Effects of Dominance Status on Neural Activity in Stress-Sensitive Neuronal Pathways

The central amygdala, CeA, is an important brain region that regulates behavioral changes in response to stressful and fear-inducing stimuli. Social subordination is a stressful experience that can activate neurons in the CeA. Social subordination is associated with increased stress sensitivity and elevated fear responses while social dominance is associated with stress resilience. The bed nucleus of the stria terminalis (BNST) is a stress-sensitive brain region that receives robust input from CeA neurons The objective of this study was to determine if dominant and subordinate hamsters differ in stress/fear-induced activation of CeA cells projecting to the BNST. I hypothesize that subordinate hamsters will activate a greater proportion of BNST-projecting CeA neurons during social defeat stress compared to their dominant counterparts. This experiment involved creating dominant-subordinate relationships in pairs of Syrian hamsters, injecting animals with the neuronal tracer cholera toxin B (CTb), exposing hamsters to social defeat stress with a resident aggressor, collecting brains to be sliced and processed through immunohistochemistry, and quantifying dual cFos-CTb expression. Our findings indicate that males express more c-Fos in CeA neurons following social defeat stress than females. The latency to submit during social defeat stress is also positively correlated with c-Fos expression in the CeA. However, no significant effects of dominance status were found in the stress-induced activation of CeA-BNST neurons. Thus, it is likely that the neural ensembles driving the effects of dominance status on stress reactivity likely exist within different neural circuits.

This is Steve Mahometano's Chancellor Thesis under the supervision of Dr. Matthew Cooper to complete the Chancellor Honors Program and the Neuroscience Honors Program.