Electrical transmission at the nexus between smooth muscle cells.

The hypothesis that nexuses between cells are responsible for the core conductor properties of tissues was tested using smooth muscle preparations from the taenia coli of guinea pigs. Action potentials recorded from small diameter preparations across a sucrose gap change from monophasic to diphasic when a shunt resistor is connected across the gap. This indicates that transmission between smooth muscle cells is electrical, because the resistor only allows current to flow. Nexal fusion of cell membranes occurs especially where one cell sends a large bulbous projection into a neighbor. Hypertonic solutions rupture the nexuses between smooth muscle cells. Hypertonicity also increases the resistance of a bundle across the sucrose gap and blocks propagation of action potentials. Thus the structural and functional changes in smooth muscle due to hypertonicity correlate with the hypothesis.