Neurotransmission in lower esophageal sphincter ofW/Wvmutant mice

2010 ◽  
Vol 298 (1) ◽  
pp. G14-G24 ◽  
Author(s):  
Y. Zhang ◽  
S. A. Carmichael ◽  
X. Y. Wang ◽  
J. D. Huizinga ◽  
W. G. Paterson
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Lower Esophageal Sphincter ◽  
Significant Proportion ◽  
Muscle Cells ◽  
Mutant Mice ◽  
Resting Membrane Potential ◽  
Wild Type ◽  
Circular Smooth Muscle ◽  
Esophageal Sphincter

To address the controversy surrounding the role of interstitial cells of Cajal (ICC) in nitrergic neurotransmission to gastrointestinal smooth muscle, circular smooth muscle from the lower esophageal sphincter (LES) of W/Wvwild-type and mutant (ICC-deficient) mice were studied by using intracellular and tension recordings in vitro. Resting membrane potential was more negative, and the spontaneous unitary potentials diminished in mutant mice. In wild-type mice, nerve stimulation induced a biphasic inhibitory junction potential (IJP) consisting of a fast initial IJP followed by a long-lasting slow IJP (LSIJP). The IJP was markedly impaired in a significant proportion of mutant mice, whereas in others it was normal. Pharmacological studies in the mice with markedly impaired IJPs revealed that cholinergic and purinergic components of the nerve-mediated responses appeared intact. In wild-type mice, caffeine hyperpolarized smooth muscle cells, inhibited the initial fast IJP, and completely abolished the LSIJP. In mutant mice, caffeine depolarized smooth muscle cells and abolished the impaired LSIJP but did not affect the initial fast IJP. Immunohistochemical staining for c-Kit confirmed deficiency of ICC in mutant mice with a normal nitrergic IJP. Rings of LES circular smooth muscle from W/Wvmutant mice generated significantly less spontaneous tone than controls. When tone was restored with carbachol, normal nitrergic LES relaxation was recorded. These data suggest that 1) there is significant variability in the generation of nitrergic neurotransmission in the LES of W/Wvmutant mice, whereas purinergic and cholinergic neurotransmission are intact; 2) the altered nitrergic responses appear to be associated with abnormal Ca2+-dependent signaling initiated by spontaneous Ca2+release from sarcoplasmic reticulum in smooth muscle cells; and 3) c-Kit-positive ICC are not essential for nitrergic neurotransmission in mouse LES smooth muscle.

Evidence for altered circular smooth muscle cell function in lower esophageal sphincter ofW/Wvmutant mice

2011 ◽  
Vol 301 (6) ◽  
pp. G1059-G1065 ◽  
Author(s):  
Francisco Bautista-Cruz ◽  
William G. Paterson
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Lower Esophageal Sphincter ◽  
Mutant Mice ◽  
Resting Membrane Potential ◽  
Circular Smooth Muscle ◽  
Significant Difference ◽  
Esophageal Sphincter ◽  
And Control ◽  
In Cells

Nitrergic neurotransmission to gut smooth muscle is impaired in W/Wvmutant mice, which lack intramuscular interstitial cells of Cajal (ICC-IM). In addition, these mice have been reported to have smaller amplitude unitary potentials (UPs) and a more negative resting membrane potential (RMP) than control mice. These abnormalities have been attributed to absence of ICC-IM, but it remains possible that they are due to alterations at the level of the smooth muscle itself. Amphotericin-B-perforated patch-clamp recordings and Ca2+imaging (fura 2) were compared between freshly isolated single circular smooth muscle cells (CSM) from W/Wvmutant and control mice lower esophageal sphincter (LES). There was no significant difference in seal resistance, capacitance, or input resistance in response to applied electrotonic current pulses between CSM cells from W/Wvmutants and controls. Compared with control mice, RMP was more negative and UPs significantly smaller in CSM cells from mutant mice LES. Administration of caffeine induced an inward current in cells from both mutant and control mice, but the current density was significantly larger in cells from W/Wvmutants. Membrane potential hyperpolarization induced by sodium nitroprusside was larger in cells from control mice vs. W/Wvmutants. In addition, intracellular Ca2+transients induced by caffeine were significantly increased in cells from mutants. These findings indicate that LES CSM is abnormal in W/Wvmutant mice. Thus some physiological functions attributed to ICC-IM based on experiments in smooth muscle of ICC deficient mice may need to be reconsidered.

