S1RA

S1RA is a sigma-1 (σ₁) receptor antagonist (K_i = 17 nM).¹ It is selective for σ₁ receptors over σ₂ receptors (K_i = 9,300 nM), as well as a panel of 170 additional receptors at 1 µM. S1RA reduces capsaicin-induced mechanical allodynia, formalin-induced licking and biting behavior, and partial sciatic nerve ligation-induced thermal hyperalgesia in mice (ED₅₀s = 26.3, 43.7, and 18.8 mg/kg, respectively). It also enhances fentanyl- or loperamide-induced analgesia without affecting gastrointestinal transit in mice.²

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1. Romero, L., Zamanillo, D., Nadal, X., et al. Pharmacological properties of S1RA, a new sigma-1 receptor antagonist that inhibits neuropathic pain and activity-induced spinal sensitization. Br. J. Pharmacol. 166(8), 2289-2306 (2012).

2. Sánchez-Fernández, C., Montilla-García, Á., González-Cano, R., et al. Modulation of peripheral μ-opioid analgesia by σ1 receptors. J. Pharmacol. Exp. Ther. 348(1), 32-45 (2014).

Garzón-Niño, J., Cortés-Montero, E., Rodríguez-Muñoz, M., et al. αN-Acetyl β-endorphin is an endogenous ligand of σ1Rs that regulates mu-opioid receptor signaling by exchanging G proteins for σ2Rs in σ1R oligomers. Int. J. Mol. Sci. 24(1), 582 (2022).