Electrophysiological changes of dorsal root ganglion neurons in rats with neuropathic pain

Objective To investigate the electrophysiological changes of the dorsal root ganglion (DRG) neurons in rats with neuropathic pain.Methods Twenty adult male SD rats, 3-4 weeks old, weighing 100-150 g, were randomly divided into 2 groups: control group (group C, n = 5), and neuropathic pain group (group NP, n = 15). The neuropathic pain was induced by chronic constrictive injury (CCI) of their right side sciatic nerve. The thermal and mechanical pain thresholds were measured at 1 d before and at 4 d after CCI. The DRG neurons were isolated acutely after the measurement of pain threshold and then whole-cell current clamp was used to record the electrophysiological activity. Results The thermal and mechanical pain thresholds were significantly lower at 4 d after CCI than at 1 d before CCI in group NP ( P 0.05). The membrane potential, threshold potential, and spontaneous discharge rate were significantly higher, the reobase was significantly lower in the medium DRG neurons in group NP than in group C ( P 0.05) . The threshold potential was significantly higher in the large DRG neurons in group NP than in group C ( P 0.05) . Conclusion The electrophysiological changes of the DRG neurons mainly occurs in the small and medium DRG neurons in the rats with neuropathic pain, which leads to an increase in the excitability, repetitive firing rate and spontaneous discharge rate. Key words: Neuralgia; Ganglia,spinal;  Electrophysiology