Relación entre la luz/dopamina sobre la actividad de la enzima N- Acetilserotonina de la retina de pollo

DIEGO J. VALDEZ; DIAZ NICOLAS M; GUIDO MARIO EDUARDO

Córdoba capital

Congreso; VII Asociación de Investigación en Visión y Oftalmología; 2010

AIVO

Circadian physiology in the vertebrate retina is regulated by light and diverse signals such as melatonin and dopamine (DA), which act as mutually inhibitory factors. We previously described that chicken retinal ganglion cells (RGCs) contain circadian oscillators synthesizing melatonin with higher levels during the day in antiphase to the nocturnal photoreceptor cell (PRC) rhythm. Here, we investigated the effect of DA on the activity of the melatonin synthesizing enzyme N-Acetylserotonin (AA-NAT) in PRC and RGC preparations. Animals were kept under a 12:12 h light-dark cycle (LD) for 7 days, released to constant darkness (DD) for 24 h and then exposed to light pulses of different durations (30-90 min) during the subjective day (circadian time: CT 3) or night (CT 17.5), or injected with DA (50 nmol/eye) in one eye and vehicle in the other (contralateral eye) at CT 17.5 in DD. A light pulse of 30-60 min at CT 3 or CT 17.5 caused a significant decrease in AA-NAT activity of PRCs while it has no effect on RGC enzyme activity. Likewise the DA treatment in the absence of light significantly inhibited AA-NAT activity in PRCs but not in RGCs. The results strongly suggest that in the chicken retina DA mimics the effect of light on AA-NAT activity on PRCs however, light and DA has no effect on RGCs implicating that responses seen in these cells are mostly driven by the circadian clock.