Electrical and mechanical effects of acetylcholine and substance P in subregions of canine colon

1992 ◽  
Vol 262 (2) ◽  
pp. G298-G307 ◽  
Author(s):  
K. D. Keef ◽  
S. M. Ward ◽  
R. J. Stevens ◽  
B. W. Frey ◽  
K. M. Sanders
Keyword(s):  
Substance P ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Proximal Colon ◽  
Slow Waves ◽  
Circular Muscle Layer ◽  
Long Duration ◽  
Low Concentrations ◽  
Excitatory Neurotransmitters ◽  
Circular Layer

Effects of acetylcholine (ACh) and substance P on the electrical and mechanical activities of the circular muscle layer of the canine proximal colon were studied. Because this muscle layer is bordered by two different pacemaker regions, responses from segments containing either a single pacemaker region or no pacemaker region were compared with responses of the complete muscle layer. Concentration-response relationships for ACh and substance P were similar between the various segments, suggesting that receptors for these agonists are expressed throughout the layer. The dominant contractile pattern induced by ACh and substance P in each segment was a 1- to 3-cycle/min rhythm. In a like manner, these agonists also elicited an electrical pattern in which a long-duration slow wave occurred one to three times per minute between short-duration slow waves. Low concentrations of nifedipine (0.01 microM) selectively antagonized the 1- to 3-cycle/min rhythm. In circular muscles with no pacemaker region, ACh (1 microM) caused depolarization, induced oscillations in membrane potential averaging 24 +/- 5 mV in amplitude and 2.9 +/- 0.9 cycles/min in frequency, and generated rhythmic contractions at the same frequency. This "interior" circular muscle was functionally innervated by cholinergic excitatory nerves. Exposure to ACh (1 microM) did not alter the conduction of slow waves through the thickness of the circular layer. In summary, the excitatory neurotransmitters, ACh and substance P, induce a dominant electrical and contractile rhythm throughout the circular muscle layer that is different from the spontaneous rhythms produced at either the myenteric or submucosal border.

Changes in electrical and mechanical activity during ontogeny of the canine proximal colon

1996 ◽  
Vol 271 (1) ◽  
pp. G184-G191 ◽  
Author(s):  
S. M. Ward
Keyword(s):  
Membrane Potential ◽  
Circular Muscle ◽  
Electrical Field Stimulation ◽  
Muscle Layer ◽  
Proximal Colon ◽  
Mechanical Activity ◽  
Resting Membrane Potential ◽  
Circular Muscle Layer ◽  
Circular Layer ◽  
Spontaneous Contractions

The ontogenetic development of the circular muscle layer of the canine proximal colon was studied in animals from midway through gestation to 30 days old. With age, there was an increase in resting membrane potential along the submucosal surface and a decrease along the myenteric surface of the circular layer. Coinciding with the changes in membrane potential, slow waves increased in amplitude along the submucosal border and decreased in amplitude along the myenteric border. Muscle strips from animals midway through gestation were mechanically quiescent; however, 1 wk before birth spontaneous activity was observed. Electrical field stimulation of enteric nerves increased spontaneous contractions; this increase in activity was reversed to inhibition by atropine. In the presence of atropine and N omega-nitro-L-arginine or N omega-nitro-L-arginine methyl ester, a noncholinergic excitation was revealed at stimulation frequencies > 5 Hz. The results of these studies provide evidence that the canine proximal colon is spontaneously rhythmic and that a functional innervation to the circular muscle layer exists before birth. The gradient in resting membrane potential across the circular layer is absent at birth but develops within 2-3 wk after parturition.

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.

