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Effects of lysophosphatidic acid on sling and clasp fibers of the human lower esophageal sphincter. TURKISH JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY 2022; 30:404-409. [PMID: 36303683 PMCID: PMC9580277 DOI: 10.5606/tgkdc.dergisi.2022.22084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 08/05/2021] [Indexed: 11/21/2022]
Abstract
Background
This study aims to explore the role of lysophosphatidic acid receptors in the regulation mechanisms of contraction and relaxation of human lower esophageal sphincter.
Methods
Between July 2015 and March 2016, muscle strips were collected from a total of 30 patients (19 males, 11 females; mean age: 62±9.9 years; range, 52 to 68 years) who underwent an esophagectomy for mid-third esophageal carcinomas. The specimens were maintained in oxygenated Krebs solution. Muscle tension measurement technique in vitro was used to examine the effects of non-selective lysophosphatidic acid receptors agonists and antagonists, as well as selective lysophosphatidic acid receptors agonists on the clasp and sling fibers of human lower esophageal sphincter.
Results
The non-selective dopamine receptor agonist lysophosphatidic acid induced the contraction of the clasp and sling fibers of the human lower esophageal sphincter. The response induced by nonselective lysophosphatidic acid receptor agonist was inhibited completely by non-selective lysophosphatidic acid receptor antagonist. The selective lysophosphatidic acid 1 and 2 receptor agonist and the selective lysophosphatidic acid 3 receptor agonist induced a concentration-dependent contractile response of the clasp and sling fibers of the human lower esophageal sphincter. There was no significant difference in contraction rates between the clasp and sling fibers (p>0.05).
Conclusion
This study indicates that lysophosphatidic acid regulates the lower esophageal sphincter is through its receptor; the lysophosphatidic acid receptors may be involved in the contractile response of the human lower esophageal sphincter.
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Borsdorf M, Böl M, Siebert T. Influence of layer separation on the determination of stomach smooth muscle properties. Pflugers Arch 2021; 473:911-920. [PMID: 33900446 PMCID: PMC8164583 DOI: 10.1007/s00424-021-02568-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 04/01/2021] [Accepted: 04/14/2021] [Indexed: 01/29/2023]
Abstract
Uniaxial tensile experiments are a standard method to determine the contractile properties of smooth muscles. Smooth muscle strips from organs of the urogenital and gastrointestinal tract contain multiple muscle layers with different muscle fiber orientations, which are frequently not separated for the experiments. During strip activation, these muscle fibers contract in deviant orientations from the force-measuring axis, affecting the biomechanical characteristics of the tissue strips. This study aimed to investigate the influence of muscle layer separation on the determination of smooth muscle properties. Smooth muscle strips, consisting of longitudinal and circumferential muscle layers (whole-muscle strips [WMS]), and smooth muscle strips, consisting of only the circumferential muscle layer (separated layer strips [SLS]), have been prepared from the fundus of the porcine stomach. Strips were mounted with muscle fibers of the circumferential layer inline with the force-measuring axis of the uniaxial testing setup. The force-length (FLR) and force-velocity relationships (FVR) were determined through a series of isometric and isotonic contractions, respectively. Muscle layer separation revealed no changes in the FLR. However, the SLS exhibited a higher maximal shortening velocity and a lower curvature factor than WMS. During WMS activation, the transversally oriented muscle fibers of the longitudinal layer shortened, resulting in a narrowing of this layer. Expecting volume constancy of muscle tissue, this narrowing leads to a lengthening of the longitudinal layer, which counteracted the shortening of the circumferential layer during isotonic contractions. Consequently, the shortening velocities of the WMS were decreased significantly. This effect was stronger at high shortening velocities.
