Circuit specificity in the inhibitory architecture of the VTA regulates cocaine-induced behavior

Afferent inputs to the ventral tegmental area (VTA) control reward-related behaviors through regulation of dopamine neuron activity. The nucleus accumbens (NAc) provides one of the most prominent projections to the VTA; however, recent studies have provided conflicting evidence regarding the function of these inhibitory inputs. Using optogenetics, cell-specific ablation, whole cell patch-clamp and immuno-electron microscopy, we found that NAc inputs synapsed directly onto dopamine neurons, preferentially activating GABA_B receptors. GABAergic inputs from the NAc and local VTA GABA neurons were differentially modulated and activated separate receptor populations in dopamine neurons. Genetic deletion of GABA_B receptors from dopamine neurons in adult mice did not affect general or morphine-induced locomotor activity, but markedly increased cocaine-induced locomotion. Collectively, our findings demonstrate notable selectivity in the inhibitory architecture of the VTA and suggest that long-range GABAergic inputs to dopamine neurons fundamentally regulate behavioral responses to cocaine.