Exploring the Effects of Chronic Stress on Hippocampal CA3 Dendrites in Female Rats
Slinkey Jr., James; Baran, Sarah E.; and Conrad, Cheryl D.
Behavioral Neuroscience Area, Department of Psychology, Arizona State University
The hippocampus is a brain structure that is involved with memory and is sensitive to stress. Following chronic stress, the hippocampus is one of the first brain regions to show structural changes, which includes dendritic retraction, characterized by the reduction of total branch length and bifurcations. Corticosterone, a steroid secreted in response to stress, mediates the stress-induced dendritic retraction in males, but, whether the same mechanism occurs in females is unknown. We studied whether chronic corticosterone treatment in gonadectomized (the removal of the gondads) male and female rats would cause dendritic retraction in the hippocampus. The gonads were removed because ovarian hormones may alter dendritic properties. Therefore, we also investigated whether estrogen replacement would attenuate the corticosterone-induced dendritic retraction in both males and females. A day after the end of chronic corticosterone and estrogen treatment (day 22), rats were tested on the Y-maze to assess spatial memory ability and then the brains were removed and processed for Golgi to assess dendritic retraction. My contribution to this project was to use an Olympus light microscope and a camera lucida drawing tube to magnify and trace CA3 neurons that were stained with a Golgi silver impregnating technique. I traced neurons in the CA3 region because CA3 neurons are highly sensitive to stress and corticosterone by exhibiting dendritic retraction first before other hippocampal regions. In two other studies, I learned to restrain rats in wire mesh tubing to stimulate the stress response, which include activating the HPA-Axis (Hypothalamic-Pituitary-Adrenal axis). which secretes corticosterone as a part of the stress response that may cause dendritic retraction. In the other study, I learned to restrain rats, to extract rat brains, and to perform adrenalectomies (the removal of the adrenal glands that secrete corticosterone) and to sample blood from the lateral saphenous vein, a technique that allows one to repeatedly sample blood so that corticosterone levels can be determined..