Neurotransmission in lower esophageal sphincter of W/Wv mutant mice.

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

Wait times for gastroenterology consultation in Canada: the patients' perspective.

Long wait times for health care have become a significant issue in Canada. As part of the Canadian Association of Gastroenterology's Human Resource initiative, a questionnaire was developed to survey patients regarding wait times for initial gastroenterology consultation and its impact. A total of 916 patients in six cities from across Canada completed the questionnaire at the time of initial consultation. Self-reported wait times varied widely, with 26.8% of respondents reporting waiting less than two weeks, 52.4% less than one month, 77.1% less than three months, 12.5% reported waiting longer than six months and 3.6% longer than one year. One-third of patients believed their wait time was too long, with 9% rating their wait time as 'far too long'; 96.4% believed that maximal wait time should be less than three months, 78.9% believed it should be less than one month and 40.3% believed it should be less than two weeks. Of those working or attending school, 22.6% reported missing at least one day of work or school because of their symptoms in the month before their appointment, and 9.0% reported missing five or more days in the preceding month. A total of 20.2% of respondents reported being very worried about having a serious disease (ie, scored 6 or higher on 7-point Likert scale), and 17.6% and 14.8%, respectively, reported that their symptoms caused major impairment of social functioning and with the activities of daily living. These data suggest that a significant proportion of Canadians with digestive problems are not satisfied with their wait time for gastroenterology consultation. Furthermore, while awaiting consultation, many patients experience an impaired quality of life because of their gastrointestinal symptoms.

Opportunity costs of gastrointestinal endoscopic training in Canada.

BACKGROUND: No data exist to define the opportunity costs related to instruction in endoscopic procedures in Royal College of Physicians and Surgeons of Canada-accredited teaching centres. Academic and institutional administrators expect staff to achieve acceptable performance standards. There is a need to measure some of the effects of training activity in the establishment of such standards. OBJECTIVE: To measure the effect of resident training in colonoscopy on real procedure times and, as a secondary goal, to estimate procedural losses related to the process of training. METHODS: Real procedure times for ambulatory colonoscopy in a single academic, hospital-based endoscopy unit were documented. Times for certified endoscopy instructors functioning solo were compared with times for procedures involving trainees at several levels of colonoscopic experience. Procedural reductions associated with resident training were estimated based on the parameters derived from the results. The analysis was executed retrospectively using prospectively collected data. RESULTS: Resident training prolonged procedure times for ambulatory colonoscopy by 50%. The trainee effect was consistent, although variable in degree, among a variety of endoscopy instructors. Such increased procedure times have the potential to reduce case throughput and endoscopist remuneration. CONCLUSIONS: Resident training in colonoscopy in a Canadian certified training program has significant negative effects on case throughput and endoscopist billings. These factors should be considered in any assessment of performance in similar training environments.

Diffuse Esophageal Narrowing in Eosinophilic Esophagitis: A Barium Contrast Study.

BACKGROUND: Patients with eosinophilic esophagitis (EoE) present with mechanical type dysphagia. Barium esophagrams occasionally demonstrate focal strictures or multiple concentric rings. Diffuse narrowing has also been reported but may be difficult to recognize because of lack of normative data. AIM: The aim of this study is to assess esophageal diameters at multiple sites in healthy controls in comparison with EoE patients. METHODS: A standardized barium swallow was performed in 22 healthy male volunteers without esophageal symptoms and compared with 10 untreated EoE patients. A radiopaque ruler attached at the subject's back was used to measure maximal esophageal diameter at three esophageal sites by a blinded observer. Peak intraepithelial eosinophil counts and Mayo Dysphagia Questionnaire scores were correlated to esophageal diameters in EoE patients. RESULTS: Two of 10 EoE patients had areas of focal narrowing on barium Xray. Esophageal diameters were significantly less at all three esophageal sites in EoE patients compared with controls. Using a total esophageal diameter score (i.e., sum of the three diameters) to establish the 95th percentile for minimal diameter in controls, four of 10 EoE patients fell below the normal range. There was no significant correlation between esophageal diameters, peak eosinophil counts and any of the Mayo Dysphagia Questionnaire severity scores. CONCLUSION: Patients with EoE have a diffusely narrow esophagus in comparison to healthy controls, and this abnormality may not be appreciated without using appropriate normative data.

