Figure 3.

Effects of reciprocal modulation of I_K1 and I_Na and changes in gap junction conductance, G_gj, on fiber thresholds. (A) Changes in fiber threshold due to reciprocal modulation of G_K1–G_Na (1:1 ratio). At any particular value of G_K1–G_Na, increasing G_gj raises the threshold for initiating a propagating action potential. The curves for G_gj = 0.1 and 0.2 μS (top two curves) overlap considerably. Magnitudes of current thresholds increase monotonically with increasing G_K1–G_Na for G_gj = 0.1–1 μS while higher values of G_gj result in biphasic dependence. (B) Changes in fiber conduction velocity due to reciprocal modulation of G_K1–G_Na. At any particular value of G_K1–G_Na, increasing G_gj increases the conduction velocity of propagating action potentials. Markers are the same as panel A: top curve is for G_gj = 20 μS.