Efeito da cronoruptura por T22 nas fases pós-natal da infância e adolescência sobre a expressão neuroquímica de NeuN e PV no hipocampo, córtex pré-frontal, amígdala e núcleo supraquiasmático de ratos Wistar adultos

Abstract

Many studies of circadian disruptions in animal models have involved a forced internal circadian desynchronization using abnormal exposure to light/dark cycles. These abnormal cycles may affect emotional and cognitive behavior, although the mechanisms underlying the long-term consequences remains unclear. Aimed to evaluate circadian disruptions on locomotor activity and parvalbumin and NeuN signalization, we exposed newborns Wistar rats a symmetric 22hr LD cycle (11hr light, 11hr dark) during infancy (DI group) and adolescence (DA group). Rats of the DI group were exposed to 22hr LD cycle throughout pregnancy and lactation, while rats of DA group were exposed to a same LD schedule from weaning to postnatal day 61. All rats were resynchronized and maintained in a 24hr LD cycle until adulthood. The control group was exposed to regular 12:12h light-dark cycle over lifetime. We found that the DI (PV = 27,12 ± 4,49) and DA (PV = 29,56 ±6,69) group presented lower rhythm stability when compared with Control group (PV = 33,25± 6,39). Both DI and DA groups expressed two circadian rhythms on locomotor activity analyzed using Sokolove Bushell actograms and periodograms, while Control group showed a stable rhythm synchronized with 24hr LD cycle. We did not observed differences in NeuN or parvalbumin expression in the prefrontal cortex, hippocampus, amygdala, and suprachiasmatic nucleus between groups (p>0.05) although both DI and DA desynchronized groups had showed qualitatively fewer neurons labeling, which deserve to be investigated further. Thus, we conclude that animals exposed to 22hr LD cycle along development recovery the rhythm stability on locomotor activity and did not change the number of neurons or parvalbumin expression in brain areas related to emotional-cognitive behaviors after resynchronization under 24hr LD cycles.