The effect of repetitive transcranial magnetic stimulation on neuropathic pain and nNOS in dorsal root ganglia in a rat model / 中华物理医学与康复杂志

ABSTRACT

Objective In order to explore the mechanism of repetitive transcranial magnetic stimulation rTMS) on neuropathic pain,we observed the effect of different frequencies of rTMS on neuropathic pain and the expression of neuronal nitric oxide synthase (nNOS) in the dorsal root ganglion (DRG).Methods A total of 28 male Sprague-Dawley rats were used and divided into a control group,in which sham-operation was performed,and an experimental group which was further divided into a sham-rTMS group,a 1 Hz group and a 20 Hz group after successful neuropathic pain model was established by operation to ligate the left sciatic nerves,with 7 rats in each group.Three days after the operation,rTMS was applied to the primary motor cortex (M1) contralateral to the pain once dai ly for 10 consecutive days.The pain behavior and nNOS expression in the DRG were measured before and after 10 days of rTMS intervention.Results All the neuropathic pain model rats demonstrated pain-related behaviors 3 days postoperation,the mechanical pain thresholds were significantly lower than those in the control group (P ＜ 0.05).After rTMS treatment,the mechanical hyperalgsia was significantly relieved in 20 Hz group but not 1 Hz group as demonstrated by a comparison with the sham-rTMS group (P ＜ 0.05).The expression of nNOS in DRG ipsilateral to the neuropathic pain was significantly increased in sham-rTMS group and 1 Hz group (P ＜ 0.05) when compared with the control group.Meanwhile,it was shown that expression of nNOS was down-regulated in 20 Hz group but not 1 Hz group (P ＜ 0.05).The degree of pain relief in 20 Hz group was negatively correlated with the expression of nNOS in DRG (P ＜0.05).Conclusions Neuropathic pain induced by peripheral nerve injury is associated with elevated expression of nNOS in the DRG.High-frequency rTMS can relieve neuropathic pain through down-regulating the overexpression of nNOS in the DRG,but the low-frequency rTMS has no such effect.