Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700, China.
Zhen Ci Yan Jiu. 2024 Feb 25;49(2):103-109. doi: 10.13702/j.1000-0607.20221248.
To observe the analgesic effects of different levels and intensities of electrical stimulation on the local acupoints in the pain source area and their impact on wide dynamic range (WDR) neurons in the spinal dorsal horn, in order to provide a basis for selecting appropriate parameters for electroacupuncture (EA) stimulation.
Wistar rats were used in 3 parts of the experiment. Complete Freund's adjuvant was used to establish a model of inflammation-induced pain in the gastrocnemius muscle. After modeling, 6 rats were randomly selected for multi-channel extracellular electrophysiological recording of the electrical activity of WDR neurons, to determine the threshold for activating the A-component (Ta) and the C-component (Tc), which were used as the intervention intensities for skin transcutaneous electrical acupoint stimulation (TEAS) or EA. Thirty-six rats were randomly divided into normal , model , TEAS-Ta , TEAS-Tc, EA-Ta , and EA-Tc groups, with 6 rats in each group. In the pain source area , Ta or Tc intensity of TEAS or EA intervention at"Chengshan"(BL57) was performed for 30 min each time, once a day, for 3 consecutive days. A small animal pressure pain measurement instrument was used to measure the mechanical pressure pain threshold of the gastrocnemius muscle in rats, and the Von Frey filament was used to measure the mechanical pain threshold of the footpad. Thirteen rats were randomly selected to observe the immediate responsiveness of WDR neurons to Ta/Tc intensity of EA or TEAS in BL57.
The thresholds of TEAS to activate WDR neuron A-component or C-component were (2.43±0.57) mA and (7.00±1.34) mA, respectively, while the thresholds for EA to activate muscle WDR neuron A-component or C-component were (0.72±0.34) mA and (1.58±0.35) mA, respectively. After injection of CFA into the gastrocnemius muscle, compared with the normal group both the mechanical pressure pain threshold of the gastrocnemius muscle and the mechanical pain threshold of the footpad of rats in the model group were significantly decreased (<0.001). After TEAS-Ta, TEAS-Tc or EA-Ta intervention in the BL57, both the mechanical pressure pain threshold of the gastrocnemius muscle and the mechanical pain threshold of the footpad were significantly higher than those in the model group (<0.05, <0.001). Compared with the normal group, the electrical threshold for evoking WDR neuron C-component discharge was significantly decreased (<0.001) in the model group, while increased after TEAS-Ta, TEAS-Tc, or EA-Ta intervention (<0.01) compared with the model group. The evoked discharge frequency of muscle WDR neurons decreased significantly after immediate intervention with TEAS-Ta, TEAS-Tc, or EA-Ta (<0.01, <0.05). EA-Tc had no significant improvement on the evoked electrical activity of WDR neurons or pain behavior.
TEAS-Ta, TEAS-Tc, or EA-Ta can all alleviate the local and footpad mechanical pain in rats with muscle inflammation and inhibit the responsiveness of WDR neurons, indicating that different intensities are required for analgesic effects at different levels of acupoints in the pain source area.
观察不同强度和水平的电刺激对疼痛源区局部穴位的镇痛效果及其对脊髓背角宽动态范围（WDR）神经元的影响，为选择合适的电针（EA）刺激参数提供依据。
本实验分 3 部分，采用完全弗氏佐剂建立大鼠腓肠肌炎症性疼痛模型。造模后，随机选取 6 只大鼠进行多通道细胞外电生理记录 WDR 神经元电活动，以确定激活 A 成分（Ta）和 C 成分（Tc）的阈强度，作为皮透电穴位刺激（TEAS）或 EA 的干预强度。36 只大鼠随机分为正常组、模型组、TEAS-Ta 组、TEAS-Tc 组、EA-Ta 组和 EA-Tc 组，每组 6 只。在疼痛源区，对“承山”（BL57）进行 Ta 或 Tc 强度的 TEAS 或 EA 干预，每次 30 min，每天 1 次，连续 3 天。采用小动物压痛测量仪测量大鼠腓肠肌的机械压痛阈，用 Von Frey 细丝测量足底的机械痛阈。随机选取 13 只大鼠观察 BL57 处 EA 或 TEAS 的 Ta/Tc 强度对 WDR 神经元即刻反应的影响。
TEAS 激活 WDR 神经元 A 成分或 C 成分的阈强度分别为（2.43±0.57）mA 和（7.00±1.34）mA，而 EA 激活肌肉 WDR 神经元 A 成分或 C 成分的阈强度分别为（0.72±0.34）mA 和（1.58±0.35）mA。向大鼠腓肠肌注射 CFA 后，与正常组相比，模型组大鼠腓肠肌的机械压痛阈和足底机械痛阈均显著降低（<0.001）。与模型组相比，BL57 处 TEAS-Ta、TEAS-Tc 或 EA-Ta 干预后，大鼠腓肠肌的机械压痛阈和足底机械痛阈均显著升高（<0.05，<0.001）。与正常组相比，模型组 C 成分诱发 WDR 神经元放电的电阈值显著降低（<0.001），而 TEAS-Ta、TEAS-Tc 或 EA-Ta 干预后显著升高（<0.01）。TEAS-Ta、TEAS-Tc 或 EA-Ta 即刻干预后，肌肉 WDR 神经元的诱发放电频率均显著降低（<0.01，<0.05）。EA-Tc 对 WDR 神经元的诱发电活动和疼痛行为无明显改善。
TEAS-Ta、TEAS-Tc 或 EA-Ta 均可缓解大鼠肌肉炎症引起的局部和足底机械痛，并抑制 WDR 神经元的反应性，表明疼痛源区不同水平的穴位需要不同的强度才能产生镇痛效果。
