The Relationships of Receptors for Phencyclidine and Sigma Opiates in Rat Cerebellum: An Electrophysiological Analysis

Abstract

Two groups of opioid compounds seem to share many pharmacological properties with PCP, even though their structures are markedly different: benzomorphans such as cyclazocine and N-allylnormetazocine (SKF-10,047; Zukin et al., 1984; Teal and Holtzman, 1979; Mendelsohn, et al., 1985) and dioxolanes such as dexoxadrol (Cone et al., 1985; Shannon, 1983). This finding has led some to the postulate that the “sigma receptor”, one of the multiple opiate receptors reported in the CNS, is identical to the PCP receptor. Supporting this conjective, both cyclazocine and SKF-10,047, which have been shown to have high affinity for sigma opioid receptors (Neil 1985), displace [³H]-PCP binding in rat brain homogenates (Zukin et al., 1984; Mendelsohn et al., 1985). Although dexoxadrol has no analgesic actions in mice, it produces PCP-like catalepsy in the pigeon (Zimmerman et al. 1983) and also displaces [³H]-PCP binding-in rat brain homogenates (Zukin, 1982; Hampton et al., 1982). However, other types of receptor-mediated interactions could also account for the behavioral parallelisms of these agents. Thus, PCP could augment release of sigma opiates or visa versa. Alternatively, PCP and sigma opiates could interact with separate receptors which possess synergistic effector mechanisms postsynaptically.