Impacto de um modelo experimental de estresse precoce na cognição, motricidade e correlatos neurobiológicos durante a adolescência

Abstract

Early life stress exposure is a global issue and is associated with decreased quality of life and it is considered a risk factor for several diseases. There are several evidences in the literature suggesting that early life stress impact brain development, as well as cognition and motricity. The neurobiological mechanisms behind these effects are poorly understood. Aim: This study aims to investigate the impact of an experimental model of early life stress on cognitive abilities and walk adaptability during adolescence, looking at the gene expression of targets related to learning and memory in different brain regions. Methods: Briefly, we exposed male C56BL/6 mice to the limited bedding protocol postnatal day (PND)2 to PND9 and then tested animals in the radial 8-arm maze, Y-maze and Step-Down avoidance task and Ladder Rung Walking Test at the end of adolescence. RT-qPCR was used to investigate BDNF exon IV, Drd1 and Drd2 gene expression in the mPFC, Motor Cortex and Cerebellum 2h after the task. Results: Mice raised in Limited Bedding conditions presented fewer perseverative errors compared to our reference group. This effect was followed by an increased BDNF exon IV expression in the mPFC with no differences in Drd1 and Drd2. When looking at the ability of adapt walking of mice, we found two distinct subgroups of animals that presented a superior performance (SP) when compared to controls or an inferior performance (IP). We observed that Drd1 expression is increased in the mPFC of IP animals and in the cerebellum of SP with no differences regarding Drd2 expression on mPFC, motor cortex and cerebellum. We observed that both SP and IP groups increased BDNF expression in the mPFC together with a significant difference between SP and IP groups in BDNF expression on motor cortex. We found a strong negative correlation between BDNF exon IV expression in the motor cortex and walking adaptability. No differences between groups regarding TrkB mRNA expression in any brain region investigated were observed although there is a positive correlation between TrkB expression in the mPFC and a better ability to adapt walking. Conclusions: Our study showed that mice exposed to Limited Bedding showed fewer perseveration and increased BDNF exon IV expression in the mPFC during adolescence. Also, our data suggest that exposure to Limited Bedding early in life can lead to distinct phenotypes followed by differential expression in Drd1 and BDNF in brain regions involved in the regulation of walking adaptability.