Periaqueductal gray neurotensin neurons drive simultaneous threat response and reinforcement

The periaqueductal gray (PAG) is a midbrain structure known to influence responses to both threat and reward. The PAG sends projections to the ventral tegmental area (VTA), a region critical for regulating motivated behavior via dopamine release. We previously identified a population of VTA-projecting PAG neurons that express the peptide neurotensin (Nts), a potent dopamine neuron activator. Here we find that PAG-Nts neurons co-release glutamate and Nts in the VTA to drive dopamine neuron activation. These neurons are activated by threats and threat-predictive cues and are inhibited by entry into a shelter and during reward consumption. Optogenetic stimulation elicits a robust threat response, including freezing and tail rattle, but remarkably can also drive intracranial self-stimulation. This operant reinforcement behavior is dopamine dependent while the threat response is not. Together, these results identify a dual-output circuit that engages the dopamine system, likely to increase the salience of environmental stimuli, while simultaneously driving specific threat response behaviors.