Opposite effects of SK&F 38393, a dopamine D-1 agonist, and SCH 23390, a dopamine D-1 antagonist, in tests of salt preference/aversion in the rehydrating rat.

Male rats were adapted to a 22-hr water-deprivation schedule, and to a 15-min choice test, in which water was available in one drinking tube, and water, 0.064%, 0.16%, 0.4%, 1.0%, or 2.5% NaCl solution, respectively, was available in a second. A typical saline preference-aversion function was obtained. The selective dopamine D-1 agonist, SK&F 38393 (3.0 mg/kg, IP), significantly depressed choice of hypertonic saline solutions (1.0% and 2.5% NaCl solutions), without affecting preference for hypotonic saline solutions. In contrast, the selective dopamine D-1 antagonist, SCH 23390 (0.1 mg/kg, SC), significantly increased the preference measure in the case of hypertonic solutions. These data indicate a role for D-1 receptors in dopaminergic mediation of the descending limb of the saline preference-aversion function.