CaMKIIα-GluA1 Activity Underlies Vulnerability to Adolescent Binge Alcohol Drinking

Abstract

Background: Binge drinking during adolescence is associated with increased risk for developing alcohol use disorders; however, the neural mechanisms underlying this liability are unclear. In this study, we sought to determine whether binge drinking alters expression or phosphorylation of 2 molecular mechanisms of neuroplasticity, calcium/calmodulin-dependent kinase II alpha (CaMKIIα) and the GluA1 subunit of AMPA receptors (AMPARs) in addiction-associated brain regions. We also asked whether activation of CaMKIIα-dependent AMPAR activity escalates binge-like drinking.

Methods: To address these questions, CaMKIIαT286 and GluA1S831 protein phosphorylation and expression were assessed in the amygdala and striatum of adolescent and adult male C57BL/6J mice immediately after voluntary binge-like alcohol drinking (blood alcohol >80 mg/dl). In separate mice, effects of the CaMKIIα-dependent GluA1S831 phosphorylation (pGluA1S831 )-enhancing drug tianeptine were tested on binge-like alcohol consumption in both age groups.

Results: Binge-like drinking decreased CaMKIIαT286 phosphorylation (pCaMKIIαT286 ) selectively in adolescent amygdala with no effect in adults. Alcohol also produced a trend for reduced pGluA1S831 expression in adolescent amygdala but differentially increased pGluA1S831 in adult amygdala. No effects were observed in the nucleus accumbens or dorsal striatum. Tianeptine increased binge-like alcohol consumption in adolescents but decreased alcohol consumption in adults. Sucrose consumption was similarly decreased by tianeptine pretreatment in both ages.

Conclusions: These data show that the adolescent and adult amygdalae are differentially sensitive to effects of binge-like alcohol drinking on plasticity-linked glutamate signaling molecules. Tianeptine-induced increases in binge-like drinking only in adolescents suggest that differential CaMKIIα-dependent AMPAR activation may underlie age-related escalation of binge drinking.

Keywords: Adolescence; Alcohol; Binge; CaMKII; GluA1.

Figure 1. Adolescent and adult mice achieve binge levels of alcohol consumption in a daily limited access procedure

(A) Timeline of binge-like drinking procedure. Adolescent and adult alcohol (B) and water (C) intake did not differ over two weeks of daily drinking sessions. (D) Alcohol drinking did not alter body weight in either adolescents or adults. (E) Blood ethanol concentration did not differ between alcohol-drinking adolescent and adult mice immediately following the drinking session on the last drinking day. Dashed line indicates the NIAAA criteria for a binge drinking session (≥ 80 mg/dL).

Figure 2. CaMKII phosphorylation is altered by two weeks of daily binge-like alcohol drinking in the adolescent but not adult amygdala

(A) Phospho-CaMKIIα_T286 (pCaMKIIα_T286) was decreased in the amygdala of adolescent mice exposed to alcohol in the daily binge drinking procedure (*p <0.05). (B) Total CaMKIIα expression was not different between alcohol and water drinking adolescents. (C) pCaMKIIα_T286 did not differ in the amygdala of adult mice exposed to alcohol or water in the daily binge drinking procedure. (D) tCaMKIIα expression was also not altered by alcohol treatment in adults.

Figure 3. Differential effects of a two-week history of daily binge alcohol exposure on GluA1 phosphorylation in the adolescent and adult amygdala

(A) Phospho-GluA1_S831 (pGluA1_S831) had a tendency to decrease in the amygdala of adolescent mice exposed to alcohol in the daily binge drinking procedure (#p <0.1). (B) Total GluA1 expression was not different between alcohol and water drinking adolescents. (C) pGluA1_S831 was increased in the amygdala of adult mice exposed to alcohol in the daily binge drinking procedure (*p =0.05). (D) Total GluA1 expression was not different between alcohol and water drinking adults.

Figure 4. Tianeptine pretreatment alters alcohol, but not sucrose, intake in opposite directions in adolescent and adult male mice

(A) Timeline of tianeptine pretreatment binge drinking procedure. (B) Tianeptine dose-dependently increased alcohol intake in adolescent mice but decreased alcohol intake in adult mice (*p <0.05). (C) Tianeptine comparably decreased sucrose intake in adolescent and adult mice. The open-field locomotor behavior of adolescent (D) and adult (E) mice injected with the effective dose of tianeptine in each age did not differ from age-matched controls injected with vehicle. Adolescent (F) and adult (G) mice pretreated with tianeptine did not differ in blood alcohol concentration following an acute alcohol injection.