Mucosal Schwann cell hamartoma of the gastroesophageal junction: A series of 6 cases and comparison with colorectal counterpart.

Mucosal Schwann cell hamartoma (MSCH) is an uncommon neural lesion characterized by an ill-defined proliferation of S100-positive Schwann cells in the lamina propria, with reported cases exclusively occurring in the colorectum. Here we describe the first series of MSCHs arising in the gastroesophageal junction (GEJ) and discuss their clinicopathologic features in comparison with their colorectal counterparts. We searched the UCLA pathology database from 01/2014 to 12/2018 to identify cases carrying the diagnosis of MSCH. A total of 48 cases (45 in-house, 3 consults) of colorectal MSCHs and 6 cases (1 in-house, 5 consults) of GEJ MSCHs were identified. For GEJ MSCHs, there were 4 males and 2 females with an average age of 70.2 years (range: 57-76 years). Clinical indications for endoscopy included history of gastroesophageal reflux disease (n = 2), heartburn (n = 2), dysphagia (n = 1), and iron deficiency anemia (n = 1). Endoscopic findings at the GEJ were available for 5 patients including irregular Z-line (n = 3), mild nodular carditis (n = 1), and normal (n = 1). None of them showed a polyp or nodule. The mean size of the lesion was 2.8 mm (range: 2-4 mm) microscopically. None of the colorectal or GEJ MSCH cases had an association with inherited syndromes. In conclusion, MSCH of the gastrointestinal tract is predominantly seen in the colorectum, but also infrequently seen in the GEJ. GEJ MSCH shares histologic and immunohistochemical features with its colorectal counterpart, but is usually an incidental finding with no endoscopically visible lesion. As there is no syndromic association with MSCH, additional treatment, work-up and follow-up are unnecessary.

The Contribution of the Left Phrenic Nerve to Innervation of the Esophagogastric Junction.

The contribution of the left phrenic nerve to innervation of the esophagogastric junction. The esophagogastric junction is part of the barrier preventing gastroesophageal reflux. We have investigated the contribution of the phrenic nerves to innervation of the esophagogastric junction in humans and piglets by dissecting 30 embalmed human specimens and 14 piglets. Samples were microdissected and nerves were stained and examined by light and electron microscopy. In 76.6% of the human specimens, the left phrenic nerve participated in the innervation of the esophagogastric junction by forming a neural network together with the celiac plexus (46.6%) or by sending off a distinct phrenic branch, which joined the anterior vagal trunk (20%). Distinct left phrenic branches were always accompanied by small branches of the left inferior phrenic artery. In 10% there were indirect connections with a distinct phrenic nerve branch joining the celiac ganglion, from which celiac plexus branches to the esophagogastric junction emerged. Morphological examination of phrenic branches revealed strong similarities to autonomic celiac plexus branches. There was no contribution of the left phrenic nerve or accompanying arteries from the caudal phrenic artery in any of the piglets. The right phrenic nerve made no contribution in any of the human or piglet samples. We conclude that the left phrenic nerve in humans contributes to the innervation of the esophagogastric junction by providing ancillary autonomic nerve fibers. Experimental studies of the innervation in pigs should consider that neither of the phrenic nerves was found to contribute. Clin. Anat. 33:265-274, 2020. © 2019 Wiley Periodicals, Inc.

Jackhammer esophagus with and without esophagogastric junction outflow obstruction demonstrates altered neural control resembling type 3 achalasia.

