Regulation of sociability by the cortico-habenula pathway in an animal model of depression

Impaired sociability is a hallmark behavioral symptom frequently associated with depression. The medial prefrontal cortex (mPFC) is known to regulate both social behaviors and stress responses. Given the mPFC's projections to the lateral habenula (LHb) and the abnormal hyperactivity of the LHb observed in depression, the mPFC-LHb pathway may play a pivotal role in mediating impaired social behaviors in depressive disorders. Recent studies have reported increased activity of the mPFC-LHb pathway in depressive animal models. However, how this pathway responds to social stimuli and the synaptic dynamics underlying this process remain unexamined. Utilizing an acute learned helplessness (aLH) mouse model, we demonstrated that exposure to non-social stress resulted in heightened excitability and enhanced excitatory synaptic transmission at mPFC-LHb synapses. Furthermore, during social interactions, aLH mice exhibited significantly elevated Ca^2 + transient signals in mPFC neurons projecting to the LHb. This synaptic enhancement was specifically observed in LHb neurons projecting to the ventral tegmental area (VTA). Importantly, optogenetic suppression of the mPFC-LHb pathway effectively restored sociability, underscoring its crucial role in the social deficits associated with depression. These findings highlight the mPFC-LHb pathway as a promising target for investigating the neural mechanisms underlying sociability deficits in depressive disorders.