PD 144418 is a highly affinity, potent and selective sigma 1 (σ1) receptor ligand (K_i values of 0.08 nM and 1377 nM for σ1 and σ2 respectively), devoid of any significant affinity for other receptors, ion channels and enzymes. PD 144418 shows potential antipsychotic activity^[1][2]. IC50 & Target: Ki: 0.08 nM (σ1receptor) and 1377 nM (σ2 receptor)^[1] In Vitro: In vitro, PD 144418 reverses the N-methyl-D-aspartate (NMDA)-induced increase in cyclic GMP (cGMP) in rat cerebellar slices without affecting the basal levels, suggesting that σ1 sites may be important in the regulation of glutamine-induced actions. PD 144418 potentiates the decrease in 5-hydroxytryptophan caused by Haloperidol in the mesolimbic region, but by itself has no effect in 5-HT and dopamine (DA) synthesis^[1]. In Vivo: PD 144418 (10 mg/kg; intraperitoneal injection; male CD-1 mice) treatment antagonizes Mescaline-induced scratching at doses that did not alter spontaneous motor activity, with PD 144418 showing ED₅₀ values of 7.0 mg/kg i.p.^[1].