RACLOPRIDE REDUCES SUCROSE PREFERENCE IN RATS

Dopaminergic D-1 and D-2 antagonists decrease the intake of sweet solu tions during sham feeding. Because the decreased intake of 10% sucrose produced by the D-1 and D-2 antagonists has been demonstrated to occu r in the absence of significant deficits in the initiation of ingestio n, or of its motor performance, we investigated the hypothesis that ra clopride decreases intake by lowering the reinforcing potency of the o rosensory stimulation provided by sucrose during sham feeding. Rats we re adapted to ingest two differently flavored 10% sucrose solutions fo r 5 min in one-bottle tests. The flavored solution that rats preferred was paired with pretreatment with a dose of raclopride (400 mu g/kg, IP, 15 min) that produced a mean decrease of intake of 55%. The other flavored 10% sucrose solution was paired with vehicle (0.15 M NaCl) in jections. After three or six pairings with raclopride or vehicle injec tion, two two-bottle preference tests were given without raclopride pr etreatment. Preference for the flavored 10% sucrose solution previousl y paired with raclopride decreased significantly in both tests. We int erpret this decreased preference as evidence that raclopride decreased the reinforcing potency of flavored 10% sucrose during one-bottle tes ts. This is consistent with our hypothesis and with the more general h ypothesis of Wise that central dopaminergic mechanisms mediate the rei nforcing effect of food.