Wu Baishan, Ni Jiaxiang, Zhang Chunlei, Fu Paul, Yue Jianning, Yang Liqiang
Beijing Xuanwu Hospital Capital Medical University, Beijing, China.
Neurol Res. 2012 May;34(4):408-14. doi: 10.1179/1743132812Y.0000000026.
The present study investigated changes in the met-enkephalin (M-ENK) levels in the spinal cord. We also determined the mechanical threshold value of pain in spared nerve injury (SNI) rats after applying pulsed radiofrequency (PRF) on L5 dorsal root ganglion (DRG).
Sixty-four rats were divided into four groups: the normal group (n = 16), the control group (n = 16), the sham intervention group (n = 16), and the PRF group (n = 16). With exception for the normal group, the other three groups were treated with an established SNI model. After 7 days, PRF or sham intervention was applied on the right L5 DRG. The M-ENK levels in the spinal cord were examined by radioimmunoassay 24 hours after applying PRF or sham operation. Mechanical threshold values of pain were also tested 1 day before SNI procedure, 1 and 2 days after SNI procedure, and 2 and 24 hours after applying PRF or sham operation.
Twenty-four hours after treatment with PRF, M-ENK levels in spinal cord increased significantly, while no changes were detected in the sham intervention group. Hyperalgesia was found in rats 1-2 days after SNI procedure and was improved by PRF. This was demonstrated by an increased mechanical threshold of pain 2 and 24 hours after the PRF. The sham intervention group showed no change in the mechanical threshold of pain.
This study demonstrates that applying PRF on the DRG can improve hyperalgesia and increase M-ENK levels in the spinal cord of SNI rats within 24 hours. These findings indicate that the endogenous M-ENK in the spinal cord is involved in the mechanism of PRF on the therapy of neuropathic pain.
本研究调查脊髓中甲硫氨酸脑啡肽（M-ENK）水平的变化。我们还测定了对L5背根神经节（DRG）施加脉冲射频（PRF）后， spared神经损伤（SNI）大鼠的疼痛机械阈值。
64只大鼠分为四组：正常组（n = 16）、对照组（n = 16）、假干预组（n = 16）和PRF组（n = 16）。除正常组外，其他三组均采用已建立的SNI模型进行处理。7天后，对右侧L5 DRG施加PRF或假干预。在施加PRF或假手术后24小时，通过放射免疫测定法检测脊髓中的M-ENK水平。在SNI手术前1天、SNI手术后1天和2天以及施加PRF或假手术后2小时和24小时，也测试疼痛的机械阈值。
PRF治疗24小时后，脊髓中的M-ENK水平显著升高，而假干预组未检测到变化。在SNI手术后1 - 2天发现大鼠存在痛觉过敏，PRF可改善这种情况。这通过PRF后2小时和24小时疼痛机械阈值的升高得到证明。假干预组的疼痛机械阈值没有变化。
本研究表明，对DRG施加PRF可改善痛觉过敏，并在24小时内增加SNI大鼠脊髓中的M-ENK水平。这些发现表明，脊髓中的内源性M-ENK参与了PRF治疗神经性疼痛的机制。
