title: Induction of rhythmic transient depolarizations associated with waxing and waning of slow wave activity in intestinal smooth muscle.
abstract: Cannon described in 1902 the segmentation motor activity of the small intestine (Canon WB. J Med Res 7: 72-75, 1902). This motor pattern can arise when low-frequency transient depolarizations are evoked in the interstitial cells of Cajal associated with the deep muscular plexus (ICC-DMP) network, which then affect the omnipresent slow wave activity: changing its regular amplitude into a waxing and waning pattern. The objective of the present study was to investigate physiological stimuli that could induce the low-frequency component. Intracellular recordings were obtained from circular muscle with or without attached mucosa. Decanoic acid (1 mM) and butyric acid (10 mM) both evoked low-frequency transient depolarizations but through different mechanisms. Decanoic acid-induced waxing and waning was initiated by purely myogenic means when perfused onto exposed circular muscle. Butyric acid required the intact mucosa and uninhibited neural activity to elicit the low-frequency response. Evidence is provided that the transient rhythmic depolarizations occur in the absence of interstitial cells of Cajal associated with the myenteric plexus (ICC-MP). Onset of the slow transient depolarizations was stimulated by addition of N(ω)-nitro-l-arginine (l-NNA; 100 μM); thus the low-frequency component seems to be under chronic inhibition by nitric oxide. Excitatory tachykinergic stimulation induced the low-frequency component since substance P (0.5 μM) evoked it in the presence of neural blockade. In summary, interplay between two networks of myogenic pacemakers, neural activity, and nutrient factors such as fatty acids plays a role in the generation of the rhythmic low-frequency component that is essential for the development of the checkered segmentation motor pattern.
authors.affiliation: Farncombe Family Digestive Health Research Institute, Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Pawelka
authors.affiliation: Farncombe Family Digestive Health Research Institute, Department of Medicine, McMaster University, Hamilton, Ontario, Canada huizinga@mcmaster.ca.
authors.forename: Jan D
authors.initials: JD
authors.lastname: Huizinga
mesh_terms: D000200:Action Potentials; D000818:Animals; D020148:Butyric Acid / Q000494:pharmacology; D003652:Decanoic Acids / Q000494:pharmacology; D005260:Female; D056885:Interstitial Cells of Cajal / Q000502:physiology; D007413:Intestinal Mucosa / Q000502:physiology; D007583:Jejunum / Q000166:cytology / Q000294:innervation / Q000502:physiology*; D008564:Membrane Potentials; D051379:Mice; D009130:Muscle, Smooth / Q000294:innervation / Q000502:physiology*; D009197:Myenteric Plexus / Q000187:drug effects / Q000502:physiology; D019335:Nitroarginine / Q000494:pharmacology
chemical_list: D003652:Decanoic Acids; D020148:Butyric Acid; D019335:Nitroarginine; C031071:decanoic acid
keywords: interstitial cells of Cajal; intestinal motility; pacemaking; segmentation