Figure 5. Calculation of coupling resistances between the ICC_my, longitudinal and circular muscle layers.

Aa, slow waves recorded simultaneously from two different points in the circular muscle layer. Ab, the waveforms 3 min after caffeine (1 mm) was added to the solution. Note that while the regenerative component of the slow wave was reduced, the amplitude of the initial component was little altered. Ac, the average of 20 electrotonic potential responses to current (5 nA, Ad) injected into the circular muscle layer. B, a slow wave recorded from the a circular muscle cell, and a pacemaker potential recorded from ICC_my, in control conditions (a) and in the presence of caffeine (b). C, simultaneous recordings of a follower potential and a slow wave in control conditions (a) and in the presence of caffeine (b), recorded from the circular and longitudinal muscle layers, respectively. Examples of steady-state membrane potentials V₁-V₅ are illustrated in panels Ac, Bc, Cc and Bb, respectively. The voltage and current calibration bars apply to all traces. The membrane potentials of the circular smooth muscle layer, ICC_my and longitudinal layer were −64, −65 and −59 mV, respectively.