NAcc KORs presynaptically inhibit glutamate synapses in a pathway-specific manner KORs inhibit D1 MSN collaterals more robustly than they inhibit D2 MSN collaterals KORs preferentially inhibit glutamate and GABA onto D1 and D2 MSNs, respectively KORs inhibit excitatory drive of D1 MSNs and disinhibit excitatory drive of D2 MSNs