APOMORPHINE AND 7-OH DPAT REDUCE ETHANOL INTAKE OF P AND HAD RATS

Adult male rats of the alcohol-preferring (P) line (N = 10) and high a lcohol drinking (HAD) line (N = 12) were used to study the effects of IP administration of 0.125-0.50 mg/kg 7-OH DPAT (a putative D-3 agonis t) and 0.25-1.0 mg/kg apomorphine (a dopamine agonist with 50-fold hig her affinities for the D-1 and D-2 receptors than for the D-3 receptor ) on the concurrent intakes of 10% (v/v) ethanol and 0.0125% (g/v) sac charin during a daily 4-h scheduled access period. Control intakes by the P rats for the 4-h period were 17.9 +/- 0.5 and 7.2 +/- 0.4 mi for the ethanol and saccharin solutions, respectively. For the HAD line, ethanol consumption was 18.7 +/- 0.2 mi and saccharin intake was 8.7 /- 1.6 mi for the 4-h period. In terms of grams ethanol/kg body wt., t he 4-h intakes were 2.2 +/- 0.2 for the P line and 3.0 +/- 0.3 for the HAD rats. Both P and HAD rats consumed approximately 40% of their tot al ethanol intake in the first 15 min of access while consuming only a bout 15% of their total saccharin intake during this Ii-min period. Th e putative D-3 agonist 7-OH DPAT produced a decrease in ethanol intake in the first h to 45-55% of control levels for the P rat (p < 0.01) a nd to 25-70% of control values in the HAD line (p < 0.001). Apomorphin e caused a dose-dependent decrease in ethanol intake in the first hour to 15-70% of control values in the P rat (p < 0.001) and to 25-60% of control levels in the HAD line (p < 0.001). Saccharin and 4-h food in takes for bath lines were not altered by either 7-OH DPAT or apomorphi ne. Overall, these results suggest that D-2 and D-3 dopamine receptors may play a role in mediating alcohol drinking behavior of the selecti vely bred HAD and P lines of rats.