Myogenic regulation of propagation in gastric smooth muscle

1985 ◽  
Vol 248 (5) ◽  
pp. G512-G520 ◽  
Author(s):  
N. G. Publicover ◽  
K. M. Sanders
Keyword(s):  
Wave Propagation ◽  
Conduction Velocity ◽  
Circular Muscle ◽  
Slow Waves ◽  
Gastric Distension ◽  
Gastric Smooth Muscle ◽  
Conduction Velocities ◽  
Axis Parallel ◽  
Myogenic Regulation

Experiments were performed to test the effects of frequency and stretch on the velocity of slow wave propagation parallel and perpendicular to the long axis of circular muscle fibers in the canine gastric antrum. Slow waves were evoked from one corner of a rectangular sheet of muscle and propagated throughout the tissue. Mathematics were derived and are presented, which simultaneously compute conduction velocities in each direction, regardless of electrode positions. Increased rate of stimulation had no significant effect on conduction velocity in the circumferential axis, but propagation slowed in the axis perpendicular to the circular fibers by an average of 25% over interstimulus intervals between 12 and 60 s. Conduction velocity was also a function of the degree of stretch. The most rapid conduction velocity occurred when muscles were stretched to an average of 118% of the resting, fasted length found in situ in the axis parallel to the circular fibers and 140% in the axis perpendicular to the circular fibers. Propagation was blocked by stretching muscles past 200% of resting length. These results suggest that the frequency of slow waves and gastric distension are intrinsic mechanisms capable of regulating the spread of slow waves.

Origin and spread of slow waves in canine gastric antral circular muscle

1985 ◽  
Vol 249 (6) ◽  
pp. G800-G806 ◽  
Author(s):  
A. J. Bauer ◽  
N. G. Publicover ◽  
K. M. Sanders
Keyword(s):  
Wave Propagation ◽  
Slow Wave ◽  
Myenteric Plexus ◽  
Circular Muscle ◽  
Slow Waves ◽  
Three Dimensions ◽  
Muscle Strip ◽  
Velocity Measurements ◽  
Conduction Velocities ◽  
Axis Parallel

Electrical slow waves recorded from circular muscle cells near the myenteric and submucosal plexuses were found to be significantly different. By measuring the latencies between the arrival of evoked events at two recording sites, slow wave conduction velocities were determined in the three dimensions of circular muscle. Slow waves propagated more rapidly in the axis parallel to the circular fibers than in the axes perpendicular to the circular fibers. The rates of slow wave propagation were also determined in axes parallel and perpendicular to fibers in myenteric and submucosal circular muscles. Slow waves conducted more slowly in the circular muscle near the submucosa than in circular muscle near the myenteric plexus. From conduction velocity measurements, a technique was developed to determine the pacemaker site of spontaneous slow waves in a muscle strip. These data demonstrate that slow waves originate from multiple discrete foci; in muscle strips cut along the long axis of the stomach, these foci are found predominantly in the orad region of the muscle strip; and slow waves originate in the outer myenteric half of the muscle.

Slow waves actively propagate at submucosal surface of circular layer in canine colon

1990 ◽  
Vol 259 (2) ◽  
pp. G258-G263 ◽  
Author(s):  
K. M. Sanders ◽  
R. Stevens ◽  
E. Burke ◽  
S. W. Ward
Keyword(s):  
Wave Propagation ◽  
Slow Wave ◽  
Proximal Colon ◽  
Slow Waves ◽  
Pacemaker Cells ◽  
Transverse Axis ◽  
Active Mechanism ◽  
Conduction Velocities ◽  
Circular Layer ◽  
Thin Band

Colonic slow waves originate from pacemaker cells along the submucosal surface of the circular layer in the dog proximal colon. These events propagate in a nonregenerative manner into the bulk of the circular layer. Conduction velocities consistent with an active mechanism for slow-wave propagation in the longitudinal and circumferential axes of the colon have been reported. Experiments were performed using intracellular recording techniques on canine colonic muscles to determine the regenerative pathway for slow-wave propagation. In a thin band of muscle adjacent to the submucosal border of the circular layer, slow-wave amplitude was independent of distance from a pacing source, and events propagated at a rate of approximately 17 mm/s in the long axis of the circular fibers and 6 mm/s in the transverse axis of the circular fibers. These findings suggest that slow waves propagate in a regenerative manner in this region. Slow waves decayed as they conducted through regions from which the pacemaker cells had been removed with space constants of a few millimeters. Thus the integrity of the thin pacemaker region along submucosal surface is critical for propagation of slow waves and the organization of motility into segmental contractions.

