MEL. These findings provide, for the first time, evidence for an inverse relationship between the DA system and MEL in the duck retina.
authors.affiliation: Department of Biogenic Amines, Polish Academy of Sciences, POB-225, Łódź-1 90-950, Poland. jolantaz@anima1.zabpan.lodz.pl
authors.forename: Jolanta B
authors.initials: JB
authors.lastname: Zawilska
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Berezińska
authors.forename: Jolanta
authors.initials: J
authors.lastname: Rosiak
authors.forename: Berthe
authors.initials: B
authors.lastname: Vivien-Roels
authors.forename: Jerzy Z
authors.initials: JZ
authors.lastname: Nowak
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000121:Acetylserotonin O-Methyltransferase / Q000378:metabolism; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism; D002940:Circadian Rhythm; D004298:Dopamine / Q000378:metabolism*; D018491:Dopamine Agonists / Q000494:pharmacology; D004372:Ducks; D005260:Female; D066298:In Vitro Techniques; D008027:Light; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D019257:Quinpirole / Q000494:pharmacology; D017448:Receptors, Dopamine D2 / Q000187:drug effects; D050638:Receptors, Dopamine D4; D012160:Retina / Q000378:metabolism*
chemical_list: D018491:Dopamine Agonists; D017448:Receptors, Dopamine D2; D015102:3,4-Dihydroxyphenylacetic Acid; D050638:Receptors, Dopamine D4; D019257:Quinpirole; D000121:Acetylserotonin O-Methyltransferase; D001191:Arylamine N-Acetyltransferase; D008550:Melatonin; D004298:Dopamine