Fig. 2.

Cell-attached recordings from axon initial segment. A, Na⁺ channel activity after depolarizing steps from −90 to −10, −30, and −40 mV.Traces are individual consecutive sweeps. Note single channel openings throughout the steps to −40 mV. Cell c95064. B, I–V plot of Na⁺ channel activity. Unitary current amplitudes are plotted as a function of membrane potential. The linear regression crosses the membrane potential axis at +58 mV and has a slope of 14.8 pS. Error bars are SEM. C, Summary of peak Na⁺ currents in cell-attached patches from initial segment (n = 27) and soma (n = 20). Peak current per area of patch (pA/μm²) is plotted as a function of the distance of the patch from the soma. The points at zero distance correspond to somatic patches. The linear regression line through all points has a slope of 0.018 pA/μm² per micrometer from soma.