The behavioral and molecular mechanisms underlying excessive alcohol drinking behavior and relapse are not fully understood and are vital for mapping the pathological course of alcoholism/dependence. Recent evidence indicates that chronic alcohol consumption leads to strengthening of excitatory synapses in key limbic brain regions that mediate reward and drinking behavior. This strengthening of synapses is highly dependent on the actions and synaptic incorporation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs);fast action ion channel receptors that are activated by the excitatory neurotransmitter glutamate. However, the mechanistic role of enhanced AMPAR signaling in alcohol reinforcement and alcohol-seeking behavior remains unclear. Thus, the proposed experiments in this application seek to elucidate the behavioral and molecular mechanisms that underlie AMPAR-mediated increases in operant alcohol-self-administration and potentiated relapse-like behavior using a preclinical model of high alcohol consumption, the alcoholpreferring (P-) rat. Preliminary data indicate that enhancement of AMPAR signaling by pretreatment with aniracetam (positive allosteric modulator of AMPARs), increases operant alcohol self-administration and potentiates cue-induced reinstatement to alcohol seeking in P-rats, suggesting that enhanced AMPAR activity may be critical in facilitating increased drinking and susceptibility to relapse. Experiments will further characterize the role of enhanced AMPAR signaling in modulating operant self-administration and relapse-like behavior. AMPAR activity can be potentiated by post-translational modification (e.g. phosphorylation of the AMPAR GluR1 subunit amino acid residue 831;pGluR1{831}). Using immunohistochemistry techniques, experiments will map neuroadaptive changes in pGluR1{831} subunits in limbic brain regions after a history of alcohol self-administration or exposure to an alcohol-related cue during cue-induced reinstatement to determine brain regions that may influence enhanced AMPAR-mediated increases in self-administration and alcohol-seeking. We predict to see changes in pGluR1{831} in the nucleus accumbens (self-administration studies) or amygdala (reinstatement studies), and these regions will be targeted to investigate functional neuroanatomical control of enhanced AMPAR activity-mediated facilitation of alcohol self-administration and seeking behavior using aniracetam. Control experiments will address neuroanatomical and reinforcer specificity and non-specific locomotor effects. Lastly we will determine if aniracetam-induced increases in alcohol self-administration and seeking behavior are dependent on Ca2+/calmodulin-dependent protein kinase II (CamKII;known to phosphorylate GluR1 and enhance AMPAR activity) by blocking aniracetam-induced effects during self administration and reinstatement sessions with KN93 (CamKII inhibitor). Key findings from these studies will provide novel insight into AMPAR-related mechanisms in excessive alcohol drinking behavior and vulnerability to relapse.
Alcoholism is a major public health issue throughout the world. It remains unclear how the changes that occur in the brain after long-term alcohol use can lead to increased alcohol consumption and subsequent addiction. This work will focus on characterizing the role of neurotransmitter receptors in increased drinking behavior to better understand the underlying causes of alcohol addiction.
