Figure 13.
Whole-cell I–V relationships of inspiratory XII MNs. A, B, I–V relationships obtained from 30 mV/s voltage-clamp ramps (−100 to +10 mV; inset) for MN before (A) and after (B) subtraction of Leak, obtained by linear fit of the I–V curve at hyperpolarized voltages (less than −65 mV). Leak reversal potential (ELeak, −64 mV) is indicated. TTX eliminates major inward current component (TTX-sensitive NaP) in the Leak-subtracted I–V relationships (B) between −60 and −30 mV. C, Plots of NaP g/gmax versus voltage for both MN (black) with superimposed first-order Boltzmann function fit (gray curve) with half-maximal activation voltage (V1/2max) and slope factor k indicated. D, Expanded current scale for MN shown in B indicates small (<25 pA) residual TTX-insensitive subthreshold inward current.