1
|
Ernani V, Du L, Ross HJ, Yi JE, Wampfler JA, Schild SE, Xie H, Swanson KL, Tazelaar HD, Yang P. Gastroesophageal reflux disease and paraneoplastic neurological syndrome associated with long-term survival in limited stage small-cell lung cancer. Thorac Cancer 2022; 13:925-933. [PMID: 35194958 PMCID: PMC8977164 DOI: 10.1111/1759-7714.14318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 12/29/2021] [Accepted: 01/02/2022] [Indexed: 11/28/2022] Open
Abstract
Introduction Patients with small‐cell lung cancer (SCLC) have a very poor prognosis. However, a subset of SCLC achieves long‐term survival. The objective of this study was to investigate factors and pattern of long‐term survival in patients with limited‐stage small cell lung cancer (LS‐SCLC) who achieved a complete response (CR) after chemoradiotherapy. Patient and Methods This was a single‐center retrospective study. The analysis of hazard ratio (HR) and 95% confidence interval (CI) was performed using Cox proportional hazards model. For pattern analysis, the date of recurrence was used as the endpoint. The nominal categorical variables were analyzed by the χ2 test. Survival was estimated using the Kaplan–Meier model, and the results were reported as the median and interquartile range. Results We identified 162 patients, median age was 64.7 (56.2–70.2) years, and 94 (58%) were females. Eighty‐one patients (50%) had recurrence during follow‐up. Gastroesophageal reflux disease (GERD) (HR, 0.65; 95% CI, 0.45–0.93; p = 0.016) and neurological paraneoplastic syndrome (PNS) (HR, 0.46; 95% CI, 0.29–0.72; p < 0.001) were independent factors associated with improved overall survival (OS). Patients with GERD had prolonged recurrence free survival (RFS) compared to patients without GERD (median, 29.1 months vs. 13.9 months, p < 0.001), whereas patients with neurological PNS had a reduced recurrence rate compared to those patients without neurological PNS (No. [%], 8 [20.5] vs. 73 [59.3], p < 0.001). Conclusions Patients with LS‐SCLC achieving a CR after chemoradiotherapy, GERD, and neurological PNS were associated with improved OS. GERD and neurological PNS were associated with longer RFS and lower recurrence rate, respectively.
Collapse
Affiliation(s)
- Vinicius Ernani
- Department of Hematology/Oncology, Mayo Clinic, Phoenix, Arizona, USA
| | - Lin Du
- Department of Thoracic Surgery, Tianjin Chest Hospital, Tianjin, China.,Department of Department of Quantitative Health Science, Mayo Clinic, Rochester, Minnesota, USA.,Graduate School, Tianjin Medical University, Tianjin, China
| | - Helen J Ross
- Department of Hematology/Oncology, Mayo Clinic, Phoenix, Arizona, USA.,Hematology/Oncology, Banner MD Anderson Cancer Center, Gilbert, Arizona, USA
| | - Joanne E Yi
- Department of Anatomic Pathology, Mayo Clinic, Rochester, Minnesota, USA
| | - Jason A Wampfler
- Department of Department of Quantitative Health Science, Mayo Clinic, Scottsdale, Arizona, USA
| | - Steven E Schild
- Department of Radiation Oncology, Mayo Clinic, Phoenix, Arizona, USA
| | - Hao Xie
- Department of Oncology, Mayo Clinic, Rochester, Minnesota, USA.,Department of Gastrointestinal Oncology, Moffitt Cancer Center, Tampa, Florida, USA
| | - Karen L Swanson
- Department of Pulmonary Medicine, Mayo Clinic, Phoenix, Arizona, USA
| | - Henry D Tazelaar
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Arizona, USA
| | - Ping Yang
- Department of Department of Quantitative Health Science, Mayo Clinic, Rochester, Minnesota, USA
| |
Collapse
|
2
|
Lee SE, Kim DH, Son SM, Choi SY, You RY, Kim CH, Choi W, Kim HS, Lim YJ, Han JY, Kim HW, Yang IJ, Xu WX, Lee SJ, Kim YC, Yun HY. Physiological function and molecular composition of ATP-sensitive K + channels in human gastric smooth muscle. J Smooth Muscle Res 2020; 56:29-45. [PMID: 32581184 PMCID: PMC7324727 DOI: 10.1540/jsmr.56.29] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Gastric motility is controlled by slow waves. In general, the activation of the
ATP-sensitive K+ (KATP) channels in the smooth muscle
opposes the membrane excitability and produces relaxation. Since metabolic
inhibition and/or diabetes mellitus are accompanied by dysfunctions of gastric
smooth muscle, we examined the possible roles of KATP channels in
human gastric motility. We used human gastric corpus and antrum smooth muscle
preparations and recorded the mechanical activities with a conventional
contractile measuring system. We also identified the subunits of the
KATP channels using Western blot. Pinacidil (10 μM), a
KATP channel opener, suppressed contractions to 30% (basal tone
to −0.2 g) of the control. The inhibitory effect of pinacidil on contraction was
reversed to 59% of the control by glibenclamide (20 μM), a KATP
channel blocker. The relaxation by pinacidil was not affected by a pretreatment
with L-arginine methyl ester, tetraethylammonium, or 4-aminopyridine. Pinacidil
also inhibited the acetylcholine (ACh)-induced tonic and phasic contractions in
a glibenclamide-sensitive manner (42% and 6% of the control, respectively).
