Differential Regulation of Arylalkylamine N-Acetyltransferase Activity in Chicken Retinal Ganglion Cells by Light and the Circadian Clock

VALDEZ DJ; GARBARINO PICO E; DÍAZ NM; SILVESTRE D; GUIDO ME

TAYLOR & FRANCIS INC

Lugar: Londres; Año: 2012 vol. 29 p. 1011 - 1011

div> Retinal ganglion cells (RGCs) contain circadian clocks driving melatonin synthesis during the day, a subset of these cells acting as nonvisual photoreceptors sending photic information to the brain. In this work, the authors investigated the temporal and light regulation of arylalkylamine N-acetyltransferase (AA-NAT) activity, a key enzyme in melatonin synthesis. The authors first examined this activity in RGCs of wild-type chickens and compared it to that in photoreceptor cells (PRs) from animals maintained for 48 h in constant dark (DD), light (LL), or regular 12-h:12-h light-dark (LD) cycle. AA-NAT activity in RGCs displayed circadian rhythmicity, with highest levels during the subjective day in both DD and LL as well as in the light phase of the LD cycle. In contrast, AA-NAT activity in PRs exhibited the typical nocturnal peak in DD and LD, but no detectable oscillation was observed under LL, under which conditions the levels were basal at all times examined.