Pimozide Blocks Reinforcement but Not Priming from MFB Stimulation in the Rat

When given non-contingent pretrial stimulation (priming stimulation) rats ran an alley for brain-stimulation reward faster than when there was no priming. This is one manifestation of the priming effect of rewarding stimulation. After treatment with the neuroleptic, pimozide, the first few trials fell in the range of normal primed performance when the rats were primed, and in the range of normal unprimed performance when they were not. In either case, an extinction-like decline in performance occurred after the first few trials. Run in a T-maze with water in one arm and a lever producing brain stimulation reward in the other, thirsty rats chose the stimulation reward when primed and the water reward when unprimed. Pimozide in doses that produced extinction of Skinner box responding did not alter this effect of priming on reward preference. These results demonstrate that the priming effect is unaltered by doses of pimozide that block the reinforcing effect of the stimulation.