Voltage-gated Ca2+ currents are necessary for slow-wave propagation in the canine gastric antrum

2007 ◽  
Vol 293 (5) ◽  
pp. C1645-C1659 ◽  
Author(s):  
Orline Bayguinov ◽  
Sean M. Ward ◽  
James L. Kenyon ◽  
Kenton M. Sanders
Keyword(s):  
Wave Propagation ◽  
Slow Wave ◽  
Propagation Velocity ◽  
Circular Muscle ◽  
Slow Waves ◽  
Dependent Manner ◽  
Voltage Dependent ◽  
Lesser Curvature ◽  
Propagation Velocities ◽  
Upstroke Velocity

Electrical slow waves determine the timing and force of peristaltic contractions in the stomach. Slow waves originate from a dominant pacemaker in the orad corpus and propagate actively around and down the stomach to the pylorus. The mechanism of slow-wave propagation is controversial. We tested whether Ca2+ entry via a voltage-dependent, dihydropyridine-resistant Ca2+ conductance is necessary for active propagation in canine gastric antral muscles. Muscle strips cut parallel to the circular muscle were studied with intracellular electrophysiological techniques using a partitioned-chamber apparatus. Slow-wave upstroke velocity and plateau amplitude decreased from the greater to the lesser curvature, and this corresponded to a decrease in the density of interstitial cells of Cajal in the lesser curvature. Slow-wave propagation velocity between electrodes impaling cells in two regions of muscle and slow-wave upstroke and plateau were measured in response to experimental conditions that reduce the driving force for Ca2+ entry or block voltage-dependent Ca2+ currents. Nicardipine (0.1–1 μM) did not affect slow-wave upstroke or propagation velocities. Upstroke velocity, amplitude, and propagation velocity were reduced in a concentration-dependent manner by Ni2+ (1–100 μM), mibefradil (10–30 μM), and reduced extracellular Ca2+ (0.5–1.5 mM). Depolarization (by 10–15 mM K+) or hyperpolarization (10 μM pinacidil) also reduced upstroke and propagation velocities. The higher concentrations (or lowest Ca2+) of these drugs and ionic conditions tested blocked slow-wave propagation. Treatment with cyclopiazonic acid to empty Ca2+ stores did not affect propagation. These experiments show that voltage-dependent Ca2+ entry is obligatory for the upstroke phase of slow waves and active propagation.

Visualization of origins and propagation of excitation in canine gastric smooth muscle

1999 ◽  
Vol 277 (3) ◽  
pp. C448-C460 ◽  
Author(s):  
Randel J. Stevens ◽  
Jeffery S. Weinert ◽  
Nelson G. Publicover
Keyword(s):  
Smooth Muscle ◽  
Slow Wave ◽  
Longitudinal Muscle ◽  
Circular Muscle ◽  
Gastrointestinal Smooth Muscle ◽  
Gastric Smooth Muscle ◽  
Conduction Velocities ◽  
Spread Of Excitation ◽  
Order Of Magnitude ◽  
Propagation Velocities

The origin and spread of excitation were visualized with fluo 3 fluorescence in tissues isolated from canine gastric antrum. Sheets of circular muscle (5 × 6 mm) had at least 1 (30%) and up to 3 discrete slow-wave pacing sites located near the longitudinal-circular muscle boundary, whereas similarly sized longitudinal sheets had an average of 5 sites (range 3–12 sites) that initiated Ca2+ waves. Superimposed fluorescent oscillations (circular muscle) and spikes (longitudinal muscle) were seen to initiate and propagate as distinct events, separate from their underlying activities. Average propagation velocities transverse (6–7 mm/s) and parallel (39–45 mm/s) to the long axis of muscle fibers were similar for each type of event in circular and longitudinal tissues; however, distinct regions where velocities of some (but not all) events decreased by up to an order of magnitude were present. The distance propagated by individual events was limited by collisions with concurrent excitable events or recently activated regions. Complex patterns of excitation in gastrointestinal smooth muscle arise as a result of interactions between multiple pacing sites, heterogeneous conduction velocities, and the interplay of adjacent pacemaker domains.

