2-Arachidonoylglycerol-mediated endocannabinoid signaling modulates mechanical hypersensitivity associated with alcohol withdrawal in mice

Background: Alcohol use disorder (AUDs) commonly co-occurs in patients with chronic pain, and a major barrier to achieving abstinence and preventing relapse is the emergence of hyperalgesia during alcohol withdrawal. Elucidating novel therapeutic approaches to target hyperalgesia associated with alcohol withdrawal could have important implications for the treatment of AUD. Here we examined the role of 2-arachidonoylglycerol (2-AG)-mediated endocannabinoid (eCB) signaling in the regulation of hyperalgesia associated with alcohol withdrawal in mice and tested the hypothesis that pharmacological augmentation of 2-AG signaling could reduce hyperalgesia during withdrawal.

Methods: Male and female C57BL/6J mice were tested during withdrawal from a continuous access two-bottle choice (2BC) paradigm to investigate the how eCB signaling modulates mechanical and thermal sensitivity during withdrawal. Mice were pretreated with the monoacylglycerol lipase (MAGL) inhibitor JZL184 to elevate levels of 2-AG. Rimonabant or AM630 were given to block CB₁ and CB₂ receptor activity, respectively. DO34 was given to reduce 2-AG by inhibiting 2-AG synthetic enzyme diacylglycerol lipase (DAGL).

Results: After 72 hours of withdrawal, male and female mice exhibited increased mechanical but not thermal, hypersensitivity, which normalized by 7 days. This effect was reversed by pretreatment with JZL184. The effects of JZL184 were prevented by coadministration of either the CB₁ or CB₂ antagonist. DO34, Rimonabant, and AM630 exacerbated mechanical hypersensitivity during alcohol withdrawal, causing an earlier onset and persistent hypersensitivity even one week into withdrawal.

Conclusions: Our findings demonstrate the critical role of 2-AG signaling in the bidirectional regulation of mechanical sensitivity during alcohol withdrawal, with enhancement of 2-AG levels reducing sensitivity, and inhibition of 2-AG signaling exacerbating sensitivity. These data suggest 2-AG augmentation could represent a novel approach to the treatment of alcohol withdrawal-associated hyperalgesia and AUD in patients with comorbid pain disorders.