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Affiliation(s)
- Mischa Borsdorf
- Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany.
| | - Markus Böl
- Institute of Mechanics and Adaptronics, Department of Mechanical Engineering, Braunschweig University of Technology, Braunschweig, Germany
| | - Tobias Siebert
- Department of Motion and Exercise Science, University of Stuttgart, Stuttgart, Germany
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L’Heureux MC, Muinuddin A, Gaisano HY, Diamant NE. Nitric oxide activation of a potassium channel (BK Ca) in feline lower esophageal sphincter. World J Gastroenterol 2010; 16:5852-60. [PMID: 21155007 PMCID: PMC3001977 DOI: 10.3748/wjg.v16.i46.5852] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To assess the effect of nitric oxide (NO) on the large conductance potassium channel (BKCa) in isolated circular (CM) and sling (SM) muscle cells and muscle strips from the cat lower esophageal sphincter (LES) to determine its regulation of resting tone and relaxation.
METHODS: Freshly enzymatically-digested and isolated circular smooth muscle cells were prepared from each LES region. To study outward K+ currents, the perforated patch clamp technique was employed. To assess LES resting tone and relaxation, muscle strips were mounted in perfused organ baths.
RESULTS: (1) Electrophysiological recordings from isolated cells: (a) CM was more depolarized than SM (-39.7 ± 0.8mV vs -48.1 ± 1.6 mV, P < 0.001), and maximal outward current was similar (27.1 ± 1.5 pA/pF vs 25.7 ± 2.0 pA/pF, P > 0.05); (b) The NO donor sodium nitroprusside (SNP) increased outward currents only in CM (25.9 ± 1.9 to 46.7 ± 4.2 pA/pF, P < 0.001) but not SM (23.2 ± 3.1 to 27.0 ± 3.4 pA/pF, P > 0.05); (c) SNP added in the presence of the BKCa antagonist iberiotoxin (IbTX) produced no increase in the outward current in CM (17.0 ± 2.8 vs 13.7 ± 2.2, P > 0.05); and (d) L-NNA caused a small insignificant inhibition of outward K+ currents in both muscles; and (2) Muscle strip studies: (a) Blockade of the nerves with tetrodotoxin (TTX), or BKCa with IbTX had no significant effect on resting tone of either muscle; and (b) SNP reduced tone in both muscles, and was unaffected by the presence of TTX or IbTX.
CONCLUSION: Exogenous NO activates BKCa only in CM of the cat. However, as opposed to other species, exogenous NO-induced relaxation is predominantly by a non-BKCa mechanism, and endogenous NO has minimal effect on resting tone.
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Okamoto T, Kurokawa M. The Role of the Peripheral Enteric Nervous System in the Control of Gut Motility in the SnailLymnaea stagnalis. Zoolog Sci 2010; 27:602-10. [DOI: 10.2108/zsj.27.602] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Wang XM, Zhang MX, Zhao L, Han B, Xu P, Xue M. The Starling mechanism of the urinary bladder contractile function and the influence of hyperglycemia on diabetic rats. J Diabetes Complications 2010; 24:121-8. [PMID: 19674919 DOI: 10.1016/j.jdiacomp.2009.06.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Revised: 06/08/2009] [Accepted: 06/19/2009] [Indexed: 10/20/2022]
Abstract
UNLABELLED Diabetic cystopathy is one of the common complications of diabetes. Bladder dysfunction in diabetes is attributable to diabetic neuropathy that induces sensory and autonomic nerve dysfunction. MATERIALS AND METHODS In the present study, the contractile mechanism of the bladder was evaluated both with and without electrical stimulation in normal rats, streptozotocin (STZ)-induced diabetic rats, and diabetic rats with insulin treatment. RESULTS Both the normal and diabetic rats had optimal capacity of bladder and optimal length of detrusor muscle strips. The peak values of the volume-pressure curves of the bladder and length-tension curves of detrusor muscle strips as well as the enhanced values after electrical stimulation in 6- and 10-week diabetic groups were lower than in the 6- and 10-week normal groups and insulin-treated groups. However, there was no significant difference in peak and enhanced values between normal rats and diabetic rats treated with insulin, indicating that voiding function was improved after insulin treatment. CONCLUSIONS The contractile function of rat's bladder including normal rats, diabetic rats, and diabetic rats treated with insulin is similar to the 'Starling mechanism.' It can be impaired by hyperglycemia, and insulin treatment is helpful to restore this function.
