THE LOCALIZATION OF THE SITE OF ARYLALKYLAMINE N-ACETYLTRANSFERASE CIRCADIAN EXPRESSION IN THE PHOTORECEPTOR CELLS OF MAMMALIAN RETINA

To investigate the molecular mechanism of the melatonin rhythm in the mammalian retina, we examined the temporal mRNA expression pattern of arylalkylamine (serotonin) N-acetyltransferase (AA-NAT), the rate-limi ting enzyme in melatonin synthesis in the rat retina. Rat AA-NAT mRNA was detected exclusively in the retinal photoreceptors in the outer nu clear layer-low during the day and increased more than threefold at ni ght. The nocturnal AA-NAT expression in rat retina was also confirmed by RNase protection and the AA-NAT enzymatic activity. This is the fir st report to localize the site of AA-NAT mRNA circadian expression in mammalian photoreceptor cells. (C) 1998 Academic Press.