Effects of the dopamine D-1 antagonist SCH 23390 and the D-2 antagonist sulpiride on saline acceptance-rejection in water-deprived rats.

Separate groups of water-deprived rats were familiarized with drinking water or one of a range of NaCl solutions (0.45-2.7%) in a 30 min test. The substituted benzamide, sulpiride, a selective dopamine D-2 receptor antagonist, significantly increased the consumption of water and hypotonic saline at 30 mg/kg. In contrast, the selective dopamine D-1 receptor antagonist, SCH 23390 (0.01-0.1 mg/kg SC) significantly reduced the intake of water and of saline at different concentrations in a dose-dependent manner. Consumption of water and 0.45% saline were most sensitive to the antidipsogenic effect of SCH 23390. These results suggest that previously-reported antidipsogenic effects of neuroleptics may depend, to at least some degree, on dopamine D-1 receptor blockade. The increase in drinking produced by sulpiride indicates that dopamine may act at D-2 receptors to inhibit the consumption of water and hypotonic saline, but not of stronger salt solutions.