Lighting conditions in the early infancy modifies the further functionality of the circadian and the antioxidant systems in rats.

CARPENTIERI AR; A DIEZ-NOGUERA; CAMBRAS T

Congreso; 16th International Congress on Photobiology; 2014

Light is the main factor that influences circadian system. In adult rats, exposure to constant light (LL) produces a period lengthening and a further arhythmicity, which has been described as an uncoupling of the oscillators of the circadian system. However, rats that during suckling were maintained in LL manifested a robust circadian rhythm of motor activity under LL [1]. Melatonin (MEL) could be a good pharmacological candidate to favor coupling between the oscillators. MEL is also able to act as a scavenger of reactive oxygen and nitrogen species, preventing damage and cell death. Here, we studied the oxidative and behavioral changes caused by prolonged exposure to LL, in 4 groups of rats which differed in the lighting conditions during suckling, light-dark cycle (LD) or LL, and the MEL or vehicle treatment. As control we used a group of rats that were maintained in LD since birth. After 20 days post-weaning, rats were treated for two weeks with a subcutaneous injection of MEL (10 mg /kg body weight) or vehicle, at CT12. Blood samples were taken, before and after treatment, to test catalases activity and nitrites level. Motor activity was registered during the whole experiment. As expected, LL-born rats showed a more stable circadian rhythm than LD-born rats. MEL treatment was able to control the phase of the motor activity rhythm of LD rats, but not in LL rats, and increased the amplitude of their rhythm. There were no significant effects on nitrites level but an increment of catalases activity in the LL group treated with MEL, was observed. Results suggest that the lighting conditions are very important in the early infancy for the good functionality of the circadian and antioxidant systems. [1] Canal-Corretger MM, Cambras T, Vilaplana J, Díez-Noguera A. Am J Physiol, 2000; 278:R201-8.