In two groups of female CD-rats nocturnal urine (19-23 h, 23-3 h, 3-7 h) was collected at monthly intervals over 658 days (I: 1997-1999) and 494 days (II: 1999-2000) coinciding with the ascending limb (1996-2000) of the 23rd sunspot cycle (1996-2008). The excretion of 6-sulfatoxymelatonin (aMT6s: I, II) was determined as well as the ratio of noradrenaline/adrenaline (NA/A: I) reflecting the act...

Seasonal variations of environmental factors are translated into annual fluctuations in synthesis and release of melatonin, which in turn acts as a neuroendocrine messenger for the synchronization of annual functions. So far, most studies performed to understand the regulation of melatonin synthesis have used the non seasonal laboratory rat. It was demonstrated that nocturnal melatonin synthesi...

The evolution of N-acetyltransfeases (NATs) seems complex. Vertebrate arylalkylamine N-acetyltransferase (aaNAT) has been extensively studied since it leads to the synthesis of melatonin, a multifunctional neurohormone prevalent in photoreceptor cells, and is known as a chemical token of the night. Melatonin also serves as a scavenger for reactive oxygen species. This is also true with inverteb...

PURPOSE Melatonin synthesis in mammalian retinal photoreceptors is under photic and circadian control and regulated by changes in the activity of arylalkylamine N-acetyltransferase (AANAT). Recent studies have suggested that retinal dopaminergic neurons contain a circadian pacemaker, and dopamine is the neurotransmitter that drives circadian rhythmicity in the mammalian retina. METHODS To inv...