Phencyclidine-like discriminative stimuli of (+)- and (-)-N-allylnormetazocine in rats.

The phencyclidine(PCP)-like discriminative stimulus properties of the (+)- and (-)-isomers of the prototypic sigma-receptor agonist N-allylnormetazocine (NANM) were evaluated in rats trained to discriminate between saline and 3.0 mg/kg of PCP. The rats were trained under a FR5 schedule of stimulus-shock termination. Both (+)- and (-)-NANM produced PCP-like stimuli and were approximately one-half and one-sixth, respectively, as potent as PCP. The two isomers were equipotent in decreasing response rates. None of the effects of either (+)- or (-)-NANM were antagonized by naloxone. These results demonstrate that the PCP-like effects of NANM exhibit stereoselectivity but not stereospecificity and are additional evidence that the common actions of PCP and NANM are mediated by sigma-receptors.