Subchronic treatment of rats with remoxipride fails to modify σ binding sites in the brain

Pharmacology of the atypical antipsychotic remoxipride, a dopamine D2 receptor antagonist

Remoxipride is a substituted benzamide that acts as a weak but very selective antagonist of dopamine D2 receptors. It was introduced by Astra (Roxiam) at the end of the eighties and was prescribed as an atypical antipsychotic. This article reviews its putative selective effects on mesolimbic versus nigrostriatal dopaminergic systems. In animals, remoxipride has minimal cataleptic effects at doses that block dopamine agonist-induced hyperactivity. These findings are predictive of antipsychotic activity with a low likelihood of extrapyramidal symptoms. Remoxipride also appears to be effective in more recent animal models of schizophrenia, such as latent inhibition or prepulse inhibition. In clinical studies, remoxipride shows a relatively low incidence of extrapyramidal side effects and its effects on prolactin release are short-lasting and generally mild. The clinical efficacy of remoxipride is similar to that of haloperidol or chlorpromazine. Although its clinical use was severely restricted in 1993, due to reports of aplastic anemia in some patients receiving remoxipride, this drug has been found to exhibit relatively high selectivity for dopamine D2 receptors making remoxipride an interesting tool for neurochemical and behavioral studies.

Heterogenous binding of 3H-remoxipride to membranes of rat liver and brain

The binding of the antipsychotic agent 3H-remoxipride to membranes of rat liver and brain (whole brain and cerebellum) was studied with filtration technique. Saturable high affinity binding was obtained for all three types of tissue preparations. Heterogenous binding sites were found since various types of compounds inhibited the binding of 3H-remoxipride with shallow dose-response curves. In the liver preparation it was possible to differentiate between two different binding sites. One site, called rem1, was defined with 100 nM alaproclate and bound sigma 2 ligands with high affinity, e.g. haloperidol, GBR 12909, DTG and (+)-3-PPP. High correlation (r = 0.93) was obtained between the inhibition of the binding of 3H-remoxipride to the rem1 site and the inhibition of the binding of the sigma ligand 3H-DTG reported previously (Ross 1991), indicating that the rem1 site is identical to a sigma 2-like binding site. The other 3H-remoxipride binding site in the rat liver, rem2 appears to be identical to the site binding alaproclate, proadifen and cocaine with high affinity. Cd2+ and Zn2+ were potent inhibitors of both binding sites, Cd2+ particularly of rem2 binding and Zn2+ preferably of rem1 binding. The apparent Bmax (pmol/g original tissue) and KD (nM) values for rem1 binding were 441 +/- 43 and 80 +/- 14, and for rem2 binding 727 +/- 116 and 95 +/- 6. The binding of 3H-remoxipride to the brain preparations was also inhibited with shallow dose-response curves.(ABSTRACT TRUNCATED AT 250 WORDS)

NE-100, a novel sigma receptor ligand: in vivo tests

It has been suggested that sigma receptor antagonists may be useful as antipsychotic drugs. N, N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]-ethylamine monohydrochloride (NE-100) is a novel compound with high affinity for the sigma receptor (IC50 = 4.16 nM), but low affinity (IC50 > 10,000 nM) for D1, D2, 5-HT1A, 5-HT2 and phencyclidine (PCP) receptors. The head-weaving behavior induced by either (+)SKF10047 or PCP was dose-dependently antagonized by NE-100 with oral ED50 at 0.27 and 0.12 mg/kg, respectively. NE-100 did not affect dopamine agonists-induced stereotyped behavior and/or hyperactivity. NE-100 failed to induce catalepsy in rats. These findings indicate that NE-100 may have antipsychotic activity without the liability of motor side effects typical of neuroleptics.