A Paranigral VTA Nociceptin Circuit that Constrains Motivation for Reward.

Nociceptin and its receptor are widely distributed throughout the brain in regions associated with reward behavior, yet how and when they act is unknown. Here, we dissected the role of a nociceptin peptide circuit in reward seeking. We generated a prepronociceptin (Pnoc)-Cre mouse line that revealed a unique subpopulation of paranigral ventral tegmental area (pnVTA) neurons enriched in prepronociceptin. Fiber photometry recordings during progressive ratio operant behavior revealed pnVTA^Pnoc neurons become most active when mice stop seeking natural rewards. Selective pnVTA^Pnoc neuron ablation, inhibition, and conditional VTA nociceptin receptor (NOPR) deletion increased operant responding, revealing that the pnVTA^Pnoc nucleus and VTA NOPR signaling are necessary for regulating reward motivation. Additionally, optogenetic and chemogenetic activation of this pnVTA^Pnoc nucleus caused avoidance and decreased motivation for rewards. These findings provide insight into neuromodulatory circuits that regulate motivated behaviors through identification of a previously unknown neuropeptide-containing pnVTA nucleus that limits motivation for rewards.

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