Pharmacological inhibition of glycogen synthase kinase 3 increases operant alcohol self-administration in a manner associated with altered pGSK-3β, protein interacting with C kinase and GluA2 protein expression in the reward pathway of male C57BL/6J mice

Abstract

Glycogen synthase kinase 3 (GSK-3) is a constitutively active serine-threonine kinase that regulates numerous signaling pathways and has been implicated in neurodegenerative and neuropsychiatric diseases including Alzheimer's, Parkinson's, schizophrenia, and bipolar disorder. Evidence indicates that alcohol exposure increases GSK-3β (ser9) phosphorylation (pGSK-3β); however, few studies have investigated whether GSK-3 regulates the positive reinforcing effects of alcohol, which drive repetitive drug use. This study aimed to address the potential role of GSK-3 in alcohol self-administration by investigating whether direct pharmacological inhibition of GSK-3 alters the positive reinforcing effect of alcohol in mice. Male C57BL/6J mice were trained to lever press on a fixed-ratio 4 schedule of sweetened alcohol or sucrose-only reinforcement in operant conditioning chambers. The GSK-3 inhibitor CHIR 99021 trihydrochloride (0-10 mg/kg, ip) was injected 45-min prior to self-administration sessions in a counterbalanced design. After completion of the self-administration dose-effect curve, potential locomotor effects of the GSK-3 inhibitor were assessed. To determine molecular efficacy, CHIR 99021 (10 mg/kg, ip) was evaluated on pGSK-3β, GSK-3β PICK1, and AMPA receptor GluA2 subunit protein expression in amygdala, nucleus accumbens (NAcb), and frontal cortex in the absence of alcohol. CHIR 99021 (10 mg/kg) dose-dependently increased alcohol reinforced responding with no effect on sucrose self-administration or locomotor activity. CHIR 99021 (10 mg/kg) significantly decreased pGSK-3β expression in all brain regions tested, reduced PICK1 and increased GluA2 total expression only in the NAcb. We conclude that GSK-3 inhibition increased the reinforcing effects of alcohol in mice. This was associated with reduced pGSK-3β and PICK1, and increased GluA2 protein expression. Given prior results showing that AMPA receptor activity regulates alcohol selfadministration, we propose that signaling through the GSK-3 / PICK1 / GluA2 molecular pathway drives the positive reinforcing effects of the drug, which are required for abuse liability.

Alcohol drinking exacerbates neural and behavioral pathology in the 3xTg-AD mouse model of Alzheimer's disease

“…For example, glycogen synthase kinase-3 (GSK3) is critical to the hyperphosphorylation of Tau, has been linked to increased Aβ production, and Aβ mediated cell death (Avila et al, 2012; de la Monte et al, 1999; Hernandez, 2013; Hooper, Killick, & Lovestone, 2008). GSK3 also regulates the positive reinforcing effects of alcohol and is sensitive to acute alcohol treatment and withdrawal (Faccidomo et al, 2019; Neasta, Ben Hamida, Yowell, Carnicella, & Ron, 2011; van der Vaart et al, 2018). Additional proteins in the mTOR/Akt pathway such as Akt, PTEN, p70S6K, RPS6, ERK 1/2 and mTOR are targets of interest in understanding the pathogenesis of AD as this cell signaling pathway is an important modulator of cell growth and macroautophagy maintaining a balance critical to the health of cells (Norambuena et al, 2017; Pei & Hugon, 2008; Ro, Cao, Otto, & Kim, 2010).…”

Inhibition of AMPA receptors (AMPARs) containing transmembrane AMPAR regulatory protein γ‐8 with JNJ‐55511118 shows preclinical efficacy in reducing chronic repetitive alcohol self‐administration

“…In the experiments described here, JNJ‐55511118 was administered to male and female C57BL/6J mice prior to operant self‐administration sessions where lever‐press responses were reinforced by presentation of sweetened alcohol (9% EtOH v/v + 2% sucrose w/v) or sucrose‐only (2% w/v) as a behavior‐matched nondrug control. This well‐characterized method (Faccidomo et al, 2009, 2015, 2016, 2019; Salling et al, 2016, 2017) provides a parallel behavior‐matched nondrug control, which is critical for evaluating the behavioral specificity of changes in alcohol self‐administration; thus, altered sucrose‐only self‐administration as a control can reveal nonspecific motor, memory, or general reward‐related disruption. In general, use of sweetened alcohol solutions in preclinical research also provides enhanced face validity to the binge‐intoxication stage of alcohol addiction in humans where sweeteners are commonly added to alcohol (Crabbe et al, 2011).…”

Calcium-Permeable AMPA Receptor Activity and GluA1 Trafficking in the Basolateral Amygdala Regulate the Positive Reinforcing Effects of Alcohol

“…NASPM also dose-dependently reduced alcohol dose (g/kg) consumed ( Fig 2D ). NASPM had no effect on the number of head pokes per reinforcer ( Fig 2E ), which indicates the absence of nonspecific changes in general consummatory behavior (e.g., 29 ). Mice emitted 57.3±20 (MEAN±SEM) total responses on the inactive lever (31% of total responding) under aCSF control conditions, and this was unchanged by NASPM.…”

“…Self-administration sessions were conducted in computer controlled two-lever operant conditioning chambers (Med Associates, St. Albans, VT) as previously reported 14,[28][29][30][31]39,40 .…”

“…Sweetened solutions have been used in preclinical alcohol research for many years and offer a variety of advantages over unsweetened alcohol including enhanced face validity to the human condition where sweeteners are commonly added to alcohol during the initial binge-intoxication stage of addiction (reviewed by 27 ). Here, we utilized a well-characterized method that compares operant self-administration of sweetened alcohol (ethanol 9% v/v + sucrose 2% w/v) to parallel behavior-matched sucroseonly (sucrose 2% w/v) controls 14,[28][29][30][31] . Availability of a non-drug behavior-matched control is important when evaluating the role of CP-AMPARs in alcohol self-administration because the BLA sends numerous glutamatergic projections to reward-related brain regions including the (which was not certified by peer review) is the author/funder.…”