Studies directed toward characterizing the discriminative stimulus properties of phencyclidine (PCP) in the rat and squirrel monkey will be continued. It is hypothesized that the components of action of PCP and related compounds that enable them to function as discriminative stimuli in animals are analogous to the components of action that engender subjective effects in man. Thus, drug discrimination paradigms could provide animal models for the preclinical identification and evaluation of the components of action of PCP and analogs that underlie their potential for abuse. In the coming year, monkeys trained to discriminate between intramuscular injections of saline and PCP (0.25 mg/kg) in a two-choice paradigm will be tested for stimulus generalization with a series of PCP analogues in order to assess the structural requirements of the molecule for exerting PCP-like stimulus control of behavior. Rats trained to discriminate between subcutaneous injections of saline and PCP (2.0 mg/kg) will be surgically prepared with a cannula in the lateral ventricle. The rats will be tested for stimulus generalization to various putative neurotransmitters, such as serotonin and dopamine, which will be administered intracerebroventricularly as an approach toward assessing the neurochemical basis of PCP-like stimulus control of behavior.