(R)-AM1241 avidly binds the peripheral cannabinoid receptor (CB2) (Ki = 15 nM) with over 100-fold selectivity over central cannabinoid receptor (CB1). Like the racemate AM1241 , (R)-AM1241 is an agonist of human CB2, but an inverse agonist of rat and mouse CB2. In rats, (R)-AM1241 produces antinociception to thermal, but not mechanical, pain. The pain-reducing effect of (R)-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.