Impaired platelet-derived growth factor receptor expression and function in cultured lower esophageal sphincter circular smooth muscle cells from W/Wv mutant mice

2014 ◽  
Vol 92 (1) ◽  
pp. 34-41 ◽  
Author(s):  
Francisco Bautista-Cruz ◽  
Dileep G. Nair ◽  
Sandra Lourenssen ◽  
David V. Miller ◽  
Michael G. Blennerhassett ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Growth Factor ◽  
Lower Esophageal Sphincter ◽  
Mutant Mice ◽  
Platelet Derived Growth Factor ◽  
Wild Type ◽  
Rt Pcr ◽  
Circular Smooth Muscle ◽  
Esophageal Sphincter ◽  
And Function

We have previously demonstrated that lower esophageal sphincter (LES) circular smooth muscle (CSM) is functionally impaired in W/Wv mutant mice that lack interstitial cells of Cajal, and speculated that this could be due to altered smooth muscle differentiation. Platelet-derived growth factor (PDGF) is involved in the maturation and differentiation of smooth muscle. To determine whether PDGF expression and (or) function is altered in W/Wv mutant mice, PDGF-Rβ expression was measured using RT-PCR, qPCR, and immunocytochemistry, and Ca2+ imaging and perforated patch clamp recordings performed in isolated LES CSM cells. RT-PCR and immunocytochemistry showed significantly reduced PDGF-Rβ expression in the LES from mutant as opposed to wild-type mice. Quantitative comparison of CSM cell numbers in histological specimens revealed a significantly increased average cell size in the mutant tissue. The specific PDGF-Rβ ligand, PDGF-BB, caused a significant increase in intracellular Ca2+ in cells from the wild-type mice compared with the mutants. Using a ramp protocol, PDGF-BB caused a 2-fold increase in outward K+ currents in cells from the wild-type mice, whereas no significant increase was measured in the cells from the mutants. We conclude that the expression and function of PDGF-Rβ in LES CSM from W/Wv mice is impaired, providing further evidence that LES CSM is abnormal in W/Wv mutants.

Role of HERG-like K+ currents in opossum esophageal circular smooth muscle

1999 ◽  
Vol 277 (6) ◽  
pp. C1284-C1290 ◽  
Author(s):  
Hamid I. Akbarali ◽  
Hemant Thatte ◽  
Xue Dao He ◽  
Wayne R. Giles ◽  
Raj K. Goyal
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Smooth Muscle Cells ◽  
Single Cells ◽  
Circular Muscle ◽  
Muscle Cells ◽  
Resting Membrane Potential ◽  
Channel Blockers ◽  
Circular Smooth Muscle ◽  
Inward Currents

An inwardly rectifying K+ conductance closely resembling the human ether-a-go-go-related gene (HERG) current was identified in single smooth muscle cells of opossum esophageal circular muscle. When cells were voltage clamped at 0 mV, in isotonic K+ solution (140 mM), step hyperpolarizations to −120 mV in 10-mV increments resulted in large inward currents that activated rapidly and then declined slowly (inactivated) during the test pulse in a time- and voltage- dependent fashion. The HERG K+ channel blockers E-4031 (1 μM), cisapride (1 μM), and La3+ (100 μM) strongly inhibited these currents as did millimolar concentrations of Ba2+. Immunoflourescence staining with anti-HERG antibody in single cells resulted in punctate staining at the sarcolemma. At membrane potentials near the resting membrane potential (−50 to −70 mV), this K+ conductance did not inactivate completely. In conventional microelectrode recordings, both E-4031 and cisapride depolarized tissue strips by 10 mV and also induced phasic contractions. In combination, these results provide direct experimental evidence for expression of HERG-like K+ currents in gastrointestinal smooth muscle cells and suggest that HERG plays an important role in modulating the resting membrane potential.

Pharmacological and biophysical isolation of K+ currents encoded by ether-à-go-go-related genes in murine hepatic portal vein smooth muscle cells

2007 ◽  
Vol 292 (1) ◽  
pp. C468-C476 ◽  
Author(s):  
Shuk Yin M. Yeung ◽  
Iain A. Greenwood
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Portal Vein ◽  
Smooth Muscle Cells ◽  
Significant Proportion ◽  
Muscle Cells ◽  
Resting Membrane Potential ◽  
Perforated Patch ◽  
Inward Currents ◽  
Channel Currents

