Local application of TTX to the proximal axon blocks whole-cell I_NaP, whereas somatic and dendritic applications have little or no effect. A, Whole-cell somatic voltage-clamp recording of I_NaP, and the effect of application of 0.1 μm TTX near the apical dendrite (75 μm), near the soma, and near the proximal axon (−10 μm). Superimposed are current traces before (gray) and after TTX application (black) at a time indicated by arrow. Currents were elicited by applying the 2-s-long voltage ramps from −70 to 0 mV. Note that blockade of I_NaP by TTX applied near the axon was partially reversible. B, The graph showing the relative effect of TTX on I_NaP amplitude as a function of application site. The dots are pooled data from nine neurons including that shown in A. Each dot represents a ratio of I_NaP amplitude at −35 mV before and after TTX application.