MDA 19 is a selective agonist of the human peripheral cannabinoid (CB2) receptor, with an EC50 value for activation (63.4 nM) that is 14-fold lower than that for central cannabinoid (CB1) activation (EC50 = 867 nM). Surprisingly, it acts as an inverse agonist at the rat CB2 receptor in cell-based functional assays. MDA19 attenuates tactile allodynia produced by spinal nerve ligation or paclitaxel in a dose-related manner in rats and in CB2+/+ mice but not in CB2-/- mice, indicating that CB2 receptors mediated the effects of MDA19. These effects of MDA 19 are blocked by the selective CB2 antagonist AM630.
