Attenuation of existing thermal hyperalgesia by HDACI. Mice were treated with CFA i.pl. for indicated time and then intrathecally injected with 25 μg SAHA for 30 min before measurement of thermal response. Control animals were treated with i.t. saline after CFA injection for the same time. Basal line was measured before the CFA injection. Student t-test was used to examine the significance as indicated groups. * P < 0.01.