BACKGROUND: Esophageal hypercontractility can manifest with and without esophagogastric junction (EGJ) outflow obstruction. We investigated clinical presentations and motility patterns in patients with esophageal hypercontractile disorders. METHODS: Esophageal HRM studies fulfilling Chicago Classification 3.0 criteria for jackhammer esophagus (distal contractile integral, DCI >8000 mmHg.cm.s in ≥ 20% swallows) with (n = 30) and without (n = 83) EGJ obstruction (integrated relaxation pressure, IRP > 15 mm Hg) were retrospectively reviewed from five centers (4 in Europe, 1 in US). Single swallows (SS) and multiple rapid swallows (MRS) were analyzed using HRM software tools (IRP, DCI, distal latency, DL); MRS: SS DCI ratio >1 defined contraction reserve. Comparison groups were achalasia type 3 (n = 72, positive control for abnormal inhibition and EGJ obstruction) and healthy controls (n = 18). Symptoms, HRM metrics, and MRS contraction reserve were analyzed within jackhammer subgroups and comparison groups. KEY RESULTS: The esophageal smooth muscle was excessively stimulated at baseline in jackhammer subgroups, with lack of augmentation following MRS identified more often compared with controls (P = .003) and type 3 achalasia (P = .07). Consistently abnormal inhibition was identified in type 3 achalasia (47%), and to a lower extent in jackhammer with obstruction (37%, P = .33), jackhammer esophagus (28%, P = .01), and controls (11%, P < .01 compared with type 3 achalasia). Perceptive symptoms (heartburn, chest pain) were common in jackhammer esophagus (P < .01 compared with type 3 achalasia), while transit symptoms (dysphagia) were more frequent with presence of EGJ obstruction (P ≤ .01 compared with jackhammer without obstruction). CONCLUSIONS AND INFERENCES: The balance of excessive excitation and abnormal inhibition defines clinical and manometric manifestations in esophageal hypercontractile disorders.

The microscopic anatomy of the esophagus including the individual layers, specialized tissues, and unique components and their responses to injury.

The esophagus, a straight tube that connects the pharynx to the stomach, has the complex architecture common to the rest of the gastrointestinal tract with special differences that relate to its function as a conduit of ingested substances. For instance, it has submucosal glands that are unique and have a specific protective function. It has a squamous lining that exists nowhere else in the gut except the anus and it has a different submucosal nerve plexus when compared to the stomach and intestines. All of the layers of the esophageal wall and the specialized structures including blood and lymphatic vessels and nerves have specific responses to injury. The esophagus also has unique features such as patches of gastric mucosa called inlet patches at the very proximal part and it has a special sphincter mechanism at the most distal aspect. This review covers the normal microscopic anatomy of the esophagus and the patterns of reaction to stress and injury of each layer and each special structure.

[The pathophysiology of motor disorders of cardioesophageal transition in children].

The review highlighted some issues on ontogeny of the nervous system of the esophagus. Data on burdened heredity role and gestosis risk of the pregnancy interruption in the development of GERD in childhood are presented. The role of nitrergic and serotoninergic systems and prostaglandins in the development of GERD in children is discussed.

Roles of gastro-oesophageal afferents in the mechanisms and symptoms of reflux disease.

Oesophageal pain is one of the most common reasons for physician consultation and/or seeking medication. It is most often caused by acid reflux from the stomach, but can also result from contractions of the oesophageal muscle. Different forms of pain are evoked by oesophageal acid, including heartburn and non-cardiac chest pain, but the basic mechanisms and pathways by which these are generated remain to be elucidated. Both vagal and spinal afferent pathways are implicated by basic research. The sensitivity of afferent fibres within these pathways may become altered after acid-induced inflammation and damage, but the severity of symptoms in humans does not necessarily correlate with the degree of inflammation. Gastro-oesophageal reflux disease (GORD) is caused by transient relaxations of the lower oesophageal sphincter, which are triggered by activation of gastric vagal mechanoreceptors. Vagal afferents are therefore an emerging therapeutic target for GORD. Pain in the absence of excess acid reflux remains a major challenge for treatment.

Brainstem sites controlling the lower esophageal sphincter and crural diaphragm in the ferret: a neuroanatomical study.

