Electrical coupling and pacemaker activity in colonic smooth muscle

The effect of heptanol on electrical coupling between submucosal circular muscle cells of the dog colon and consequences for slow-wave activity were investigated. Electrotonic potentials showed exponential decay giving a length constant of 2.6 +/- 0.5 mm and a time constant of 157 +/- 48 ms. Heptanol reversibly abolished electrotonic current spread, and subsequently no slow-wave activity was recorded. The length constant decreased to less than 0.2 mm. The input resistance increased from 3 to 36 M omega, suggesting a change from tissue syncytium to electrically isolated cells. D600 (5 X 10(-6) M) also abolished slow wave activity but had opposite effects on electrotonic current spread. The data are consistent with the hypothesis that heptanol reversibly inhibits intercellular coupling, resulting in loss of spread of extracellularly applied current, uncoupling of cells, and loss of pacemaker activity. Regulation of intercellular communication may be important in the control of intestinal motility.

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Pacemaker activity recorded in interstitial cells of Cajal of the gastrointestinal tract

AJP Cell Physiology ◽

10.1152/ajpcell.1989.257.4.c830 ◽

1989 ◽

Vol 257 (4) ◽

pp. C830-C835 ◽

Cited By ~ 84

Author(s):

C. Barajas-Lopez ◽

I. Berezin ◽

E. E. Daniel ◽

J. D. Huizinga

Keyword(s):

Methylene Blue ◽

Slow Wave ◽

Interstitial Cells Of Cajal ◽

Circular Muscle ◽

Interstitial Cells ◽

Wave Activity ◽

Slow Wave Activity ◽

Resting Membrane Potential ◽

Pacemaker Activity ◽

Cells Of Cajal

The hypothesis was tested that interstitial cells of Cajal can generate slow wave activity. Intracellular recordings were performed only in the most superficial cells at the submucosal surface of the canine colonic circular muscle layer. An omnipresent and characteristic slow wave activity was present in all cells with a mean amplitude of 37 +/- 3 mV, a frequency of 4.6 +/- 0.1 counts/min (cpm), and a duration of 5.6 +/- 0.5 s; the average resting membrane potential was -70 +/- 1 mV. To determine the type of cell from which these recordings were obtained, methylene blue was injected by microiontophoresis. The strips were immediately fixed while the microelectrode was kept in the cell. A small segment of the tissue containing this cell was then processed for electron microscopy and serially sectioned. Electron-microscopic evidence showed that the microelectrode tip was positioned in an interstitial cell of Cajal (ICC): 1) several sections were observed with round cytoplasmic lesions of decreasing diameter followed by sections from the same cell without the lesion and 2) electron-dense material was observed in these sections due to the injected methylene blue. These cells were identified as part of the ICC network present at the muscle-submucosa interface of the circular muscle and were positively identified as ICC by the presence of cell processes. This is the first report giving direct evidence for the occurrence of electrical slow waves in ICC. It is essential support for the hypothesis that ICC are the actual pacemaker cells of the gut musculature.

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Pacemaker activity in septal structures of canine colonic circular muscle

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1990.259.2.g264 ◽

1990 ◽

Vol 259 (2) ◽

pp. G264-G273 ◽

Cited By ~ 9

Author(s):

S. M. Ward ◽

K. M. Sanders

Keyword(s):

