The effect of morphological interdigitation on field coupling between smooth muscle cells

The electrical control activity (ECA) in the distal stomach, small intestine, and colon has been modeled by populations of coupled nonlinear oscillators. Coupling has traditionally been explained through gap junctions, but gap junctions alone are inadequate, as they are not always present or cannot account for the observed behavior. Coupling through extracellular electric fields has been proposed as another coupling path which may work instead of, or in conjunction with, gap junctions. A morphological structure, the interdigitation, is studied for its effect on fields produced by a spherical cell. Using boundary element methods, the potential produced by a cell and the transmembrane potential induced in an adjacent cell are considered. Computer simulation results indicate that the presence of an interdigitation between two neighboring cells produces a 60% increase in extracellular potential and a 50% increase in induced transmembrane voltage. The interdigitation length is the most important factor, with radius playing a very small part in determining peak values of potential and voltage. These interdigitation fields may be of appreciable magnitude with regard to coupling. Also, the upstroke phase of the ECA can play a major role in intercellular communication.