(S)-AM1241 binds to cannabinoid (CB) receptors and is selective for the CB2 over the CB1 receptor (Kis = 658 and >10,000 nM, respectively, in a membrane assay using human receptors). (S)-1241 acts as an agonist at human, rat, and mouse CB2 receptors but shows greater activity at human CB2 (EC50 = 131 nM) than at rat and mouse CB2 receptors (EC50 = 785 and 2,000 nM, respectively). Similar to the racemate AM1241 , (S)-AM1241 produces antinociception to thermal, but not mechanical, pain in rats. 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 .