Large conductance potassium (BK) channels are among the most sensitive molecular targets of ethanol and genetic variations in the channel-forming α subunit have been nominally associated with alcohol use disorders. However, whether the action of ethanol at BK α influences the motivation to drink alcohol remains to be determined. To address this question, we first tested the effect of systemically administered BK channel modulators on voluntary alcohol consumption in C57BL/6J males. Penitrem A (blocker) exerted dose-dependent effects on moderate alcohol intake, while paxilline (blocker) and BMS-204352 (opener) were ineffective. Because pharmacological manipulations are inherently limited by non-specific effects, we then sought to investigate the behavioral relevance of ethanol’s direct interaction with BK α by introducing in the mouse genome a point mutation known to render BK channels insensitive to ethanol while preserving their physiological function. The BK α K361N substitution prevented ethanol from reducing spike threshold in medial habenula neurons. However, it did not alter acute responses to ethanol in vivo, including ataxia, sedation, hypothermia, analgesia, and conditioned place preference. Furthermore, the mutation did not have reproducible effects on alcohol consumption in limited, continuous, or intermittent access home cage two-bottle choice paradigms conducted in both males and females. Notably, in contrast to previous observations made in mice missing BK channel auxiliary β subunits, the BK α K361N substitution had no significant impact on ethanol intake escalation induced by chronic intermittent alcohol vapor inhalation. It also did not affect the metabolic and locomotor consequences of chronic alcohol exposure. Altogether, these data suggest that the direct interaction of ethanol with BK α does not mediate the alcohol-related phenotypes examined here in mice.

Background: Alcohol withdrawal-induced hyperalgesia (AWH) is characterized as an increased pain sensitivity observed after cessation of chronic alcohol use. Alcohol withdrawal-induced hyperalgesia can contribute to the negative affective state associated with abstinence and can increase susceptibility to relapse. We aimed to characterize pain sensitivity in mice during withdrawal from two different models of alcohol exposure: chronic drinking in the dark (DID) and the Lieber-DeCarli liquid diet. We also investigated whether treatment with a histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA), could ameliorate AWH in mice treated with the Lieber-DeCarli diet.

Methods: Male and female C57BL/6J mice were used for these studies. In the DID model, mice received bottles of 20% ethanol or water during the dark cycle for 4 h per day on four consecutive days per week for 6 weeks. Peripheral mechanical sensitivity was measured weekly the morning of Day 5 using von Frey filaments. In the Lieber-DeCarli model, mice received ethanol (5% v/v) or control liquid diet for 10 days, along with a single binge ethanol gavage (5 g/kg) or control gavage, respectively, on Day 10. Peripheral mechanical sensitivity was measured during the liquid diet administration and at 24 and 72 h into ethanol withdrawal. An independent group of mice that received the Lieber-DeCarli diet were administered SAHA (50 mg/kg, i.p.) during withdrawal.

Results: Male mice exhibited mechanical hypersensitivity after consuming ethanol for 5 weeks in the DID procedure. In the Lieber-DeCarli model, ethanol withdrawal led to hyperalgesia in both sexes. Suberoylanilide hydroxamic acid treatment during withdrawal from the ethanol liquid diet alleviated AWH.

Conclusions: These results demonstrate AWH in mice after chronic binge drinking in males and after Lieber-DeCarli liquid diet administration in both sexes. Like previous findings in rats, HDAC inhibition reduced AWH in mice, suggesting that epigenetic mechanisms are involved in AWH.

Keywords: alcohol withdrawal; allodynia; binge drinking; epigenetic; pain.

Alternative splicing is a co-transcriptional process that significantly contributes to the molecular landscape of the cell. It plays a multifaceted role in shaping gene transcription, protein diversity, and functional adaptability in response to environmental cues. Recent studies demonstrate that drugs of abuse have a profound impact on alternative splicing patterns within different brain regions. Drugs like alcohol and cocaine modify the expression of genes responsible for encoding splicing factors, thereby influencing alternative splicing of crucial genes involved in neurotransmission, neurogenesis, and neuroinflammation. Notable examples of these alterations include alcohol-induced changes in splicing factors such as HSPA6 and PCBP1, as well as cocaine's impact on PTBP1 and SRSF11. Beyond the immediate effects of drug exposure, recent research has shed light on the role of alternative splicing in contributing to the risk of substance use disorders (SUDs). This is exemplified by exon skipping events in key genes like ELOVL7, which can elevate the risk of alcohol use disorder. Lastly, drugs of abuse can induce splicing alterations through epigenetic modifications. For example, cocaine exposure leads to alterations in levels of trimethylated lysine 36 of histone H3, which exhibits a robust association with alternative splicing and serves as a reliable predictor for exon exclusion. In summary, alternative splicing has emerged as a critical player in the complex interplay between drugs of abuse and the brain, offering insights into the molecular underpinnings of SUDs.

Keywords: Addiction; Alcohol; Alternative splicing; Cocaine; Spliceosome; Splicing factor; Substance use disorder.

Animal genetic models have and will continue to provide important new information about the behavioral and physiological adaptations associated with alcohol use disorder (AUD). This chapter focuses on two models, ethanol preference and drinking in the dark (DID), their usefulness in interrogating brain gene expression data and the relevance of the data obtained to interpret AUD-related GWAS and TWAS studies. Both the animal and human data point to the importance for AUD of changes in synaptic transmission (particularly glutamate and GABA transmission), of changes in the extracellular matrix (specifically including collagens, cadherins and protocadherins) and of changes in neuroimmune processes. The implementation of new technologies (e.g., cell type-specific gene expression) is expected to further enhance the value of genetic animal models in understanding AUD.

Keywords: Alcohol use disorder; Animal genetic models; Brain gene expression; Drinking in the dark; Ethanol preference; GWAS; RNA sequencing; TWAS.

Ethanol (EtOH) has effects on numerous cellular molecular targets, and alterations in synaptic function are prominent among these effects. Acute exposure to EtOH activates or inhibits the function of proteins involved in synaptic transmission, while chronic exposure often produces opposing and/or compensatory/homeostatic effects on the expression, localization, and function of these proteins. Interactions between different neurotransmitters (e.g., neuropeptide effects on release of small molecule transmitters) can also influence both acute and chronic EtOH actions. Studies in intact animals indicate that the proteins affected by EtOH also play roles in the neural actions of the drug, including acute intoxication, tolerance, dependence, and the seeking and drinking of EtOH. The present chapter is an update of our previous Lovinger and Roberto (Curr Top Behav Neurosci 13:31–86, 2013) chapter and reviews the literature describing these acute and chronic synaptic effects of EtOH with a focus on adult animals and their relevance for synaptic transmission, plasticity, and behavior.