Regional differences in nitrergic innervation of the smooth muscle of murine lower oesophageal sphincter.

BACKGROUND AND PURPOSE: Anatomical and pharmacological studies have demonstrated that the lower oesophageal sphincter (LES) is not a simple homogenous circular muscle with uniform innervation. Regional differences have been demonstrated in several species including humans. We investigated, for the first time in mice LES, regionally distinct physiological and pharmacological characteristics of the neuromusculature. EXPERIMENTAL APPROACH: Conventional intracellular recordings and pharmacological techniques were employed to evaluate electrical properties and functional innervation of smooth muscle cells. Results from CD1 (control), nNOS((-/-)) and eNOS((-/-)) genetic knockout mice were compared. KEY RESULTS: Smooth muscle of sling and clasp LES displayed unitary membrane potentials of 1- 4 mV. Transmural nerve stimulation produced a monophasic inhibitory junction potential (IJP) in the sling, whereas in the clasp a biphasic IJP, consisting of a brief IJP followed by a long-lasting slow IJP (lsIJP), was induced. Pharmacological interventions and genetically modified mice were used to demonstrate a monophasic apamin-sensitive (purinergic) component in both LES regions. However, the nitrergic IJP was monophasic in the sling and biphasic in the clasp. Unitary membrane potentials and IJPs were not different in CD1 and eNOS((-/-)) mice, suggesting no involvement of myogenic NOS. CONCLUSION AND IMPLICATIONS: These data in mouse LES indicate that there are previously unreported regional differences in the IJP and that both the apamin-resistant monophasic and biphasic IJPs are mediated primarily by nitrergic innervation.

Access to specialist gastroenterology care in Canada: comparison of wait times and consensus targets.

BACKGROUND: Monitoring wait times and defining targets for care have been advocated to improve health care delivery related to cancer, heart, diagnostic imaging, joint replacements and sight restoration. There are few data on access to care for digestive diseases, although they pose a greater economic burden than cancer or heart disease in Canada. The present study compared wait times for specialist gastroenterology care with recent, evidence-based, consensus-defined benchmark wait times for a range of digestive diseases. METHODS: Total wait times from primary care referral to investigation were measured for seven digestive disease indications by using the Practice Audit in Gastroenterology program, and were benchmarked against consensus recommendations. RESULTS: Total wait times for 1903 patients who were undergoing investigation exceeded targets for those with probable cancer (median 26 days [25th to 75th percentiles eight to 56 days] versus target of two weeks); probable inflammatory bowel disease (101 days [35 to 209 days] versus two weeks); documented iron deficiency anemia (71 days [19 to 142 days] versus two months); positive fecal occult blood test (73 days [36 to 148 days] versus two months); dyspepsia with alarm symptoms (60 days [23 to 140 days] versus two months); refractory dyspepsia without alarm symptoms (126 days [42 to 225 days] versus two months); and chronic constipation and diarrhea (141 days [68 to 264 days] versus two months). A minority of patients were seen within target times: probable cancer (33% [95% CI 20% to 47%]); probable inflammatory bowel disease (12% [95% CI 1% to 23%]); iron deficiency anemia (46% [95% CI 37% to 55%]); positive occult blood test (41% [95% CI 28% to 54%]); dyspepsia with alarm symptoms (51% [95% CI 41% to 60%]); refractory dyspepsia without alarm symptoms (33% [95% CI 19% to 47%]); and chronic constipation and diarrhea (21% [95% CI 14% to 29%]). DISCUSSION: Total wait times for the seven indications exceeded the consensus targets; 51% to 88% of patients were not seen within the target wait time. Multiple interventions, including adoption of evidence-based management guidelines and provision of economic and human resources, are needed to ensure appropriate access to digestive health care in Canada. Outcomes can be evaluated by the 'point-of-care', practice audit methodology used for the present study.

