Effect of body position changes on postprandial gastroesophageal reflux and gastric emptying in the healthy premature neonate

OBJECTIVE

To identify a body-positioning regimen that promotes gastric emptying (GE) and reduces gastroesophageal reflux (GER) by changing body position 1 hour after feeding.

STUDY DESIGN

Ten healthy preterm infants (7 male; mean postmenstrual age, 36 weeks [range, 33 to 38 weeks]) were monitored with combined esophageal impedance-manometry. Infants were positioned in the left lateral position (LLP) or right lateral position (RLP) and then gavage-fed. After 1 hour, the position was changed to the opposite side. Subsequently, all infants were restudied with the order of positioning reversed.

RESULTS

There was more liquid GER in the RLP than in the LLP (median, 9.5 [range, 6.0 to 22.0] vs 2.0 [range, 0.0 to 5.0] episodes/hour; P = .002). In the RLP-first protocol, the number of liquid GER episodes per hour decreased significantly after position change (first postprandial hour [RLP], 5.5 [2.0 to 13.0] vs second postprandial hour [LLP], 0.0 [0.0 to 1.0]; P = .002). GE was faster in the RLP-first protocol than in the LLP-first protocol (37.0 +/- 21.1 vs 61.2 +/- 24.8 minutes; P = .006).

CONCLUSIONS

A strategy of right lateral positioning for the first postprandial hour with a position change to the left thereafter promotes GE and reduces liquid GER in the late postprandial period and may prove to be a simple therapeutic approach for infants with GER disease.

Approaches to driving the evolving understanding of lower oesophageal sphincter mechanical function

This article reviews and places into context the development of lower oesophageal sphincter (LOS) manometry, the key technique for researching the mechanics of this region. The first of two major challenges, being able to record sphincter pressure accurately with generally available equipment, was solved by the advent of perfused manometry in the 1960s. The other main challenge was to achieve reliable, continuous recording of LOS pressure, despite the constant movements of the LOS relative to the manometric catheter. Though well documented, this challenge is still poorly understood and prioritised, as many clinical/diagnostic and research manometric studies use methods for LOS manometry that are invalidated by LOS movement. There are two techniques that can record continuously from the LOS, despite its movements: high resolution manometry (HRM), which uses multiple point pressure sensors spaced at 1 cm interval or less, and the sleeve, which is a single long sensor. HRM provides valuable additional information on the varied topography of pressure patterns across the gastro-oesophageal junction and how this can change in an individual, second to second. HRM especially, but also sleeve manometry continue to advance understanding of the mechanics of gastro-oesophageal reflux, to unravel the mysteries of the mechanics of hiatus hernia and the diaphragmatic hiatus, to define why antireflux surgery fails or causes dysphagia, to recognise patients with dysphagia due to isolated defects of LOS relaxation and to test novel therapies for reflux disease directed at LOS function. Ample evidence now exists that accurate monitoring of LOS and gastro-oesophageal junction pressures is important for the diagnostic assessment of many patients and for advancing research into several aspects of the mechanical function of the LOS and its surrounding structures. This evidence now needs to be better reflected in the methods used for routine clinical practice and research.

Circumferential and axial distribution of esophageal mucosal damage in reflux disease