Cholinergic nerve-mediated excitation in the guinea pig choledochoduodenal junction activated by distension

1994 ◽  
Vol 267 (5) ◽  
pp. G938-G946 ◽  
Author(s):  
F. Vogalis ◽  
R. R. Bywater ◽  
G. S. Taylor
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Action Potential ◽  
Action Potentials ◽  
Discharge Rate ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Circular Muscle Layer ◽  
Circular Layer ◽  
Longitudinal Layer

The electrical basis of propulsive contractions in the guinea pig choledochoduodenal junction (CDJ), which are triggered by distension, was investigated using intracellular microelectrode recording techniques. The isolated CDJ was placed in a continuously perfused tissue chamber at 37 degrees C. Membrane potential was recorded from smooth muscle cells in either the ampulla or in the upper CDJ (upper junction) regions, which were immobilized by pinning. Distension of the upper junction (20-30 s) by increasing intraductal hydrostatic pressure (mean elevation: 2.0 +/- 0.3 kPa, n = 13) triggered "transient depolarizations" (TDs: < 5 mV in amplitude and 2-5 s in duration) and action potentials in the circular muscle layer of the ampulla. The frequency of TDs in the ampulla was increased from 2.2 +/- 0.2 to 15.9 +/- 2.2 min-1 (n = 13) during distension. Simultaneous impalements of cells in the longitudinal and circular muscle layers in the ampulla revealed that subthreshold TDs in the circular layer were associated with an increased rate of action potential discharge in the longitudinal layer. Atropine (Atr; 1.4 x 10(-6) M) and tetrodotoxin (TTX; 3.1 x 10(-6) M blocked the distension-evoked increase in TD frequency, without affecting the frequency of ongoing TDs. The sulfated octapeptide of cholecystokinin (1-5 x 10(-8) M) increased the amplitude of TDs recorded in the circular muscle layer of the ampulla and increased action potential discharge rate. In separate recordings, radial stretch of the ampulla region increased the rate of discharge of action potentials in the smooth muscle of the upper junction.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrical and mechanical interactions between the muscle layers of canine proximal colon

1990 ◽  
Vol 258 (3) ◽  
pp. G484-G491 ◽  
Author(s):  
P. J. Sabourin ◽  
Y. J. Kingma ◽  
K. L. Bowes
Keyword(s):  
Membrane Potential ◽  
Circular Muscle ◽  
Longitudinal Direction ◽  
Proximal Colon ◽  
Slow Waves ◽  
The Other ◽  
Potential Oscillations ◽  
Circular Layer ◽  
Longitudinal Layer ◽  
Membrane Potential Oscillations

Electrical and mechanical interactions between the two smooth muscle layers of canine colon have been studied using a dual sucrose gap apparatus. Muscle samples were dissected into an L-shape, with one leg cut in the circular direction and the other cut in the longitudinal direction. Longitudinal muscle was removed from the circular leg and circular muscle was removed from the longitudinal leg. The bend of the L contained both layers. The activity of the two layers was studied simultaneously under basal conditions, after stimulation by neostigmine and carbachol, and in the presence of tetrodotoxin. Interactions were more common after stimulation and were marked by modification of one layer's mechanical and electrical activity during increased activity in the other layer. Two patterns were commonly observed. First, during a burst of membrane potential oscillations and spike potentials in the longitudinal layer, slow waves in the circular layer developed spike potentials and some slow waves were also prolonged. Second, during a slow-wave cycle in the circular layer, the amplitude of membrane potential oscillations in the longitudinal layer was increased with an associated increase in the incidence of spike potentials. These interactions were associated with contractions of increased strength, which were similar in both layers. All interactions continued after nerve-conduction blockade by tetrodotoxin.

Excitatory and inhibitory neural regulation of canine pyloric smooth muscle

1990 ◽  
Vol 259 (1) ◽  
pp. G125-G133 ◽  
Author(s):  
F. Vogalis ◽  
K. M. Sanders
Keyword(s):  
Action Potentials ◽  
Slow Component ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Slow Waves ◽  
Cross Sectional ◽  
Intrinsic Innervation ◽  
Circular Layer ◽  
Neuromuscular Apparatus ◽  
Excitatory Junction Potentials

