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. Briefly, evidence suggests that acute estradiol initially enhances and subsequently suppresses cell proliferation in the dentate gyrus of adult female rodents, but may have limited effects in male rodents. Intriguingly, repeated exposure to estradiol modulates hippocampal neurogenesis and cell death in adult female, but not male, rodents. Furthermore, testosterone and dihydrotestosterone upregulate hippocampal neurogenesis (via cell survival) in adult male rodents. We have found that estradiol can dose-dependently affect different brain regions that are involved in working memory (prefrontal cortex and hippocampus), reference memory (hippocampus) and conditioned place preference (amygdala). Pregnancy and motherhood differentially regulate adult hippocampal neurogenesis in the adult female rodent, with primiparous rats displaying lower levels of hippocampal cell proliferation and survival after parturition but better spatial working memory after weaning. These studies and others demonstrate that the female brain is organized differently and 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 the incidence, etiology or treatment. This is especially important if we are to use our knowledge of how adult neurogenesis is regulated to develop strategies to repair neuron loss in neurodegenerative diseases such as Alzheimer’s disease and depression that exhibit clear sex differences.Arts, Faculty ofMedicine, Faculty ofPsychology, Department ofReviewedFacultyResearcherPostdoctoralGraduat