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Affiliation(s)
- Xin-min Wang
- Department of Endocrinology, The Second Clinical Medical College of Jinan University, Shenzhen, China
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Burton PR, Brown WA, Laurie C, Hebbard G, O'Brien PE. Mechanisms of bolus clearance in patients with laparoscopic adjustable gastric bands. Obes Surg 2010; 20:1265-72. [PMID: 20066500 DOI: 10.1007/s11695-009-0063-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Accepted: 12/09/2009] [Indexed: 01/26/2023]
Abstract
BACKGROUND The components of esophageal function important to success with laparoscopic adjustable gastric banding (LAGB) are not well understood. A pattern of delayed, however, successful bolus transit across the LAGB is observed. METHODS Successful LAGB patients underwent a high-resolution video manometry study in which bolus clearance, flow, and intraluminal pressures were recorded. Liquid and semi-solid swallows and stress barium (a combination of semi-solid swallows and liquid barium) were performed. A new measurement, the lower esophageal contractile segment (LECS), was defined and evaluated. RESULTS Twenty patients participated (mean age 48.3 +/- 12.0 years, four men, %excess weight loss 65.6 +/- 18.0). During semi-solid swallows, two patterns of esophageal clearance were observed: firstly, a native pattern (n = 10) similar to that which is expected in non-LAGB patients; secondly, a lower esophageal sphincter-dependent pattern (n = 7), where flow only occurred when the intrabolus pressure increased during the lower esophageal sphincter (LES) aftercontraction. In both patterns, if there was incomplete bolus clearance, reflux was observed and was usually followed by another swallow. A mean of 4.5 +/- 2.9 contractions were required to clear the semi-solid bolus. Contractions with an intact LECS demonstrated longer flow duration: 7.1 +/- 3.8 vs.1.6 +/- 3.2 s, p < 0.005. During the stress barium, an intrabolus pressure of 44.5 +/- 16.0 mm Hg leads to cessation of intake. CONCLUSIONS In LAGB patients, normal esophageal peristaltic contractions transition to a LES aftercontraction, producing trans-LAGB flow. Repeated contractions are required to clear a semi-solid bolus. Incorporating measurements of the LECS into assessments of esophageal motility in LAGB patients may improve the usefulness of this investigation.
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Affiliation(s)
- Paul Robert Burton
- Centre for Obesity Research and Education (CORE), Monash Medical School, The Alfred Hospital, Commercial Rd, Prahran, 3181, Melbourne, Australia.
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Criteria for assessing esophageal motility in laparoscopic adjustable gastric band patients: the importance of the lower esophageal contractile segment. Obes Surg 2009; 20:316-25. [PMID: 20012706 DOI: 10.1007/s11695-009-0043-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2009] [Accepted: 11/17/2009] [Indexed: 10/20/2022]
Abstract
BACKGROUND Esophageal function appears critical in laparoscopic adjustable gastric band (LAGB) patients; however, conventional motility assessments have not proven to be clinically useful. Recent combined video fluoroscopic and high-resolution manometric studies have identified important components of esophageal function in LAGB patients. METHODS Successful and symptomatic LAGB patients, with normal or mildly impaired esophageal peristalsis, underwent a standardized, water swallow, high-resolution manometry protocol designed specifically to assess the lower esophageal contractile segment (LECS), in combination with conventional measures of esophageal motility. Differences in response to changes in LAGB volume were assessed. RESULTS There were 101 symptomatic and 29 successful patients. More symptomatic patients had a mild impairment in esophageal motility (39.6% vs. 3.4%, p < 0.005). Successful patients demonstrated an intact LECS during normal swallows more frequently than symptomatic patients (95% vs. 43%, p < 0.005). Absolute intraluminal pressures were not different between the groups. Removing all fluid from the LAGB revealed more hypotensive swallows in the symptomatic patients (30% vs. 17%, p = 0.002), an effect not observed when the LAGB volume was increased (8% vs. 5%, p = 0.21). Receiver operator characteristic analysis determined that an intact LECS in 70% of normal swallows defined normal motility in LAGB patients. CONCLUSIONS The LECS is a valuable measure of esophageal function in LAGB patients and complements conventional manometric criteria. Symptomatic patients have less normal swallows; however, these also frequently demonstrate a deficient LECS. Further information can be elucidated by performing swallows at differing LAGB volumes. High-resolution manometry, using these adapted criteria, is now a useful in the investigation in symptomatic LAGB patients.
