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(I_(NaP)) and transient Na^+ current(I_(NaT)) were elicited in voltage clamp mode.Results:The presence of I_(NaP) 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 I_(NaP) 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 I_(NaP) was observed and found that I_(NaP) could be blocked by 0.2μmol/L tetrodotoxin easily.Furthermore,the does-effect relationship of lidocaine on I_(NaP) and I_(NaT) were also examined.I_(NaP) and I_(NaT) were suppressed by different concentrations of li- docaine,the range for I_(NaP) was 5-20μmol/L and for I_(NaT) was 0.05-2 mmol/L.Conclusion:I_(NaP) and I_(NaT) were suppressed by different concentrations of iidocaine.I_(NaP) was suppressed by very low concentration of lidocaine(5-20μmol/L).However,I_(NaT) could only be blocked by high concentration of lidocaine(0.05-2 mmol/L).
