Phospho-CREB Regulation on NMDA Glutamate Receptor 2B and Mitochondrial Calcium Uniporter in the Ventrolateral Periaqueductal Gray Controls Chronic Morphine Withdrawal in Male Rats

Abstract

Opioid use disorder (OUD) is a chronic disease of the brain, and it currently continues at crisis proportions in the United States. Opioid physical withdrawal is a major driver of compulsive drug-taking behavior, triggering short-term relapse of opioid addiction. Early pharmacological evidence shows that midbrain periaqueductal gray (PAG) plays an important role in morphine withdrawal (MW). However, we still know few details about the underlying molecular mechanisms. Improving our understanding of such mechanisms will enable increasingly safe and effective treatments for patients with OUD. Here, MW was induced by the naloxone precipitation after chronic intraperitoneal administration of morphine for a period of 5 d in Sprague Dawley male rats. MW increased phosphorylation of cAMP response element binding protein (pCREB, a primary marker of CREB functional activation), NMDA glutamate receptor 2B subunit (NR2B), and mitochondrial calcium uniporter (MCU) within the ventrolateral PAG (vlPAG). Inhibition of pCREB, NR2B, or MCU within this brain region reduced the severity of MW. Chromatin immunoprecipitation (ChIP) assay and luciferase report assay demonstrated that pCREB mediated the transcription of the Grin2b (glutamate ionotropic receptor NMDA type subunit 2B, encoding NR2B) and Ccdc109a (encoding MCU) genes. These findings describe the role of pCREB in Grin2b and Ccdc109a gene transcription levels in the vlPAG during MW. The study may provide a novel therapeutic approach for OUD.