Figure 10.

Comparison between experimental data and radial cable model predictions. (A) Di-8-ANEPPS transients recorded in response to 0-, 50-, 55-, 60-, 70-, and 100-mV depolarizing pulses (black, red, blue, green, orange, and purple traces, respectively). The deconvolution of ΔF/F (left vertical axis) into membrane potential (right vertical axis) was done according to the regression formula: $V=-\frac{(\Delta \text{F/F}+0.0111)}{1.24\times {10}^{-3}}$ (in mV). (B) Model predictions of the TTS membrane potential assuming that the Na channel permeability density is 5.64 × 10⁻⁴ cm/s at the TTS membranes ($\stackrel{-}{{\text{P}}_{\text{Na}}}$-TTS) and 3.76 × 10⁻⁴ cm/s at the surface membrane (P_Na-S). The access resistance for the TTS (R_s) was 10 Ωcm². Other model parameters are listed in Table A1. (C) Model predictions of the TTS membrane potentials assuming that I_Li is only generated at in the surface membrane ($\stackrel{-}{{\text{P}}_{\text{Na}}}$-TTS = 0 and $\stackrel{-}{{\text{P}}_{\text{Na}}}$-S = 11.1 × 10⁻⁴). (D) Experimental ionic currents corresponding to the optical records in A. (E and F) The predicted ionic currents associated with the simulated traces in B and C, respectively. The same color code was used in A–F. Fiber parameters: radius, 30 µm; length, 572 µm; capacitance, 4.9 µF/cm².