The aim of this study was to evaluate the axial and radial distribution of histological markers including hyperplasia of the basal cell layer, elongation of the papillae and dilatation of the intercellular spaces of the squamous epithelium in patients with nonerosive reflux disease compared to controls and to relate this to the macroscopic topography in erosive reflux disease. Two different study populations were included in this report. Endoscopic esophageal biopsies were taken from 21 healthy control subjects and 21 nonerosive reflux disease patients before and after 4 weeks of esomeprazole therapy. Endoscopic still images from 50 erosive reflux disease patients were reviewed for the radial orientation of LA grade A and/or B esophagitis (Los Angeles criteria for grading of reflux esophagitis). The 3 o'clock position of the squamocolumnar junction showed significantly thicker basal cell layer (P=0.011) and more intercellular space dilatation (P=0.01) in nonerosive reflux disease patients compared to the 9 o'clock position. Only a significant difference in dilatation of the intercellular spaces (P=0.018) between nonerosive reflux disease patients and controls were observed in the 3 o'clock region at the squamocolumnar junction, whereas 1-2 cm orally, all three histological criteria differed significantly (P<or=0.01). After treatment, on the contrary, papillary length was significantly less pronounced at the squamocolumnar junction (P<0.01). Endoscopically, erosions were predominantly visualized in the 3 o'clock region (P<0.05). Histological mucosal changes in nonerosive reflux disease patients and visible mucosal erosions in erosive reflux disease patients occur most frequently at the same position, namely in the 3 o'clock quadrant in the distal esophagus. The histological difference between nonerosive reflux disease patients and controls are more distinct 1-2 cm oral to rather than at the squamocolumnar junction. However the effect of therapy is most pronounced at the squamocolumnar junction.

Design, implementation and evaluation of a medical education programme using the ambulatory diagnostic and treatment centre

BACKGROUND

In the UK a central government initiative is seeking to transfer aspects of specialist NHS care to community settings using ambulatory diagnostic and treatment centres (ADTCs).

AIMS

Following the redevelopment of a district general hospital as an ADTC, we were interested in the feasibility of using this new facility to deliver a structured programme for undergraduate medical students.

METHOD

Twenty self-selected fifth year medical students at the University of Dundee, together with teaching and administration staff in the ADTC, took part in the study during the academic year 2005-2006.

RESULTS

One hundred percent of students and 73% of staff responded to a questionnaire pitched at the level of reaction to the course. The key findings were that the students found the teaching venues useful, the general environment conducive to learning, and the content appropriate to their needs. Staff felt that patients were not unhappy or disturbed by having students present and did not think the presence of students inhibited their clinical work. They appreciated the new opportunity to teach.

CONCLUSIONS

An ADTC is a viable setting for structured teaching of undergraduate medical students. It provides a context for medical student leaning away from the main teaching hospital.

Magnification endoscopy for diagnosis of nonerosive reflux disease: a proposal of diagnostic criteria and critical analysis of observer variability

BACKGROUND AND STUDY AIMS

This study tested the diagnostic value of high-resolution endoscopy for the recognition of subtle diagnostic esophageal mucosal changes in nonerosive reflux disease.

PATIENTS AND METHODS

Ten control subjects and eleven patients with nonerosive reflux disease confirmed by a validated questionnaire, standard endoscopy, and 24-hour pH-metry participated in the study. Still images were collected by high-resolution endoscopes from the distal esophagus in a standardized manner, incorporating iodine staining. Assessments were repeated in the patients with reflux disease after 4 weeks of esomeprazole therapy. Interobserver variability in the recognition of the proposed criteria was initially evaluated by 27 endoscopists using an Internet-based process. After optimisation of image quality the evaluation was repeated face-to-face with six expert endoscopists.

RESULTS

No criterion was identified in either assessment that was sufficiently sensitive and specific to patients with reflux disease to be clinically useful. The kappa value, used to assess interobserver variation, was acceptably high only for invisibility of palisade vessels (0.59). Triangular indentations, apical mucosal breaks, and pinpoint blood vessels at the squamocolumnar junction were identified more frequently in the patients with reflux disease ( P < 0.05). These changes and the invisibility of the palisade vessels were significantly less prevalent in reflux patients after therapy ( P < 0.01).

CONCLUSIONS

Though some distal esophageal mucosal appearances observed with the high-resolution endoscope appeared to be related to nonerosive esophageal mucosal injury, none of these changes proved to be sufficiently sensitive and specific to justify their use as a diagnostic criterion for nonerosive reflux disease.

