Evaluation of dopamine receptor involvement in rat feeding behaviour.

1. The anorectic effect of dopamine agonists and antagonists were studied in rats. 2. Dopamine agonists bromocriptine, quinpirole or SKF 38393 treatment induced, a dose-dependent anorexia in rats. 3. Anorectic effect of bromocriptine was decreased in animals pretreated with pimozide (D-2 antagonist), but not by sulpiride (D-2 antagonist) or SCH 23390 (D-1 antagonist) pretreatment. 4. Anorexia induced by quinpirole was decreased by sulpiride or pimozide, but not by SCH 23390 administration. 5. While sulpiride and SCH 23390 failed to antagonize the anorectic response of SKF 38393, methergoline (5-HT antagonist) decreased anorexia induced by the drug. 6. A combination of quinpirole with SKF 38393 did not elicit potentiated anorectic response. 7. Decrease in food intake induced by bromocriptine, quinpirole or SKF 38393 was potentiated in reserpinized animals, although single administration of reserpine also induced a marked decrease in feeding. 8. Single administration of sulpiride, pimozide or methergoline did not change the feeding behaviour of rats, but SCH 23390 induced anorexia. 9. It is concluded that D-2 activation may induce inhibition of feeding and anorexia induced by SKF 38393 may be mediated through serotonergic mechanism(s).