Figure 3

Propagation of APs simulated by PSpice along a chain of ten smooth muscle cells. The termination resistance at the ends of the chain (R_bt) was 1.0 KΩ, similar to that for the fluid bathing the surface of the long chain. The six panels show the effect of varying the number of gj-channels from zero (panel A, R_gj = 100,000 MΩ), to one (panel B, R_gj = 10,000 MΩ), to 10 (panel C, R_gj = 1,000 MΩ), to 100 (panel D, R_gj = 100 MΩ), to 1000 (panel E, R_gj = 10 MΩ), to 10,000 (panel F, R_gj = 1.0 MΩ). At the R_bt of 1.0 KΩ, the last cell in the strand (cell #10) failed to become excited (panel A), or it fired after a long delay (panel B), when there were no gj-channels (A) or only one gj-channel (B), and so transmission from cell to cell relied on the EF mechanism. Thus, there was a prominent end (edge) effect. In addition, the overshoot amplitude of the AP in cell #10, as well as in cell #1, was greater (A, B, C). Thus, end effects occurred at both ends of the strand. Note the presence of a hyperpolarizing after-potential following the repolarizing phase of the AP. When there were many gj-channels (EF), the APs of all 10 cells were superimposed, indicating extremely fast propagation velocity.