脊髓星形胶质细胞TLR3与大鼠痛觉过敏形成的关系

Relationship between toll-like receptor 3 of spinal astrocytes and development of hyperalgesia in rats

目的评价脊髓星形胶质细胞Toll样受体3（TLR3）与大鼠痛觉过敏形成的关系。方法雄性SD大鼠，体重180～250g，取鞘内置管成功的大鼠126只，随机分为3组（n=42），正常对照组（C组）；生理盐水组（NS组）鞘内注射生理盐水0．5ml／kg，1次，d，连续7d；痛觉过敏组（H组）腹腔注射米诺环素40mg／kg＋鞘内注射Poly（I：C）0．5mg／kg，1次／d，连续7d。各组于鞘内给药前1d和鞘内给药后1、3、5、7、10、14、21、28d时测定机械痛阈和热痛阈；各组于鞘内给药后7d时处死6只大鼠，取L4.5脊髓节段，采用免疫组化法测定脊髓背角胶质纤维酸性蛋白（GFAP）表达；各组于鞘内给药前1d和鞘内给药后1、7、14、21、28d时各处死6只大鼠，取L4.5脊髓节段，采用RT-PCR法测定TLR3mRNA表达。结果与C组和NS组比较，H组机械痛阈降低，脊髓背角GFAP和TLR3mRNA表达上调（P〈0．05）。结论TLR3与其特异性配体结合后，激活脊髓背角星形胶质细胞，诱发大鼠痛觉过敏。

Objective To evaluate the relationship between toll-like receptor 3 （TLR3） of spinal astrocytes and development of hyperalgesia induced by intrathecal Poly （I：C） in rats. Methods Male SD rats weighing 180-250 g were anesthetized with intraperitoneal （IT） 10% chloral hydrate 3-3.5 ml/mg. Intrathecal catheter was placed at L6-S1 interspace with the tip positioned at lumbar enlargement. One hundred and twenty-six SD rats in which IT catheters were successfully placed were randomly divided into 3 groups （ n = 42 each） ： group Ⅰ normal control （C） ; groupl/ receiv.ed normal saline 0.5 ml/kg IT, once a day for 7 consecutive days （NS） ; group Ⅲ received minocycline 40 mg/kg IP ＋ Poly （I：C） 0.5 mg/kg IT once a day for 7 consecutive days （H）. Paw withdrawal threshold to von Frey filament stimulation （PWT） and paw withdrawal latency to nociceptive thermal stimulation （PWL） were measured at 1 d before operation and 1, 3, 5, 7, 10, 14, 21, 28 day after IT injection. Six animals were killed at 1 d before operation and 1, 7, 14, 21, 28 d after IT injection respectively in each group and the lumbar segment of the spinal cord was removed for determination of the expression of TLR3 mRNA （by RT-PCR） and GFAP in the spinal dorsal horn （by immuno-histochemistry） （only on day 7 after IT injection）. Results PWT was significantly decreased and the expression of GFAP and TLR3 mRNA in the spinal dorsal horn were significantly up-regulated in group H as compared with group C and NS. Conclusion TLR3- ligand binding can activate astrocytes in the spinal dorsal horn and then induce hyperalgesia in rats.