神经病理性疼痛大鼠背根神经节神经元中小白蛋白的分布特征及表达变化

目的 观察神经病理性疼痛大鼠背根神经节(DRG)神经元中小白蛋白(PV)的分布特征及表达变化.方法 成年雄性SD大鼠42只,随机分为空白对照组(Control组)、假手术组(Sham组)、CCI术后1、3、5、7、14 d组,6只/组.所有动物隔日进行热、机械痛觉过敏痛觉阈值测定,行为学测试完成后取出术侧L5 DRG作冰冻切片,用免疫荧光双标技术经PV单克隆抗体和MAP-2多克隆抗体检测PV神经元的分布特征和表达变化规律.结果 (1)与Control组和Sham组比较,CCI组大鼠分别于术后1、3 d出现明显的机械、热痛觉过敏(P＜0.05),术后7 d 50%机械缩爪阈值(50%PWT)和热缩爪潜伏期(PWL)均降至最低(P＜0.01),术后14 d有所恢复,但仍低于术前水平.(2)在正常大鼠L5DRG中仅有少量PV阳性神经元,多以大型、中型神经元为主,少数为小型神经元.PV阳性神经纤维交织成网环绕在PV阴性神经元的胞体周围.(3)手术侧PV阳性神经元数目在CCI 1、3 d未见明显改变.在术后5、7 d明显减少(P＜0.05),术后14 d恢复至正常水平(P＞0.05).结论 CCI模型大鼠DRG中PV的表达水平呈时间依赖性改变,这种改变与疼痛行为学变化在时相上基本保持一致,因此推测外周感觉神经元中PV表达下降可能参与神经病理性疼痛的发展过程.

Distribution and altered expression of parvalbumin in dorsal root ganglion induced by neuropathtic pain

Objective To explore the distribution and expression changes of parvalbumin in the dorsal root ganglion (DRG) neurons in chronic constriction injury rat models. Methods Forty-two adult male SD rats, weighing 180-200 g, were randomly divided into control group, sham operation group, chronic constriction injury (CCI) 1-, 3- 5-, 7-, 14-day groups, with 6 rats in each group. The right sciatic nerves of rats in CCI groups were moderately ligated proximal to its bifurcation using 4-0 chromic gut, ligation of 4, 1 mm intervals. The sciatic nerves in sham group were only exposed and isolated but not ligated.The changes of naturopathic pain behavior in all animals were observed one day before surgery and 1,3, 5,7 and 14 days after surgery. DRG of L5 spinal nerve was removed for analysis of parvalbumin and MAP2-immunoreactive neurons in DRG in relation to chronic constriction injury. Results ( 1 ) CCI, but not sham surgery, produced significant mechanical allodynia and thermal hyperalgesia ( P ＜ 0. 05 ). The mechanical hyperalfesia was significantly decreased one day after CCI, and the thermal hyperalgesia was greatly attenuated on the 3th day after CCI. Both the thermal and mechanical hyperalgesia was decreased at the lowest level at the 7th day after surgery ( P ＜0. 01 ). (2) In normal rats, there was only a small amount of PV-IR neurons in DRG that were mostly large-and medium-sized neurons, but a few small-sized neurons.PV-IR nerve fibers constituted a network of nerve fibers around cell body of non-PV neurons. In the deep tissue of DRG, bundles of PV-positive nerve fibers traversed between PV-negative neurons. (3) PV-IR neurons in DRG had no significant changes at CCI day 1,3. MAP-2 in PV positive neurons was relatively in good condition, compared with non-PV neurons. PV-IR neurons were decreased from the 5th day after surgery, reduced more significantly until the 7th day (P ＜0. 05), and recovered at the 14th day (P ＞0. 05), compared with the control group. Conclusion The reduction of PV-IR neurons in DRG was accompanied by change of pain behavior of CCI rats, suggesting that the reduction of PV-IR neurons is in relation to peripheral noxious stimulation and the down-regulation of the PV expression in the imbalance of calcium homeostasis mechanisms, which may involve in the development and maintenance of neuropathic pain.