Afferent Inputs to Neurotransmitter-Defined Cell Types in the Ventral Tegmental Area.

The ventral tegmental area (VTA) plays a central role in the neural circuit control of behavioral reinforcement. Though considered a dopaminergic nucleus, the VTA contains substantial heterogeneity in neurotransmitter type, containing also GABA and glutamate neurons. Here, we used a combinatorial viral approach to transsynaptically label afferents to defined VTA dopamine, GABA, or glutamate neurons. Surprisingly, we find that these populations received qualitatively similar inputs, with dominant and comparable projections from the lateral hypothalamus, raphe, and ventral pallidum. However, notable differences were observed, with striatal regions and globus pallidus providing a greater share of input to VTA dopamine neurons, cortical input preferentially on to glutamate neurons, and GABA neurons receiving proportionally more input from the lateral habenula and laterodorsal tegmental nucleus. By comparing inputs to each of the transmitter-defined VTA cell types, this study sheds important light on the systems-level organization of diverse inputs to VTA.