Microscopic esophageal mucosal injury in nonerosive reflux disease

This review evaluates the current knowledge about the recognition of histologic esophageal mucosal changes in patients with nonerosive gastroesophageal reflux disease and analyzes the technical factors relevant to their interpretation. Studies investigating histologic changes in individuals with nonerosive reflux disease were identified by systematic Medline/PubMed searches from January 1966 to October 2005. Dilation of intercellular spaces was the most consistently reported histologic change in the esophageal mucosa of patients with nonerosive reflux disease, being observed in 41%-100% of patients and 0%-30% of controls. The mean intercellular space width was at least 2 times greater in patients than in controls, irrespective of esophageal acid exposure. Basal cell hyperplasia was observed in 9%-90% of patients compared with 10%-55% of controls. Papillary elongation was observed in 0%-85% of patients and 5%-20% of controls. Both of these features were more prevalent in reflux disease patients with abnormal esophageal acid exposure. All histologic changes responded to acid-suppressive therapy. Inflammatory cell infiltration was seldom observed or had a similar prevalence in patients and controls. Disparities in reported frequencies of change among studies were most likely caused by methodologic factors, most importantly the use of different methods for identifying patients and controls, for histologic sampling, and for biopsy scoring. The reviewed studies suggest that at least two thirds of patients with nonerosive reflux disease have histologic evidence of esophageal injury. Additional work is needed to assess the potential of these histologic changes for the diagnosis and assessment of reflux disease.

Review article: from 1906 to 2006--a century of major evolution of understanding of gastro-oesophageal reflux disease

BACKGROUND

Our understanding of gastro-oesophageal reflux disease has undergone significant changes over the last century.

AIM

To trace the rise in understanding of gastro-oesophageal reflux disease and highlight remaining areas of uncertainty.

METHODS

Literature review.

RESULTS

In 1906, Tileston published his observations on 'peptic ulcer of the oesophagus'. Winkelstein, in 1934, first correlated symptoms of heartburn with acid regurgitation and reflux oesophagitis. In 1946, Allison described hiatus hernia as a causal factor in the development of gastro-oesophageal reflux disease. In 1958, Bernstein and Baker showed a direct relationship between oesophageal acidification and heartburn in patients with gastro-oesophageal reflux disease, irrespective of endoscopic findings, leading to the recognition of non-erosive gastro-oesophageal reflux disease. In the 1980s, continuous recordings of the lower oesophageal sphincter showed that episodes of reflux were related to transient relaxations of lower oesophageal sphincter tone. There is now increasing recognition that gastro-oesophageal reflux disease arises from the interaction of several anatomical and physiological factors. A turning point in the medical treatment of gastro-oesophageal reflux disease came with the introduction of the first proton pump inhibitor, omeprazole, in 1989.

CONCLUSIONS

Future efforts need to identify the multifactorial interactions of gastro-oesophageal junction anatomy and physiology in patients with gastro-oesophageal reflux disease. Increased understanding of the disease will guide development of new therapies.

The development and validation of an endoscopic grading system for Barrett's esophagus: the Prague C & M criteria

BACKGROUND & AIMS

Barrett's esophagus (BE) is a premalignant condition for esophageal adenocarcinoma, its diagnosis relying initially on recognition of a columnar-lined distal esophagus. We aimed to develop and validate explicit, consensus-driven criteria for the endoscopic diagnosis and grading of BE.

METHODS

An international working group agreed on criteria and developed materials for their formal evaluation using video-endoscopic recordings gathered in a standardized manner in 29 patients. The criteria included assessment of the circumferential (C) and maximum (M) extent of the endoscopically visualized BE segment as well as endoscopic landmarks. The recordings were scored according to these criteria by a separate international panel of 29 endoscopists.

RESULTS

The Prague C & M Criteria give explicit guidance on the endoscopic recognition of BE and grading of its extent. The overall reliability coefficients (RC) for the assessment of the C & M extent of the endoscopic BE segment above the gastroesophageal junction were 0.95 and 0.94, respectively. The rates of exact agreement (for C & M values) for pairwise comparisons of individual patient values were 53% and 38%, respectively, whereas the values for agreement within a 2-cm interval were 97% and 95%, respectively. The overall RC for endoscopic recognition of BE >/=1 cm was 0.72, whereas for BE <1 cm, it was 0.22. The RCs for recognizing the location of the gastroesophageal junction and the diaphragmatic hiatus were 0.88 and 0.85, respectively.

