Description_x000D_ Biochem/physiol Actions_x000D_ SA4503 is a high affinity, orally active non-opioid intracellular receptor sigma-1 (σ1R) selective agonist (IC50 = 17.4 nM against 200 nM (+)-pentazocine for binding σ1R), exhibiting ~100-fold less affinity for the sigma 2 receptor subtype (σ2R) and little or no affinity toward 36 other receptors, ion channels and second messenger systems. Oral administration is reported to elicit cerebral acetylcholine (ACh) release in rat frontal cortex and hippocampus (5-20 mg/kg p.o.) and reduce immobility time in a mouse forced swimming test (Immobility time = 214.8 s without vs. 111.6 s with 1.0 mg/kg oral dosage).