This study was performed to characterize pharmacologically the discriminative stimulus effects of dextromethorphan, an antitussive that binds with high affinity to a subtype of sigma site in the brain. Dextrorphan, a metabolite of dextromethorphan, has phencyclidine (PCP)-like effects. Therefore, training was conducted with dextromethorphan injected by the SC route, which minimizes dextrorphan...