Relationships between Mu-opioid receptors brain expression and depressive-like behaviors in animal models: A systematic review.

Abstract

The endogenous opioid system is highly expressed in many species, including mammals, and is responsible for a variety of physiological and behavioral processes. Mu-opioid receptors (MORs) attract scientific interest due to their involvement in rewarding, decision-making, and cognitive processes, domains prominently disrupted in psychiatric conditions such as Major depressive disorder (MDD). Historically, opioids were among the earliest treatments for depression, but their use declined in favor of antidepressants with lower addictive potential. However, with growing insights into strategies to minimize misuse, MORs remain a promising target for developing novel treatment approaches for MDD. The current manuscript aims to systematically review preclinical studies examining the relationships between depressive-like behaviors and µ-opioid receptors, with a focus on identifying key brain regions involved.