Neurotensin expressing lateral hypothalamic neurons alleviate neuropathic and inflammatory pain via Nts signaling

The plague of chronic pain has fueled the U.S. opioid epidemic, creating a critical need for novel pain therapeutics that do not cause dependence. In preclinical models, central treatment with the neuropeptide Neurotensin (Nts) or Nts receptor agonists promotes analgesia, suggesting that augmenting Nts system signaling may be useful to treat pain. However, the lack of clarity of the endogenous Nts mechanisms regulating pain has hindered understanding of how to leverage the Nts system for pain relief. The objective of this study was to determine whether the large population of lateral hypothalamic area (LHA) neurons expressing Nts (referred to as LHA Nts neurons) contribute to analgesia. We hypothesized that activating LHA Nts neurons can alleviate chronic pain in an Nts-dependent manner. To test this, we injected Nts Cre mice in the LHA with AAVs to cre-dependently express either mCherry (Control) or excitatory Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) in LHA Nts neurons, permitting their activation after treatment with the DREADD ligand clozapine N-oxide (CNO, 0.3 mg/kg, i.p.). We then measured how DREADD-activation of LHA Nts neurons impacts acute thermal pain (using the hot plate test), spared nerve injury (SNI) pain or complete Freund’s adjuvant (CFA)-induced inflammatory pain measured using the von Frey test. Activating LHA Nts neurons had no effect on thermal pain responses in naïve mice. By contrast, SNI-induced pain hypersensitivity (indicated by reduced paw withdrawal threshold at 7- and 28-days post-injury) was completely reversed by CNO-mediated activation of LHA Nts neurons compared to VEH control. In CFA-treated mice (a model of inflammatory pain), CNO-activating LHA Nts neurons also relieved pain hypersensitivity, increasing paw withdrawal threshold by 30 mins post treatment that gradually reduced to baseline in 5 hours. However, pretreatment with the brain permeable Nts receptor pan-antagonist SR142948 (1mg/kg, i.p, 30 min before VEH/CNO) blocked CNO-mediated analgesia, indicating that LHA Nts neurons alleviate chronic pain in an Nts-dependent manner. Intriguingly, RNAscope analysis revealed that Nts mRNA expression was increased in the LHA in response to CFA and SNI, suggesting that prolonged pain may increase endogenous Nts, with potential to provide analgesia. Taken together these data suggest that activation of LHA Nts neurons alleviates neuropathic and inflammatory pain via Nts signaling, and augmenting Nts signaling via these neurons could hold promise for treating pain. This research was supported by an award from the National Institute of Neurological Disorders under an award to Geoffroy Laumet (R01-NS121259) and an award from the National Institute of Diabetes and Digestive and Kidney Diseases to Gina Leinninger (R01-DK103808). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.