Generalization of the discriminative stimulus properties of phencyclidine to other drugs in the pigeon using color tracking under second order schedules.

Pigeons were trained to track the location of a red or green key color under a second order schedule, with reinforcement of responses to each color contingent upon whether 1.5 mg/kg phencyclidine (PCP) or saline had been administered before the session. When cumulative dose-effect curves were determined for other drugs substituted for PCP, pigeons responded predominantly on the PCP key after other doses of PCP, ketamine, pentobarbital, d-cyclazocine and l-cyclazocine, but not after saline, lactic acid solution, d-amphetamine, chlordiazepoxide, scopolamine, morphine, naltrexone, or d-, or l-methadone. l-Cyclazocine was slightly more potent than d-cyclazocine in producing PCP key responding. PCP key responding after the optical isomers of cyclazocine was not blocked by naltrexone.