Chronic alcohol induces subcircuit-specific striatonigral plasticity shifting action control to the sensorimotor striatum

While cortico-striatal circuit deficits contribute to Alcohol Use Disorder, the impact of alcohol on synaptic function in the basal ganglia output, the substantia nigra pars reticulata (SNr), remains unclear. Here, we found that the inputs from the dorsomedial (DMS) and dorsolateral striatum (DLS) differ in their presynaptic properties and target molecularly distinct subpopulations of SNr neurons. We also discovered that indirect pathway subthalamic (STN) inputs to the medial and lateral SNr have different presynaptic properties and that STN inputs are stronger in the lateral SNr. Chronic alcohol exposure (CIE) potentiated DLS inputs but did not affect the strength and presynaptic release properties of DMS and subthalamic inputs to SNr neurons. Chemogenetic inhibition of DLS direct pathway projection neurons impaired action performance in an operant conditioning task in CIE mice but not control mice. Overall, our work identifies a synaptic mechanism whereby chronic alcohol induces a gain of function for action control in direct pathway neurons in the dorsolateral striatum. Teaser Chronic alcohol selectively potentiates DLS synaptic inputs to the SNr, enhancing their role in action control.