PHARMACOLOGICAL CHARACTERIZATION OF PERFORMANCE ON A CONCURRENT LEVERPRESSING FEEDING CHOICE PROCEDURE - EFFECTS OF DOPAMINE ANTAGONIST, CHOLINOMIMETIC, SEDATIVE AND STIMULANT-DRUGS

This experiment was undertaken to provide a pharmacological characteri zation of performance on a task involving food-related instrumental an d consummatory behavior. Rats were tested in an operant chamber in whi ch there was a choice between pressing a lever to receive a preferred food (Bioserve pellets) or approaching and consuming a less-preferred food (Lab Chow). The lever pressing schedule was a fixed ratio 5 (FR5) . Rats usually pressed the lever at high rates to obtain the preferred food, and typically ate little of the lab chow even though it was fre ely available in the chamber concurrently with the lever pressing sche dule. Previous work has shown that injection of dopamine (DA) antagoni sts, or depletion of DA in the nucleus accumbens, caused a substantial shift in behavior such that lever pressing was reduced but chow consu mption increased. In the present study it was shown that the DA antago nist haloperidol decreased lever pressing and increased chow consumpti on at doses of 0.1 and 0.15 mg/kg. The D1 antagonist SCH 23390 (0.05, 0.1 and 0.15 mg/kg) and the non-selective DA antagonist cis-flupenthix ol (0.3 and 0.45 mg/kg) decreased lever pressing and produced substant ial increases in chow consumption. The D2 antagonist sulpiride decreas ed lever pressing, but produced only slight increases in chow intake a t the highest dose. Pentobarbital reduced lever pressing and increased chow consumption at 10.0 mg/kg. The muscarinic agonist pilocarpine pr oduced dose-related decreases in lever pressing, but failed to increas e chow consumption. Amphetamine produced dose-related decreases in bot h lever pressing and chow consumption. These results indicate that low /moderate doses of the DA antagonists haloperidol, cis-flupenthixol an d SCH 23390 can suppress lever pressing in doses that leave the animal directed towards food acquisition and consumption.