Adolescent Mice Are Resilient to Alcohol Withdrawal-Induced Anxiety and Changes in Indices of Glutamate Function within the Nucleus Accumbens

Abstract

Binge-drinking is the most prevalent form of alcohol abuse and while an early life history of binge-drinking is a significant risk factor for subsequent alcoholism and co-morbid affective disorders, relatively little is known regarding the biobehavioral impact of binge-drinking during the sensitive neurodevelopmental period of adolescence. In adult mice, a month-long history of binge-drinking elicits a hyper-glutamatergic state within the nucleus accumbens (Acb), coinciding with hyper-anxiety. Herein, we employed a murine model of binge-drinking to determine whether or not: (1) withdrawal-induced changes in brain and behavior differ between adult and adolescent bingers; and (2) increased behavioral signs of negative affect and changes in Acb expression of glutamate-related proteins would be apparent in adult mice with less chronic binge-drinking experience (14 days, approximating the duration of mouse adolescence). Adult and adolescent male C57BL/6J mice were subjected to a 14-day binge-drinking protocol (5, 10, 20 and 40% alcohol (v/v) for 2 h/day), while age-matched controls received water. At 24 h withdrawal, half of the animals from each group were assayed for negative affect, while tissue was sampled from the shell (AcbSh) and core (AcbC) subregions of the remaining mice for immunoblotting analyses. Adult bingers exhibited hyper-anxiety when tested for defensive marble burying. Additionally, adult bingers showed increased mGlu1, mGlu5, and GluN2b expression in the AcbSh and PKCε and CAMKII in the AcbC. Compared to adults, adolescent mice exhibited higher alcohol intake and blood alcohol concentrations (BACs); however, adolescent bingers did not show increased anxiety in the marble-burying test. Furthermore, adolescent bingers also failed to exhibit the same alcohol-induced changes in mGlu and kinase protein expression seen in the adult bingers. Irrespective of age, bingers exhibited behavioral hyperactivity in the forced swim test (FST) compared to water drinkers, which was paralleled by an increase in AcbC levels of GluN2b. Thus, a 2-week period of binge-drinking is sufficient to produce a hyper-anxious state and related increases in protein indices of Acb glutamate function. In contrast, adolescents were resilient to many of the effects of early alcohol withdrawal and this attenuated sensitivity to the negative consequences of binge drinking may facilitate greater alcohol intake in adolescent drinkers.

Cue-induced reinstatement of alcohol-seeking behavior is associated with increased CaMKII T286 phosphorylation in the reward pathway of mice

“…Similarly, chronic alcohol produces a 25% increase in kinase activity in rat cortical astrocytes (Smith and Navratilova, 1999). Results from in vivo studies show that forced exposure to alcohol in the drinking water from conception through postnatal day 8, 30, or 90 upregulates CaMKIIα protein in rat cortex (Mahadev et al, 2001) and that binge-like drinking (~6 g/kg/day) increases expression of CaMKII in the nucleus accumbens of adult mice (Lee et al, 2016). We have shown that voluntary alcohol drinking (24-h home-cage) increases total CaMKIIα protein expression in mouse amygdala and nucleus accumbens, and that low-dose operant self-administration (~1 g/kg/day) increases pCaMKII-T286 IR in the amygdala immediately after intake (Salling et al, 2016).…”

“…Higher levels of alcohol exposure induced by binge-like alcohol drinking also increase CaMKII protein expression in the nucleus accumbens (Lee et al, 2016). At the mechanistic level, pharmacological inhibition of CaMKII activity in the amygdala reduces operant alcohol self-administration in C57BL/6J mice (Salling et al, 2016) and alcohol-preferring P-rats (Cannady et al, 2016), indicating that the reinforcing effects of alcohol require CaMKII activation in the amygdala.…”

Negative Affect and Excessive Alcohol Intake Incubate during Protracted Withdrawal from Binge-Drinking in Adolescent, But Not Adult, Mice

“…For example, we demonstrated recently that, in contrast to adult binge-drinking mice that exhibit robust anxiety-like behavior during early (24 h) withdrawal across several conventional behavioral tests of negative affect (e.g., light-dark shuttle box, novel object encounter, Porsolt swim test, elevated plus-maze), adolescent binge-drinking mice resemble water-drinking controls (Lee et al, 2015, 2016). In the present study, we sought to expand these findings to assess the adult consequences of adolescent binge-drinking on negative affect and subsequent alcohol-drinking.…”

mGlu5-dependent modulation of anxiety during early withdrawal from binge-drinking in adult and adolescent male mice

“…Recent work in our laboratory has successfully recapitulated these age-related differences in withdrawal-induced negative affect using a mouse model of voluntary binge-drinking. We have shown that adult alcohol-drinking mice exhibit increased behavioral indices of anxiety during early (24 h) withdrawal (Lee et al, 2016). This elevated anxiety coincides with increased expression of metabotropic glutamate receptor 5 (mGlu5) within the nucleus accumbens shell (AcbSh) during acute withdrawal, as indicated by western blotting (Cozzoli et al, 2012; Obara et al, 2009; Lee et al, 2016, 2017b).…”

“…We have shown that adult alcohol-drinking mice exhibit increased behavioral indices of anxiety during early (24 h) withdrawal (Lee et al, 2016). This elevated anxiety coincides with increased expression of metabotropic glutamate receptor 5 (mGlu5) within the nucleus accumbens shell (AcbSh) during acute withdrawal, as indicated by western blotting (Cozzoli et al, 2012; Obara et al, 2009; Lee et al, 2016, 2017b). In contrast, adolescent drinkers were resilient to both withdrawal-induced hyperanxiety and increased mGlu5 expression within the AcbSh during early withdrawal (Lee et al, 2016, 2017b).…”