Studies were performed to characterize the intrinsic innervation of the circular muscle layer of the canine pylorus. Cross-sectional strips of muscle were studied with intracellular recording techniques, and junction potentials were elicited with transmural nerve stimulation. Neurally mediated responses were recorded from cells at several points through the thickness of the circular layer. Excitatory junction potentials (EJPs) increased and inhibitory junction potentials (IJPs) decreased in amplitude with distance from the myenteric border of the circular muscle. Atropine blocked EJPs throughout the circular layer, demonstrating that excitatory inputs are primarily cholinergic. The gradient in IJP amplitude persisted after blockade of EJPs. Three components of IJPs were identified: 1) a fast, apamin-sensitive component that reached a peak and decayed within approximately 1 s; 2) a slower, apamin-insensitive component that reached a peak within 800 ms but decayed slowly over 5 s; and 3) a very slow component that reached a maximum in 7-10 s. Junctional potentials affected the pattern of myogenic electrical activity. Transmural stimulation could evoke premature slow waves in the myenteric portion of the circular layer but when excitatory inputs were blocked, IJPs greatly reduced the amplitude of slow waves. EJPs elicited action potentials in submucosal portion of circular muscles, and IJPs hyperpolarized these cells. The influence of intrinsic nerves on contractile patterns of pyloric muscles was also characterized. These data demonstrate that a neuromuscular apparatus exists within the gastroduodenal junction for 1) local regulation of slow waves and 2) independent control of the myenteric and submucosal regions of the circular layer.

Longitudinal contractions in the duodenum: their fluid-mechanical function

1975 ◽  
Vol 228 (6) ◽  
pp. 1887-1892 ◽  
Author(s):  
J Melville ◽  
E Macagno ◽  
J Christensen
Keyword(s):  
Longitudinal Muscle ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Slow Waves ◽  
Longitudinal Muscle Layer ◽  
Circular Muscle Layer ◽  
Model Flow ◽  
Displacement Wave ◽  
Marked Points

The hypothesis examined was that contractions of the longitudinal muscle layer occurin the duodenum which are independent of those of the circular muscle layer and that they induce flow of duodenal contents. A segment of opossum duodenum isolated in vitro was marked and photographed during periods of longitudinal muscle contraction, when the circular muscle layer appeared inactive. The prequency of longitudinal oscillation of the marked points was 20.5 cycles/min. The longitudinal displacement wave spread caudad with an average velocity of 3.27 cm/s. Frequency and velocity of electrical slow waves were determined in similiar duodenal segments. Slow-wave frquencywas 18.9 cycles/min. In a two-dimensional mechanical model, flow induced by simulatedlongitudinal muscle layer appear to be driven by the electrical slow waves of the duodenum. They are capable of inducing a pattern of flow in which ocntents flow betweenthe core and the periphery of the intestinal conduit.

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

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)

Voltage-gated ionic currents in smooth muscle cells of guinea pig proximal colon

1993 ◽  
Vol 264 (3) ◽  
pp. C527-C536 ◽  
Author(s):  
F. Vogalis ◽  
R. J. Lang ◽  
R. A. Bywater ◽  
G. S. Taylor
Keyword(s):  
Guinea Pig ◽  
Circular Muscle ◽  
Ionic Currents ◽  
Muscle Layer ◽  
Proximal Colon ◽  
Inward Current ◽  
Voltage Gated ◽  
Outward Currents ◽  
Low Concentrations ◽  
K Current

Smooth muscle cells enzymatically dispersed from the circular muscle layer of the guinea pig colon were examined for the expression of voltage-gated ionic currents using the whole cell patch-clamp technique. Three outward currents and one inward current were identified and characterized. The inward current, at physiological potentials, was generated by a voltage-gated Ca2+ conductance that was permeable to Ba2+ but blocked by Cd2+ (0.1 mM) or nifedipine (10 microM). The three outward currents were carried by K+, abolished when cells were internally perfused with Cs+, and distinguished by their sensitivity to known K(+)-channel blockers. A K+ current dependent on Ca2+ entry was activated at potentials positive to -40 mV and abolished by low concentrations (2-5 mM) of tetraethylammonium (TEA). A delayed rectifier-type K+ current activated slowly at potentials positive to -30 mV, showed little inactivation, and was abolished by higher concentrations (> 5 mM) of TEA. A rapidly activating and inactivating transient outward K+ current (IKto), activated at potentials positive to -60 mV, was abolished by low concentrations (3-5 mM) of 4-aminopyridine and was relatively insensitive to TEA (10-126 mM) blockade. The overlapping steady-state activation and inactivation curves of IKto revealed a "window current" phenomenon between -60 and -40 mV. The rapid activation of IKto at membrane potentials more negative than those for Ca2+ current suggests that IKto will influence cell excitability by delaying the upstroke of the action potential. The present data provide an ionic basis for the regenerative excitatory activity in the circular muscle layer of the guinea pig proximal colon.

