GABAergic neurons in the ventrolateral periaqueductal gray mediate fentanyl withdrawal and self-administration in...

Opioid addiction is characterized by compulsive drug seeking and use, accompanied by pain and heightened pain sensitivity (hyperalgesia) during withdrawal, yet the underlying neural mechanisms remain incompletely understood, especially for fentanyl. Using whole-brain Fos mapping and network analysis, we found that the periaqueductal gray is a central hub brain region engaged during fentanyl withdrawal, suggesting a prominent role for this region in withdrawal-associated neural signaling and warranting further examination. The ventrolateral periaqueductal gray (vlPAG) is a key site for nociceptive processing and shows robust neuronal responses during opioid withdrawal, but the role of its GABAergic neurons in fentanyl withdrawal has not been defined, and their contribution to the self-administration of drugs has not been investigated. We combined behavioral, molecular, electrophysiological, and chemogenetic approaches to examine the role of GABAergic vlPAG neurons during fentanyl withdrawal, and their contribution to withdrawal-induced hyperalgesia and fentanyl intake. During withdrawal from fentanyl, we observed increased Fos expression in GABAergic vlPAG neurons and enhanced inhibitory synaptic transmission revealed by channelrhodopsin-assisted circuit mapping, indicating increased GABAergic neuronal activity and inhibitory synaptic activity due to fentanyl use and withdrawal. Chemogenetic inhibition of GABAergic vlPAG neurons alleviated withdrawal-induced hyperalgesia. Male control mice exhibited overall escalating fentanyl self-administration across the final four intravenous self-administration sessions, whereas this escalation was not observed in males whose GABAergic vlPAG neurons were inhibited. Female mice did not exhibit a comparable effect. Together, these findings demonstrate that GABAergic vlPAG neurons are recruited during fentanyl withdrawal and contribute to withdrawal-associated nociceptive hypersensitivity. In addition, modulation of this population affects fentanyl self-administration in a sex-dependent manner. Targeting inhibitory signaling within the vlPAG may represent a strategy to alleviate withdrawal-associated hyperalgesia and limit fentanyl use.