CONCLUSIONS

The Prague C & M Criteria have high overall validity for the endoscopic assessment of visualized BE lengths.

Effect of baclofen on esophagogastric motility and gastroesophageal reflux in children with gastroesophageal reflux disease: a randomized controlled trial

OBJECTIVE

To evaluate the effect of baclofen, a gamma-amino-butyric-acid B receptor agonist that inhibits transient lower esophageal sphincter relaxation (TLESR), on the rates of TLESR, gastroesophageal reflux (GER), and gastric emptying (GE) in children with GER disease.

STUDY DESIGN

The efficacy of 0.5 mg/kg baclofen was evaluated in a randomized, double-blinded, placebo-controlled trial in 30 children. Patients were intubated with a manometric/pH assembly and given 250 mL of cow's milk. Esophageal motility and pH were then measured for 2 hours (control period). Baclofen or placebo was then administered, and 1 hour later 250 mL of milk was given again and measurements performed for another 2 hours (test period). The GE rate was measured by the (13)C octanoate breath test.

RESULTS

Baclofen significantly reduced the incidence of TLESR (mean, 7.3 +/- 1.5 vs 3.6 +/- 1.2 TLESR/2 hours; P < .05) and acid GER (mean 4.2 +/- 0.7 vs 1.7 +/- 1.0 TLESR + GER/2 hours; P < .05) during the test period compared with the control period. Baclofen significantly accelerated the GE rate (median [interquartile range], GE(t1/2), 61 minutes [39, 81 minutes] vs 114 minutes [67, 170 minutes]; P < .05). Baclofen had no effect on the swallowing rate, pattern of esophageal peristalsis, or lower esophageal sphincter pressure.

CONCLUSIONS

Baclofen reduces GER in children by inhibiting the triggering of TLESR. Baclofen also accelerates GE.

Comparison of gastro-oesophageal reflux disease and heartburn diagnoses in UK primary care

OBJECTIVE

It is unclear how gastro-oesophageal reflux disease (GORD) is diagnosed in primary care. The aim of this study is to compare patients given a diagnosis of GORD with those diagnosed with heartburn.

RESEARCH DESIGN AND METHODS

Data from the UK General Practice Research Database were extracted for patients newly diagnosed with heartburn (n = 1841) or GORD (n = 5318) in 1996.

MAIN OUTCOME MEASURES

Patient characteristics, morbidity, healthcare use and prescribed treatments were compared using unconditional logistic regression analysis.

RESULTS

GORD was diagnosed more frequently than heartburn (3.2 vs. 1.1 per 1000 patient-years). A diagnosis of GORD was less likely among females (odds ratio (OR): 0.8; confidence interval (CI): 0.7-0.9), smokers (OR: 0.8; CI: 0.7-0.9) and patients who consulted their physician frequently (OR: 0.8; CI: 0.7-0.9). There was a wide distribution in the ratio of GORD-to-heartburn diagnoses between primary care practices (mean 2.9; range 0-infinity). GORD patients were more likely to receive proton pump inhibitors (OR: 2.9; CI: 2.6-3.4), but 24% of GORD patients and 40% of heartburn patients received no acid-suppressive treatment in the month after diagnosis.

CONCLUSIONS

Several factors influenced the diagnosis of gastro-oesophageal reflux symptoms by primary care physicians. Further research is needed to aid the diagnosis of GORD in primary care.

The Montreal definition and classification of gastroesophageal reflux disease: a global evidence-based consensus

OBJECTIVES

A globally acceptable definition and classification of gastroesophageal reflux disease (GERD) is desirable for research and clinical practice. The aim of this initiative was to develop a consensus definition and classification that would be useful for patients, physicians, and regulatory agencies.

