4-{2-[5-methyl-1-(naphthalen-2-yl)-1H-pyrazol-3-yloxy]ethyl}morpholine (S1RA, E-52862) is an 1-arylpyrazole class of sigma-1 receptor antagonist. Formalin-induced nociception (both phases), capsaicin-induced mechanical hypersensitivity and sciatic nerve injury-induced mechanical and thermal hypersensitivity were dose-dependently inhibited by systemic administration of S1RA. Occupancy of sigma-1 receptors in the CNS was significantly correlated with the antinociceptive effects. As a mechanistic correlate, electrophysiological recordings demonstrated that pharmacological antagonism of sigma-1 receptors attenuated the wind-up responses in spinal cords sensitized by repetitive nociceptive stimulation. Esteve is developing E 52862 for the treatment of several pain indications, including diabetic neuropathies, chemotherapy-induced neuropathic pain, postherpetic neuralgia, postoperative pain. Phase II development of this first-in-class agent is underway in Romania, Spain and Greece.

SKF83959 is a benzodiazepine derivative which acts as an agonist of D1 receptor. Activation of D1 receptors by SKF83959 fails to stimulate adenylyl cyclase and inhibits the stimulation of adenylyl cyclase induced by dopamine but stimulates phosphatidylinositol 4,5-biphosphate hydrolysis in membranes of frontal cortex. SKF83959 was identified as a specific agonist for the heteromer D1/D2 complex. SKF83959 elicit anti-parkinsonism effects in monkeys and rodents. In lower concentrations, SKF83959 inhibits serotonin, norepinephrine and dopamine transporters and is an allosteric regulator of sigma 1 receptor. The compound has demonstrated activity in a preclinical model of depression.

(+)-3-(3-Hydroxyphenyl)-N-(1-propyl)piperidine ((+)-3-PPP or preclamor, (R)) is an agonist of the sigma receptors and also acts as a dopamine receptor agonist with autoreceptor as well as postsynaptic receptor stimulatory properties. In vivo experiments have shown, that preclamor, (R) inhibited DOPA accumulation in the striatum, nucleus accumbens, and medial prefrontal cortex.