Alcohol dependence modifies brain networks activated during abstinence and reaccess: a c-fos-based analysis in mice

Abstract

High-level alcohol consumption causes neuroplastic changes in the brain that lead to negative affective and somatic symptoms when alcohol is withdrawn, promoting relapse drinking. We have some understanding of these plastic changes in defined brain circuits and cell types, but unbiased approaches are needed to explore broader patterns of adaptations. Here, we employed whole-brain c-fos mapping and network analysis to assess how brain-wide patterns of neuronal activity are altered during acute alcohol abstinence and reaccess in a well-characterized model of alcohol dependence. Mice underwent four cycles of chronic intermittent ethanol vapor exposure (CIE) with alternating weeks of voluntary alcohol drinking, and a subset of mice underwent forced swim stress (FSS) prior to drinking sessions to further escalate alcohol consumption. After four CIE cycles, brains were collected from mice in each group either 24 hours (abstinence) or immediately following a one-hour period of alcohol reaccess. Brains from CIE mice during acute abstinence displayed widespread neuronal activation relative to those from AIR mice, independent of FSS, and this increase in c-fos was reversed by reaccess drinking. For network analysis, mice were then classified as high or low drinkers (HD or LD). We computed Pearson correlations for all pairs of brain regions and used graph theoretical methods to identify changes in network properties associated with high-drinking behavior. Network modularity, a measure of network segregation into communities, was increased in HD mice after alcohol reaccess relative to abstinence. Within-community strength and diversity measures were computed for each region and condition, and highly coactive regions were identified. One high-diversity region, the cortical amygdala (COA), was further interrogated using a chemogenetic approach. COA silencing in CIE mice reduced voluntary drinking, validating our network analysis and indicating that this region may play an important but underappreciated role in alcohol dependence.

Hyperconnectivity of Two Separate Long-Range Cholinergic Systems Contributes to the Reorganization of the Brain Functional Connectivity during Nicotine Withdrawal in Male Mice

“…Changes in the patterns of neuronal coreactivity, also called the functional connectome, can be observed in humans and rodents during withdrawal from nicotine (Hobkirk et al, 2018;Cheng et al, 2019;Kimbrough et al, 2021). Whole-brain imaging with single-cell resolution using light-sheet microscopy on cleared brains (Renier et al, 2014(Renier et al, , 2016Ueda et al, 2020) has made the study of brain-wide functional networks at single-cell resolution possible by looking at the expression of the immediate-early gene Fos (Wheeler et al, 2013;Vetere et al, 2017;Kimbrough et al, 2020;Smith et al, 2021;Roland et al, 2022), a marker of neuronal reactivity, which integrates neuronal activation during a period of 1-2 h, an ideal temporal window to characterize nicotine withdrawal. Using this approach, we have found that mice in withdrawal exhibit a pronounced increase in coactivation patterns throughout the brain (Kimbrough et al, 2020(Kimbrough et al, , 2021.…”