Retinal ganglion cells are autonomous circadian oscillators synthesizing N-acetylserotonin during the day.

GARBARINO PICO E; CARPENTIERI AR; CONTÍN MA; SARMIENTO MI; BROCCO MA; PANZETTA P; ROSENSTEIN RE; CAPUTTO BL; GUIDO ME

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Año: 2004 vol. 279 p. 51172 - 51172

p class="abstract">Retinal ganglion cells send visual and circadian information to the brain regarding the environmental light-dark cycles. We investigated the capability of retinal ganglion cells of synthesizing melatonin, a highly reliable circadian marker that regulates retinal physiology, as well as the capacity of these cells to function as autonomous circadian oscillators. Chick retinal ganglion cells presented higher levels of melatonin assessed by radioimmunoassay during both the subjective day in constant darkness and the light phase of a light-dark cycle. Similar changes were observed in mRNA levels and activity of arylalkylamine N-acetyltransferase, a key enzyme in melatonin biosynthesis, with the highest levels of both parameters during the subjective day. These daily variations were preceded by the elevation of cyclic-AMP content, the second messenger involved in the regulation of melatonin biosynthesis. Moreover, cultures of immunopurified retinal ganglion cells at embry