Other KATP channel openers such as diazoxide, cromakalim and
nicorandil also inhibited the spontaneous and ACh-induced contractions.
Calcitonin gene-related peptide (CGRP), a gastric neuropeptide, induced muscle
relaxation by the activation of KATP channels in human gastric smooth
muscle. Finally, we have found with Western blot studies, that human gastric
smooth muscle expressed KATP channels which were composed of Kir 6.2
and SUR2B subunits.
Collapse
Affiliation(s)
- Sang Eok Lee
- Department of Surgery, College of Medicine, Konyang University, 158 Gwanjeodong-ro, Seo-gu, Daejeon 35365, Korea
| | - Dae Hoon Kim
- Department of Surgery, College of Medicine, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Korea
| | - Seung Myeung Son
- Department of Pathology, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Korea
| | - Song-Yi Choi
- Department of Pathology, School of Medicine, Chungnam National University, Daejeon, Chungnam 35015, Korea
| | - Ra Young You
- Department of Physiology, College of Medicine, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Korea
| | - Chan Hyung Kim
- Department of Pharmacology, College of Medicine, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Korea
| | - Woong Choi
- Department of Pharmacology, College of Medicine, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Korea
| | - Hun Sik Kim
- Department of Pharmacology, College of Medicine, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Korea
| | - Yung Ji Lim
- College of Medicine, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Korea
| | - Ji Young Han
- CheongDam I Plastic surgery, 21, Sinheung-ro 240, Uijeonbu-si, Gyronggido 11651, Korea
| | - Hyun Woo Kim
- College of Medicine, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Korea
| | - In Jun Yang
- Department of Surgery, Seoul Nantional University Bundang Hospital, 166 Gumi-ro, Bundang-gu 13620, Seongnam, Korea
| | - Wen-Xie Xu
- Department of Physiology, College of Medcine, Shanghai Jiaotong University, 800 Dongchun Rd. Shanghai, 200240, P.R. China
| | - Sang Jin Lee
- Department of Physiology, College of Medicine, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Korea
| | - Young Chul Kim
- Department of Physiology, College of Medicine, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Korea
| | - Hyo-Yung Yun
- Department of Surgery, College of Medicine, Chungbuk National University, Chungdae-ro 1, Seowon-gu, Cheongju, Chungbuk 28644, Korea
| |
Collapse
|
3
|
Zhang Y, Miller DV, Paterson WG. TREK-1 channels do not mediate nitrergic neurotransmission in circular smooth muscle from the lower oesophageal sphincter. Br J Pharmacol 2009; 159:362-73. [PMID: 20002101 DOI: 10.1111/j.1476-5381.2009.00531.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE The ionic mechanisms underlying nitrergic inhibitory junction potentials (IJPs) in gut smooth muscle remain a matter of debate. Recently, it has been reported that opening of TWIK-related K(+) channel 1 (TREK-1) K(+) channels contributes to the nitrergic IJP in colonic smooth muscle. We investigated the effects of TREK-1 channel blockers on nitrergic neurotransmission in mouse and opossum lower oesophageal sphincter (LOS) circular smooth muscle (CSM). EXPERIMENTAL APPROACH The effects of TREK-1 channel blockers were characterized pharmacologically in murine and opossum gut smooth muscle using conventional intracellular and tension recordings. KEY RESULTS In LOS, L-methionine depolarized the resting membrane potential (RMP) but did not inhibit the nitrergic IJP. Cumulative application of theophylline hyperpolarized the RMP and inhibited the nitrergic IJP concentration dependently. The induced membrane hyperpolarization was prevented by pre-application of caffeine, but not by 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one. 8-Br-cAMP significantly hyperpolarized membrane potential and increased the amplitude of the nitrergic IJP. In opossum LOS muscle strips, L-methionine increased resting tone but had no effect on nerve-mediated LOS relaxation. On the other hand, theophylline markedly inhibited tone. In CSM from mouse proximal colon, L-methionine caused modest inhibition of nitrergic IJPs. CONCLUSIONS AND IMPLICATIONS TREK-1 channels were not involved in the nitrergic IJP in LOS CSM. Not only does L-methionine have no effect on the nitrergic IJP or LOS relaxation, but the effect of theophylline appears to be due to interruption of Ca(2+)-releasing pathways (i.e. caffeine-like effect) rather than via blockade of TREK-1 channels.
