Light-induction of the enzyme Aralkylamine N-acetyltransferase (AANAT) in the chicken inner retina and its potential physiological role.

GARBARINO PICO E; GUIDO ME; RÍOS MN

Congreso; XIV Latin American Symposium on Chronobiology 2017 (LASC); 2017

The neurohormone melatonin is synthesized from serotonin through two steps of which serotonin is converted first to N-acetyl-serotonin (NAS) by the enzyme Aralkylamine N- Acetyltransferase (AANAT). AANAT is present mainly in the pineal gland, retina and other regions while NAS can activate the TrkB receptor to generate neuroprotective effects and neurogenesis. Melatonin synthesis is controlled by light (L) and the circadian clock. In photoreceptor cells, AANAT activity peaks during the dark and at subjective night while activity is significantly decreased by L exposure. By contrast, melatonin synthesis, AANAT expression and activity are high during the subjective day or L phase in chicken retinal ganglion cells (RGCs) (Garbarino et al 2004). Here we investigate the expression of AANAT and of nonvisual opsins in highly enriched RGC cultures obtained from embryos by a discontinuous BSA gradient, and exposure to different L conditions. Cultures expressed melanopsins, Opn3 and Opn5 which may confer intrinsic photosensitivity. In fact, cultures exhibited blue L induction of AANAT immunoreactivity as compared with dark or red L treated cells. In addition, expression of this enzyme was significantly increased by forskolin (10 uM), an adenylate cyclase activator, in the dark. Results suggest that AANAT is a blue L-induced enzyme in RGCs controlled by cAMP. Further studies will investigate the cascade controlling AANAT expression in RGCs and its effects on retinal cells.(Supported by ANPCyT-FONCyT, CONICET, SECyT UNC).