A comparison between classes of drugs having phencyclidine-like behavioral properties on dopamine efflux in vitro and dopamine metabolism in vivo.
L. Snell, Z. Mueller, R. Gannon, P. B. Silverman, K. Johnson
Journal of Pharmacology and Experimental Therapeutics November 1, 1984 DOI: 10.1016/s0022-3565(25)21585-3 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | In vitro and in vivo pharmacological comparison Peer reviewed |
|---|---|
| Population | Rat striatal slices and rat cortical membranes |
| Interventions | m-amino-PCP ketamine m-nitro-PCP PCE NANM EKC etoxadrol dexoxadrol levoxadrol haloperidol |
| Key points | PCP and certain arylcycloalkylamines (m-amino-PCP, PCE) increased basal striatal dopamine efflux and significantly elevated haloperidol-induced dopamine metabolism, whereas ketamine and m-nitro-PCP did not affect haloperidol-induced metabolism. Benzomorphans and substituted dioxolanes were much weaker at enhancing dopamine efflux, requiring 10-30 microM compared to 3 microM PCP, and most did not alter haloperidol-induced dopamine metabolism, though levoxadrol and EKC significantly decreased the HVA/DA ratio. |
Abstract
Phencyclidine [(l-phenylcyclohexyl) piperidine] (PCP) is known to increase the basal efflux of striatal dopamine (DA) in vitro and to enhance haloperidol (HAL)-induced striatal DA metabolism in vivo. This study compared these activities of PCP to several representatives of the arylcyloalkylamine, benzomorphan and substituted dioxolane classes whose behavioral similarities to PCP have been well studied. The affinity of these drugs for the PCP/sigma opiate receptor also was estimated by determining the concentration of these drugs required to inhibit the specific binding of 10 nM [3H]PCP to rat cortical membranes by 50%. Of the arylcycloalkylamines tested on the basal efflux of [3H]DA, we found the rank-order effectiveness to be as follows: PCP greater than 1-[l-(napthyl)cyclohexyl]piperidine HCl (m-amino-PCP) greater than ketamine greater than or equal to 1-[l-(m-nitrophenyl)cyclohexyl]piperidine HCl (m-nitro-PCP) greater than N-ethyl-l-phencyclohexylamine (PCE). However, in vivo we found that PCP, m-amino-PCP and PCE significantly elevated HAL-induced DA metabolism, whereas ketamine and m-nitro-PCP were without effect. Although each of the benzomorphans tested [N-allylnormetazocine (NANM) and ethylketocyclazocine (EKC)] slightly enhanced the basal efflux of [3H]DA from striatal slices, concentrations of 10 to 30 microM were required to elicit the same magnitude of [3H]DA release caused by 3 microM PCP. Quantitatively similar responses were produced by the substituted dioxolanes tested (etoxadrol, dexoxadrol and levoxadrol). Neither (+)-NANM, (-)-NANM, (+/-)-NANM, etoxadrol nor dexoxadrol had any effect on HAL-induced DA metabolism. On the other hand, both levoxadrol and EKC significantly decreased the ratio of HVA/DA after HAL administration.(ABSTRACT TRUNCATED AT 250 WORDS)