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 ΔVm 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 ΔVm 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 ΔVm 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).