The lower esophageal sphincter (LES) and the crural diaphragm (CD) surrounding the esophagogastric junction are key components of the gastroesophageal reflex mechanism, which engages the vago-vagal brainstem circuitry. Although both components work in conjunction to prevent gastroesophageal reflux, little is known about the brain area(s) where this integration takes place. The aims of this study were to: (1) trace the brainstem circuitry associated with the CD and the LES, and (2) determine possible sites of convergence. Experiments were done in adult male ferrets. Under isoflurane anesthesia, recombinant strains of the transneuronal pseudorabies virus (PRV-151 or PRV-Bablu) or the monosynaptic retrograde tracer cholera toxin beta-subunit (CTb) were injected into either the CD or the LES. Following a survival period of 5-7 days, animals were euthanized, perfused and their brains removed for dual-labeling immunofluorescence processing. In animals injected with recombinants of PRV into the CD and the LES, distinct labeling was found in various brainstem nuclei including: area postrema, DMV, nucleus tractus solitarius (NTS), medial reticular formation (MRF) and nucleus ambiguous (NA). Double-labeled cells were only evident in the DMV, NTS and MRF. Injections of CTb into the CD or the LES resulted in retrograde labeling only in the DMV. These findings demonstrate the presence of a direct projection from the DMV to the CD. They further suggest that the neuronal connections responsible for CD or LES function are contained in circuitries that, though largely independent, may converge at the level of DMV, NTS and MRF.

Reduction of interstitial cells of Cajal (ICC) associated with neuronal nitric oxide synthase (n-NOS) in patients with achalasia.

BACKGROUND: The etiology of achalasia is still unknown. The current theories of chronic inflammation leading to autoimmune response with destruction and loss of the inhibitory myenteric ganglion cells enlighten its pathogenesis in a limited way only. Interstitial cells of Cajal (ICC) have been shown to be involved in nitrergic neurotransmission of the lower esophageal sphincter (LES). AIM: To investigate the significance of ICC and neuronal nitric oxide synthase (n-NOS) in esophageal wall tissue of patients undergoing surgery for achalasia. METHODS: In 53 patients with a median age of 45 (6-78) yr undergoing surgery for achalasia, the immunoreactivity of ICC (CD117/c-kit) and n-NOS was assessed. In 42 patients, biopsies were taken from the LES high-pressure zone during Heller myotomy, whereas in 11 patients with end-stage achalasia and a decompensated megaesophagus, the complete esophagus was resected. A semiquantitative analysis was carried out and ICC and n-NOS impairments were classified into four grades. Staining intensity was correlated with preoperative clinical, radiologic, and manometric findings and with long-term postoperative Eckardt score. RESULTS: Grade III/IV ICC reduction (severe reduction to complete loss) was seen in 59.5% of all biopsy specimens of the LES high-pressure zone. Patients with grade III/IV ICC reduction had a significantly longer duration of achalasia symptoms (3 [0-43] yr) than patients with minor to marked (grade I/II) impairment (1 [0-16] yr, P= 0.028). A majority (72.5%) of tissue samples revealed severe reduction to complete loss of n-NOS immunoreactivity. The preoperative Eckardt score was statistically significantly different between patients with grade I/II and those with grade III/IV n-NOS reductions (P= 0.031). CD117 (c-kit) positivity was statistically significantly correlated with n-NOS staining intensity (correlation coefficient r= 0.781, P < 0.0001). CONCLUSION: The present results suggest that in the pathogenesis of achalasia, especially in the development of the LES high-pressure zone, depletion of ICC networks and potential changes in the electrical activity of smooth muscle cells may play a crucial role. The reduction in CD117-positive ICC in a few patients also seemed to be of relevance, even if the cells of Auerbach's plexus were unscathed. The associated reduced NOS release might underlie the profound ICC impairment and could possibly be responsible for the lack of LES relaxation, because of missing inhibitory neurotransmission. It is unclear, however, whether the ICC loss is primarily caused by the accelerated attrition of mature cells or their impaired regeneration.

Alterations in the density of interstitial cells of Cajal in achalasia.