Slow Wave ◽

Electrical Coupling ◽

Circular Muscle ◽

Proximal Colon ◽

Slow Waves ◽

Pacemaker Activity ◽

Electrical Measurements ◽

Morphological Studies ◽

Circular Layer ◽

And Function

Morphological and electrophysiological experiments were performed to characterize the pacemaker areas of the circular muscle in the canine proximal colon. Morphological studies showed interstitial cells of Cajal lining the submucosal surface of the circular layer and the septal structures that separate the circular layer into bundles. Electrical measurements suggested that slow waves may propagate into the thickness of the circular muscle in a regenerative manner along the surface of these septa. Removal of the submucosal pacemaker region blocked generation of slow waves in nonseptal regions of the circular muscle, but slow-wave activity continued in the circular muscle near septa. These data suggest that slow-wave pacemaker activity is not limited to a two-dimensional surface at the submucosal surface but extends into the interior of the circular layer along septal invaginations. Experiments were also performed to determine the dominance of pacemaker activity (i.e., septal vs. submucosal), and examples were found in which both areas appeared to initiate slow waves in intact muscles. Other studies showed that slow waves could propagate across septa, suggesting some form of electrical coupling between circular muscle bundles. This study provides a more complete view of the structure and function of pacemaker areas in the canine proximal colon.

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Electrical slow-wave activity from the circular layer of cat terminal antrum

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1991.261.1.g78 ◽

1991 ◽

Vol 261 (1) ◽

pp. G78-G82

Author(s):

L. M. Renzetti ◽

M. B. Wang ◽

J. P. Ryan

Keyword(s):

Slow Wave ◽

Circular Muscle ◽

Muscle Cells ◽

Muscle Layer ◽

Wave Activity ◽

Slow Waves ◽

Slow Wave Activity ◽

Plateau Phase ◽

Circular Layer ◽

Upstroke Velocity

Intracellular recording techniques were used to characterize the electrical slow-wave activity through the thickness of the circular muscle layer of the cat terminal antrum. Muscle strips were pinned out in cross section to the floor of a recording chamber perfused with Krebs buffer. Circular muscle cells from the myenteric to the submucosal border then were impaled with 20- to 40-M omega glass microelectrodes, and slow-wave activity was recorded. Slow waves from the myenteric side of the circular layer consisted of an upstroke depolarization, a prominent plateau phase, and a downstroke repolarization. Slow-wave characteristics for cells along the myenteric border were Em, -74.2 +/- 1.3 mV; duration, 5.3 +/- 0.5 s; upstroke amplitude, 29.4 +/- 3.4 mV; upstroke velocity, 0.20 +/- 0.03 V/s; and frequency, 5.8 +/- 0.5/min. Slow waves from muscle cells along the submucosal side of the preparation lacked a discernible plateau phase. Slow waves from submucosal border cells had the following characteristics: Em, -80.4 +/- 1.4 mV (P less than 0.01); duration, 3.5 +/- 0.4 s (P less than 0.01); upstroke amplitude, 44.0 +/- 2.4 mV (P less than 0.01); upstroke velocity, 0.56 +/- 0.06 V/s (P less than 0.01); and frequency, 4.2 +/- 0.4/min (P less than 0.05). Slow waves were not affected by 10(-7)M tetrodotoxin and 10(-6)M atropine or by removal of the longitudinal muscle layer. Slow-wave activity within each region was maintained after dissecting the circular layer into submucosal and myenteric segments. The results suggest that two distinct slow waves exist within the circular muscle layer of the cat terminal antrum.(ABSTRACT TRUNCATED AT 250 WORDS)

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Quinidine and quinine effects on the slow wave activity of colonic circular muscle

European Journal of Pharmacology ◽

10.1016/0014-2999(89)90407-x ◽

1989 ◽

Vol 163 (1) ◽

pp. 137-140 ◽

Cited By ~ 1

Author(s):

Carlos Barajas-López ◽

Jan D. Huizinga

Keyword(s):

Slow Wave ◽

Circular Muscle ◽

Wave Activity ◽

Slow Wave Activity

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Slow-wave activity in colon: role of network of submucosal interstitial cells of Cajal

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1991.260.4.g636 ◽

1991 ◽

Vol 260 (4) ◽

pp. G636-G645 ◽

Cited By ~ 4

Author(s):

R. Serio ◽

C. Barajas-Lopez ◽

E. E. Daniel ◽

I. Berezin ◽

J. D. Huizinga

Keyword(s):

