Slow wave heterogeneity within the circular muscle of the canine gastric antrum.

Abstract

SUMMARY1. A bross-sectional preparation was designed in which multiple micro-electrodes can be precisely positioned to impale smooth muscle cells anywhere from the serosa to the submucosa.2. Intracellular electrical recordings were obtained from gastric antral circular muscle cells from the myenteric plexus to the submucosa.3. The resting membrane potential changed linearly as a function of distance from the myenteric plexus to the submucosa.4. Slow wave upstroke d V/dt, upstroke potential amplitude, and plateau potential amplitude changed linearly as a function of distance from the myenteric plexus to the submucosa.5. When slow waves were recorded simultaneously from a circular cell near the myenteric plexus and from a cell near the submucosa, the event always occurred first in the cell near the myenteric plexus.6. Electrical differences did not appear to be caused by electrotonic decay of slow waves as they propagated through the circular muscle.7. Electrical differences could not be explained on the basis ofdifferences in intrinsic neural activity or prostaglandin synthesis.8. Membrane polarization could not explain the differences in slow waves between myenteric and submucosal circular muscle cells.9. The conclusion of this paper is that fundamental differences exist between the excitability mechanisms and/or passive membrane properties of cells near the myenteric plexus and the submucosa. These differences might be manifest in different motor performance of these two muscle cell populations.

Sodium pump isozymes are differentially expressed in electrically dissimilar regions of colonic circular smooth muscle.

“…Previous studies have demonstrated that circular muscles of the gastrointestinal tract are electrically and mechanically heterogenous (20)(21)(22)(23)(24). In the present study we have described a possible molecular basis for part of the electrical heterogeneity: the gradient in resting potential that exists across the circular muscle layers of the proximal (21,22) and distal (25) colon and stomach (26).…”

“…These results provide evidence that the expression of some genes in circular smooth muscle cells is dependent upon their anatomical location and/or microenvironment. Regional differences in gene expression may provide an explanation for variations in electrical excitability (20)(21)(22)(23)(24), mechanical activity (20), and other cellular processes.…”

Time‐dependent changes in Ca2+ sensitivity during phasic contraction of canine antral smooth muscle.

“…1). We also removed the submucosal half of the circular layer and studied only the myenteric region of the circular layer, since electrical and mechanical characteristics differ between the myenteric and submucosal regions (Bauer & Sanders, 1985;Bauer et al 1985 a;Bauer, Reed & Sanders, 1985b). Electrical stimulation was performed in some experiments by the placement of a suction electrode near the region where the myenteric border was left intact.…”

Ca2+ regulation of the contractile apparatus in canine gastric smooth muscle.

“…This left the myenteric region of the circular muscle and the longitudinal layer. The contractile activity of the myenteric circular muscle was studied, but the longitudinal layer was left attached because spontaneous electrical activity originates at the border between the circular and longitudinal fibres (Bauer, Reed & Sanders, 1985b). …”