Converging Effects of Chronic Pain and Binge Alcohol Consumption on Anterior Insular Cortex Neurons Projecting to the Dorsolateral Striatum in Male Mice

Abstract

Chronic pain and alcohol use disorder (AUD) are highly comorbid, and patients with chronic pain are more likely to meet the criteria for AUD. Evidence suggests that both conditions alter similar brain pathways, yet this relationship remains poorly understood. Prior work shows that the anterior insular cortex (AIC) is involved in both chronic pain and alcohol use disorder. However, circuit-specific changes elicited by the combination of pain and alcohol use remain understudied. The goal of this work was to elucidate the converging effects of binge alcohol consumption and chronic pain on AIC neurons that send projections to the dorsolateral striatum (DLS). Here, we used the Drinking-in-the-Dark (DID) paradigm to model binge-like alcohol drinking in mice that underwent spared nerve injury (SNI), after which whole-cell patch-clamp electrophysiological recordings were performed in acute brain slices to measure intrinsic and synaptic properties of AIC-DLS neurons. In male, but not female mice, we found that SNI mice with no prior alcohol exposure consumed less alcohol compared to sham mice. Electrophysiological analyses showed that AIC-DLS neurons from SNI-alcohol male mice displayed increased neuronal excitability and increased frequency of miniature excitatory postsynaptic currents. However, mice exposed to alcohol prior to SNI consumed similar amounts of alcohol compared to sham mice following SNI. Together, our data suggest that the interaction of chronic pain and alcohol drinking have a direct effect on both intrinsic excitability and synaptic transmission onto AIC-DLS neurons in mice, which may be critical in understanding how chronic pain alters motivated behaviors associated with alcohol.Significant StatementWe currently have a poor understanding of how the brain processes the interaction of pain and alcohol. Commonly, pain is associated with increased alcohol consumption. However, our data indicate that nerve-injury pain reduces alcohol consumption in mice with no prior exposure to alcohol. Only in these pain-alcohol mice, we found that a specific population of neurons in the anterior insular cortex (AIC) displayed an increase in excitability. Together, this suggests that pain and alcohol interaction can sensitize an AIC circuit that could be targeted for attenuating alcohol intake for treating alcohol-use disorders.