Estradiol protects against pain-facilitated fentanyl use via suppression of opioid-evoked dopamine activity in males.

Pain relief is the most frequently reported motivation for opioid misuse, but it remains unclear how pain alters reward pathway function contributing to maladaptive opioid use and whether these neuroadaptations occur in a sex-specific manner. Here, we show that persistent inflammatory pain leads to augmented fentanyl self-administration in male, not female, rats. Wireless in vivo fiber photometry recordings and chemogenetic manipulations indicate that pain-facilitated fentanyl use is mediated by enhanced ventral tegmental area dopamine (VTA) neuron responses during self-administration.

A locus coeruleus to dorsal hippocampus pathway mediates cue-induced reinstatement of opioid self-administration in male and female rats.

Opioid use disorder is a chronic relapsing disorder encompassing misuse, dependence, and addiction to opioid drugs. Long term maintenance of associations between the reinforcing effects of the drug and the cues associated with its intake are a leading cause of relapse. Indeed, exposure to the salient drug-associated cues can lead to drug cravings and drug seeking behavior.