Involvement of the mesopallidal dopamine system in ethanol reinforcement

Melendez, Roberto I; Rodd, Zachary A; McBride, William J; Murphy, James M

doi:10.1016/j.alcohol.2003.12.002

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Volume 32, Issue 2 , Pages 137-144, February 2004

Involvement of the mesopallidal dopamine system in ethanol reinforcement

Roberto I Melendez
- Department of Psychology, Program in Psychobiology of Addictions, Purdue School of Science, Indiana University-Purdue University at Indianapolis, Indianapolis, IN 46202, USA
- Present address: Department of Physiology and Neuroscience, Medical University of South Carolina, 167 Ashley Avenue BSB-403, Charleston, SC 29425, USA.
- Corresponding author. Department of Psychology, LD 124, Purdue School of Science, IUPUI, 402 North Blackford Street, Indianapolis, IN 46202-3275, USA. Tel.: +1-317-274-6762; fax: +1-317-274-6756.
Zachary A Rodd
- Department of Psychiatry, Indiana University School of Medicine, Indiana University-Purdue University at Indianapolis, Indianapolis, IN 46202, USA
William J McBride
- Department of Psychiatry, Indiana University School of Medicine, Indiana University-Purdue University at Indianapolis, Indianapolis, IN 46202, USA
James M Murphy
- Department of Psychology, Program in Psychobiology of Addictions, Purdue School of Science, Indiana University-Purdue University at Indianapolis, Indianapolis, IN 46202, USA
- Department of Psychiatry, Indiana University School of Medicine, Indiana University-Purdue University at Indianapolis, Indianapolis, IN 46202, USA

Received 31 July 2003; received in revised form 24 December 2003; accepted 24 December 2003.

Editor: T.R. Jerrells

Abstract

The current study was designed to test the hypothesis that acquisition of signal-induced anticipation of self-administered ethanol and operant oral self-administration of ethanol increases the extracellular levels of dopamine in the ventral pallidum of alcohol-preferring (P) rats. The study was also designed to explore the association between behavioral activity and dopamine efflux in the ventral pallidum. Adult, female P rats were randomly assigned to operantly self-administer 15% (volume/volume) ethanol, 0.0125% (weight/volume) saccharin, or water. In addition, all groups were acclimated in the operant chambers to periods of habituation, anticipation, and postadministration. The ethanol group showed significant increases in extracellular levels of dopamine in the ventral pallidum during (1) the first 10 min of the anticipation period, (2) the last 10 min of the self-administration period, and (3) the initial 10 min of the postadministration period. There were no significant differences in motor activity during anticipation and self-administration of ethanol, saccharin, or water. These findings support the suggestion that dopaminergic activation in the ventral pallidum is involved in ethanol-seeking and ethanol-drinking behaviors and directly implicate the mesopallidal dopamine system in the reinforcing actions of ethanol.

Keywords: Ventral pallidum, Dopamine, Ethanol, Reinforcement, Alcohol preferring (P) rats, Microdialysis