Stationarity of sodium channel gating kinetics in excised patches from neuroblastoma N1E 115

Na channel gating parameters in a number of preparations are translated along the voltage axis in excised patches compared to cell attached or whole cell recording. The aim of this study is to determine whether these changes in gating behavior continue over an extended period or, rather, develop rapidly on excision with stationary kinetics thereafter. Average currents were constructed from single-channel records from neuroblastoma N1E 115 at various times after excision, excluding the first 5 min, in eight inside-out excised patches. Single exponentials were fitted to the current decay of the average records, and the mean time constant for each patch was determined. Values were plotted as the percentage difference from these means for each patch against time from excision. Collected results show no obvious trend in values from 5 min to 2 h. Kinetics are stationary, and shifts in Na channel gating parameters along the Voltage axis seen in excised as compared to whole cell configuration in neuroblastoma must be complete by the first few minutes after excision. Raising the internal Na concentration reduced the single channel current amplitude, confirming that these are Na channels.