Connectivity and functional characterization of the mouse contralateral projecting neurons in basolateral amygdala

Amygdala is widely known as a critical neural hub for modulating negative emotions such as fear and anxiety. Recent studies have shown that the basolateral amygdala (BLA) has reciprocal innervation, which plays an important role in regulating social interaction and associative memory. However, the connectivity pattern and functional role of the contralateral projecting BLA neurons in stress-related anxiety are not fully understood. Here, using the virus tracing strategy, we first characterized the connectivity pattern of the contralateral projecting neurons in BLA. Then, we examined the effect of stress on the functional changes of those specific neuronal populations using a mouse model of inescapable footshock stress. The results showed that the fibers of the contralateral projecting BLA neurons labeled by enhanced green fluorescent protein (EGFP) have no collateral projections to the ipsilateral or contralateral hippocampus. Interestingly, they have some collateral projections to the ipsilateral medial prefrontal cortex. Behavioral results showed that footshock stress increases the anxiety-like behavior in mice; however, the excitatory synaptic transmission and intrinsic excitability of the contralateral projecting BLA neurons measured by whole-cell patch clamp recording did not change after stress exposure. In conclusion, our results indicate that contralateral projecting BLA neurons may not contribute to footshock stress-related anxiety-like behavior.