Electrical coupling of longitudinal and circular intestinal muscle

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Abstract
Space constants (.lambda.) were determined for longitudinal-circular muscle strips of cat jejunum by the partition method. Pulses of hyperpolarizing current spread along the major axes of circular muscle cells. In the absence of electrical coupling .lambda. measured from the longitudinal side of the strips should have been .apprx. 20 times shorter than .lambda. measured from the circular side. Median values were found to be statistically the same, 2.4 mm for the longitudinal side (n = 13) and 2.9 mm for the circular (n = 25). Methyl blue, iontophoretically injected into cells on the longtidunal side after recording large hyperpolarizing responses, was found in muscle cells located superficially in the longitudinal layer. The radial .lambda. for longitudinal muscle, determined from the change in magnitude of the hyperpolarizing response as the microelectrode was advanced through the layer, was 0.27 mm. This is too large to cause differences in depth of recording to significantly affect the circumferential .lambda. in this layer. A high degree of electrical coupling between the 2 muscle layers of cat jejunum is suggested.