IC50: 17 nM (BZ1 receptor)

SX-3228 is a selective ligand for the BZ1 receptor. Among the BZ-receptor subtypes, SX-3228 preferentially binds to the BZ1 receptor (IC ₅₀ =17 nM). It has very weak affinity for the BZ2 receptor (spinal cord: IC ₅₀ =127 nM), and virtually no affinity for the peripheral type BZ receptor (kidney: IC ₅₀ >10000 nM). A compound with similar selectivity, SX-3228 has been shown to bind to BZ receptors, but not to dopamine (D ₁ , D ₂ ), serotonin (5-HT ₁ , 5-HT ₂ and 5-HT ₃ subtypes), noradrenaline (α ₁ , α ₂ , β), GABA or acetylcholine (muscarinic) subtypes.

Administration of 0.5-2.5 mg/kg SX-3228 to rats during the light phase induces a significant reduction of rapid-eye-movement sleep (REMS) (P<0.05) during the third recording hour. Administration of SX-3228 (0.5-2.5 mg/kg) at the beginning of the dark period significantly and dose-dependently reduces waking (W) and increases slow wave sleep (SWS) during the 6-h recording period (P<0.05-0.01); however, significant changes during the last recording hour are restricted to the 2.5 mg/kg dose (P<0.01).