NSC PhD Thesis Defense Seminar: Michele Saul
Changes in Exploratory Behavior and Cell Proliferation in the Amygdala Following Repeated Variable Stress in Male Rats: Focus on Adolescence
Monday, April 7
Adolescence is a developmental stage characterized by changes in exploratory behavior and neural organization. The amygdala, a key structure in the temporal lobe, is important for mediating exploratory behaviors, and continues to undergo plastic changes during adolescence. Stressful events can cause long-lasting changes in both exploratory behavior and brain development, suggesting that the adolescent amygdala may be affected. In these studies I examined whether a repeated variable stress (RVS) in male rats influenced exploratory behavior and a unique form of amygdala plasticity-- cellular proliferation-- focusing on adolescent animals.
In Aim 1, I compared the effects of RVS exposure in adolescent and adult rats on exploratory behavior six weeks later. Exploratory behavior in a novel anxiogenic, but not an anxiolytic, environment was significantly decreased in both age groups.
In Aim 2, I quantified the number of dividing cells in the amygdala of adolescent and adult animals, assayed using bromodeoxyuridine (BrdU) and immunocytochemical expression of neural markers. Normal adolescent rats showed 4-5 times more dividing cells in the amygdala than young adult animals. BrdU pulse-chase studies indicated that at least a portion of cells divide locally in the adolescent amygdala, leaving open the possibility that dividing cells are also migrating in. Further characterization with neural markers showed that BrdU-labeled cells do not show the developmental profile of typical neuronal precursors.
Finally, in Aim 3, I determined how RVS, which significantly altered exploratory behavior (Aim 1), influences cell proliferation/survival in the adolescent amygdala. Adolescent rats were administered RVS, injected with BrdU, and sacrificed either 24 hours or 10 days later. In stressed animals, the number of BrdU-positive cells significantly decreased 10 days post-BrdU (12 days post-RVS), but did not change 24 hours post-BrdU (2 days post-RVS). This suggests that RVS exerts effects over a delayed time course, possibly through apoptosis or cell cycle arrest.
In sum, RVS exposure decreases exploratory behavior in a novel anxiogenic environment and has delayed consequences for the number of dividing cell in the adolescent amygdala. RVS-induced behavioral changes may correlate with cell proliferation reduction, suggesting a potential anatomical link between amygdala plasticity and future behavior in anxiogenic environments.
Subscribe to the Neuroscience Graduate Program LISTSERV to receive news and events via email.
Sneak Peak of The Brain with Dr. David Eagleman at The Little Theater Followed by Panel Discussion Featuring Liz Romanski