Longitudinal and Circular Muscle of the Canine Colon have Different and Characteristic Electrical and Mechanical Activities

1984 ◽  
pp. 397-403 ◽  
Author(s):  
L. Debski ◽  
K. L. Bowes ◽  
Y. J. Kingma ◽  
R. Gill
Keyword(s):  
Circular Muscle ◽  
Electrical And Mechanical Activities

Evidence that prostaglandins are local regulatory agents in canine ileal circular muscle

1984 ◽  
Vol 246 (4) ◽  
pp. G361-G371 ◽  
Author(s):  
K. M. Sanders
Keyword(s):  
Action Potentials ◽  
Circular Muscle ◽  
Prostaglandin Synthesis ◽  
Mechanical Activity ◽  
Mechanical Effects ◽  
Endogenous Prostaglandin ◽  
Endogenous Prostaglandins ◽  
Electrical Activities ◽  
Electrical And Mechanical Activities

Studies were performed to determine the role of endogenous prostaglandins (PG) in regulating mechanical and electrical activities of canine ileal circular muscles. Indomethacin, a prostaglandin synthesis blocker, enhanced the amplitude of spontaneous and acetylcholine-stimulated contractions. The increase in mechanical activity caused by indomethacin was accompanied by decreased release of 6-keto-PGF1 alpha, the spontaneous metabolite of prostacyclin, from the muscle. The electrical mechanisms responsible for the changes in mechanical activity caused by indomethacin were investigated by intracellular measurement of electrical activity. The enhanced contractions due to indomethacin correlated with enhanced electrical slow-wave amplitude and generation of action potentials. After indomethacin treatment muscles were exposed to several exogenous prostaglandins to determine which of these compounds might reverse the mechanical effects of indomethacin. Prostacyclin reversed the effects of indomethacin, and PGE2 reversed some of the effects of indomethacin. Prostacyclin also decreased the amplitude of electrical slow waves and abolished action potentials. These electrical effects were associated with decreased contractile amplitude. It is concluded that the dominant prostaglandin responsible for the "prostaglandin effect" in canine ileal circular muscle must be inhibitory to spontaneous and acetylcholine-stimulated contractions. The mechanical effects attributed to endogenous prostaglandin appear to be due to an electrical mechanism. Based on the evidence presented prostacyclin emerges as the most likely candidate for the role of "dominant" prostaglandin, but PGE2 may also contribute as a modulator of electrical and mechanical activities.

scholarly journals EFFECTS OF L-NITROARGININE AND SODIUM NITROPRUSSIDE ON ELECTRICAL AND MECHANICAL ACTIVITIES OF RAT PORTAL VEIN CIRCULAR MUSCLE

2000 ◽  
Vol 82 ◽  
pp. 208
Author(s):  
Keiichi Shimamura ◽  
Kazuo Yamamoto ◽  
Fumiko Sekiguchi ◽  
Kyoko Matsuda ◽  
Satoru Sunano
Keyword(s):  
Portal Vein ◽  
Sodium Nitroprusside ◽  
Circular Muscle ◽  
Rat Portal Vein ◽  
Electrical And Mechanical Activities

Does endogenous prostaglandin affect gastric antral motility?

1981 ◽  
Vol 241 (2) ◽  
pp. G191-G195 ◽  
Author(s):  
K. M. Sanders ◽  
J. H. Szurszewski
Keyword(s):  
Action Potential ◽  
Electrical Activity ◽  
Muscle Contraction ◽  
Circular Muscle ◽  
Plateau Phase ◽  
Phasic Contraction ◽  
Mechanical Responses ◽  
Endogenous Prostaglandin ◽  
Electrical And Mechanical Activities ◽  
Indomethacin Treatment

Intracellular electrical activity and muscle contraction were recorded simultaneously from circular muscle of the canine antrum. Treatment with indomethacin enhanced the plateau phase of the spontaneously occurring gastric action potential and the amplitude of the phasic contraction. Exogenous PGE2 reversed this effect of indomethacin. Treatment with indomethacin also enhanced the electrical and mechanical responses to pentagastrin; this enhancement was also reversed by PGE2. Considered together, these results suggest that endogenous prostaglandin, probably of the E series, tonically suppresses the spontaneous electrical and mechanical activities of antral circular muscle and the responsiveness of the muscle to excitatory stimuli.