Collapse
Affiliation(s)
- Y Zhang
- Gastrointestinal Diseases Research Unit, Kingston General Hospital and Queen's University, Kingston, Ontario, Canada
| | | | | |
Collapse
|
4
|
Sanmiguel CP, Hagiike M, Mintchev MP, Cruz RD, Phillips EH, Cunneen SA, Conklin JL, Soffer EE. Effect of electrical stimulation of the LES on LES pressure in a canine model. Am J Physiol Gastrointest Liver Physiol 2008; 295:G389-94. [PMID: 18687754 DOI: 10.1152/ajpgi.90201.2008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Gastric electrical stimulation modulates lower esophageal sphincter pressure (LESP). High-frequency neural stimulation (NES) can induce gut smooth muscle contractions. To determine whether lower esophageal sphincter (LES) electrical stimulation (ES) can affect LESP, bipolar electrodes were implanted in the LES of four dogs. Esophageal manometry during sham or ES was performed randomly on separate days. Four stimuli were used: 1) low-frequency: 350-ms pulses at 6 cycles/min; 2) high-frequency-1: 1-ms pulses at 50 Hz; 3) high-frequency-2: 1-ms pulses at 20 Hz; and 4) NES: 20-ms bipolar pulses at 50 Hz. Recordings were obtained postprandially. Tests consisted of three 20-min periods: baseline, stimulation/sham, and poststimulation. The effect of NES was tested under anesthesia and following IV administration of l-NAME and atropine. Area under the curve (AUC) and LESP were compared among the three periods, by ANOVA and t-test, P < 0.05. Data are shown as means +/- SD. We found that low-frequency stimulation caused a sustained increase in LESP: 32.1 +/- 12.9 (prestimulation) vs. 43.2 +/- 18.0 (stimulation) vs. 50.1 +/- 23.8 (poststimulation), P < 0.05. AUC significantly increased during and after stimulation. There were no significant changes with other types of ES. With NES, LESP initially rose and then decreased below baseline (LES relaxation). During NES, N(G)-nitro-l-arginine methyl ester increased both resting LESP and the initial rise in LESP and markedly diminished the relaxation. Atropine lowered resting LESP and abolished the initial rise in LESP. In conclusion, low frequency ES of the LES increases LESP in conscious dogs. NES has dual effect on LESP: an initial stimulation, cholinergically mediated, followed by relaxation mediated by nitric oxide.
Collapse
Affiliation(s)
- Claudia P Sanmiguel
- Center for Digestive Diseases, GI Motility Program, 8730 Alden Dr., Thalians Bldg., 2nd floor East, Los Angeles, CA 90048, USA
| | | | | | | | | | | | | | | |
Collapse
|
5
|
Regulation of basal tone, relaxation and contraction of the lower oesophageal sphincter. Relevance to drug discovery for oesophageal disorders. Br J Pharmacol 2007; 153:858-69. [PMID: 17994108 DOI: 10.1038/sj.bjp.0707572] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The lower oesophageal sphincter (LOS) is a specialized region of the oesophageal circular smooth muscle that allows the passage of a swallowed bolus to the stomach and prevents the reflux of gastric contents into the oesophagus. The anatomical arrangement of the LOS includes semicircular clasp fibres adjacent to the lesser gastric curvature and sling fibres following the greater gastric curvature. Such anatomical arrangement together with an asymmetric intrinsic innervation and distinct proportion of neurotransmitters in both regions produces an asymmetric pressure profile. The LOS tone is myogenic in origin and depends on smooth muscle properties that lead to opening of L-type Ca(2+) channels; however it can be modulated by enteric motor neurons, the parasympathetic and sympathetic extrinsic nervous system and several neurohumoral substances. Nitric oxide synthesized by neuronal NOS is the main inhibitory neurotransmitter involved in LOS relaxation. Different putative neurotransmitters have been proposed to play a role together with NO. So far, only ATP or related purines have shown to be co-transmitters with NO. Acetylcholine and tachykinins are involved in the LOS contraction acting through acetylcholine M(3) and tachykinin NK(2) receptors. Nitric oxide can also be involved in the regulation of LOS contraction. The understanding of the mechanisms that originate and modulate LOS tone, relaxation and contraction and the characterization of neurotransmitters and receptors involved in LOS function are important to develop new pharmacological tools to treat primary oesophageal motor disorders and gastro-oesophageal reflux disease.
