Figure 5

Experiment to measure the spread of current in the linear chain of 100 cells. The myocardial cells were rendered inexcitable by removing their GTABLEs. Depolarizing current pulses (10 nA, 5 ms) were applied intracellularly to cell #51 near the mid-point of the chain, and the resulting membrane voltage changes were recorded from cell #51 and its immediate neighbors (e.g., cells 44–58). The number of gj-channels was varied over a wide range (namely 0, 10, 30, 100, 300, 1000, and 3000), but the results from only 4 are illustrated in this figure: 0 gj-channels (A), 10 (B), 100 (C), and 1,000 (D). A: With no gj-channels, the voltage change in cell #51 was very large (ca 215 mV), whereas there was almost zero voltage change in the contiguous cells (49, 50, 52, 53). B: with 10 gj-channels, the ΔV_m in cell 51 was ca 200 mV, whereas that in cells on either side (cells 50 & 52) was only about 8 mV. C: With 100 gj-channels, the ΔV_m in cell 51 was ca 120 mV, that in cells 50 and 52 was ca 40 mV, and that in cells 49 and 53 was ca 8 mV. D: With 1000 gj-channels, the ΔV_m in cell 51 was ca 84 mV and those in the contiguous cells were ca 44 mV (cells 50 & 52), ca 26 mV (cells 49 & 53), ca 15 mV (cells 48 & 54), and ca 8 mV (cells 47 & 55).