title: Effect of constant and fluctuating temperature on daily melatonin production by eyecups from Rana perezi.
abstract: We analysed the effect of daily temperature cycles in relation to constant temperature on day/night melatonin synthesis in frog eyecups in culture. Eyecups were cultured for 24 h under 12L:12D photoperiod and two thermal regimes, constant temperature (25, 15 and 5 degrees C) and thermoperiod (WL/CD, thermophase coinciding with photophase and cryophase coinciding with scotophase; and CL/WD, cryophase coinciding with photophase and thermophase coinciding with scotophase). A negative correlation between ocular serotonin N-acetyltransferase activity and culture temperature for both diurnal and nocturnal activities has been observed. This effect of increased ocular activity at low temperature is more pronounced than the well-known stimulatory effect of darkness, and it does not depend on the photoperiod phase. The lack of interactions between the phase of photoperiod and culture temperature indicates that the effects of both factors are independent. Night-time temperature is the key factor in determining the amplitude of the melatonin rhythm in the Rana perezi retina. However, daytime temperature can not counteract the inhibitory effect of light on ocular melatonin synthesis.
authors.affiliation: Departamento de Biología Animal II (Fisíología Animal), Facultad de Biología, Universidad Complutense, Madrid, Spain.
authors.forename: A I
authors.initials: AI
authors.lastname: Valenciano
authors.forename: A L
authors.initials: AL
authors.lastname: Alonso-Gómez
authors.forename: M
authors.initials: M
authors.lastname: Alonso-Bedate
authors.forename: M J
authors.initials: MJ
authors.lastname: Delgado
mesh_terms: D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism; D002940:Circadian Rhythm; D005123:Eye / Q000378:metabolism*; D008550:Melatonin / Q000378:metabolism*; D009924:Organ Culture Techniques; D017440:Photoperiod; D011898:Ranidae; D012044:Regression Analysis; D012160:Retina / Q000737:chemistry / Q000378:metabolism*; D012621:Seasons; D013696:Temperature
chemical_list: D001191:Arylamine N-Acetyltransferase; D008550:Melatonin