Sexual Dimorphism in How Chronic Corticosterone and Estrogen Treatment Influence Hippocampal Function and Morphology
Hamilton, Gillian F.; Baran, Sarah E.; and Conrad, Cheryl D.
Behavioral Neuroscience Area, Department of Psychology, Arizona State University
Chronic stress impairs spatial memory and induces hippocampal CA3 dendritic retraction in males. Chronic corticosterone mediates the chronic stress effects on morphology, but not behavior. In females, differences following chronic stress may arise from ovarian hormone effects on cognition. This study investigated whether chronic corticosterone and estrogen impacted cognition and dendritic remodeling in CA3 hippocampal neurons. Male and female rats were gonadectomized and received one of three estrogen implants (blank=B, cholesterol to produce low estrogen levels=C, or 25% estrogen to produce high estrogen levels=E). Rats received chronic corticosterone-treated water (or vehicle) for 21 days and then were tested on the Y-maze to assess spatial memory. Brains were removed and processed using Golgi, which is in progress and may be presented if available. Since the small number of rats (n=6/group) produced high behavioral variability, we set the p-level at 0.1 and are testing additional rats that will be included later. For the males, all groups appeared to exhibit novel arm recognition at some point (min 1 or min 2-5), by entering the novel arm more than the other arm. Moreover, corticosterone and estrogen interacted in the first minute of exploration because estrogen (C,E) impaired novel arm preference of corticosterone-treated males (B), but control males preferred the novel arm over the other arm regardless of estrogen treatment (B,C,E). More data are being collected to elucidate the data on the females but indicate that estrogen can influence male spatial ability.