Figure 4. Variability in electrical coupling between ICC_my and the circular muscle layer in different preparations.

A, superimposed simultaneous membrane potential traces recorded from an ICC_my and a circular muscle cell (smaller amplitude trace). Note the modest initial component of the slow wave. B, electrotonic potentials recorded from ICC_my (a) and circular muscle (b) in response to current (c) injected into the circular muscle layer: the membrane potentials of the circular smooth muscle layer and ICC_my were −60 and −62 mV, respectively. C, superimposed simultaneous membrane potential traces recorded from a different bundle obtained from the same animal. Note the large initial component of the slow wave. D, electrotonic potentials recorded from ICC_my (a) and circular muscle (b) in response to current (c) injected into the circular muscle layer: the membrane potentials of the circular smooth muscle layer and ICC_my were −63 and −63 mV, respectively. The voltage and current calibration bars apply to all traces. E, relationship between the coupling ratio (see text) and the amplitude of the initial component of the slow wave, together with a straight-line fit.