Previous studies have shown that murine portal vein myocytes express ether-à-go-go related genes (ERGs) and exhibit distinctive currents when recorded under symmetrical K+ conditions. The aim of the present study was to characterize ERG channel currents evoked from a negative holding potential under conditions more pertinent to a physiological scenario to assess the possible functional impact of this conductance. Currents were recorded with ruptured or perforated patch variants of the whole cell technique from a holding potential of −60 mV. Application of three structurally distinct and selective ERG channel blockers, E-4031, dofetilide, and the peptide toxin BeKM-1, all inhibited a significant proportion of the outward current and abolished inward currents with distinctive “hooked” kinetics recorded on repolarization. Dofetilide-sensitive currents at negative potentials evoked by depolarization to +40 mV had a voltage-dependent time to peak and rate of decay characteristic of ERG channels. Application of the novel ERG channel activator PD-118057 (1–10 μM) markedly enhanced the hooked inward currents evoked by membrane depolarization and hyperpolarized the resting membrane potential recorded by current clamp and the perforated patch configuration by ∼20 mV. In contrast, ERG channel blockade by dofetilide (1 μM) depolarized the resting membrane potential by ∼8 mV. These data are the first record of ERG channel currents in smooth muscle cells under quasi-physiological conditions that suggest that ERG channels contribute to the resting membrane potential in these cells.

Membrane potential gradient is carbon monoxide-dependent in mouse and human small intestine

2007 ◽  
Vol 293 (2) ◽  
pp. G438-G445 ◽  
Author(s):  
Lei Sha ◽  
Gianrico Farrugia ◽  
W. Scott Harmsen ◽  
Joseph H. Szurszewski
Keyword(s):  
Carbon Monoxide ◽  
Smooth Muscle ◽  
Small Intestine ◽  
Smooth Muscle Cells ◽  
Circular Muscle ◽  
Muscle Cells ◽  
Muscle Layer ◽  
Wild Type ◽  
Circular Smooth Muscle ◽  
Human Small Intestine

The aims of this study were to quantify the change in resting membrane potential (RMP) across the thickness of the circular muscle layer in the mouse and human small intestine and to determine whether the gradient in RMP is dependent on the endogenous production of carbon monoxide (CO). Conventional sharp glass microelectrodes were used to record the RMPs of circular smooth muscle cells at different depths in the human small intestine and in wild-type, HO2-KO, and W/WV mutant mouse small intestine. In the wild-type mouse and human intestine, the RMP of circular smooth muscle cells near the myenteric plexus was −65.3 ± 2 mV and −58.4 ± 2 mV, respectively, and −60.1 ± 2 mV and −49.1 ± 1 mV, respectively, in circular smooth muscle cells at the submucosal border. Oxyhemoglobin (20 μM), a trapping agent for CO, and chromium mesoporphyrin IX, an inhibitor of heme oxygenase, abolished the transwall gradient. The RMP gradients in mouse and human small intestine were not altered by NG-nitro-l-arginine (200 μM). No transwall RMP gradient was found in HO2-KO mice and W/WV mutant mice. TTX (1 μM) and 1H-[1,2,4-]oxadiazolo[4,3-a]quinoxalin-1-one (10 μM) had no effect on the RMP gradient. These data suggest that the gradient in RMP across the thickness of the circular muscle layer of mouse and human small intestine is CO dependent.

Cannabinoid-1 (CB1) receptors regulate colonic propulsion by acting at motor neurons within the ascending motor pathways in mouse colon

2009 ◽  
Vol 296 (1) ◽  
pp. G119-G128 ◽  
Author(s):  
Andrei Sibaev ◽  
Birol Yüce ◽  
Markus Kemmer ◽  
Luc Van Nassauw ◽  
Ulli Broedl ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Motor Neurons ◽  
Muscle Cells ◽  
Type I ◽  
Wild Type ◽  
Myenteric Neurons ◽  
Circular Smooth Muscle ◽  
Mouse Colon

Cannabinoid-1 (CB1) receptors on myenteric neurons are involved in the regulation of intestinal motility. Our aim was to investigate CB1receptor involvement in ascending neurotransmission in mouse colon and to characterize the involved structures by functional and morphological means. Presence of the CB1receptor was investigated by RT-PCR, and immunohistochemistry was used for colabeling studies. Myenteric reflex responses were initiated by electrical stimulation (ES) at different distances, and junction potentials (JP) were recorded from circular smooth muscle cells by intracellular recording in an unpartitioned and a partitioned recording chamber. In vivo colonic propulsion was tested in wild-type and CB1−/−mice. Immunostaining with the cytoskeletal marker peripherin showed CB1immunoreactivity both on Dogiel type I and type II neurons. Further neurochemical characterization revealed CB1on choline acetyltransferase-, calretinin-, and 5-HT-immunopositive myenteric neurons, but nitrergic neurons appeared immunonegative for CB1immunostaining. Solitary spindle-shaped CB1-immunoreactive cells in between smooth muscle cells lacked specific markers for interstitial cells of Cajal or glial cells. ES elicited neuronally mediated excitatory JP (EJP) and inhibitory JP. Gradual increases in distance resulted in a wave-like EJP with EJP amplitudes being maximal at the location of stimulating electrode 6 and a maximal EJP projection distance of ∼18 mm. The CB1receptor agonist WIN 55,212-2 reduced the amplitude of EJP and was responsible for shortening the oral spreading of the excitatory impulse. In a partitioned chamber, WIN 55,212-2 reduced EJP at the separated oral sites, proving that CB1activation inhibits interneuron-mediated neurotransmission. These effects were absent in the presence of the CB1antagonist SR141716A, which, when given alone, had no effect. WIN 55,212-2 inhibited colonic propulsion in wild-type mice but not in SR141716A-pretreated wild-type or CB1−/−mice. Activation of the CB1receptor modulates excitatory cholinergic neurotransmission in mouse colon by reducing amplitude and spatial spreading of the ascending electrophysiological impulses. This effect on electrophysiological spreading involves CB1-mediated effects on motor neurons and ascending interneurons and is likely to underlie the here reported in vivo reduction in colonic propulsion.

