CB2受体激动剂JWH015对大鼠神经病理性疼痛的治疗作用

目的 研究鞘内注射CB2受体激动剂JWH015对背根节慢性压迫(chronic compression of the dorsal root ganglia,CCD)大鼠痛阈和脊髓背角磷酸化NMDA受体NR2B亚基表达的影响,探讨CB2受体激动剂的镇痛作用及其可能机制.方法 鞘内置管成功后的雄性SD大鼠84只,随机分为3组:假手术+50%二甲基亚砜(dimethyl sulphoxide,DMSO)组(Sham组)、CCD+50%DMSO组(Vehicle组)、CCD+JWH015组(JWH015组).Sham组和Vehicle组各有6只大鼠在假手术或CCD后第7天(鞘内未给药)取脊髓标本,作为免疫组织化学法检测脊髓背角Tyr-1472磷酸化NR2B亚基表达的基础值.其余大鼠在假手术或CCD后第7天分别鞘内注射50%DMS010μl或JWH015 10μg.假手术或CCD之前、鞘内给药之前、之后1、2、4、8、24、72 h分别记录机械刺激缩足反射阈值(paw withdrawal mechanical threshold,PWMT)和热刺激缩足反射潜伏期(paw withdrawalthermal latency,PWTL)(n=6),鞘内给药之后4、8、24、72 h分别取脊髓标本(n=6),应用免疫组织化学法检测脊髓背角Tyr-1472磷酸化NR2B亚基的表达情况.结果 鞘内给药前Vehicle组和JWH015组大鼠的PWMT和PWTL均较基础值明显下降(P<0.01);与Vehicle组相比,JWH015组在给药后1、2、4 h PWMT和PWTL显著升高(P<0.01),但在给药后8、24、72 h差异无统计学意义(P>0.05);Sham组大鼠脊髓背角Tyr-1472磷酸化NR2B业基均呈低水平表达,但在CCD后第7天表达水平明显增强;鞘内注射50%DMSO后在各时间点均未能减弱CCD大鼠脊髓背角Tyr-1472磷酸化NR2B亚基的表达;鞘内注射JWH015在给药后4、8 h能明显减弱CCD大鼠脊髓背角Tyr-1472磷酸化NR2B亚基的表达,但在给药后24、72 h Tyr-1472磷酸化NR2B亚基的表达再次增强.结论 CB2受体激动剂JWH015对大鼠的神经病理性疼痛有治疗作用,该作用可能与抑制脊髓背角Tyr-1472磷酸化NR2B亚基的表达有关.

The antinociceptive effect of intrathecal CB2 cannabinoid receptor agonist (JWH015) in rats with chronic compression of the dorsal root ganglia

Objective To test whether activation of CB2 receptor would induce antinociception and investigate the role of in-trathecal JWH015 in the modulation of Tyr-1472 phosphorylation of the spinal NR2B subunit in a model of neuropathic pain. Meth-otis 84 male SD rats with intrathecal catheter insertion were randomly divided into 3 groups: sham + 50% DMSO group (Sham group); CCD + 50%DMSO group(Vehicle group); CCD+JWH015 group(JWH015 group). Seven days after Sham or CCD(without in-trathecal injection), the lumbosacral spinal cords of 6 Sham rats and 6 CCD rats were collected for immunohistochemical study to de-termine the spinal expression of Tyr-1472 phosphorylated NR2B subunit(baseline). The rest were intrathcally injected with 50%DMSO 10 μl or JWH015 10 μg seven days after Sham or CCD. For behavioral studies, the data of paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) were measured in Sham group or CCD group, before intrathecal injection and 1, 2, 4, 8, 24, 72 h after intrathecal injection (n=6). For immunohistochemical study, the lumbosacral spinal cords were collected 4, 8, 24, 72 h after intrathecal injection(n=6). Results Compared with the baseline before operation, the PWMT and the PWTL of Vehicle group and JWHOI5 group began to decrease before intrathecal injection(P<0.01). Compared with Vehicle group, PWMT and PWTL of JWH015 group increased markedly 1, 2 and 4 h after intrathecal injection (P0.05). Tyr-1472 phosphorylated NR2B subunit expression in the superficial dorsal horn was weak in all sham groups, but increased significantly 7 days after CCD. While intrathecal 50%DMSO did not decrease the expres-sion of Tyr-1472 phosphorylated NR2B subunit in the superficial dorsal horn, the expression of Tyr-1472 phosphorylated NR2B sub-unit in the superficial dorsal horn decreased obviously 4 h and 8 h after intrathcal JWH015. However, the expression of Tyr-1472 phosphorylated NR2B subunit in the superficial dorsal horn increased again 24 h and 72 h after intrathcal JWH015. Conclusion In-trathecal administration of CB2 receptor agonist JWHOI5 may provide analgesic effect, which is probably attributed to the decrease in the spinal expression of Tyr-1472 phosphorylated NR2B subunit.