Activation of peripheral cannabinoid CB1 receptors inhibits mechanically evoked responses of spinal neurons in noninflamed rats and rats with hindpaw inflammation

The presence of cannabinoid1 (CB1) receptors on primary afferent fibres may provide a novel target for cannabinoid analgesics. The present study investigated the ability of peripheral CB1 receptors to modulate innocuous and noxious transmission in noninflamed rats and rats with peripheral carrageenan inflammation. Effects of peripheral injection of arachidonyl‐2‐choroethylamide (ACEA; 10 and 30 µg in 50 µL), a selective CB1 receptor agonist, on mechanically evoked responses of dorsal horn neurons were studied in noninflamed rats and rats with peripheral carrageenan inflammation. Peripheral injection of ACEA (30 µg in 50 µL) significantly inhibited innocuous (12 g) mechanically evoked responses of spinal neurons in noninflamed (27 ± 4% of control; P