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L'Heureux MC, Muinuddin A, Gaisano HY, Diamant NE. Feline lower esophageal sphincter sling and circular muscles have different functional inhibitory neuronal responses. Am J Physiol Gastrointest Liver Physiol 2006; 290:G23-9. [PMID: 16166343 DOI: 10.1152/ajpgi.00303.2005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The lower esophageal sphincter (LES) has a circular muscle component exhibiting spontaneous tone that is relaxed by nitric oxide (NO) and a low-tone sling muscle that contracts vigorously to cholinergic stimulation but with little or no evidence of NO responsiveness. This study dissected the responses of the sling muscle to nitrergic innervation in relationship to its cholinergic innervation and circular muscle responses. Motor responses were induced by electrical field stimulation (EFS; 1-30 Hz) of muscle strips from sling and circular regions of the feline LES in the presence of cholinergic receptor inhibition (atropine) or NO synthase inhibition [NG-nitro-L-arginine (L-NNA)+/-atropine]. This study showed the following. First, sling muscle developed less intrinsic resting tone compared with circular muscle. Second, with EFS, sling muscle contracted (most at <or=10 Hz), whereas circular muscle relaxed >50% by 5 Hz. Third, on neural blockade with atropine or L-NNA+/-atropine, 1) sling muscle, although predominantly influenced by excitatory cholinergic stimulation, had a small neural NO-mediated inhibition, with no significant non-NO-mediated inhibition and 2) circular muscle, although little affected by cholinergic influence, underwent relaxation predominantly by neural release of NO and some non-NO inhibitory influence (at higher EFS frequency). Fourth, the sling, precontracted with bethanecol, could relax with NO and some non-NO inhibition. Finally, the tension range of both muscles is similar. In conclusion, sling muscle has limited NO-mediated inhibition to potentially augment or replace sling relaxation effected by switching off its cholinergic excitation. Differences within the LES sling and circular muscles could provide new directions for therapy of LES disorders.
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Muinuddin A, Naqvi K, Sheu L, Gaisano HY, Diamant NE. Regional differences in cholinergic regulation of potassium current in feline esophageal circular smooth muscle. Am J Physiol Gastrointest Liver Physiol 2005; 288:G1233-40. [PMID: 15691872 DOI: 10.1152/ajpgi.00310.2004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Potassium channels are important contributors to membrane excitability in smooth muscles. There are regional differences in resting membrane potential and K(+)-channel density along the length of the feline circular smooth muscle esophagus. The aim of this study was to assess responses of K(+)-channel currents to cholinergic (ACh) stimulation along the length of the feline circular smooth muscle esophageal body. Perforated patch-clamp technique assessed K(+)-channel responses to ACh stimulation in isolated smooth muscle cells from the circular muscle layer of the esophageal body at 2 (distal)- and 4-cm (proximal) sites above the lower esophageal sphincter. Western immunoblots assessed ion channel and receptor expression. ACh stimulation produced a transient increase in outward current followed by inhibition of spontaneous transient outward currents. These ACh-induced currents were abolished by blockers of large-conductance Ca(2+)-dependent K(+) channels (BK(Ca)). Distal cells demonstrated a greater peak current density in outward current than cells from the proximal region and a longer-lasting outward current increase. These responses were abolished by atropine and the specific M(3) receptor antagonist 4-DAMP but not the M(1) receptor antagonist pirenzipine or the M(2) receptor antagonist methoctramine. BK(Ca) expression along the smooth muscle esophagus was similar, but M(3) receptor expression was greater in the distal region. Therefore, ACh can differentially activate a potassium channel (BK(Ca)) current along the smooth muscle esophagus. This activation probably occurs through release of intracellular calcium via an M(3) pathway and has the potential to modulate the timing and amplitude of peristaltic contraction along the esophagus.
