Effect of transient receptor potential A1 antagonists on post-operation pain in a rat model of incisional pain

Abstract

Objective To investigate the effect of intrathecal and intraplantar injection of transient receptor potential A1 (TRPA1) antagonists on post-operation pain in a rat model of incisional pain.Methods Seventy-two adult male Sprague-Dawley rats weighing 200-250 g were randomly divided into 6 groups (n =12):control group (group C),incision group (Ⅰ group).intrathecal injection of DMSO group (DMSO1 group),intraplantar injection of DMSO group (DMSO2 group),intrathecal injection of HC-030031 group (H1 group),intraplantar injection of HC-030031 group (H2 group).Rats in Ⅰ,DMSO1,DMSO2,H1,and H2 groups were operated with incision.Intrathecal or intraplantar injections were performed 24 h after operation.The rats in DMSO1 and H1 groups were respectively intrathecally injected with 10％ DMSO (20 μl) and HC-030031 (50 μg).DMSO2 and H2 groups were respectively intraplantarlly injected with 10％ DMSO (40 μ l) and HC-030031 (100 μg).The paw withdrawal mechanical threshold (PWMT) was measured at 1 h before injection (T0),and 0.5 h (T1),1.0 h (T2),2.0 h (T3),4.0 h (T4) and 6.0 h (T5) after intrathecal or intraplantar injections.Four SD rats in each group were sacrificed at T4 and the segments of the spinal cord were obtained for determination of TRPA1 expression in the spinal cord by using Western blotting.Results As compared with C group [(34.4 ± 4.7) g] and Ⅰ group [(23.8 ±4.3) g],PWMT was significantly decreased and the expression of TRPA1 was up-regulated in DMSO1 and DMSO2 groups at T4 in spinal dorsal horn.The PWMT in H1 group [(28.3 ± 2.4) g] and H2 group [(29.1 ±4.2) g] was increased and the expression of TRPA1 was down-regulated at T4 as compared with DMSO1 group [(24.6 ±3.5) g] and DMSO2 group [(22.1 ±4.7) g].Conclusion Intrathecal or intraplantar administration with TRPA1 antagonists could attenuate incisional pain in rats. Key words: Incisional pain; Spinal cord; Transient receptor potential A1