Ethanol (alcohol) dependence is a chronic relapsing behavioral/brain disorder characterized by an inability to self-regulate alcohol intake. Neuroadaptation (i.e., changes in gene expression) within brain regions that mediate ethanol's reinforcing properties may be associated with loss of control over ethanol intake, or binge drinking. We will investigate the GABAergic systems of the anterior and posterior ventral tegmental area (VTA), nucleus accumbens (NAcc) shell, and medial prefrontal cortex (mPFC). Evidence suggests that the GABAergic systems in each of these structures has at least some role in the modulation of ethanol self-administration, but the role of these structures in the modulation of voluntary binge-like ethanol intake has not been examined. The goals of the current proposal are to 1) investigate the role of GABAergic receptor systems in the anterior and posterior VTA, NAcc shell, and mPFC in the modulation of binge-like ethanol intake using a recently developed limited access mouse model, and to 2) ascertain whether GABAA subunit, GABAB subtype, or other GABA-associated gene expression in the above brain structures is altered by daily binge-like ethanol intake using the same mouse model.
In aims 1 and 2, mice will receive anterior or posterior intra-VTA, -NAcc shell, or -mPFC microinjections of zolpidem or 4,5,6,7-tetrahydroisoxazolo-[5,4- c]pyridin-3-ol (THIP), known to target synaptic and extrasynaptic GABAA receptors respectively, or baclofen, an agonist at GABAB receptors, immediately prior to assessment of binge-like ethanol intake. We predict that microinjection of these drugs will reduce the behavior in a brain region specific manner.
In aim 3, binge-like ethanol intake-associated changes in GABA-related mRNA expression will be examined in the anterior and posterior VTA, NAcc shell, and mPFC using real-time polymerase chain reaction (PCR) and Western blot. We expect that binge-like ethanol intake will alter the expression of certain GABAA subunits, GABAB subtypes, and other GABA-associated transcripts in these structures. The proposed work will contribute to our general knowledge concerning the involvement of GABAergic circuits in the VTA, NAcc, and mPFC in the modulation of binge-like ethanol intake. We hope it will advance our understanding of the neurobiological factors associated with alcohol abuse and dependence in humans and ultimately lead to the development of better pharmacological tools in the treatment of alcoholism.
The proposed work will contribute to our general knowledge concerning the involvement of GABA circuits in the ventral tegmental area, nucleus accumbens, and prefrontal cortex in the maintenance of binge-like ethanol intake. It will advance our understanding of the neurobiological factors associated with the transition from casual alcohol use to alcohol abuse and dependence in humans, and may ultimately lead to better pharmacological treatment strategies for alcoholism.
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