Smooth Muscle ◽

Slow Wave ◽

Interstitial Cells Of Cajal ◽

Circular Muscle ◽

Interstitial Cells ◽

Wave Activity ◽

Slow Waves ◽

Slow Wave Activity ◽

Plateau Potentials ◽

Cells Of Cajal

The present study compares the electrophysiological properties of two preparations dissected from the canine colon circular muscle layer: first, containing the submucosal network of interstitial cells of Cajal (ICC) with two to four associated smooth muscle cell layers, and second, a circular muscle preparation devoid of the submucosal ICC network. In the ICC-rich preparations, consistent slow-wave activity was observed with prolonged plateau potentials of approximately 10-s duration. The plateau potentials were sensitive to D 600. In approximately 45% of circular muscle preparations devoid of the submucosal ICC network (confirmed using electron microscopy) slow waves, of different waveshape, were recorded at frequencies identical to those in whole circular muscle preparations. These slow waves did not show a plateau potential. Compared with ICC-rich preparations with a resting membrane potential of about -80 mV, circular muscle preparations had lower membrane potentials, about -70 mV when active, and about -60 mV when quiescent. Heptanol (1 mM) electrically uncoupled cells, since it abolished electrotonic current spread and allowed measurement of the input resistance by intracellular current injection. Heptanol also affected ionic conductances. Heptanol abolished slow waves; the underlying mechanism needs further investigation. In the presence of heptanol, cells in the isolated ICC network and in circular smooth muscle preparations showed spontaneous hyperpolarizing potential fluctuations at a frequency of four to six per second. These oscillations were abolished by current-induced hyperpolarization and TEA (30 mM) and are therefore likely due to spontaneously active K+ conductance.

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Sa1640 NONINVASIVE MEASUREMENT OF SMALL BOWEL SLOW WAVE ACTIVITY IN NEONATES - A PILOT STUDY

Gastroenterology ◽

10.1016/s0016-5085(20)31606-1 ◽

2020 ◽

Vol 158 (6) ◽

pp. S-364

Author(s):

Suseela Somarajan ◽

Nicole D. Muszynski ◽

Aurelia s. Monk ◽

Joseph D. Olson ◽

Alexandra Russell ◽

...

Keyword(s):

Pilot Study ◽

Small Bowel ◽

Slow Wave ◽

Wave Activity ◽

Slow Wave Activity ◽

Noninvasive Measurement

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Slow Wave Activity Related to Working Memory Maintenance in the N-Back Task

Journal of Psychophysiology ◽

10.1027/0269-8803/a000164 ◽

2016 ◽

Vol 30 (4) ◽

pp. 141-154 ◽

Cited By ~ 7

Author(s):

Kira Bailey ◽

Gregory Mlynarczyk ◽

Robert West

Keyword(s):

Working Memory ◽

Slow Wave ◽

Time Course ◽

Relevant Information ◽

Wave Activity ◽

Slow Wave Activity ◽

Response Accuracy ◽

Functional Neuroanatomy ◽

Stimulus Interval ◽

Back Task

Abstract. Working memory supports our ability to maintain goal-relevant information that guides cognition in the face of distraction or competing tasks. The N-back task has been widely used in cognitive neuroscience to examine the functional neuroanatomy of working memory. Fewer studies have capitalized on the temporal resolution of event-related brain potentials (ERPs) to examine the time course of neural activity in the N-back task. The primary goal of the current study was to characterize slow wave activity observed in the response-to-stimulus interval in the N-back task that may be related to maintenance of information between trials in the task. In three experiments, we examined the effects of N-back load, interference, and response accuracy on the amplitude of the P3b following stimulus onset and slow wave activity elicited in the response-to-stimulus interval. Consistent with previous research, the amplitude of the P3b decreased as N-back load increased. Slow wave activity over the frontal and posterior regions of the scalp was sensitive to N-back load and was insensitive to interference or response accuracy. Together these findings lead to the suggestion that slow wave activity observed in the response-to-stimulus interval is related to the maintenance of information between trials in the 1-back task.

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