Collapse
|
6
|
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.
Collapse
|
7
|
González AA, Farré R, Clavé P. Different responsiveness of excitatory and inhibitory enteric motor neurons in the human esophagus to electrical field stimulation and to nicotine. Am J Physiol Gastrointest Liver Physiol 2004; 287:G299-306. [PMID: 15016616 DOI: 10.1152/ajpgi.00534.2003] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
To compare electrical field stimulation (EFS) with nicotine in the stimulation of excitatory and inhibitory enteric motoneurons (EMN) in the human esophagus, circular lower esophageal sphincter (LES), and circular and longitudinal esophageal body (EB) strips from 20 humans were studied in organ baths. Responses to EFS or nicotine (100 microM) were compared in basal conditions, after N(G)-nitro-l-arginine (l-NNA; 100 microM), and after l-NNA and apamin (1 microM). LES strips developed myogenic tone enhanced by TTX (5 microM) or l-NNA. EFS-LES relaxation was abolished by TTX, unaffected by hexamethonium (100 microM), and enhanced by atropine (3 microM). Nicotine-LES relaxation was higher than EFS relaxation, reduced by TTX or atropine, and blocked by hexamethonium. After l-NNA, EFS elicited a strong cholinergic contraction in circular LES and EB, and nicotine elicited a small relaxation in LES and no contractile effect in EB. After l-NNA and apamin, EFS elicited a strong cholinergic contraction in LES and EB, and nicotine elicited a weak contraction amounting to 6.64 +/- 3.19 and 9.20 +/- 5.51% of that induced by EFS. EFS elicited a contraction in longitudinal strips; after l-NNA and apamin, nicotine did not induce any response. Inhibitory EMN tonically inhibit myogenic LES tone and are efficiently stimulated both by EFS and nicotinic acetylcholine receptors (nAChRs) located in somatodendritic regions and nerve terminals, releasing nitric oxide and an apamin-sensitive neurotransmitter. In contrast, although esophageal excitatory EMN are efficiently stimulated by EFS, their stimulation through nAChRs is difficult and causes weak responses, suggesting the participation of nonnicotinic mechanisms in neurotransmission to excitatory EMN in human esophagus.
Collapse
Affiliation(s)
- Asensio A González
- Fundació de Gastroenterologia Dr. Francisco Vilardell, 08025 Barcelona, Spain
| | | | | |
Collapse
|
8
|
Zhang Y, Paterson WG. Nitric oxide contracts longitudinal smooth muscle of opossum oesophagus via excitation-contraction coupling. J Physiol 2001; 536:133-40. [PMID: 11579163 PMCID: PMC2278847 DOI: 10.1111/j.1469-7793.2001.00133.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
1. The effects of sodium nitroprusside (SNP) and diethylenetriamine/nitric oxide adduct (DETA/NO), putative nitric oxide (NO) donors, on opossum oesophageal longitudinal smooth muscle were investigated using isometric tension and intracellular micro-electrode recordings. 2. SNP produced concentration-dependent contractions of oesophageal longitudinal smooth muscle with an EC(50) of 239.6 +/- 78.2 microM (mean +/- S.E.M., n = 10). Maximal contraction induced by SNP (1 mM) was about 75.5 +/- 8.5 % (n = 10) of the 60 mM KCl-induced contraction. The SNP-induced contraction was resistant to tetrodotoxin (TTX; 1 microM), but abolished by nifedipine (1 microM), as well as by niflumic acid (300 microM) and 9-anthroic acid (9-AC; 1 mM), Ca(2+)-activated Cl(-) channel blockers. 3. DETA/NO at concentrations of 100 and 500 microM induced 83.1 +/- 24.4 and 104.1 +/- 34.9 % of the 60 mM KCl-induced contraction (n = 4), respectively, which was abolished by nifedipine (1 microM), niflumic acid (300 microM) and 9-AC (1 mM). 4. Pre-application of 1H-[1,2,4]oxidiazolo[4,3,-alpha]quinoxalin-1-one (ODQ) (10 microM), a guanylate cyclase inhibitor, significantly inhibited the SNP-induced contraction, whereas 8-bromo-cGMP (1 mM), a membrane-permeable analogue of cGMP, mimicked the SNP-induced contraction. 5. Intracellular recordings revealed that SNP (300 microM) depolarized resting membrane potentials (RMPs) and increased the frequency of spontaneous spike-like action potentials. However, these electrical alterations were eliminated by pretreatment with niflumic acid (300 microM). 6. These results suggest that NO produces an excitation-contraction coupling in opossum oesophageal longitudinal smooth muscle via a cGMP-dependent signalling pathway. This contraction depends on extracellular Ca(2+) entry through activation of L-type Ca(2+) channels.
