Pimozide does not shift palatability: separation of anhedonia from sensorimotor suppression by taste reactivity

Several "taste reactivity" studies of dopamine and reward have concluded that pimozide suppresses the hedonic reaction patterns normally elicited by sucrose but enhances aversive reaction patterns elicited by quinine. However, other taste reactivity studies have failed to find hedonic/aversive shifts in reaction patterns after dopamine antagonists or dopamine lesions. The divergent conclusions have come from two different laboratories. To resolve the controversy regarding dopamine blockade and palatability, the present study joined the two laboratories to investigate the effect of pimozide on taste reactivity patterns elicited by sucrose and quinine. The results replicated many (but not all) of the earlier findings and identified procedural factors responsible for different outcomes. Overall, the results provide evidence for sensorimotor effects of pimozide on taste reactivity but not for a hedonic shift in palatability. Pimozide suppressed both hedonic and aversive reaction patterns in a gradual sensorimotor fashion when the eliciting taste stimulus was repeated or continued for several minutes. The general suppression typically did not alter the initial reaction to a taste but emerged only after an oral infusion of sucrose or quinine continued for several minutes or trials. Aversive reactions were never enhanced. The balance between hedonic and aversive reaction patterns was not shifted by pimozide. We conclude that pimozide produces a sensorimotor impairment of taste reactivity patterns but does not shift taste palatability toward anhedonia or aversion.