PROJECT SUMMARY Obesity and chronic pain frequently occur together, which is exacerbated by current pain medications that induce further weight gain. Our limited understanding of the common neurobiological factor(s) underlying obesity and pain is a major knowledge gap preventing design of effective treatment strategies. The neuropeptide Neurotensin (Nts) acts centrally to promote analgesia and weight loss, hence, augmenting Nts signaling could combat comorbid obesity and chronic pain. Yet, the endogenous source of Nts and the signaling mechanisms mediating these effects remained elusive. Over the last funding periods we began to address this knowledge gap by characterizing an endogenous source of Nts that mediates weight loss: Nts-expressing neurons in the lateral hypothalamic area (LHANts neurons). We’ve published that activating LHANts neurons in normal weight mice reduces feeding and body weight via an Nts-dependent mechanism. Our new data show that activating LHANts neurons also alleviates pain. The next challenge is understanding how LHANts neurons elicit these effects to leverage them for treating obesity-pain. This is important because activating all LHANts neurons in normal weight mice reduces weight but fails to do in obese mice. Our studies will explain why the anorectic effect is lost in the obese state and how we can reinstate it. Our pilot data suggest that obesity disrupts Nts expression, which may impair its suppression of feeding/pain. However, our data support that this may be overcome in obese mice by activating LHANts input to the ventral tegmental area (VTA) or the NtsR-expressing neurons there, which can restore anorectic and analgesic effects. We therefore hypothesize that obesity reduces endogenous Nts signaling via the LHANtsVTA pathway, but augmenting this pathway can reduce feeding, weight, and pain in obese mice via Nts-NtsR signaling. Aim 1 defines how expression of Nts, its receptors, and Nts release to the VTA is altered in obesity. Aim 2 combines dual recombinase mice and optogenetics to establish how augmenting the LHANts neuronal input to the VTA restrains feeding and to identify which Nts Receptor isoform mediates these effects. Aim 3 uses the same approach to reveal how LHANts neuronal input to the VTA alleviates pain in obese mice. Our basic neuroscience studies will provide rationale for leveraging the central Nts system to support weight loss and pain relief, and mechanistic evidence for identifying the best cell/receptor target. Ultimately, this knowledge has potential to recognize Nts as a common actionable target for both obesity and pain and could guide development of Nts-based strategies to safely treat and alleviate the suffering of the millions of Americans with obesity-induced pain.