Role of caspase-1 in spinal cord in a rat model of incisional pain

Abstract

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 enzyme-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). 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). 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. Key words: Pain, postoperative; Caspase1; Interleukin-1beta; Spinal cord