Collapse
Affiliation(s)
- Y Zhang
- Gastrointestinal Disease Research Unit and Departments of Medicine and Physiology, Queen's University, Kingston, Ontario, Canada K7L 5G2
| | | |
Collapse
|
9
|
Zhang Y, Miller DV, Paterson WG. Opposing roles of K(+) and Cl(-) channels in maintenance of opossum lower esophageal sphincter tone. Am J Physiol Gastrointest Liver Physiol 2000; 279:G1226-34. [PMID: 11093945 DOI: 10.1152/ajpgi.2000.279.6.g1226] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The ionic basis underlying the maintenance of myogenic tone of lower esophageal sphincter circular muscle (LES) was investigated in opossum with the use of standard isometric tension and conventional intracellular microelectrode recordings in vitro. In tension recording studies, nifedipine (1 microM) reduced basal tone to 27.7 +/- 3.8% of control. The K(+) channel blockers tetraethylammonium (TEA, 2 mM), charybdotoxin (100 nM), and 4-aminopyridine (4-AP, 2 mM) enhanced resting tone, whereas apamin and glibenclamide were without affect. Cl(-) channel blockers DIDS (500 microM) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (500 microM), as well as niflumic acid (0.1-300 microM), decreased basal tone, but tamoxifen was without effect. Intracellular microelectrode recordings revealed ongoing, spontaneous, spike-like action potentials (APs). Nifedipine abolished APs and depolarized resting membrane potential (RMP). Both TEA and 4-AP significantly depolarized RMP and augmented APs, whereas niflumic acid dose-dependently hyperpolarized RMP and abolished APs. These data suggest that, in the opossum, basal tone is associated with continuous APs and that K(+) and Ca(2+)-activated Cl(-) channels have important opposing roles in the genesis of LES tone.
Collapse
Affiliation(s)
- Y Zhang
- Gastrointestinal Diseases Research Unit and Departments of Medicine and Physiology, Queen's University, Kingston, Ontario, Canada K7L 5G2
| | | | | |
Collapse
|
10
|
Shahin W, Murray JA, Clark E, Conklin JL. Role of cGMP as a mediator of nerve-induced motor functions of the opossum esophagus. Am J Physiol Gastrointest Liver Physiol 2000; 279:G567-74. [PMID: 10960356 DOI: 10.1152/ajpgi.2000.279.3.g567] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Stimulation of esophageal nerves produces biphasic relaxation of the lower esophageal sphincter (LES) and an off response of circular esophageal muscle. Previously, we proposed that cGMP mediates nerve-induced hyperpolarization of circular LES muscle but not LES relaxation. These experiments explore whether cGMP mediates LES relaxation or the off response. Strips of muscle from the opossum esophagus and LES were connected to force-displacement transducers, placed in tissue baths containing oxygenated Krebs solution at 37 degrees C, and stimulated by an electrical field. 1H-[1,2, 4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ), a selective inhibitor of guanylyl cyclase, antagonized the off response, shortened its latency, and blocked the first phase of LES relaxation. ODQ also antagonized LES relaxation by exogenous nitric oxide (NO) but not relaxations by vasoactive intestinal polypeptide (VIP). Part of the nerve-induced LES relaxation and the off response appear to be mediated by the second messenger cGMP. These studies indicate that VIP-induced LES relaxation is not mediated by cGMP and therefore do not support the hypothesis that VIP produces LES relaxation by causing the generation of NO.
Collapse
Affiliation(s)
- W Shahin
- Department of Internal Medicine, University of Iowa College of Medicine and Department of Veterans Affairs Medical Center, Iowa City, Iowa 52242, USA
| | | | | | | |
Collapse
|