SA 4503 is a sigma-1 (σ1) receptor agonist that is selective for σ1 over σ2 receptors in a radioligand binding assay using guinea pig brain homogenates (Kis = 4.6 and 63 nM, respectively).1,2 SA 4503 (10 μM) reduces light-induced cell death, decreases in σ1 expression, disruption of the mitochondrial membrane potential, and activation of caspase-3/7 in murine 661W cells, effects that are blocked by the σ1 receptor antagonist BD 1047 (Item No. 22928).2 In vivo, SA 4503 (10 mg/kg) increases extracellular acetylcholine concentrations in the frontal cortex and improves step-through latency in a passive avoidance test in rats with scopolamine-induced memory impairment.3 SA 4503 reduces working and reference memory errors induced by a time delay and MK-801 (Item No. 10009019) in a radial arm maze in rats when administered at a dose of 0.3 mg/kg, effects which are ameliorated by the σ1 antagonist NE-100 (Item No. 19642).4 Pre-administration of SA 4503 (500 μM) into the intravitreal space reduces light-induced thinning of the mouse retina outer nuclear layer by approximately 50%. 2WARNING This product is not for human or veterinary use.