Salvinorin A propionate is a selective partial agonist at κ1-opioid receptors (KOR) with a Ki value of 32.6 nM. It inhibits adenylate cyclase (EC50 = 4.7 nM) in HEK293 cells transfected with human KOR. It is selective for KORs over μ, δ, and ORL-1 opioid receptors and has no effect at serotonin, dopamine, muscarinic, or adrenergic receptors. In mice, salvinorin A propionate (13 μg, i.c.v.) reduces nociceptive responses in a radiant heat tail-flick assay, though not as potently as salvinorin A .