The animals were allowed a 2-day adaptation period before burn injury. The nociceptive behaviors of the rats in the Sham + Veh2, Burn + Veh2, Burn + SB203580, Sham + SB203580, and Burn + R(L) groups (n = 6 per group) were tested before the intraspinal injection, and 15, 30, 60, and 120 min upon the intraspinal injection 7 days after burn injury. The nociceptive behaviors of the other groups (n = 6 per group) were tested before burn injury and at 1, 3, 5, 7, and 14 days post-burn injury. Upon adaptation (30 min), mechanical thresholds were measured by hind paw withdrawal to a graded series of von Frey filaments (Stoelting, USA) (4–26 g) applied to the plantar area of each hind paw. The modified Dixon “up–down” technique was applied to determine the mechanical nociceptive threshold, as described previously.22 (link) The experimenter was blinded to the groups of rats.