Dissociable contributions of the amygdala and ventral hippocampus to stress-induced changes in defensive behavior.

Severe stress can produce multiple persistent changes in defensive behavior. While much is known about the circuits supporting stress-induced associative fear responses, how circuit plasticity supports the broader changes in defensive behavior observed after severe stress remains unclear. Here, we find that stress-induced plasticity in the ventral hippocampus (vHC) and basolateral amygdala (BLA) support doubly dissociable defensive behavioral changes. Stress-induced protein synthesis in the BLA was found to support lasting enhancements in stress sensitivity but not enhancements in exploratory anxiety-related behaviors, whereas protein synthesis in the vHC was found to support enhancements in anxiety-related behavior but not enhancements in stress sensitivity. Like protein synthesis, neuronal activity of the BLA and vHC were found to differentially support the expression of these same defensive behaviors. Lastly, blockade of associative fear had no impact on stress-induced changes in anxiety-related behavior. These findings highlight that multiple memory-systems support stress-induced defensive behavior changes.