Aversion or Salience Signaling by Ventral Tegmental Area Glutamate Neurons.

Ventral tegmental area (VTA) neurons play roles in reward and aversion. The VTA has, in addition to dopamine neurons, glutamatergic neurons expressing VGluT2. Here, by determining the firing patterns of VTA-VGluT2 neurons expressing channelrhodopsin 2, we identified a major subpopulation of VTA-VGluT2 neurons whose firing rates decreased or were unchanged during sucrose consumption and increased during facial airpuff presentation. We identified a small subpopulation of VTA-VGluT2 neurons whose firing rates increased in response to both rewarding and aversive stimuli. We also found that the changes in firing rate of some VTA-VGluT2 neurons were greater following reward delivery compared with reward omission, whereas others did not differ. We conclude that VTA-VGluT2 neurons are responsive to aversive stimuli, but subpopulations of VTA-VGluT2 neurons are differentially affected by sucrose reward. Reward-responsive subpopulations of VTA-VGluT2 neurons are also divided into those affected by reward expectation alone or the real-time delivery of reward.