Distribution of cocaine- and amphetamine-regulated transcript-like immunoreactive (CART-LI) nerve structures in the porcine large intestine

2009 ◽  
Vol 57 (4) ◽  
pp. 509-520 ◽  
Author(s):  
Slawomir Gonkowski ◽  
Piotr Burliński ◽  
Cezary Skobowiat ◽  
Mariusz Majewski ◽  
Marcin Arciszewski ◽  
...  
Keyword(s):  
Distribution Pattern ◽  
Large Intestine ◽  
Transverse Colon ◽  
Circular Muscle ◽  
Muscle Layer ◽  
Proximal Colon ◽  
Intestinal Wall ◽  
Circular Muscle Layer ◽  
Mucosal Layer ◽  
Colon And Rectum

The aim of the present study was to investigate the number of cocaine- and amphetamine-regulated transcript-like immunoreactive (CART-LI) nerve structures in the large intestine of juvenile pigs. The distribution pattern of CART-LI structures was studied by immunohistochemistry in the circular muscle layer, myenteric (MP), outer submucous (OSP) and inner submucous plexus (ISP) as well as in the mucosal layer of six regions of the large bowel: caecum, centripetal and centrifugal turns of the proximal colon, transverse colon, descending colon and rectum. CART-LI neural structures were observed in all gut fragments studied. CART-LI nerve fibres were numerous within the circular muscle layer and in the MP of all the regions studied, while they were moderate or few in number in other layers of the intestinal wall. The numbers of CART-LI neurons within the MP amounted to 2.02% in the caecum to 7.92% in the rectum, within the OSP from 2.73% in the centrifugal turns of the proximal colon to 5.70% in the rectum, and within the ISP from 2.23% in the transverse colon to 5.32% in the centrifugal turns of the proximal colon. The present study reports for the first time a detailed description of the CART distribution pattern within the enteric nervous system (ENS) of the porcine large intestine.

Effects of membrane potential on electrical slow waves of canine proximal colon

1988 ◽  
Vol 255 (6) ◽  
pp. C828-C834 ◽  
Author(s):  
T. K. Smith ◽  
J. B. Reed ◽  
K. M. Sanders
Keyword(s):  
Membrane Potential ◽  
Circular Muscle ◽  
Input Resistance ◽  
Proximal Colon ◽  
Slow Waves ◽  
Cross Sectional ◽  
Electrical Pulses ◽  
Length Constant ◽  
Circular Layer ◽  
External K

The effects of membrane potential on the waveforms and propagation of slow waves were tested using circular muscles of the canine colon. Studies were conducted with intracellular recording techniques on cross-sectional strips of canine proximal colon. Circular muscle cells near the submucosa generated slow waves that decayed in amplitude as they spread through the circular layer. The membrane potentials of cells were less negative as a function of distance from the submucosal border. Cells near the submucosa were depolarized with elevated external K+ and electrical pulses using the partitioned chamber technique. The waveforms of depolarized submucosal cells were compared with events recorded from cells in the bulk of the circular layer. The waveform changes caused by experimental depolarization were different from the changes in waveform that occur during propagation, suggesting the latter are due to a different mechanism than depolarization. The effects of the membrane potential on syncytial input resistance and length constant were also evaluated. The results of these studies are consistent with the hypothesis that slow-wave propagation across the circular layer in canine proximal colon occurs passively.

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