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Affiliation(s)
- Ahmad Muinuddin
- Departments of Medicine, University of Toronto, Toronto, Ontario, Canada
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Muinuddin A, Kang Y, Gaisano HY, Diamant NE. Regional differences in L-type Ca2+ channel expression in feline lower esophageal sphincter. Am J Physiol Gastrointest Liver Physiol 2004; 287:G772-81. [PMID: 15178551 DOI: 10.1152/ajpgi.00102.2004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In humans and cats, muscle from the lower esophageal sphincter (LES) circular region exhibits greater spontaneous tone than LES sling muscle, whereas the sling muscle is much more responsive to cholinergic stimulation. Despite physiological and pharmacological evidence for the presence of L-type Ca2+ channel current (ICa,L) activity in LES circular muscle, the identity of this channel has not been demonstrated biochemically or electrophysiologically fingerprinted. Furthermore, there is no information on the channel's presence and role in the sling region of the LES. We hypothesized that regional differences in the expression of ICa,L between LES circular and sling muscles, if present, could contribute to the functional asymmetry observed within the LES. ICa,L expression was compared between circular and sling regions of the LES by Western blot analysis. The patch-clamp technique was used to study ICa,L. Muscle strip studies assessed ICa,L contribution to contractile activity. We found both protein expression of ICa,L and ICa,L density to be greater in LES circular muscle than sling muscle. ICa,L voltage- and time-dependent activation and inactivation curves were similar in cells from both regions. ICa,L blockade with nifedipine inhibited spontaneous tone and ACh-induced contractions only in circular muscle but was able to abolish depolarization (KCl)-induced contractions in both sling and circular muscles. In contrast, La3+ inhibited tone and ACh-induced contractions in muscles from both regions. Therefore, regional myogenic differences in ICa,L expression within the LES circular and sling muscle exist and provide one explanation for the differential contribution of sling and circular muscle to LES contractility.
