(S)-AM1241 binds the peripheral cannabinoid (CB2) receptor from human, rat, and mouse with Ki values of 658, 893, and 577 nM, respectively). It exhibits weak binding for central cannabinoid receptor (CB1) with a Ki value exceeding 10 μM. (S)-1241 is an agonist for CB2 for all three species, but shows greater activity at human CB2 (EC50 = 131 nM) than for either rat or mouse CB2 (EC50 = 785, 2000 nM, respectively). Like the racemate AM1241 , (S)-AM1241 produces antinociception in rats to thermal, but not mechanical, pain. The pain-reducing effect of (S)-AM1241 is blocked by the CB2-specific inhibitor SR 144528, but not by either the CB1-selective inhibitor rimonabant or the opioid receptor blocker naloxone.
