Efeito de variações de fotoperíodo na expressão de Per2 e Bdnf no cérebro de camundongos da linhagem C57BL/6

Abstract

Although there are some studies demonstrating the effect of different photoperiods on the cerebral morphology, there are still many gaps in the investigation of the modulation of physiological and behavioral processes, by photoperiod changes in a gradual way, that approximates the variations that occur in the environment Whereas the studies show the effect of constant photoperiod regimes.In order to understand how the photoperiod can have an effect on structures involved with executive functions (mPFC and mRFC), we analyzed the expression of a gene involved with neuroplasticity (Bdnf) and a central gene of the circadian timer system (Per2) in different photoperiod, in two moments of a 24 hour cycle (ZT06 and ZT18).In addition to the photoperiod regimes conventionally described in the literature (12:12, 08:16 and 16:08), we evaluated the expression of these genes in gradual photoperiod transition regimes,with increment (TCL) or daily decrease of one hour of light, simulating seasonal environmental variations. The results demonstrate that the gradual transition regime of the short photoperiod changes the expression profile of the transcripts of Per2 and Bdnf in striatum, since the levels of these transcripts only do not differ in the TCL group. The absence of the difference of the levels of expression of the analyzed genes between ZTs 06 and 18 in the TCL group suggests that this transition regime modulates the expression of these genes more significantly. Analysis of the daily profile along a 24 h cycle of these genes in the 12:12 and TCL regimes de, demosntrated that Per2 and Bdnf show gradual variation only in the 12:12 group. In the TCL regime, no rhythmicity of these genes was identified in any of the tissues. The expression levels of these genes are significantly lower in the TCL group compared to the 12:12 group in mPFC, suggesting that this reduction in expression level is associated with loss of hythmicity. Thus, this scheme, which simulates environmental contexts associated with suicidal behavior, affected the rhythmic expression of the Per2 and Bdnf genes, suggesting a temporal maladaptation of these structures to photoperiod variations in the model studied.