Establishment of secondary reinforcement in sign tracking and place preference tests following pimozide treatment

The effects of pimozide (1.0 mg/kg), a DA receptor blocker, on the capacity of environmental stimuli to acquire secondary reinforcing properties was investigated using two different paradigms. In the first experiment rats pretreated with either pimozide or its vehicle, were exposed to light-food pairings. When tested under drug-free extinction conditions, these animals approached the light cue significantly more frequently than did control animals who never had the cue associated with food during training. No differences in approach behavior were observed between the pimozide and vehicle groups that received the light-food pairings. The second experiment employed a place preference paradigm where animals were confined in distinctive compartments under reinforced (S+) or nonreinforced (S-) conditions. Pimozide and vehicle treated animals, when tested drug-free and given unrestricted access to both chambers under extinction conditions, spent comparable amounts of time in the S+ chamber relative to vehicle subjects that had never received food in either chamber. The results from these two studies indicate that an animal's ability to code relevant environmental information and to use this encoded information to guide and direct food seeking behavior is relatively independent of dopaminergic activity. The results also have significance for any theory which assumes that dopamine mediates reward processes.