Objective ：To investigate the different suppressive effect of lidocaine on persistent Na^＋ current and transient Na^＋ current in injured or uninjured dorsal root ganglion neurons. Methods： Totally 23 SD rats were randomly divided into 2 groups： control group （n： 10） and chronically compressed DRG （dorsal root ganglion） group （CCD group, n= 13）. Rats were anesthetized and DRG was isolated. Single DRG neuron was isolated by enzymatic disassociation method. Persistent Na^＋ current （INap） and transient Na^＋ current （INaT） were elicited in voltage clamp mode. Results： The presence of INap was testified in most DRG neurons （38/46 neurons in CCD group and 31/39 neurons in control group, P〉0. 05）. However, the cur- rent density of INap in CCD group （4. 6±0. 6 pA/pF, n=38 neurons） was greater than that in control group （2.5±0.4 pA/pF, n=31 neurons） （P〈0. 05）. The characteristics of INap was observed and found that INap could he blocked by 0.2 μmol/L tetrodotoxin easily. Furthermore, the does-effect relationship of lidocaine on INaP and IN.T were also examined. INaP and IN.T were suppressed by different concentrations of li- docaine, the range for INap was 5-20 μmol/L and for INaT was 0. 05-2 mmol/L. Conclusion： INap and INaT were suppressed by different concentrations of lidocaine. INap was suppressed by very low concentration of lidocaine （5-20 μmol/L）. However, INaT could only be blocked by high concentration of lidocaine （0.05-2 mmol/L）.
