title: Diurnal variations in cyclic AMP and melatonin content of golden hamster retina.
abstract: The diurnal variations and photic regulation of cyclic AMP and melatonin content in golden hamster retina were studied. Both parameters showed significant diurnal variations with maximal values at night. Light exposure during the night inhibited retinal cyclic AMP and melatonin levels, whereas exposure to darkness during the day significantly increased cyclic AMP and melatonin content. Incubation with melatonin of retinas excised at different intervals indicated that the methoxyindole inhibited cyclic AMP accumulation in a time-dependent manner. The inhibitory effect of melatonin at 2400 h and at noon showed a threshold concentration of 1 and 10 pM, respectively. At 0400 h melatonin did not affect cyclic AMP accumulation. The results indicate a diurnal variability of retinal cyclic AMP and melatonin content in hamsters, mainly influenced by a photic stimulus. Cyclic AMP could be a putative second messenger for melatonin action in golden hamster retina.
authors.affiliation: Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
authors.forename: M P
authors.initials: MP
authors.lastname: Faillace
authors.forename: M I
authors.initials: MI
authors.lastname: Sarmiento
authors.forename: L N
authors.initials: LN
authors.lastname: Siri
authors.forename: R E
authors.initials: RE
authors.lastname: Rosenstein
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism*; D003624:Darkness; D008027:Light; D008297:Male; D008550:Melatonin / Q000378:metabolism* / Q000494:pharmacology; D008647:Mesocricetus; D011863:Radioimmunoassay; D012160:Retina / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000242:Cyclic AMP; D008550:Melatonin