Tucciarone, J. M. | Search bioRxiv

bioRxiv2026

Local control of dopamine release in nucleus accumbens gates opioid withdrawal aversion

The opioid crisis has emphasized the need for more effective treatments for opioid use disorder (OUD)1-3, which is characterized by habitual opioid use to avoid withdrawal symptoms4,5. Both physical and affective symptoms contribute to opioid withdrawal yet whether different neural mechanisms mediate these different symptom domains and contribute distinctly to opioid relapse is unknown. While neurons expressing mu opioid receptors (MORs) gate opioids reinforcing effects6-8 by increasing dopamine (DA) release in nucleus accumbens (NAc), sharp decreases in NAc DA release are associated with withdrawal9-11, the cellular and circuit mechanisms of which are unknown. Here we describe an unusual population of evolutionarily-conserved MOR+ neurons in the NAc expressing the transcription factor Tshz1. Increased activity in these neurons is required for withdrawal aversion learning. Deletion of MORs in Tshz1 neurons prevented withdrawal-induced decreases in DA release and affective aversion, but not physical symptoms associated with withdrawal. Pharmacological activation of mGluR8, which is preferentially expressed in Tshz1 neurons, reduced withdrawal aversion. Thus, by dissociating the circuit mechanisms contributing to the physical and affective components of opioid withdrawal focusing on the critical role of Tshz1 neurons, we have identified a novel druggable target with therapeutic potential for treating key OUD withdrawal symptoms.

neuroscience↗

bioRxiv2025

Habenular μ-opioid receptor knockout and chronic systemic receptor blockade promote negative affect and heighten nociceptive sensitivity

The -opioid receptor (MOR), a subtype of opioid G protein-coupled receptor, is expressed in multiple brain circuits and is particularly enriched in the habenula, a small epithalamic structure implicated in aversive states. MOR dysfunction has been linked to several psychiatric and nociceptive disorders. Identifying the key brain regions mediating the behavioral consequences of disrupted MOR signaling can shed light on the role of the opioid system in mood and pain regulation. In this study, we administered methocinnamox (MCAM), a long-acting, pseudo-irreversible MOR antagonist, acutely or chronically to adult C57BL/6J mice. A comprehensive behavioral battery was used to assess affective, social, and pain behavior. A single MCAM administration (10 mg/kg, s.c.) did not alter baseline behavior, but blocked opioid-induced analgesia, suggesting that basal {micro}-opioid tone does not contribute to these behaviors. In contrast, chronic MCAM administration (10 mg/kg, s.c., 3x/week for 4 weeks) led to increased anxiety-like behavior and decreased sociability, as well as enhanced mechanical allodynia and thermal hyperalgesia. Remarkably, selective knockout of habenular MORs in adult Oprm1fl/fl mice reproduced key features of the chronic MCAM phenotype, including anxiety-like behavior and mechanical hyperalgesia. Together, these findings reveal that sustained inhibition of MOR signaling disrupts affective and nociceptive processing and highlight the habenula as a node mediating key behavioral deficits of disrupted opioid signaling.

neuroscience↗