4-PPBP maleate

Antagonism of N-methyl-D-aspartate receptors by sigma site ligands: potency, subtype-selectivity and mechanisms of inhibition.[Pubmed:9223571]

J Pharmacol Exp Ther. 1997 Jul;282(1):326-38.

Recent studies propose that sigma site ligands antagonize N-methyl-D-aspartate (NMDA) receptors by either direct, or indirect mechanisms of inhibition. To investigate this question further we used electrical recordings to assay actions of seventeen structurally diverse sigma site ligands on three diheteromeric subunit combinations of cloned rat NMDA receptors expressed in Xenopus oocytes: NR1a coexpressed with either NR2A, 2B or 2C. The sigma site ligands had a wide range of potency for antagonizing NMDA receptor currents. Steady-state IC50 values ranged between approximately 0.1 to >100 microM. In all cases inhibition was non-competitive with respect to glycine and glutamate. Five structurally related sigma ligands [eliprodil, haloperidol, ifenprodil, 4-phenyl-1-(4-phenylbutyl)-piperidine and trifluperidol] were strongly selective for NR1a/2B receptors. The other drugs were weakly selective or nonselective inhibitors. There was no correlation between sigma site affinity and potency of NMDA receptor antagonism for any subunit combination. Inhibition of NR1a/2B receptors by the selective antagonists was independent of voltage whereas inhibition by the weakly selective antagonists was voltage dependent. Potency of 10 sigma ligands was cross-checked on NMDA currents in cultured rat cortical neurons. There was close correspondence between the two assay systems. Our results argue that antagonism of NMDA receptor currents by the sigma ligands tested is due to direct effects on the receptor channel complex as opposed to indirect effects mediated by sigma receptors. Inhibition occurs via sites in the NMDA receptor channel pore, or via allosteric modulatory sites associated with the NR2B subunit.

Novel 1-phenylpiperazine and 4-phenylpiperidine derivatives as high-affinity sigma ligands.[Pubmed:1662725]

J Med Chem. 1991 Dec;34(12):3360-5.

sigma receptors may represent an exciting new approach for the development of novel psychotherapeutic agents. Unfortunately, many of the commonly used sigma ligands lack selectivity (e.g., many bind at phencyclidine or dopamine receptors) or suffer from other serious drawbacks. Recently, we described a series of 2-phenylaminoethanes that bind at sigma receptors with high affinity and selectivity. Because there is evidence that 1-phenylpiperazines can structurally mimic the 2-phenylaminoethane moiety, we prepared a series of 1-phenylpiperazines and related analogues and incorporated structural features already shown to enhance the sigma binding of the 2-phenylaminoethanes. Several of these derivatives bind at sigma receptors with high affinity (Ki = 1-10 nM) and lack appreciable affinity for phencyclidine and dopamine receptors. In as much as certain of these agents structurally resemble the high-affinity, but nonselective, sigma ligand haloperidol, and because they bind with 10 times the affinity of haloperidol, we have apparently identified what appears to be the primary sigma pharmacophore of that agent.