METHODS

A modified Delphi process was employed to reach consensus using repeated iterative voting. A series of statements was developed by a working group of five experts after a systematic review of the literature in three databases (Embase, Cochrane trials register, Medline). Over a period of 2 yr, the statements were developed, modified, and approved through four rounds of voting. The voting group consisted of 44 experts from 18 countries. The final vote was conducted on a 6-point scale and consensus was defined a priori as agreement by two-thirds of the participants.

RESULTS

The level of agreement strengthened throughout the process with two-thirds of the participants agreeing with 86%, 88%, 94%, and 100% of statements at each vote, respectively. At the final vote, 94% of the final 51 statements were approved by 90% of the Consensus Group, and 90% of statements were accepted with strong agreement or minor reservation. GERD was defined as a condition that develops when the reflux of stomach contents causes troublesome symptoms and/or complications. The disease was subclassified into esophageal and extraesophageal syndromes. Novel aspects of the new definition include a patient-centered approach that is independent of endoscopic findings, subclassification of the disease into discrete syndromes, and the recognition of laryngitis, cough, asthma, and dental erosions as possible GERD syndromes. It also proposes a new definition for suspected and proven Barrett's esophagus.

CONCLUSIONS

Evidence-based global consensus definitions are possible despite differences in terminology and language, prevalence, and manifestations of the disease in different countries. A global consensus definition for GERD may simplify disease management, allow collaborative research, and make studies more generalizable, assisting patients, physicians, and regulatory agencies.

The Montreal definition and classification of gastroesophageal reflux disease: a global evidence-based consensus

OBJECTIVES

A globally acceptable definition and classification of gastroesophageal reflux disease (GERD) is desirable for research and clinical practice. The aim of this initiative was to develop a consensus definition and classification that would be useful for patients, physicians, and regulatory agencies.

METHODS

A modified Delphi process was employed to reach consensus using repeated iterative voting. A series of statements was developed by a working group of five experts after a systematic review of the literature in three databases (Embase, Cochrane trials register, Medline). Over a period of 2 yr, the statements were developed, modified, and approved through four rounds of voting. The voting group consisted of 44 experts from 18 countries. The final vote was conducted on a 6-point scale and consensus was defined a priori as agreement by two-thirds of the participants.

RESULTS

The level of agreement strengthened throughout the process with two-thirds of the participants agreeing with 86%, 88%, 94%, and 100% of statements at each vote, respectively. At the final vote, 94% of the final 51 statements were approved by 90% of the Consensus Group, and 90% of statements were accepted with strong agreement or minor reservation. GERD was defined as a condition that develops when the reflux of stomach contents causes troublesome symptoms and/or complications. The disease was subclassified into esophageal and extraesophageal syndromes. Novel aspects of the new definition include a patient-centered approach that is independent of endoscopic findings, subclassification of the disease into discrete syndromes, and the recognition of laryngitis, cough, asthma, and dental erosions as possible GERD syndromes. It also proposes a new definition for suspected and proven Barrett's esophagus.

CONCLUSIONS

Evidence-based global consensus definitions are possible despite differences in terminology and language, prevalence, and manifestations of the disease in different countries. A global consensus definition for GERD may simplify disease management, allow collaborative research, and make studies more generalizable, assisting patients, physicians, and regulatory agencies.

Pathogenesis and classification of cancer around the gastroesophageal junction--not so different in Japan

Japanese patients with early adenocarcinoma of the esophagus have well-preserved gastric acid secretion, consistent with other parts of the world, reinforcing the likely importance of the luminal environment for pathogenesis. Progress in researching carcinomas that occur around the gastroesophageal junction would be facilitated by consensus-based review of the inadequate approaches currently used for classification of these tumors with subsequent development and widespread adoption of improved criteria.

