Objectives: To observe the effect of electroacupuncture (EA) at different intensities on nociceptive discharges of wide dynamic range (WDR) neurons in the spinal dorsal horns (DHs) of rats, so as to explore its regulatory characteristics on nociceptive signals at the spinal level.
Methods: A total of 25 male SD rats were used in the present study. A microelectrode array was used to record the discharge activity of WDR neurons in the lumbar spinal DHs of normal rats. After finding the WDR neuron, electrical stimulation (pulse width of 2 ms) was administered to the plantar receptive field (RF) for determining its response component of discharges according to the latency of action potential generation (Aβ ［0 to 20 ms］, Aδ ［20 to 90 ms］, C ［90 to 500 ms］ and post-discharge ［500 to 800 ms］). High-intensity electrical stimulation was continuously applied to the RF at the paw's plantar surface to induce DHs neuronal windup response. Subsequently, EA stimulation at different intensities (1 mA and 2 mA) was applied to the left "Zusanli"(ST36) at a frequency of 2 Hz/15 Hz for 10 min. The induction of WDR neuronal windup was then repeated under the same conditions. The quantity of nociceptive discharge components and the windup response of WDR neurons before and after EA stimulations at different intensities were compared.
Results: Compared to pre-EA, both EA1 mA and EA2 mA significantly reduced the number of Aδ and C component discharges of WDR neurons during stimulation, as well as post-discharge (P<0.01, P<0.001). The inhibitory rate of C component by EA2 mA was significantly higher than that by EA1 mA (P<0.05). Meanwhile, both EA1 mA and EA2 mA attenuated the windup response of WDR neurons (P<0.05, P<0.01), and the effect of EA2 mA was stronger than that of EA1 mA (P<0.05). Further analysis showed that when EA1 mA and EA2 mA respectively applied to both non-receptive field (non-RF) and RF, a significant reduction in the number of Aδ component, C component and post-discharge was observed (P<0.05, P<0.01). EA2 mA at the non-RF and RF demonstrated a significant inhibitory effect on the windup response of WDR neurons (P<0.01, P<0.05), but EA1 mA only at the non-RF showed a significant inhibitory effect on the windup response (P<0.01).
Conclusions: EA can suppress nociceptive discharges of spinal DHs WDR neurons in rats. The inhibitory impact of EA is strongly correlated with the location and intensity of EA stimulation, and EA2 mA has a stronger inhibitory effect than EA1 mA.
目的: 观察不同强度电针对大鼠脊髓背角广动力（WDR）神经元伤害性电活动的作用，探讨电针在脊髓背角水平调控伤害性信号的效应特征。方法: 采用多通道在体电生理技术记录25只正常雄性SD大鼠脊髓背角WDR神经元的电活动，在神经元的足底感受野（RF）给予连续高强度电刺激诱发神经元的windup，而后于大鼠同侧“足三里”穴区进行不同强度（1 mA或2 mA）的电针（EA1 mA、EA2 mA）干预10 min，刺激频率为2 Hz /15 Hz，然后再次以相同条件诱发WDR神经元的windup。比较不同强度电针干预前后，WDR神经元伤害性放电成分的总数量及windup现象的变化。结果: EA1 mA和EA2 mA均显著减少了WDR神经元Aδ和C成分及后放电的数量（P<0.01，P<0.001），且EA2 mA对C成分的抑制率显著高于EA1 mA（P<0.05）；EA1 mA和EA2 mA干预减弱了WDR神经元的windup现象（P<0.05，P<0.01），且EA2 mA的效应要强于EA1 mA（P<0.05）。EA1 mA和EA2 mA作用于WDR神经元的非感受野（non-RF）和RF均明显减少了其Aδ成分、C成分和后放电的数量（P<0.05，P<0.01）；对于WDR神经元windup现象，EA2 mA作用于non-RF和RF均能发挥显著的抑制作用（P<0.01，P<0.05），而EA1 mA只有作用于non-RF时才能显著抑制（P<0.01）。结论: 电针可以抑制大鼠脊髓背角WDR神经元的伤害性电活动，抑制效应与EA干预的强度和部位直接相关，2 mA的抑制效应要强于1 mA。.
Keywords: Analgesia; Electroacupuncture; Nociceptive signal; Stimulation intensity; Wide dynamic range neurons.