Chronic stress leads to persistent and contrasting stellate neuron dendritic hypertrophy in the amygdala of male and female rats, an effect not found in the hippocampus

In males, chronic stress enhances dendritic complexity in the amygdala, a region important in emotion regulation. An amygdalar subregion, the basolateral amygdala (BLA), is influenced by the hippocampus and prefrontal cortex to coordinate emotional learning and memory. This study quantified changes in dendritic complexity of BLA stellate neurons ten days after an unpredictable chronic stressor ended in both male and female rats. In addition, dendritic complexity of hippocampal neurons in male rats was assessed at a similar timepoint. Following Golgi processing, stressed male and female rats showed enhanced BLA dendritic complexity; increased arborization occurred near the soma in males and distally in females. As the brain was sampled ten days after chronic stress ended, BLA dendritic hypertrophy persisted in both sexes after the stressor had ended. For the hippocampus, CA3 dendritic complexity was similar for control and stressed males when assessed eight days after stress ended, suggesting that any stress-induced changes had resolved. These results show persistent enhancement of BLA dendritic arborization in both sexes following chronic stress, reveal sex differences in how BLA hypertrophy manifests, and suggest a putative neurobiological substrate by which chronic stress may create a vulnerable phenotype for emotional dysfunction.