The aim of this study was to assess the quantity of interstitial cells of Cajal (ICC) in the lower esophageal sphincter (LES) in achalasia. LES muscle was obtained from 11 achalasia and nine esophageal cancer (control) patients during surgery. Immunohistochemistry was performed and average cell counts per high-power field (HPF) were obtained. Overall, more ICC were observed in achalasia (median = 14.0 cells/HPF; range = 0-22.6 cells/HPF) as compared with controls (median = 6.2 cells/HPF; range = 1.6-10.8 cells/HPF) (P = 0.047). There were two subsets of findings within the achalasia group: 8/11(73%) had an increased quantity of ICC (median = 17.1 cells/HPF; range = 11.6-22.6; P = 0.015) as compared with controls, whereas the remaining 3/11(27%) had a paucity of ICC (median = 0 cells/HPF; range = 0-2; P = 0.02). ICC levels were positively correlated with age of the patient (P = 0.043). Our study demonstrates that subsets of abnormal ICC levels are observed in idiopathic achalasia of the esophagus.

Influence of radiofrequency energy delivery at the gastroesophageal junction (the Stretta procedure) on symptoms, acid exposure, and esophageal sensitivity to acid perfusion in gastroesophagal reflux disease.

Several studies have demonstrated that radiofrequency energy delivery at the gastroesophageal junction (the Stretta procedure) induces symptom relief in gastroesophageal reflux disease (GERD), although improvement of acid exposure on pH monitoring was usually limited. A role for decreased esophageal sensitivity has been suggested. Our aim was to evaluate the influence of Stretta on symptoms, acid exposure, and sensitivity to esophageal acid perfusion in GERD. Thirteen patients with established proton pump inhibitor (PPI)-dependent GERD (three males; mean age, 51+/-10 years) participated in the study. Before and 6 months after the procedure symptom score, pH monitoring and Bernstein acid perfusion test were performed. The latter was done by infusing HCl (pH 0.1) at a rate of 6 ml/min 15 cm proximal to the gastroesophageal junction for a maximum of 30 min or until the patients experienced heartburn. Results were compared by Student's t-test. Stretta procedure time was 51+/-4 min and no complications occurred. After 6 months, the symptom score was significantly improved (12.5+/-2.0 to 7.5+/-2.1; P<0.05), seven patients no longer needed daily PPI, and acid exposure was significantly decreased (11.6%+/-1.6% to 8.5%+/-1.8% of time pH<4; P<0.05). The time needed to induce heartburn during acid perfusion decreased from 9.5+/-2.3 to 18.1+/-3.4 min (P=0.01), and five patients became insensitive to 30-min acid perfusion, versus none at baseline (P=0.04). In conclusion, the Stretta procedure induces subjective improvement of GERD symptoms and decreases esophageal acid exposure. In addition, esophageal acid sensitivity is decreased 6 months after the Stretta procedure. The mechanism underlying this finding and its relevance to symptom control require further studies.

Experimental human pain models in gastro-esophageal reflux disease and unexplained chest pain.

Methods related to experimental human pain research aim at activating different nociceptors, evoke pain from different organs and activate specific pathways and mechanisms. The different possibilities for using mechanical, electrical, thermal and chemical methods in visceral pain research are discussed with emphasis of combinations (e.g., the multimodal approach). The methods have been used widely in assessment of pain mechanisms in the esophagus and have contributed to our understanding of the symptoms reported in these patients. Hence abnormal activation and plastic changes of central pain pathways seem to play a major role in the symptoms in some patients with gastro-esophageal reflux disease and in patients with functional chest pain of esophageal origin. These findings may lead to an alternative approach for treatment in patients that does not respond to conventional medical or surgical therapy.

Functional oesophago-gastric junction imaging.

Despite its role in disease there is still no definitive method to assess oesophago-gastric junction competence (OGJ). Traditionally the OGJ has been assessed using manometry with lower oesophageal sphincter pressure as the indicator. More recently this has been shown not to be a very reliable marker of sphincter function and competence against reflux. Disorders such as gastro-oesophageal reflux disease and to a lesser extend achalasia still effects a significant number of patients. This review looks at using a new technique known as impedance planimetry to profile the geometry and pressure in the OGJ during distension of a bag. The data gathered can be reconstructed into a dynamic representation of OGJ action. This has been shown to provide a useful representation of the OGJ and to show changes to the competence of the OGJ in terms of compliance and distensibility as a result of endoluminal therapy.

