Influence of the Estrous Cycle and Chronic Stress on Hippocampal Dendritic Morphology of the Female Rat
Wilson, Jessica O.; McLaughlin, Katie J.; and Conrad, Cheryl D.
Behavioral Neuroscience Area, Department of Psychology, Arizona State University
Past research has shown that chronic stress decreases the dendritic complexity of the CA3 region of the hippocampus and suggests a dichotomous reponse to chronic stress in males and females. Recent findings from our lab suggest that ovarian hormones may mediate this dichotomous morphological response to chronic stress. The present study investigated the potential interaction between chronic stress and the estrus cycle on hippocampal dendritic morphology of the CA1 and CA3 regions. Female rats were randomly assigned to a control or chronic stress group, in which they underwent a restraint stress paradigm for 6 hrs/day for approximately 21 days. Rats were euthanized and brains processed for Golgi when the rats were in the estrous phase of estrus (low estrogen levels) or proestrus (high estrogen levels). Within the CA3 region of the hippocampus, chronic stress did not produce apical or basal dendritic retraction. Unexpectedly, chronically stressed rats in proestrus exhibited more basal branch points than in any other group. CA1 dendritic arborization was unaltered by chronic stress or the estrous cycle, which is consistent with past reports. These findings support past studies showing that the female CA3 dendritic arbors are less susceptible to chronic stress than male CA3 dendritic trees and that the CA3 dendritic tree does not change in response to the estrous cycle.