Visualizing the air-to-leaf transfer and within-leaf movement and distribution of phenanthrene: further studies utilizing two-photon excitation microscopy

Two-photon excitation microscopy (TPEM) was used to monitor the air-to-leaf transfer and within-leaf movement and distribution of phenanthrene in two plant species (maize and spinach) grown within a contaminated atmosphere. Phenanthrene was visualized within the leaf cuticle, epidermis, mesophyll, and vascular system of living maize and spinach plants. No detectable levels of phenanthrene were observed in the roots or stems of either species, suggesting phenanthrene entered the leaves only from the air. Phenanthrene was observed in both the abaxial and adaxial cuticles of both species. Particulate material (aerosols/dust) contaminated with phenanthrene was located at the surface of the cuticle and became encapsulated within the cuticularwaxes. Overtime, diffuse areas of phenanthrene formed within the adjacent cuticle. However, most of the visualized phenanthrene reaching the leaves arrived via gas-phase transfer. Phenanthrene was found within the wax plugs of stomata of both species and on the external surface of the stomatal pore, but not on the internal surface, or within the sub-stomatal cavity. Phenanthrene diffused through the cuticles of both species in 24-48 h, entering the epidermis to reside predominantly within the cell walls of maize (indicative of apoplastic transport) and the cellular cytoplasm of spinach (indicative of symplastic transport). Phenanthrene accumulated within the spinach cytoplasm where it concentrated into the vacuoles of the epidermal cells. Phenanthrene was not observed to accumulate in the cytoplasm of maize cells. Phenanthrene entered the internal mesophyll of both species, and was found within the mesophyll cell walls, at the surface of the chloroplasts, and within the cellular cytoplasm. Phenanthrene was observed within the xylem of maize following 12 days exposure. The cuticle and epidermis at the edges of spinach leaves had a systematically higher concentration of phenanthrene than the cuticle and epidermal cells at the center of the leaf. These results provide important new information about how such compounds enter, move, and distribute within leaves, and suggest that contemporary views of such processes based on data obtained from traditional analytical methods may need to be revised.

Distal small bowel motility and lipid absorption in patients following abdominal aortic aneurysm repair surgery

AIM: To investigate distal small bowel motility and lipid absorption in patients following elective abdominal aortic aneurysm (AAA) repair surgery.

METHODS: Nine patients (aged 35-78 years; body mass index (BMI) range: 23-36 kg/m²) post-surgery for AAA repair, and seven healthy control subjects (20-50 years; BMI range: 21-29 kg/m²) were studied. Continuous distal small bowel manometry was performed for up to 72 h, during periods of fasting and enteral feeding (Nutrison^®). Recordings were analyzed for the frequency, origin, length of migration, and direction of small intestinal burst activity. Lipid absorption was assessed on the first day and the third day post surgery in a subset of patients using the ¹³C-triolein-breath test, and compared with healthy controls. Subjects received a 20-min intraduodenal infusion of 50 mL liquid feed mixed with 200 μL ¹³C-triolein. End-expiratory breath samples were collected for 6 h and analyzed for ¹³CO₂ concentration.

RESULTS: The frequency of burst activity in the proximal and distal small intestine was higher in patients than in healthy subjects, under both fasting and fed conditions (P < 0.005). In patients there was a higher proportion of abnormally propagated bursts (71% abnormal), which began to normalize by d 3 (25% abnormal) post-surgery. Lipid absorption data was available for seven patients on d 1 and four patients on d 3 post surgery. In patients, absorption on d 1 post-surgery was half that of healthy control subjects (AUC ¹³CO₂ 1 323 ± 244 vs 2 646 ±365; P < 0.05, respectively), and was reduced to the one-fifth that of healthy controls by d 3 (AUC ¹³CO₂ 470 ± 832 vs 2 646 ± 365; P < 0.05, respectively).

CONCLUSION: Both proximal and distal small intestinal motor activity are transiently disrupted in critically ill patients immediately after major surgery, with abnormal motility patterns extending as far as the ileum. These motor disturbances may contribute to impaired absorption of enteral nutrition, especially when intraluminal processing is necessary for efficient digestion.