A novel surgical procedure of vagal nerve, lower esophageal sphincter, and pyloric sphincter-preserving nearly total gastrectomy reconstructed by single jejunal interposition, and postoperative quality of life.

BACKGROUND/AIMS: For early gastric cancer total gastrectomy (TG) has so far been essentially unavoidable. We performed the nearly TG reconstructed by single jejunal interposition preservation of the vagal nerve, lower esophageal sphincter (LES) and pyloric sphincter (D1 or D2 lymph node dissection, curability A) as a function-preserving surgical technique (i.e. NTG) to improve postoperative quality of life (QOL). In this report, the application criteria and points of the technique are outlined. QOL in patients after NTG was also compared with those after TG. METHODOLOGY: Sixteen subjects who underwent NTG (12 men and 4 women subjects at age 30 to 70 years, mean 55.6 years) were interviewed to inquire about abdominal symptoms and compared with 20 patients after conventional TG (excision with D2 lymph node, radical curability A) reconstructed by single jejunal interposition without preserving the vagal nerve, LES, and pyloric sphincter (i.e. TGI; 14 men and 6 women at age 26 to 70 years, mean 54.8 years). The former was named group A and the latter group B. Included were cases with early cancer localizing at the upper third and middle stomach, 2cm or further in distance from oral-side margin of the cancer to esophagogastric mucosal junction; and 3.5cm or further in distance from anal-side margin of the cancer to the pyloric sphincter. In excision with the lymph node, hepatic and celiac branches were preserved. To preserve LES, the abdominal esophagus was completely preserved. The pyloric antrum was also preserved at 1.5cm from the pyloric sphincter. The substitute stomach was created as a 30-cm-long single jejunal segment having orthodromic peristaltic movement. RESULTS: The operative procedure in group A significantly improved postoperative gastrointestinal symptoms such as appetite loss (p=0.0004), weight loss (p=0.0369), reflux esophagitis (RE) (p=0.0163), early dumping syndrome (p=0.0163), endoscopic RE (p=0.0311), and postgastrectomy cholecystolithiasis (p=0.0163) compared with group B. Oral intake per one meal 5 years after operation compared with that before operation was better in group A than in group B (p=0.0703). Postoperative epigastric fullness was significantly detected in group A compared with group B (p=0.0072). CONCLUSIONS: The proposed surgical technique of NTG is a function-preserving surgery appropriate to improve QOL of subjects with early gastric cancer. There was a defect in this technique of postprandial feeling of epigastric fullness. We think that a gut motility improvement agent is necessary to improve postprandial epigastric fullness after NTG.

[Esophageal resection for non-specific esophageal motility disorder]. / Osophagusresektion bei unspezifischer Motilitätsstörung der Speiseröhre -- Bedeutung der neuropathologischen Befunde.

A 47-year-old patient presented with a history of dysphagia for solid food for almost 10 years and weight loss of more than 50 kg. Non-resecting surgical as well as endoscopic procedures (laparoscopic cardiomyotomy with secondary antireflux operations, balloon dilation, Botulinum-toxin injection) were without success. A barium esophagogram showed a confinement of the distal esophagus with a filiform passage of the contrast medium and undigested food in the prestenotic dilated esophageal corpus. Manometry displayed a hypertensive lower esophageal sphincter with a resting pressure of 43.8 mmHg - although completely relaxing. The tubular esophagus was aperistaltic with 100 % simultaneous and repetitive contractions. As all attempts of previous therapy had failed, a transhiatal esophagectomy with gastric pull-up and cervical esophagogastrostomy ensued. Neuropathological examination of the esophagus showed that degeneration of the myenteric plexus was not severely involved, whereas inflammatory and fibrotic changes were obvious. Esophageal resection provided the only chance of a long-term benefit for our patient with relief of dysphagia.

Motor and sensory function of the esophagus: revelations through ultrasound imaging.

