title: Ontogeny of central melatonin receptors in tadpoles of the anuran Rana perezi: modulation of dopamine release.
abstract: The objective of this work was to study melatonin receptors in the eye and the brain and their possible functionality in the ontogeny of Rana perezi. The binding of 2-[(125)I]melatonin increases throughout embryonic larval development in both tissues. The most pronounced increase takes place at the end of premetamorphosis and during early prometamorphosis. This rise coincides temporarily with the appearance of the rhythmic melatonin-synthesizing capacity in the retina. In the three studied developmental stages (32G, 40G and 49-50G), melatonin-binding sites are coupled to G proteins and become functional. Moreover, melatonin inhibits dopamine (DA) release by the eyecups and brain of R. perezi tadpoles in vitro (stage 40G). Thus, the modulation of DA release could be one mechanism by which melatonin interacts with hormones, like prolactin and thyroxine that are involved in the regulation of anuran development and metamorphosis. Finally, we show that melatonin decreases K(+)-evoked cAMP content in the frog retina in vitro, suggesting that the effect of melatonin on DA release in the frog retina is mediated by the inhibition of this intracellular messenger.
authors.affiliation: Departamento de Fisiología (Fisiología Animal II). Facultad de Biología, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Isorna
authors.forename: Ana Isabel
authors.initials: AI
authors.lastname: Guijarro
authors.forename: María Jesús
authors.initials: MJ
authors.lastname: Delgado
authors.forename: Marcos A
authors.initials: MA
authors.lastname: López-Patiño
authors.forename: Nuria de
authors.initials: Nd
authors.lastname: Pedro
authors.forename: Angel
authors.initials: A
authors.lastname: Luis Alonso-Gómez
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D005123:Eye / Q000187:drug effects / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007814:Larva / Q000254:growth & development; D008550:Melatonin / Q000378:metabolism; D008675:Metamorphosis, Biological; D011898:Ranidae / Q000254:growth & development* / Q000378:metabolism; D044094:Receptors, Melatonin / Q000378:metabolism*
chemical_list: D044094:Receptors, Melatonin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D008550:Melatonin; D004298:Dopamine