RESUMO
Objective To evaluate the role of caspase-1 in the spinal cord in a rat model of incisional pain.Methods Eighteen adult male Sprague-Dawley rats,weighing 250-280 g,in which intrathecal catheters were successfully implanted,were divided into 3 groups (n =6 each) using a random number table:incision pain group (group Ⅰ),incision pain plus dimethyl sulfoxide group (group ID) and incision pain plus caspase-1 inhibitor (Ac-YVAD-CMK) group (group IA).At 10 min before establishment of the model,0.9％ normal saline 20 μl was intrathecally injected in group Ⅰ,dimethyl sulfoxide 20 μl was intrathecally injected and then the catheter was washed with 0.9％ normal saline 10 μl in group ID,and Ac-YVAD-CMK 1 nmol/μl (dissolved in 20 μl dimethyl sulfoxide) and then the catheter was washed with 0.9％ normal saline 10 μl in group IA.The mechanical paw withdrawal threshold (MWT) of the ipsilateral hind paw was measured at 2 h before intrathecal catheterization (T0),3 days after intrathecal catheterization (T1) and 2,6,24 and 48 h after establishment of model (T2-5).The rats were sacrificed after the last measurement of pain threshold at T5,and lumbar enlargement segments of the spinal cord were removed for detection of caspase-1 (p20) expression and interleukin-1beta (IL-1β) content by Western blot and enzyne-linked immunosorbent assay,respectively.Results Compared with the baseline at T0,the MWT was significantly decreased at T2-5 in Ⅰ and ID groups (P＜0.05),and no significant change was found in MWT at T1-5 in group IA (P＞0.05).Compared with Ⅰ and ID groups,the MWT at T2-5 was significantly increased at T2-5,and the caspase-1 (p20) protein expression and IL-1β content were decreased in group IA (P＜0.05).There was no significant difference in MWT,expression of caspase-1 (p20) protein or IL-1β content between group Ⅰ and group ID (P＞0.05).Conclusion The activation of caspase-1 in the spinal cord can promote the release of IL-1β and thus is involved in the incision pain in rats.