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

Abstract

Background Alcohol use disorder (AUD) commonly 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 treating 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. We 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 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 the 2‐AG synthetic enzyme diacylglycerol lipase (DAGL). Results After 72 h 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 the CB2 antagonist. DO34, Rimonabant, and AM630 exacerbated mechanical hypersensitivity during alcohol withdrawal, causing an earlier onset and persistent hypersensitivity even 1 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 that 2‐AG augmentation represents a novel approach to the treatment of alcohol withdrawal‐associated hyperalgesia and AUD in patients with comorbid pain disorders.

Histone deacetylase inhibitor decreases hyperalgesia in a mouse model of alcohol withdrawal‐induced hyperalgesia

“…Morgan et al. (2022), and Okhuarobo et al. (2020, 2023) found mechanical hypersensitivity in both female and male mice in the tail pressure test at 32 h of withdrawal from 4 days of CIE vapor (Morgan et al., 2022; Okhuarobo et al., 2020, 2023).…”

“…(2022), and Okhuarobo et al. (2020, 2023) found mechanical hypersensitivity in both female and male mice in the tail pressure test at 32 h of withdrawal from 4 days of CIE vapor (Morgan et al., 2022; Okhuarobo et al., 2020, 2023). Sex differences in AWH in these procedures are likely dependent on the method of alcohol exposure (voluntary vs. forced; continuous vs. intermittent), dose of alcohol, duration of exposure, and/or time points during which testing is conducted during withdrawal.…”

“…Administration of ethanol through an intermittent two‐bottle choice voluntary ethanol consumption procedure elicited the development of AWH in male mice (females were not tested), an effect that was attenuated with the antagonism and modulation of sigma—1 and 2 receptors, proteins that serve as chaperones and calcium sensors on the mitochondrial endoplasmic reticulum (Quadir, Tanino, Rohl, et al., 2021; Quadir, Tanino, Sami, et al., 2021). The endocannabinoid system is also involved in AWH in mice, as elevating levels of the endocannabinoid 2‐arachidonoylglycerol alleviated AWH, and inhibiting endocannabinoid receptors exacerbated AWH, following continuous two‐bottle choice ethanol administration (Morgan et al., 2022). Additionally, AWH was also observed in a modified mouse two‐bottle choice model and appeared to be inhibited by delta opioid receptor activation (Alongkronrusmee et al., 2016), which suggests a role for the endogenous opioid system.…”

“…To date, the majority of AWH studies performed in mice have utilized a range of ethanol exposure models, such as chronic intermittent ethanol vapor (CIE), intermittent access two‐bottle choice (IA2BC), and drinking in the dark (DID) (Bergeson et al., 2016; Lopez et al., 2023; Morgan et al., 2022; Okhuarobo et al., 2020, 2023; Quadir, Tanino, Rohl, et al., 2021; Quadir, Tanino, Sami, et al., 2021; Smith et al., 2016, 2017; Tonetto et al., 2023). However, to the best of our knowledge, no one has reported AWH in mice using the Lieber–DeCarli model.…”