Rescue of Infralimbic mGluR(2) Deficit Restores Control Over Drug-Seeking Behavior in Alcohol Dependence

Institute of Psychopharmacology at Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, 68159 Mannheim, Germany, Laboratory of Clinical and Translational Studies, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892, New South Wales Tissue Resource Centre, University of Sydney, 2006 Sydney, Australia, and Abbott Neuroscience Research, 67061 Ludwigshafen, Germany.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 02/2013; 33(7):2794-806. DOI: 10.1523/JNEUROSCI.4062-12.2013
Source: PubMed


A key deficit in alcohol dependence is disrupted prefrontal function leading to excessive alcohol seeking, but the molecular events underlying the emergence of addictive responses remain unknown. Here we show by convergent transcriptome analysis that the pyramidal neurons of the infralimbic cortex are particularly vulnerable for the long-term effects of chronic intermittent ethanol intoxication. These neurons exhibit a pronounced deficit in metabotropic glutamate receptor subtype 2 (mGluR(2)). Also, alcohol-dependent rats do not respond to mGluR(2/3) agonist treatment with reducing extracellular glutamate levels in the nucleus accumbens. Together these data imply a loss of autoreceptor feedback control. Alcohol-dependent rats show escalation of ethanol seeking, which was abolished by restoring mGluR(2) expression in the infralimbic cortex via viral-mediated gene transfer. Human anterior cingulate cortex from alcoholic patients shows a significant reduction in mGluR(2) transcripts compared to control subjects, suggesting that mGluR(2) loss in the rodent and human corticoaccumbal neurocircuitry may be a major consequence of alcohol dependence and a key pathophysiological mechanism mediating increased propensity to relapse. Normalization of mGluR(2) function within this brain circuit may be of therapeutic value.

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Available from: Wolfgang H Sommer, Feb 02, 2014
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    • "Chambers contained an active lever (ethanol), for which presses resulted in a delivery of 0.1 ml of 10% ethanol (fixed ratio 1, FR1), and an inactive lever, for which responses are counted as a measure of non-specific behavioral activity, but no programmed events occurred. The FR1 schedule was chosen because of our previous studies and also a large majority of other works on alcohol-dependent rats using the same procedure (Roberts et al. 2000; O'Dell et al. 2004; Meinhardt et al. 2013). Wistar rats were trained 5 days a week in 30-minute sessions for 10 weeks to self-administer a solution of 10% ethanol, using a sucrose fading procedure. "
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    • "Another possibility is that THIP may have altered adaptive learning processes governed by the ILC. Existing research has mostly focused on the role of the ILC in drug and ethanol extinction learning or seeking in animals that either are dependent or have had extensive drug experience [37] [39] [57] [58]. Collectively, these studies predominantly suggest that increased activity in the ILC is associated with enhanced extinction learning and reduced drug and ethanol seeking. "
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