Melatonin effect on circadian motor activity of the rat under different lighting conditions during suckling

AR CARPENTIERI; OLIVA C; A DIEZ-NOGUERA; T CAMBRAS

Braganca Paulista

Simposio; XIII Latin American Symposium on Chronobiology; 2015

Sociedad Latinoamericana de Cronobiología

MELATONIN EFFECT ON CIRCADIAN MOTOR ACTIVITY OF THE RAT UNDER DIFFERENT LIGHTING CONDITIONS DURING SUCKLINGAgata R. Carpentieri (a), Clara Oliva (b), Antoni Díez-Noguera (b), and Trinitat Cambras (b).aINICSA-CONICET, Fac. Cs Médicas y Cát. de Química Biológica. Facultad de Odontología. Universidad Nacional de Córdoba. Córdoba. Argentina. e-mail: arcarpentieri@hotmail.com. bDept. Fisiología. Facultad de Farmacia. Universitat de Barcelona. Barcelona España. e-mail: cambras@ub.edu.Early lighting conditions have been described to produce long term effects on circadian behavior, which may influence the response to agents acting on the circadian system. Melatonin has been suggested to act on the circadian pacemaker and is also able to act as a scavenger of reactive oxygen and nitrogen species. Here, we studied the oxidative and behavioral changes caused by prolonged exposure to constant light, in groups of rats which differed in the lighting conditions during suckling, light-dark cycle (LD) or constant light (LL), and in the melatonin administration. After 20 days post-weaning, rats were treated for two weeks with a subcutaneous injection of melatonin (10 mg /kg body weight) or vehicle at the activity onset. Blood samples were taken, before and after treatment, to determine catalases activity and nitrites level. As expected, LL-reared rats showed a more stable motor activity circadian rhythm than LD-rats. Melatonin treatment was able to control the phase of the rhythm in LD-rats, but not in LL rats, and increased the amplitude of their rhythm after treatment. There were no significant differences on nitrites level or catalases activity due to the groups, although both variables increased with time. Finally, we also tested depressive signs by means of sucrose consumption, resulting LD males treated with melatonin, the only group that manifested anhedonia. Results suggest that the lighting conditions in the early infancy are important for the long term functionality of the circadian system, including rhythm manifestation, responses to melatonin and mood alterations.