PCP and sigma receptors in brain are not altered after repeated exposure to PCP in humans

The psychotomimetic effects of phencyclidine (PCP) in humans can persist or reappear months after the drug has been eliminated, suggesting that PCP can induce long-term changes in the brain. The present study examined whether repeated exposure to PCP in a human drug-addicted population was accompanied by alterations in either PCP or σ binding sites in their postmortem brains as compared to suicide controls. Saturation studies using [³H]TCP and [³H]haloperidol in the presence of spiperone to measure PCP and σ sites, respectively, revealed no significant differences in the affinity or density of binding sites between these two clinical populations in a variety of brain areas examined. The results suggest that these brain-binding sites remain unperturbed in humans despite multiple challenges with PCP. Delayed psychotic episodes following the use of PCP may be attributed to other neurochemical changes that are initiated by interactions of PCP with these two binding sites.