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Video Imaging and Spatiotemporal Maps to Analyze Gastrointestinal Motility in Mice
Published on: February 3, 2016
Migrating motor complexes do not require electrical slow waves in the mouse small intestine
Nick J Spencer1, Kenton M Sanders, Terence K Smith
1Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA. nick@physio.unr.edu
Abstract:
We have investigated whether migrating motor complexes (MMCs) are impaired or absent in the small intestine of W/Wv mutant mice, which lack pacemaker interstitial cells of Cajal (ICC) and electrical slow waves. The intracellular electrical and mechanical activities of the small intestines of wild-type (+/+) and W/Wv mutant mice were recorded. Electrical recordings from circular muscle cells confirmed the absence of slow waves in W/Wv mice, whereas slow waves were always recorded from +/+ muscle cells. Spontaneous phasic contractions were recorded from W/Wv muscles in the absence of slow waves, but these events occurred at a lower frequency than in +/+ tissues. MMC activity was recorded consistently from the ileum of +/+ mice, and normal MMCs were also recorded from W/Wv mice. MMCs in both +/+ and W/Wv mice were abolished by tetrodotoxin (1 microM), hexamethonium (300 microM) or atropine (1 microM), suggesting that the neural control mechanisms responsible for MMCs in +/+ mice are intact and are responsible for MMCs in W/Wv mice. Transmural nerve stimulation demonstrated intact inhibitory and excitatory neural regulation of W/Wv intestinal muscles. Prolonged trains of cholinergic motor nerve stimulation failed to activate slow waves in the intestinal muscles of W/Wv mice. Our findings show that the generation and directional propagation of MMC activity in mouse small intestine does not require slow-wave activity or an intact network of myenteric ICC. The generation and propagation of MMCs appear to be an intrinsic capability of the enteric nervous system and are not related to slow waves or the gradient in slow-wave frequency.
Insights
Migrating motor complexes (MMCs) in the small intestine do not require electrical slow waves or interstitial cells of Cajal (ICC). Neural control mechanisms of the enteric nervous system drive MMC generation and propagation in W/Wv mutant mice.
Area of Science:
- Gastroenterology
- Neurogastroenterology
- Physiology
Background:
- Migrating motor complexes (MMCs) are crucial for intestinal motility and preventing bacterial overgrowth.
- Interstitial cells of Cajal (ICC) generate electrical slow waves, the basis of gut motility.
- W/Wv mutant mice lack ICC and slow waves, providing a model to study MMC dependence on these factors.
Purpose of the Study:
- To investigate if migrating motor complexes (MMCs) are impaired in the small intestine of W/Wv mutant mice lacking pacemaker interstitial cells of Cajal (ICC) and electrical slow waves.
- To determine the role of slow-wave activity and ICC in the generation and propagation of MMCs.
Main Methods:
- Recorded intracellular electrical and mechanical activities in the small intestines of wild-type (+/+) and W/Wv mutant mice.
- Administered tetrodotoxin, hexamethonium, and atropine to assess neural involvement in MMCs.
- Performed transmural nerve stimulation to evaluate neural regulation of intestinal muscles.
Main Results:
- W/Wv mice lacked electrical slow waves but exhibited spontaneous phasic contractions at a lower frequency than wild-type mice.
- Normal MMCs were recorded in both W/Wv and wild-type mice, indicating MMCs are not dependent on slow waves.
- MMCs in both genotypes were abolished by neural inhibitors (tetrodotoxin, hexamethonium, atropine), confirming intact neural control.
- Cholinergic stimulation failed to induce slow waves in W/Wv mice, despite intact neural regulation.
Conclusions:
- The generation and propagation of MMCs in the mouse small intestine do not require slow-wave activity or functional ICC networks.
- MMCs appear to be an intrinsic capability of the enteric nervous system, independent of slow waves.
- Neural control mechanisms are sufficient for driving MMCs, even in the absence of ICC-generated electrical activity.
