Electrical off response of cat esophageal smooth muscle: an analog simulation

Abstract

This investigation was performed to define characteristics and to design an electrical model of the slow membrane depolarization, or "electrical off response," that follows stimulation of cat circular esophageal smooth muscle. The electrical off response showed the following characteristics: 1) the response was preceded by hyperpolarization of the muscle membrane; 2) the amplitude of the off-response depolarization increased directly with increasing amplitude of the preceding hyperpolarization; 3) the membrane potential showed varying degrees of oscillation around the resting point; 4) the oscillation period was constant (4-5 s) and was double the time from the point of maximum hyperpolarization to the peak of the electrical off response. These characteristics suggested that the electrical off response could be represented by a linear second-order differential equation with variable damping, and an analog simulation was constructed. By varying the damping ratio and/or the natural frequency of the analog model, the characteristics of the electrical off response of esophageal muscle could be reproduced. The model provides a means to explore the behavior of esophageal smooth muscle contraction under normal and pathological conditions.

Myogenic mechanism for peristalsis in the cat esophagus

“…5A). Similar inhibitory junction potentials have been reported previously for both vagal and field stimulation of cat and opossum esophageal tissue (4,7,11,12,22,25). A single long- The electrical responses to a long-duration stimulus were qualitatively similar to the 0.5-ms pulse but of greater magnitude (Fig.…”

“…Sarna et al (27) and Helm et al (18) have shown myogenic peristaltic contraction in the opossum in vivo and in vitro, respectively, but did not record the associated electrical events in their studies. However, a number of investigators have shown, usually in isolated strips, that esophageal circular (4,6,(21)(22)(23)27) and longitudinal (5,23) smooth muscle can be stimulated to produce repetitive electrical slow-wave-type activity with superimposed spike bursts and associated repetitive contractile activity. Progression of such combined electrical and mechanical activity along the esophagus was not assessed.…”

“…Many characteristics of esophageal smooth muscle support the presence of a MCS in this organ as well. These include the morphology of esophageal smooth muscle, including the presence of interstitial cells of Cajal (ICC) (15), and the observation that esophageal circular muscle oscillates electrically and mechanically when adequately stimulated (4,6,19,21,23,30). The esophageal body in vivo is normally electrically quiescent until a primary or secondary peristaltic contraction occurs.…”

Effect of sildenafil, a phosphodiesterase‐5 inhibitor, on oesophageal peristalsis and lower oesophageal sphincter function in cats

“…In the opossum and cat, unlike humans, administration of NO synthase blockers such as L ‐NAME and L ‐NMMA significantly reduced the amplitude of swallow‐induced oesophageal contractions 5 , 6 , 39 , 40 . These findings suggested that in some species, NO may have a partially excitatory effect either in the nuclei of the so‐called swallowing programme generator (SPG) in the brain stem, at the interneurone level, or peripherally at the muscle level, in which an initial NO‐dependent short hyperpolarization is followed by membrane depolarization and contraction (off response) 39–43 . The hyperpolarization and subsequent off response appear to be mediated by cGMP 46 .…”

Swallowing: Neurophysiologic control of the esophageal phase

“…The question still unanswered is the relevance of the internal ganglionic interconnections of neurons versus a more myogenic control. Do muscle fibers affect adjacent fibers through a membrane or connective tissue connection to transmit an innate oscillatory pattern that is modulated by neural input (Chan and Diamant 1976)?…”