Catheter based high frequency intraluminal ultrasound (HFIUS) imaging is a powerful tool to study esophageal sensory and motor function and dysfunction in vivo in humans. It has provided a number of important insights into the longitudinal muscle function of the esophagus. Based on the ultrasound images and intraluminal pressure recordings, it is clear that there is synchrony in the timing as well as the amplitude of contraction between the circular and the longitudinal muscle layers of the esophagus in normal subjects. On the other hand, in patients with spastic disorders of the esophagus, there is an asynchrony of contraction related to the timing and amplitude of contraction of the two muscle layers during peristalsis. Achalasia, diffuse esophageal spasm, and nutcracker esophagus (spastic motor disorders of the esophagus) are associated with hypertrophy of the circular as well as longitudinal muscle layers. A sustained contraction of the longitudinal muscle of the esophagus is temporally related to chest pain and heartburn and may very well be the cause of symptoms. Longitudinal muscle function of the esophagus can be studied in vivo in humans using dynamic ultrasound imaging. Longitudinal muscle dysfunction appears to be important in the motor and sensory disorders of the esophagus.

Modulation of gastro-oesophageal vagal afferents by galanin in mouse and ferret.

The neuropeptide galanin is found in the central and peripheral nervous systems. It may have excitatory or inhibitory actions via three subtypes of G-protein-coupled receptor, and it modulates the mechanosensitivity of somatic sensory fibres. We aimed to determine if galanin also modulates vagal afferent mechanosensitivity, and to localize endogenous sources. The responses of ferret and mouse gastro-oesophageal vagal afferents to graded mechanical stimuli were investigated in vitro. The effects of galanin and/or the galanin receptor antagonist galantide on these responses were quantified. Immunohistochemistry for galanin was performed in ferret and mouse proximal stomach and nodose ganglion. In ferrets, retrograde labelling of gastric afferents to the nodose ganglion was combined with immunohistochemistry. When exposed to galanin (1-10 nM), 18/31 ferret and 12/15 mouse gastro-oesophageal afferents (tension, mucosal and tension/mucosal receptors) showed inhibition of mechanosensitivity. Four of 31 ferret afferents showed potentiation of mechanosensitivity, and 9/31 were unaffected (2/15 and 1/15 in mouse, respectively). Galanin effects were reversed after washout or by galantide (10-30 nM). Galantide given alone increased mechanosensitivity. Galanin immunoreactivity was found in nodose neurones, including those innervating the stomach in ferret. Enteric neurones were also galanin immunoreactive, as were endings associated with myenteric ganglia and smooth muscle. We conclude that galanin potently modulates mechanosensitivity of gastro-oesophageal vagal afferents with either facilitatory or inhibitory actions on individual afferent fibres. Both intrinsic and extrinsic (vagal) neurones contain galanin and are therefore potential sources of endogenous galanin.

NO/cyclic GMP pathway mediates the relaxation of feline lower oesophageal sphincter.

1. We examined the role of the NO/cyclic GMP (cyclic GMP) pathway in nitric oxide (NO)- and vasoactive intestinal peptide (VIP)-induced relaxation of feline lower oesophageal sphincter (LES). Furthermore, it was studied whether methylene blue, LY83583 and ODQ, which are soluble guanylate cyclase (sGC) inhibitors, could inhibit NO-induced relaxation. 2. The nitric oxide synthase (NOS) inhibitor, N omega-nitro-L-arginine (L-NNA) had no effect in sodium nitropruside (SNP)-induced relaxation, but 3-morpholinosydnonimine-N-ethylcarbamide (SIN-1)-induced relaxation was decreased by the pretreatment of L-NNA, which showed that SIN-1, not SNP, could activate NOS to cause relaxation. Methylene blue and LY83583 did not inhibit the relaxation by SNP and SIN-1. However, the more specific sGC inhibitor ODQ blocked the relaxation induced by NO donors. 3. To identify the relationship of NOS, sGC and adenylate cyclase in VIP-induced relaxation, tissue were pretreated with L-NNA and ODQ and SQ22536. These inhibitors produced significant inhibition of this response to VIP. The adenylyl cyclase inhibitor SQ 22536 also inhibited relaxation by VIP. 4. In conclusion, our data showed that SNP- and SIN-1-induced relaxation was mediated by sGC. Of sGC inhibitors, methylene blue and LY83583 were not adequate for the examination of NO donor-induced feline LES smooth muscle relaxation. VIP also caused relaxation by the pathway involving NO and cGMP and cAMP.

