Phencyclidine, the drug induces psychosis: Its neuropharmacological actions

Phencyclidine (PCP) is a major drug of abuse as well as a 'drug of choice' among substance abusers in the U.S. PCP use may result in the development of psychotic behavior. PCP-induced psychosis is characterized by confusion, excitation, aggression, paranoia, hallucinations and delusions of grandeur and may evoke violent or suicidal behavior. Therefore, many patients from PCP-induced psychosis have been diagnosed initially as schizophrenic. However, PCP-related research has not kept pace with the rise in abuse and PCP-induced psychosis. The neurochemical effects of PCP are not well defined at present, but both behavioral and biochemical studies suggest that it may interact with dopaminergic, cholinergic, noradrenergic, serotonergic, GABAergic and enkephalinergic systems. The specific reversible, saturable, high affinity ³H-PCP binding site was discovered recently in rat brain. There is now a large body of evidence to suggest that opiate receptors may be subdivided into mu, sigma, kappa and delta receptors. On the basis of behavioral and binding studies, it is proposed that the sigma receptor and the PCP binding site are one and the same. This receptor interacts with PCP and psychotomimetic epioids to produce their psychotomimetic effects. This review has served to illustrate the paucity of information currently available on the central effects of PCP. However, our current notions of the mechanisms of action of PCP are very complicated. Such a review inevitably raises more questions than it answers but it is hoped that these may stimulate further investigation in this field.