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Surface expression of GABA(A) receptors in the rat nucleus accumbens is increased in early but not late withdrawal from extended-access cocaine self-administration
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Surface expression of GABA(A) receptors in the rat nucleus accumbens is increased in early but not late withdrawal from extended-access cocaine self-administration

Anthony Purgianto, Jessica A. Loweth, Julia J. Miao, Mike Milovanovic and Marina E. Wolf
Brain research, Vol.1642, pp.336-343
07/01/2016
DOI: 10.1016/j.brainres.2016.04.014
PMCID: PMC4899143
PMID: 27060767

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Abstract

It is well established that cocaine-induced changes in glutamate receptor expression in the nucleus accumbens (NAc) play a significant role in animal models of cocaine addiction. Far less is known about cocaine-induced changes in GABA transmission, despite its importance in regulating NAc output via local interneurons and medium spiny neuron (MSN) axon collaterals (GABA 'microcircuit'). Here we investigated whether GABA(A) receptor surface or total expression is altered following an extended-access cocaine self-administration regimen that produces a time-dependent intensification (incubation) of cue induced cocaine craving in association with strengthening of AMPA receptor (AMPAR) transmission onto MSN. Rats self-administered cocaine or saline (control condition) 6 h/day for 10 days. NAc tissue was obtained and surface proteins biotinylated on three withdrawal days (WD) chosen to span incubation of craving and associated AMPAR plasticity: WD2, WD25 and WD48. Immunoblotting was used to measure total and surface expression of three GABA(A) receptor subunits (alpha 1, alpha 2, and alpha 4) that are strongly expressed in the NAc. We found a transient increase in surface, but not total, expression of the alpha 2 subunit on WD2 from cocaine self-administration, an effect that was no longer observed by WD25. The expression of alpha 1 and alpha 4 subunits was not altered at these withdrawal times. On WD48, when AMPAR transmission is significantly potentiated, we did not find any alteration in GABA(A) receptor surface or total expression. Our findings suggest that the strengthening of AMPAR-mediated glutamate transmission in the NAc is not accompanied by compensatory strengthening of GABAergic transmission through insertion of additional GABA(A) receptors. (C) 2016 Elsevier B.V. All rights reserved.
Life Sciences & Biomedicine Neurosciences Neurosciences & Neurology Science & Technology

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