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Title: Dopamine receptor regulation of ethanol intake and extracellular dopamine levels in the ventral pallidum of alcohol preferring (P) rats. Author: Melendez RI, Rodd ZA, McBride WJ, Murphy JM. Journal: Drug Alcohol Depend; 2005 Mar 07; 77(3):293-301. PubMed ID: 15734229. Abstract: Sufficient evidence exists for the inclusion of the ventral pallidum (VP) into the category of a dopaminoceptive brain region. The effects of inhibiting dopamine D(1)- or D(2)-like receptors in the VP on (a) ethanol intake and (b) extracellular levels of dopamine, were investigated in the alcohol-preferring (P) rat. The D(1)-like antagonist, SCH-23390, and the D(2)-like antagonist, sulpiride (0.25-2 microg/0.5 microl) were bilaterally injected into the VP and ethanol (15%, v/v) intake was assessed in a 1 h limited access paradigm. The results indicate that microinjections of sulpiride significantly increased ethanol consumption (65% increase at the 2.0 microg dose). Whereas the D(1) antagonists SCH-23390 tended to decrease ethanol intake, the effect was not statistically significant. In a separate group of rats, reverse microdialysis of sulpiride and SCH-23390 (10-200 microM) were conducted in the VP of P rats. Local perfusion of only the 200 microM sulpiride dose significantly increased the extracellular levels of dopamine (maximal increase: 250% of baseline). On the other hand, local perfusion of SCH-23390 (10-200 microM) dose dependently increased the extracellular levels of dopamine 180-640% of baseline. Overall, the results of this study suggest that (a) tonic activation of D(2) postsynaptic receptors in VP imposes a limit on ethanol intake in the P rat; (b) there are few D(2) autoreceptors functioning in the VP; (c) there is tonic D(1)-like receptor mediated inhibitory feedback regulation of VP-dopamine release.[Abstract] [Full Text] [Related] [New Search]