Functional evidence for Na+-activated K+ channels in circular smooth muscle of the opossum lower esophageal sphincter

2007 ◽  
Vol 292 (6) ◽  
pp. G1600-G1606 ◽  
Author(s):  
Yong Zhang ◽  
William G. Paterson
Keyword(s):  
Smooth Muscle ◽  
Patch Clamp ◽  
Lower Esophageal Sphincter ◽  
Reversal Potential ◽  
Resting Membrane Potential ◽  
Single Channels ◽  
Dependent Manner ◽  
Open Probability ◽  
Circular Smooth Muscle ◽  
Esophageal Sphincter

Na+ reduction induces contraction of opossum lower esophageal sphincter (LES) circular smooth muscle strips in vitro; however, the mechanism(s) by which this occurs is unknown. The purpose of the present study was to investigate the electrophysiological effects of low Na+ on opossum LES circular smooth muscle. In the presence of atropine, quanethidine, nifedipine, and substance P, conventional intracellular electrodes recorded a resting membrane potential (RMP) of −37.5 ± 0.9 mV ( n = 4). Decreasing [Na+] from 144.1 to 26.1 mM by substitution of equimolar NaCl with choline Cl depolarized the RMP by 7.1 ± 1.1 mV. Whole cell patch-clamp recordings revealed outward K+ currents that began to activate at −60 mV using 400-ms stepped test pulses (−120 to +100 mV) with increments of 20 mV from holding potential of −80 mV. Reduction of [Na+] in the bath solution inhibited K+ currents in a concentration-dependent manner. Single channels with conductance of 49–60 pS were recorded using cell-attached patch-clamp configurations. The channel open probability was significantly decreased by substitution of bath Na+ with equimolar choline. A 10-fold increase of [K+] in the pipette shifted the reversal potential of the single channels to the positive by −50 mV. These data suggest that Na+-activated K+ channels exist in the circular smooth muscle of the opossum LES.

Ionic basis for spontaneous depolarizations in isolated smooth muscle cells of canine colon

1992 ◽  
Vol 263 (3) ◽  
pp. C691-C699 ◽  
Author(s):  
J. M. Post ◽  
J. R. Hume
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Cell Voltage ◽  
Muscle Cells ◽  
K Channel ◽  
Resting Membrane Potential ◽  
Channel Blockers ◽  
Inward Current ◽  
Circular Smooth Muscle ◽  
Ionic Basis

The type of cell that serves as the pacemaker in the colon is presently unknown. This study evaluated the ionic basis of spontaneous depolarizations in circular smooth muscle cells isolated from canine colon using whole cell voltage and current clamp techniques. Increasing temperature increased the probability of observing spontaneous depolarizations, depolarized the resting membrane potential (RMP), and increased Ca2+ and K+ currents. Spontaneous depolarizations occurred as rhythmic events, in bursts, or as isolated events. Varying the holding potential from -100 to -40 mV inhibited a component of inward current thought to be necessary for spontaneous depolarizations. The Ca2+ channel blockers, nickel and nisoldipine, inhibited spontaneous depolarizations. Nickel caused a hyperpolarization, whereas nisoldipine did not affect RMP. Ouabain depolarized the RMP and inhibited spontaneous depolarizations. The K+ channel blocker, tetraethylammonium, depolarized the RMP and lengthened the duration of spontaneous depolarizations. The key finding is that single colon circular smooth muscle cells are capable of generating spontaneous depolarizations similar to those described for slow waves in intact tissues and that a temperature- and nickel-sensitive inward current is essential for spontaneous activity.

Sign in / Sign up

Export Citation Format

Share Document