Forced vibrations of a circular muscle ring

1973 ◽  
Vol 35 ◽  
pp. 467-474
Author(s):  
P DELSEMME ◽  
H WESTCOTTVAYO
Keyword(s):  
Circular Muscle ◽  
Forced Vibrations

Nitric oxide mediates outward potassium currents in opossum esophageal circular smooth muscle

1996 ◽  
Vol 270 (6) ◽  
pp. G932-G938 ◽  
Author(s):  
J. Jury ◽  
K. R. Boev ◽  
E. E. Daniel
Keyword(s):  
Nitric Oxide ◽  
Smooth Muscle ◽  
Circular Muscle ◽  
Outward Current ◽  
Equilibrium Potential ◽  
Patch Clamp Technique ◽  
Pipette Solution ◽  
Whole Cell ◽  
Circular Smooth Muscle ◽  
Outward Currents

Single smooth muscle cells from the opossum body circular muscle were isolated and whole cell currents were characterized by the whole cell patch-clamp technique. When the cells were held at -50 mV and depolarized to 70 mV in 20-mV increments, initial small inactivating inward currents were evoked (-30 to 30 mV) followed by larger sustained outward currents. Depolarization from a holding potential of -90 mV evoked an initial fast inactivating outward current sensitive to 4-aminopyridine but not to high levels of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). The outward currents reversed near K+ equilibrium potential and were abolished when KCl was replaced by CsCl in the pipette solution. The sustained outward current was inhibited by quinine and cesium. High EGTA in the pipette solution reduced but did not abolish the sustained outward currents, suggesting that both Ca(2+)-dependent and -independent currents were evoked. The nitric oxide (NO)-releasing agents Sin-1 and sodium nitroprusside increased outward K+ currents. High levels of EGTA in the pipette solution abolished the increase in outward current induced by Sin-1. The presence of cyclopiazonic acid, an inhibitor of the sarcoplasmic reticulum (SR) Ca2+ pump, blocked the effects of NO-releasing agents. We conclude that NO release activates K+ outward currents in opossum esophagus circular muscle, which may depend on Ca2+ release from the SR stores.

Morphology of the canine pyloric sphincter in relation to function

1989 ◽  
Vol 67 (12) ◽  
pp. 1560-1573 ◽  
Author(s):  
E. E. Daniel ◽  
I. Berezin ◽  
H. D. Allescher ◽  
H. Manaka ◽  
V. Posey-Daniel
Keyword(s):  
Smooth Muscle ◽  
Substance P ◽  
Smooth Muscle Cells ◽  
Gap Junctions ◽  
Vasoactive Intestinal Polypeptide ◽  
Interstitial Cells Of Cajal ◽  
Circular Muscle ◽  
Interstitial Cells ◽  
Pyloric Sphincter ◽  
Cells Of Cajal

The ultrastructure and immunocytochemistry of the canine distal pyloric muscle loop, the pyloric sphincter, were studied. Cells in this muscle were connected by gap junctions, fewer than in the antrum or corpus. The sphincter had a dense innervation and a sparse population of interstitial cells of Cajal. Most such cells were of the circular muscle type but a few were of the type in the myenteric plexus. Nerves were sometimes associated with interstitial cell profiles, but most nerves were neither close to nor associated with interstitial cells nor close to smooth muscle cells. Nerve profiles were characterized by an unusually high proportion of varicosities with a majority or a high proportion of large granular vesicles. Many of these were shown to contain material immunoreactive for vasoactive intestinal polypeptide (VIP) and some had substance P (SP) immunoreactive material. All were presumed to be peptidergic. VIP was present in a higher concentration in this muscle than in adjacent antral or duodenal circular muscle. Interstitial cells of Cajal made gap junctions to smooth muscle and to one another and might provide myogenic pacemaking activity for this muscle, but there was no evidence of a close or special relationship between nerves with VIP or SP and these cells. The absence of close relationships between nerves and either interstitial cells or smooth muscle cells leaves unanswered questions about the structural basis for previous observations of discrete excitatory responses or pyloric sphincter to single stimuli or nerves up to one per second. In conclusion, the structural observations suggest that this muscle has special neural and myogenic control systems and that interstitial cells may function to control myogenic activity of this muscle but not to mediate neural signals.Key words: vasoactive intestinal polypeptide, interstitial cells of Cajal, neuropeptides, gap junctions, substance P.