Conduction Velocities and Their Temperature Coefficients in Sensory Nerve Fibres of Cockroach Legs

1967 ◽  
Vol 46 (1) ◽  
pp. 63-84
Author(s):  
K. M. CHAPMAN ◽  
J. H. PANKHURST
Keyword(s):  
Conduction Velocity ◽  
Periplaneta Americana ◽  
Sensory Nerve ◽  
Point Of View ◽  
Conduction Delay ◽  
Nerve Fibres ◽  
Impulse Frequency ◽  
Temperature Coefficients ◽  
Conduction Velocities ◽  
Sensory Encoding

1. Conduction velocities of individual afferent nerve fibres from tactile spines and proprioceptive campaniform sensilla have been measured in situ over the temperature range 5-42° C., in leg preparations of the cockroach Periplaneta americana. 2. Conduction velocities at 20° C. (u20) averaged 3.3±1.4 m./sec., ranging from 1.6 to 11.0 m./sec. 3. Temperature coefficients, expressed as Q10 for the interval 20-30° C., averaged 1.7±0.24, ranging from 1.3 to 2.6. 4. The length of the propagated disturbance is about 2-3 mm., and is nearly temperature-independent. 5. Fibre diameters, estimated from conduction velocity, must be about 10 µ. 6. There is no correlation between conduction velocity and distance from the sensillum to the thoracic ganglion. Conduction delays in fibres conducting within one standard deviation of mean u20 range from about 2 to 15 msec., from the most proximal to the most distal tactile spines. 7. The effect of conduction delay on temporal and spatial sensory encoding is probably unimportant from a behavioural point of view. It contributes a factor of the form exp(-sd/u) to the sensory transfer function, and may be appreciable at upper physiological frequencies of impulse frequency modulation.

scholarly journals Abnormal gastric slow waves in patients with functional dyspepsia assessed by multichannel electrogastrography

2001 ◽  
Vol 280 (6) ◽  
pp. G1370-G1375 ◽  
Author(s):  
Xuemei Lin ◽  
Jiande Z. Chen
Keyword(s):  
Wave Propagation ◽  
Functional Dyspepsia ◽  
Slow Wave ◽  
Single Channel ◽  
Slow Waves ◽  
Lower Percentage ◽  
Healthy Controls ◽  
Fasting State ◽  
Gastric Slow Wave ◽  
Gastric Slow Waves

The aim of this study was to utilize multichannel electrogastrography to investigate whether patients with functional dyspepsia had impaired propagation or coordination of gastric slow waves in the fasting state compared with healthy controls. The study was performed in 10 patients with functional dyspepsia and 11 healthy subjects. Gastric myoelectrical activity was measured by using surface electrogastrography with a specially designed four-channel device. The study was performed for 30 min or more in the fasting state. Special computer programs were developed for the computation of the propagation and coupling of the gastric slow wave. It was found that, compared with the healthy controls, the patients showed a significantly lower percentage of slow wave propagation (58.0 ± 8.9 vs. 89.9 ± 2.6%, P < 0.002) and a significantly lower percentage of slow wave coupling (46.9 ± 4.4 vs. 61.5 ± 6.9%, P < 0.04). In addition, the patients showed inconsistencies in the frequency and regularity of the gastric slow wave among the four-channel electrogastrograms (EGGs). It was concluded that patients with functional dyspepsia have impaired slow wave propagation and coupling. Multichannel EGG has more information than single-channel EGG for the detection of gastric myoelectrical abnormalities.

Pacemaker activity in septal structures of canine colonic circular muscle

1990 ◽  
Vol 259 (2) ◽  
pp. G264-G273 ◽  
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.

Excitation conduction in Meissner's plexus of rabbit small intestine.

1977 ◽  
Vol 232 (2) ◽  
pp. E109
Author(s):  
S Yokoyama ◽  
T Ozaki ◽  
T Kajitsuka
Keyword(s):  
Small Intestine ◽  
Evoked Potentials ◽  
Longitudinal Muscle ◽  
Circular Muscle ◽  
Electrical Stimulus ◽  
High Frequencies ◽  
Nerve Impulses ◽  
Conduction Velocities ◽  
Rabbit Small Intestine ◽  
Recording Electrodes

Excitation conduction in Meissner's plexus of the rabit small intestine was investigated by analyzing the records of potentials evoked by a single electrical stimulus applied to this plexus. Experiments were performed on the Meissner's plexus that remained attached to the circular muscle after the longitudinal muscle and mucous membrane were removed from intestinal segment. Conduction velocities of nerve impulses were 0.3-0.7 m/s, chronaxie of the nerve bundle was 0.06-0.12 ms. While the distance between the stimulating and recording electrodes was increased, the latency of evoked potentials was prolonged, the number increased, and the amplitude decreased; no potentials could be recorded when the distance was more than 4 mm. Evoked potentials recorded at relatively long conduction distance were reduced in amplitude or abolished after a repeated stimulation with high frequencies above 50/s, after hexamethonium application, and in a state of lack of oxygen. It was concluded that, in Meissner's plexus, nerve impulses spread through multiple pathways and make synaptic transmission at a relatively short conduction distance.

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