Rimcazole dihydrochloride

Rimcazole analogs attenuate the convulsive effects of cocaine: correlation with binding to sigma receptors rather than dopamine transporters.[Pubmed:11684152]

Neuropharmacology. 2001 Dec;41(7):878-86.

Cocaine interacts with dopamine transporters and sigma receptors at concentrations that are achievable in vivo, suggesting that they may both be viable targets for the development of anti-cocaine agents. Rimcazole binds to both of these targets and also attenuates cocaine-induced locomotor activity and sensitization. To further characterize the mechanism(s) underlying the attenuation of cocaine-induced convulsions and lethality, rimcazole and three analogs (SH3/24, SH2/21, SH1/57), with a range of affinities for dopamine transporters and sigma receptors, were evaluated. The highly selective and potent sigma receptor ligand LR176 was used as a reference. Competition binding studies confirmed that the rank order of the compounds at dopamine transporters vs. sigma receptors differed, thus enabling a correlation between the relative anti-cocaine activities of the compounds in behavioral studies and their affinities for dopamine transporters vs. sigma receptors. In behavioral studies, male Swiss Webster mice were pre-treated with one of the compounds (0-60 mg/kg, i.p.), then challenged 15 min later with either a convulsive (60 mg/kg, i.p.) or lethal (125 mg/kg, i.p.) dose of cocaine. When the compounds were ranked according to their protective effect, there was a significant correlation between their anticonvulsant actions and their affinities for sigma receptors, but not dopamine transporters. Although the rimcazole analogs were ineffective against the lethal effects of cocaine, the selective sigma receptor ligand LR176 provided significant protection. These data thus suggest that sigma receptors may mediate some of the toxic effects associated with cocaine and that sigma receptor antagonists may be developed as pharmacotherapeutic agents for this application.

Isothiocyanate derivatives of 9-[3-(cis-3,5-dimethyl-1-piperazinyl)propyl]carbazole (rimcazole): irreversible ligands for the dopamine transporter.[Pubmed:9435903]

J Med Chem. 1997 Dec 19;40(26):4340-46.

Cocaine has been reported to bind to the dopamine transporter in a biphasic fashion, and it has been hypothesized that the low-affinity component may play a modulatory role in cocaine's psychomotor stimulant effects. In an effort to gain further insight into the roles of the two sites, we have prepared a series of irreversible ligands based on rimcazole (9-[3-(cis-3,5-dimethyl-1-piperazinyl)propyl]carbazole, 2), a compound that has been postulated to bind only to the low-affinity site. The alkylating moiety (isothiocyanate) is attached to the distal nitrogen of the piperazine ring via alkyl chains of varying lengths or directly attached to one of the aromatic groups. It was found that substitution on the piperazine nitrogen caused an initial decrease in affinity that was recovered as the alkyl chain length increased. Importantly, the analogue 16, with the highest affinity for the dopamine transporter (DAT), binds in a monophasic and irreversible manner, as evidenced by the greatly diminished binding of [3H]WIN 35,428 in tissue that had been preincubated with the ligand and then thoroughly washed using centrifugation. The dose-dependent reduction in Bmax was accompanied by a concentration-related decrease in KD values. This shift in KD to a lower value suggests that the preincubation with 16 produced a preferential irreversible binding to the low-affinity [3H]WIN 35,428 site on the dopamine transporter. These ligands may prove to be important tools with which to study the significance of the low-affinity site on the DAT. Since rimcazole does not share the behavioral profile of cocaine, and in fact appears to play a modulatory role, these compounds may provide leads for a novel cocaine-abuse treatment.

Evidence that the potential antipsychotic agent rimcazole (BW 234U) is a specific, competitive antagonist of sigma sites in brain.[Pubmed:2873494]

Life Sci. 1986 Jun 23;38(25):2329-37.

Rimcazole (BW 234U) is a potential antipsychotic agent which in open-clinical trials appears to be effective in acute schizophrenic patients. In the present study, rimcazole was found to block the specific binding of [3H]-(+)-SKF 10,047 to sigma sites in rat and guinea pig brain (IC50 = 5.0 X 10(-7) M). The compound was 100 times weaker as a blocker of phencyclidine sites (IC50 = 4.3 X 10(-5) M). At 1 X 10(-5) M, rimcazole had only weak effects on mu, delta, kappa and epsilon opioid receptors. Scatchard analysis of the binding data from guinea pig brain revealed an apparent KD for [3H]-(+)-SKF 10,047 of 85 +/- 5 nM and a Bmax of 824 +/- 27 fmole/mg protein. In the presence of 5 X 10(-7) M BW 234U, the apparent KD was 165 +/- 35 nM, but the Bmax (892 +/- 146 fmoles/mg protein) was not affected. This suggests that rimcazole is a competitive inhibitor of sigma sites. The agent was also capable of blocking sigma sites in vivo (ID50 = 6 mg/kg i.p., mice) as judged by an in vivo sigma receptor binding assay. Thus, if the antipsychotic activity of rimcazole is confirmed in double-blind, placebo-controlled trials, it would be the first compound whose mechanism of antipsychotic activity may best be explained by a direct blockade of sigma sites and not by a direct blockade of dopamine (D2) receptors in brain.