Effects of pimozide on appetitive behavior and locomotor activity: dissimilarity of effects when compared to extinction.

The effects of pimozide were examined in a runway paradigm using food reward. Rats received one of three doses of pimozide, vehicle or Ringer's prior to testing. Two additional groups received pimozide or vehicle after the test trial in the home cage. An extinction group received no food in the goal box on test days. Several components of running behavior were assessed as was food consumed in the goal box. Effects of pimozide on general locomotor activity were assessed in the open-field following the runway phase. Results of the runway indicated that pimozide-treated rats differed from the extinction group in latencies to leave the start box and enter the goal box. Pimozide-treated rats consumed less saccharin-flavored food than controls. The post-treatment pimozide group showed a reduction in saccharin-food intake suggesting a conditioned taste aversion. Thus, the reduction observed in the pretreated pimozide group may be due to some unconditioned aversion induced by the drug. Open-field revealed that pimozide resulted in lower activity than controls. This study indicates that the effects of pimozide on food reinforcement are not similar to the effects seen in extinction. These data are consistent with the hypothesis that the effects of pimozide, in this paradigm, constitute an interference with motor responses as opposed to an attenuation of reward properties of the stimuli.