FIGURE 3.

Changing pNa_max⁺ in the soma and initial segment does not affect spike propagation past the t-junction. A stimulus pulse pair was applied to the 20th peripheral node (first pulse marked with an arrow; IPI, 2.26 ms). Recordings were at R1, R2, and R5 (see Fig. 1). pNa_max⁺ was 40 × 10⁻⁵ cm/s (A, “high”) or 0 cm/s (B). The hump on the falling phase of the second spike recorded at R2 (arrowhead in A) results from the associated soma spike, which was delayed in the case of the second stimulus pulse (also see Fig. 4). In B no soma spike was evoked by either stimulus pulse, and therefore no hump occurred.