Gregus, A. | Search bioRxiv

bioRxiv2024

Chronic intermittent ethanol produces nociception through endocannabinoid-independent mechanisms in mice

Alcohol use disorder (AUD) affects millions of people and represents a significant health and economic burden. Pain represents a frequently under-treated aspect of hyperkatifeia during alcohol withdrawal, yet to date no drugs have received FDA approval for the treatment of this indication in AUD patients. This study aims to evaluate the potential of targeting bioactive lipid signaling pathways as a therapeutic approach for treating alcohol withdrawal-related pain. We utilized a chronic intermittent ethanol (CIE) vapor exposure model in C57BL/6J mice of both sexes to establish alcohol dependence, and demonstrated that CIE mice developed robust tactile allodynia and thermal hyperalgesia during withdrawal that was independent of prior blood alcohol levels. Next, we evaluated four drugs for their efficacy in reversing tactile allodynia during abstinence from CIE using a cross-over treatment design that included FDA-approved naltrexone as well as commercially available inhibitors targeting inflammatory lipid signaling enzymes including fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MAGL), and 15-Lipoxygenase (LOX). None of these compounds produced significant therapeutic benefit in reversing established CIE-induced tactile allodynia, despite attenuating pain-like behaviors at these doses in other chronic pain models. Additionally, we assessed plasma endocannabinoid levels in both sexes during withdrawal. We found that there is an inherent sex difference in the endogenous anti-inflammatory endocannabinoid tone in naive mice and CIE treatment affected endocannabinoids levels in female mice only. These findings underscore the need to better understand the driving causes of AUD induced pain and to develop novel therapeutic approaches to mitigate pain in AUD patients.

pharmacology and toxicology↗

bioRxiv2024

Medial prefrontal cortical neurotransmitters reactive to relapse-promoting and relapse-suppressing cues in rats trained to self-administer cocaine or alcohol

Environmental cues conditioned to signal drug availability (S+) or omission (S-) activate specific neurons (neuronal ensembles/engram cells) within the medial prefrontal cortex (mPFC) to promote and suppress drug relapse in rats. However, the neurochemical source of such cue-specific activation remains unknown. In this study, we determined extracellular neurotransmitter fluctuations reactive to S+ vs. S- in the infralimbic (IL) and prelimbic (PL) cortices of male rats trained to lever-press for cocaine or alcohol self-administration. In cocaine- or alcohol-trained rats exposed to S+, no significant neurotransmitter fluctuations were observed in IL or PL. In cocaine-trained rats exposed to S-, glutamate, serotonin, taurine and adenosine were increased in PL but not in IL. In alcohol-trained rats exposed to S-, glutamate was increased, while dopamine and GABA were decreased, in IL but not in PL. Although S+ reactive neurotransmitters driving neuronal activation in mPFC remains to be elucidated, glutamate is likely the source of such activation by S- in rats trained to self-administer cocaine or alcohol. While drugs used for self-administration and cue-conditioning appear to dictate the type and anatomical specificity of S- evoked neurotransmission within mPFC, glutamate may serve as a common therapeutic target to mimic relapse-suppression by S- across cocaine and alcohol use disorders (CUD and AUD). In contrast, serotonin, taurine and adenosine may serve as the targets in CUD, while dopamine and GABA may serve as the targets in AUD.

neuroscience↗