Phencyclidine-induced potentiation of brain stimulation reward: acute effects are not altered by repeated administration.

Phencyclidine (PCP; 2.5 or 5.0 mg/kg) potentiated the effects of rewarding hypothalamic brain stimulation, causing parallel leftward shifts of the functions that relate rate of responding to stimulation frequency. Thus, like a number of other drugs of abuse, PCP lowered the "dose" of stimulation required to maintain responding at a given criterion. No progressive changes in the reward-potentiating effects of PCP were evident when the rats were tested once per week for 8 weeks; there was neither tolerance nor sensitization to the initial rewarding properties of PCP. However, in subsequent locomotor tests rats appeared to be already sensitized to PCP; this raises the possibility that the electrical stimulation of the lateral hypothalamus itself maximally sensitized the animals to the stimulant effects of the drug.