Sigma receptors mediate the psychotomimetic effects of N-allylnormetazocine (SKF-10,047), but not its opioid agonistic-antagonistic properties

Our present findings suggest that SKF-10,047, the prototype sigma agonist, has its opioid entity residing with its (-) isomer, while both Its (+) and (-) isomers possess psychotogenic properties similar to those produced by PCP. We found that (-)-SKF-10,047 blocks EEG and behavioral effects of morphine in the naive rat, precipitates withdrawal in morphine-dependent rats, produces physical dependence as evidenced by naloxone-induced withdrawal, and displaces [³H]dihydromorphine from brain homogenates. (+)-SKP-10,047 did not produce dependence upon chronic treatment, and it did not displace [³H]dihydromorphine from brain homogenates. Such pharmacodynamic dissociation with SKF-10,047 suggests an association of sigma receptors with psychogenic, but not opioid effects. The latter are most likely mediated by mu or kappa receptors.