LACK OF EFFECT OF DOPAMINE D-2 BLOCKADE ON ETHANOL INTAKE IN SELECTEDAND UNSELECTED STRAINS OF RATS

Previous research has suggested that brain catecholamines may be invol ved in regulating ethanol intake. This study was designed to look more specifically at dopamine (DA) and whether DA D-2 receptor blockade wi th the antagonist pimozide would alter ethanol consumption in rats. Su bjects were male Maudsley Reactive and Wistar rats, the former previou sly shown to consume larger amounts of ethanol than the latter. Both s trains were screened for ethanol intake by presentation of ethanol sol utions (free choice with water) in increasing steps from 2% to 10% (v/ v) on an alternate-day schedule. Following the screening period, anima ls were switched to a schedule of everyday presentation of the 10% (v/ v) ethanol solution (free choice with water) for 10 baseline days. Ani mals were then divided into high and low drinking levels according to whether their mean baseline ethanol intake (g/kg) fell within +/-0.5 S D of the mean intake of their group (Maudsley Reactives: mean = 2.55 g /kg, low drinkers <1.63, high drinkers >3.47; Wistars: mean = 2.17 g/k g, low drinkers <1.53, high drinkers >2.82). The animals were assigned to one of five treatment groups for 5 subsequent days where they rece ived IP injections of pimozide (0.08, 0.24, or 0.48 mg/kg), tartaric a cid, or saline. Following the treatment period, ethanol consumption wa s recorded for 5 posttreatment days. No significant differences due to treatment were observed for either intake or preference of ethanol ac ross treatments, drinking groups, or strains. The results obtained in the present study suggested that interference in DA neurotransmission through administration of the D-2 antagonist pimozide does not signifi cantly alter ethanol consumption in either MR or Wistar animals.