Effects of ouabain on background and voltage-dependent currents in canine colonic myocytes

1990 ◽  
Vol 259 (3) ◽  
pp. C402-C408 ◽  
Author(s):  
E. P. Burke ◽  
K. M. Sanders
Keyword(s):  
Membrane Potential ◽  
Potential Gradient ◽  
Circular Muscle ◽  
Input Resistance ◽  
Pump Current ◽  
Muscle Layer ◽  
Membrane Properties ◽  
Resting Potential ◽  
Voltage Dependent ◽  
In Cells

Previous studies have suggested that the membrane potential gradient across the circular muscle layer of the canine proximal colon is due to a gradient in the contribution of the Na(+)-K(+)-ATPase. Cells at the submucosal border generate approximately 35 mV of pump potential, whereas at the myenteric border the pump contributes very little to resting potential. Results from experiments in intact muscles in which the pump is blocked are somewhat difficult to interpret because of possible effects of pump inhibitors on membrane conductances. Therefore, we studied isolated colonic myocytes to test the effects of ouabain on passive membrane properties and voltage-dependent currents. Ouabain (10(-5) M) depolarized cells and decreased input resistance from 0.487 +/- 0.060 to 0.292 +/- 0.040 G omega. The decrease in resistance was attributed to an increase in K+ conductance. Studies were also performed to measure the ouabain-dependent current. At 37 degrees C, in cells dialyzed with 19 mM intracellular Na+ concentration [( Na+]i), ouabain caused an inward current averaging 71.06 +/- 7.49 pA, which was attributed to blockade of pump current. At 24 degrees C or in cells dialyzed with low [Na+]i (11 mM), ouabain caused little change in holding current. With the input resistance of colonic cells, pump current appears capable of generating at least 35 mV. Thus an electrogenic Na+ pump could contribute significantly to membrane potential.

Chronic rejection causes early destruction of the intrinsic nervous system in rat intestinal transplants

1997 ◽  
Vol 273 (2) ◽  
pp. G413-G421 ◽  
Author(s):  
P. F. Heeckt ◽  
W. Halfter ◽  
W. H. Schraut ◽  
A. J. Bauer
Keyword(s):  
Nervous System ◽  
Chronic Rejection ◽  
Circular Muscle ◽  
Electrical Field Stimulation ◽  
Functional Changes ◽  
Diaphorase Activity ◽  
Enteric Nerves ◽  
Mucosal Changes ◽  
Oxide Synthase ◽  
Muscularis Externa

Chronic rejection is the major cause of late intestinal allograft dysfunction. We have previously shown that chronic rejection alters the muscularis externa of the graft. This study determined structural and functional changes to the enteric nerves during chronic rejection. Chronic rejection was achieved in orthotopic intestinal transplants (ACI to Lewis) by limited immunosuppression. Syngeneic transplants (ACI to ACI) and unoperated ACI rats served as controls. Animals were clinically healthy and showed no significant alterations in the mucosal architecture on postoperative day 90. Staining for NADPH diaphorase activity (nitric oxide synthase-containing neurons) and with neurofilament antibody RT-97 revealed that chronic rejection decreased the number of jejunal myenteric ganglia by approximately 50%. Inhibitory junction potentials (IJPs) to circular muscle cells were determined by electrical field stimulation (EFS). In controls and syngeneic grafts, EFS caused a stimulus-dependent increase in IJP amplitude, with a maximal amplitude of 9 +/- 0.4 and 10 +/- 0.8 mV, respectively. Chronic rejection in allografts markedly increased the threshold for IJP initiation and decreased the maximal IJP amplitude (5 +/- 0.8 mV). Our data indicate that chronic rejection severely damages the muscularis and the enteric nervous system before mucosal changes become evident.

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