Symptoms of withdrawal from chronic alcohol use are a driving force for relapse in alcohol dependence. Thus, uncovering molecular targets to lessen their severity is key to breaking the cycle of dependence. Using the nematode , we tested whether one highly conserved ethanol target, the large-conductance, calcium-activated potassium channel (known as the BK channel or Slo1), modulates ethanol withdrawal. Consistent with a previous report, we found that displays withdrawal-related behavioral impairments after cessation of chronic ethanol exposure. We found that the degree of impairment is exacerbated in worms lacking the worm BK channel, SLO-1, and is reduced by selective rescue of this channel in the nervous system. Enhanced SLO-1 function, via gain-of-function mutation or overexpression, also dramatically reduced behavioral impairment during withdrawal. Consistent with these results, we found that chronic ethanol exposure decreased SLO-1 expression in a subset of neurons. In addition, we found that the function of a distinct, conserved Slo family channel, SLO-2, showed an inverse relationship to withdrawal behavior, and this influence depended on SLO-1 function. Together, our findings show that modulation of either Slo family ion channel bidirectionally regulates withdrawal behaviors in worm, supporting further exploration of the Slo family as targets for normalizing behaviors during alcohol withdrawal.

Repeated cycles of intoxication and withdrawal enhance the negative reinforcing properties of alcohol and lead to neuroadaptations that underlie withdrawal symptoms driving alcohol dependence. Pharmacotherapies that target these neuroadaptations may help break the cycle of dependence. The sigma-1 receptor (σ1R) subtype has attracted interest as a possible modulator of the rewarding and reinforcing effects of alcohol. However, whether the sigma-2 receptor, recently cloned and identified as transmembrane protein 97 (σ2R/TMEM97), plays a role in alcohol-related behaviors is currently unknown. Using a Caenorhabditis elegans model, we identified two novel, selective σ2R/Tmem97 modulators that reduce alcohol withdrawal behavior via an ortholog of σ2R/TMEM97. We then show that one of these compounds blunted withdrawal-induced excessive alcohol drinking in a well-established rodent model of alcohol dependence. These discoveries provide the first evidence that σ2R/TMEM97 is involved in alcohol withdrawal behaviors and that this receptor is a potential new target for treating alcohol use disorder.

The severity of withdrawal from chronic ethanol is a driving force for relapse in alcohol dependence. Thus, uncovering molecular changes that can be targeted to lessen withdrawal symptoms is key to breaking the cycle of dependence. Using the model nematode Caenorhabditis elegans, we tested whether one highly conserved ethanol target, the BK potassium channel, may play a major role in alcohol withdrawal. Consistent with a previous report, we found that C. elegans displays behavioral impairment during withdrawal from chronic ethanol that can be reduced by low-dose ethanol. We discovered that the degree of impairment is exacerbated in worms lacking the BK channel, SLO-1, and is alleviated by selective rescue of the BK channel in the nervous system. Conversely, behavioral impairment during withdrawal was dramatically lower in worms with BK channel function enhanced via gain-of-function mutation or overexpression. Consistent with these results, we found that chronic ethanol exposure decreased BK channel expression in a subset of neurons. In addition, we found that a distinct, conserved large-conductance potassium channel, SLO-2, showed the inverse functional relationship, influencing withdrawal behavior via a SLO-1 channel-dependent mechanism. Our findings demonstrate that withdrawal symptoms in C. elegans are mechanistically explained in part by a functional imbalance in the nervous system associated with a reduction in SLO-1 channel expression. Therefore, selective modulation of Slo family ion channel activity may represent a novel therapeutic approach to explore for normalizing behaviors during alcohol withdrawal.ARTICLE SUMMARYPeople addicted to alcohol maintain maladaptive drinking patterns in part to avoid the terrible symptoms of withdrawal. It is unclear whether any single molecule may be genetically modified to alleviate withdrawal symptoms. Here, we discover that for the nematode C. elegans, upregulating function of the conserved BK potassium channel SLO-1 prevents alcohol withdrawal symptoms. Conversely, downregulating SLO-1 channel function makes withdrawal worse. Moreover, we identify an inverse relation between SLO-1 and a second type of BK channel named SLO-2 in the severity of withdrawal. The BK channel thus represents an attractive molecular target to consider for alleviating alcohol withdrawal symptoms.Statement on data and reagent availabilityStrains are available upon request or through the Caenorhabditis Genetics Center.