Effects of phosphodiesterase inhibitors on oesophageal neuromuscular functions.

The cyclic nucleotides adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) mediate the inhibitory effects of vasoactive intestinal polypeptide and nitric oxide on oesophageal smooth muscle. Phosphodiesterases (PDE) terminate their actions. We hypothesized that PDE inhibitors alter nerve-induced responses of oesophageal and lower oesophageal sphincter (LES) smooth muscle. An electrical field known to activate intrinsic oesophageal nerves was used to stimulate transverse muscle strips from the opossum oesophagus. This produced a contractile off-response from circular oesophageal muscle and a biphasic relaxation of the LES - an initial rapid relaxation (R1) and a slower sustained relaxation (R2). The effects on LES and oesophageal muscle of zaprinast (type V), zardaverine (type III/IV) and theophylline (non-specific) PDE inhibitors were explored. All three PDE inhibitors decreased LES tone and attenuated the off-response. Zaprinast and theophylline increased the latency of the off-response. Zaprinast prolonged R1, and slowed its recovery. It also increased the percentage relaxation of the second R2. Zardaverine increased the percentage relaxation of R2. Theophylline slowed the recovery of R2. PDEs play a role in maintaining LES tone and its recovery after LES relaxation. They may also modulate oesophageal motor activity.

Role of sarcoplasmic reticulum in control of membrane potential and nitrergic response in opossum lower esophageal sphincter.

1. We previously demonstrated that a balance of Ca2+-activated Cl- current (ICl(Ca)) and K+ current activity sets the resting membrane potential of opossum lower esophageal sphincter (LES) circular smooth muscle at approximately -41 mV, which leads to continuous spike-like action potentials and the generation of basal tone. Ionic mechanisms underlying this basal ICl(Ca) activity and its nitrergic regulation remain unclear. Recent studies suggest that spontaneous Ca2+ release from sarcoplasmic reticulum (SR) and myosin light chain kinase (MLCK) play important roles. The current study investigated this possibility. Conventional intracellular recordings were performed on circular smooth muscle of opossum LES. Nerve responses were evoked by electrical square wave pulses of 0.5 ms duration at 20 Hz. 2. In the presence of nifedipine (1 microm), substance P (1 microm), atropine (3 microm) and guanethidine (3 microm), intracellular recordings demonstrated a resting membrane potential (MP) of -38.1+/-0.7 mV (n=25) with spontaneous membrane potential fluctuations (MPfs) of 1-3 mV. Four pulses of nerve stimulation induced slow inhibitory junction potentials (sIJPs) with an amplitude of 6.1+/-0.3 mV and a half-amplitude duration of 1926+/-147 ms (n=25). 3. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), a specific guanylyl cyclase inhibitor, abolished sIJPs, but had no effects on MPfs. Caffeine, a ryanodine receptor agonist, hyperpolarized MP and abolished sIJPs and MPfs. Ryanodine (20 microm) inhibited the sIJP and induced biphasic effects on MP, an initial small hyperpolarization followed by a large depolarization. sIJPs and MPfs were also inhibited by cyclopiazonic acid, an SR Ca2+ ATPase inhibitor. Specific ICl(Ca) and MLCK inhibitors hyperpolarized the MP and inhibited MPfs and sIJPs. 4. These data suggest that (1). spontaneous release of Ca2+ from the SR activates ICl(Ca), which in turn contributes to resting membrane potential; (2). MLCK is involved in activation of ICl(Ca); (3). inhibition of ICl(Ca) is likely to underlie sIJPs induced by nitrergic innervation.