Endogenous nitric oxide modulates small intestinal nutrient transit and activity in healthy adult humans

OBJECTIVE

Nitric oxide (NO) mechanisms have been shown to modulate fasting small intestinal motility in humans, but a role in the regulation of human postprandial small intestinal motility has not been assessed. The aim of this study was to evaluate the effect of the NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) on the regulation of small intestinal nutrient transit and postprandial small intestinal motility in healthy humans.

MATERIAL AND METHODS

Seven healthy male volunteers (18-27 years) underwent antroduodenal manometry recordings for 4 h on 2 occasions after intraduodenal instillation of a 500 KJ [120 Kcal] test meal. The meal was administered 15 min after the commencement of a 60-min intravenous infusion of L-NMMA (4 mg kg-1 h-1) or saline (0.9%). Studies were separated, performed in randomized order and >3 days apart. The frequency and amplitude of duodenal pressure waves together with time to return of fasting motility (phase III) was determined. On each day, small intestinal transit was measured using a lactulose breath test.

RESULTS

The test meal interrupted fasting small intestinal motility in all subjects. The time to recurrence of fasting motility following its postprandial disruption was similar (L-NMMA versus saline 1.6+/-0.2 h versus 1.9+/-0.1 h; p>0.05). Duodenocaecal transit was delayed by infusion of L-NMMA compared with saline (L-NMMA versus saline 92.1+/-3.9 min versus 66.4+/-6.4 min; p<0.005). Infusion of L-NMMA significantly increased the frequency (L-NMMA versus saline 50.4+/-6.6 versus 34.8+/-5.5 waves per 30 min; p<0.05) and amplitude (L-NMMA versus saline 20.4+/-1.5 versus 15.5+/-1.1 mmHg; p<0.01) of duodenal pressure waves.

CONCLUSIONS

These data suggest that endogenous NO may play a role in the regulation of small intestinal nutrient transit by regulating small intestinal motility in healthy individuals.

Inhibition of transient lower esophageal sphincter relaxation and gastroesophageal reflux by metabotropic glutamate receptor ligands

BACKGROUND & AIMS

Transient lower esophageal sphincter relaxation (TLESR) is the major mechanism of gastroesophageal acid reflux. TLESR is mediated via vagal pathways, which may be modulated by metabotropic glutamate receptors (mGluRs). Group I mGluRs (mGluR1 and 5) have excitatory effects on neurons, whereas group II (mGluR2 and 3) and group III (mGluR4, 6, 7, and 8) are inhibitory. This study determined the effect of mGluRs on triggering of TLESR and reflux in an established conscious ferret model.

METHODS

Esophageal manometric/pH studies were performed in ferrets with chronic esophagostomies. TLESR were induced by a gastric load of 25 mL glucose (pH 3.5) and 30 mL air.

RESULTS

In control treated animals, gastric load induced 3.52 +/- 0.46 TLESRs per 47-minute study, 89.7% of which were associated with reflux episodes (n = 16). The mGluR5 antagonist MPEP inhibited TLESR dose dependently, with maximal 71% +/- 7% inhibition at 35 micromol/kg (n = 9; P < .0001). MPEP also significantly reduced reflux episodes (P < .001) and increased basal lower esophageal sphincter pressure (P < .05). MPEP inhibited swallowing dose dependently, suggesting a common action on trigger mechanisms for swallowing and TLESR. The more selective analogue, MTEP, had more potent effects (90% +/- 6% inhibition TLESR at 40 micromol/kg; n = 8; P < .0001). In contrast, the group I agonist DHPG tended to increase TLESR. The group II agonist (2R, 4R)-APDC was ineffective, whereas the group III agonist L-(AP4 slightly reduced TLESR (33% at 11 micromol/kg; P < .05). The selective mGluR8 agonist (S)-3, 4-DCPG inhibited TLESR by 54% at 15 micromol/kg (P < .01).

CONCLUSIONS

mGluR5 antagonists potently inhibit TLESR and reflux in ferrets, implicating mGluR5 in the mechanism of TLESR. mGluR5 antagonists are therefore promising as therapy for patients with GERD.