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Affiliation(s)
- Ahmad Muinuddin
- Department of Medicine, University of Toronto, Ontario, Canada M5T 2S8
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Muinuddin A, Neshatian L, Gaisano HY, Diamant NE. Calcium source diversity in feline lower esophageal sphincter circular and sling muscle. Am J Physiol Gastrointest Liver Physiol 2004; 286:G271-7. [PMID: 14563670 DOI: 10.1152/ajpgi.00291.2003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Within muscular equivalents of cat lower esophageal sphincter (LES), the circular muscle develops greater spontaneous tone, whereas the sling muscle is more responsive to cholinergic stimulation. Smooth muscle contraction involves a combination of calcium release from stores and of calcium entry via several pathways. We hypothesized that there are differences in the sources of Ca(2+) used for contraction in sling and circular muscles and that these differences could contribute to functional asymmetry observed within LES. Contraction of muscle strips from circular and sling regions of LES was assessed in the presence of TTX. In Ca(2+)-free Krebs, tone was inhibited to a greater degree in circular than sling muscle. L-type Ca(2+) channel blockade with nifedipine or verapamil inhibited tone in LES circular but not sling muscle. Sarcoplasmic reticulum (SR) Ca(2+)-ATPase inhibitor cyclopiazonic acid (CPA) caused greater increase in tone in sling than in circular muscle. The phospholipase C inhibitor U-73122 and the SR inositol 1,4,5-trisphosphate [Ins(1,4,5)P(3)] receptor blocker 2-aminoethoxydiphenyl borate (2-APB) inhibited tone in circular and sling muscles, demonstrating that continuous release of Ca(2+) from Ins(1,4,5)P(3)-sensitive stores is important in tone generation in both muscles. In Ca(2+)-free Krebs, ACh-induced contractions (AChC) were inhibited to a greater degree in sling than circular muscles. However, nifedipine and verapamil greatly inhibited AChC in the circular but not sling muscle. Depletion of SR Ca(2+) stores with CPA or inhibition of Ins(1,4,5)P(3)-mediated store release with either U-73122 or 2-APB inhibited AChC in both muscles. We demonstrate that LES circular and sling muscles 1) use intracellular and extracellular Ca(2+) sources to different degrees in the generation of spontaneous tone and AChC and 2) use different Ca(2+) entry pathways. These differences hold the potential for selective modulation of LES tone in health and disease.
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Affiliation(s)
- Ahmad Muinuddin
- Department of Physiology, University of Toronto, Toronto, ON, Canada
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Abstract
We tested the hypotheses that oesophageal bolus transit and motor function vary regionally, with bolus viscosity and with body position. In healthy volunteers, we measured the bolus head advance time, bolus presence time and bolus transit time in the proximal and distal oesophagus using water and viscous materials. We compared concurrent manometric responses. Bolus head advance time, bolus presence time and bolus transit time were longer in the distal oesophagus during water and viscous swallows in the upright and supine positions. The total bolus head advance time and transit time, measured across the entire oesophageal body, were shorter for water than viscous swallows. The amplitudes of peristaltic pressure waves were lower for viscous swallows, and varied as a function of region. These studies demonstrated true functional differences between the proximal and distal oesophagus using multichannel intraluminal impedance and that the viscosity of the bolus is a determinant of oesophageal function.
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Affiliation(s)
- J L Wise
- Department of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, USA
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Zhang X, Tack J, Janssens J, Sifrim DA. Neural regulation of tone in the oesophageal body: in vivo barostat assessment of volume-pressure relationships in the feline oesophagus. Neurogastroenterol Motil 2004; 16:13-21. [PMID: 14764201 DOI: 10.1046/j.1365-2982.2003.00453.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Recent combined manometric-barostat studies demonstrated that the oesophageal body exhibits both peristaltic contractions and tone. This study further characterized the neural modulation of tone in the feline oesophageal body. Simultaneous oesophageal barostat and manometry were performed in 20 adult cats under ketamine sedation. Oesophageal tone and peristalsis were assessed in the distal smooth muscle oesophagus. Cholinergic modulation was studied using neostigmine, erythromycin, atropine and vagotomy. Nitrergic regulation was assessed using sildenafil to increase cellular cyclic guanosine monophosphate and the nitric oxide synthase blocker Nomega-nitro-l-arginine (l-NNA). The presence of a tonic contractile activity in the distal oesophageal body was confirmed. Peristaltic contractions proceeded along the oesophageal body over the background tonic contraction. Neostigmine and erythromycin enhanced (20-30%) whereas bilateral vagotomy and atropine strongly decreased oesophageal tone (50-60%). However, l-NNA increased (40%) and sildenafil decreased oesophageal tone (30%). Therefore, tonic contractile activity in the oesophageal body is mainly caused by a continuous cholinergic excitatory input. A nitric oxide inhibitory mechanism may have a complementary role in the regulation of oesophageal tone.
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Affiliation(s)
- X Zhang
- Centre for Gastroenterological Research, Catholic University of Leuven, Belgium
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