Endocrine regulation of cognition and neuroplasticity: Our pursuit to unveil the complex interaction between hormones, the brain, and behaviour.

Gonadal and stress hormones modulate neuroplasticity and behaviour. This review focuses on our findings over the past decade on the effects of estrogens and androgens on hippocampal neurogenesis, hippocampus-dependent learning and memory and the effects of reproductive experience in the rodent. Evidence suggests that acute estradiol initially enhances and subsequently suppresses cell proliferation in the dentate gyrus of adult female rodents. Repeated exposure to estradiol modulates hippocampal neurogenesis and cell death in adult female, but not male, rodents while, testosterone and dihydrotestosterone upregulate hippocampal neurogenesis in adult male rodents. Estradiol dose-dependently affects different brain regions involved in working memory (prefrontal cortex, hippocampus), reference memory (hippocampus) and conditioned place preference (amygdala). Pregnancy and motherhood differentially regulate adult hippocampal neurogenesis and spatial working memory in the dam after weaning. These studies and others demonstrate that the female brain responds to steroid hormones differently than the male brain. It is of the upmost importance to investigate the effects on neuroplasticity and behaviour in both the male and the female, particularly when modelling diseases that exhibit sex differences in incidence, etiology or treatment.