Sustained esophageal longitudinal smooth muscle contraction may not be a cause of noncardiac chest pain.

BACKGROUND: The etiology of noncardiac chest pain (NCCP) is poorly understood. Some evidence suggests that it may be related to sustained esophageal contractions (SECs) of longitudinal smooth muscle. This study attempts to evaluate whether SECs play a role in symptom production in NCCP patients. METHODS: This was a prospective double-blind study comparing NCCP patients to healthy controls. Subjects underwent high-resolution esophageal manometry followed by infusions of normal saline and 0.1N hydrochloric acid into the esophagus. Pain intensity was recorded during each minute of the infusion using a visual analog scale between 0 and 10. Two blinded investigators measured the esophageal length at the end of the saline and acid infusion periods as well as the point at which esophageal shortening began using the computer based manometry software. KEY RESULTS: Seventeen NCCP patients and 16 controls completed the study. 64% of study subjects demonstrated esophageal shortening in response to acid infusion with mean shortening of 0.4 ± 0.54 cm. The mean decrease in esophageal length with acid was similar between the groups (1.9% ± 2.6% for NCCP patients vs 1.7% ± 2.4% for controls, P = .82). There was no correlation between pain onset and esophageal shortening. CONCLUSIONS AND INFERENCES: NCCP patients did not appear to have an exaggerated esophageal shortening response to intraluminal acid. As well, there was poor temporal correlation between esophageal shortening and symptoms. Thus, acid-induced SECs may not play a significant role in pain production in NCCP patients.

Experimental induction of isolated lower esophageal sphincter relaxation in anesthetized opossums.

Isolated lower esophageal sphincter (LES) relaxation, defined as a transient sphincteric relaxation unaccompanied by esophageal peristalsis, has been shown to precede most episodes of gastroesophageal reflux in humans. We studied the genesis of isolated LES relaxation in anesthetized opossums by observing the response of four components of the deglutition reflex (mylohyoid electrical activity, pharyngeal contraction, esophageal peristalsis, and LES relaxation) to pharyngeal tactile stimulation, electrical stimulation of superior laryngeal nerve (SLN) afferents or cervical vagal efferents, and to balloon distention of the esophageal body. A single pharyngeal stroking evoked isolated LES relaxation in 56% of 160 instances. The proportion of isolated relaxations in response to SLN electrical stimulation varied inversely with the stimulus frequency, occurring in 64% of the responses at 5 Hz and 4% of the responses at 30 Hz. A full four-component deglutition sequence was most likely to occur at the higher frequencies of SLN electrical stimulation. Esophageal balloon distention elicited isolated LES relaxations or no response at low distending volumes, whereas at higher volumes LES relaxation and esophageal contraction predominated. Isolated LES relaxation had significantly less magnitude than relaxations accompanied by esophageal contractions. Bilateral cervical vagotomy abolished all LES and esophageal body responses induced by pharyngeal stroking and SLN stimulation, and rendered the esophageal body and LES less responsive to small volumes of distention. Vagal efferent stimulation produced isolated LES relaxation at lower frequency stimulation and LES relaxation with esophageal contractions at higher frequency stimulation. These studies show that isolated LES relaxation represents incomplete expression of either the deglutitive reflex or the peripheral reflex mediating secondary peristalsis.

Clinical diagnosis of achalasia: how reliable is the barium x-ray?

Manometry is considered to be the gold standard for the diagnosis of achalasia. However, many physicians believe that contrast radiography, classically showing esophageal dilation with bird-beak narrowing of the gastroesophageal junction, is also accurate in either diagnosing or excluding the disorder. The aim of the current study was to determine the accuracy of barium x-ray in the diagnosis of achalasia. The radiological diagnosis of all patients manometrically diagnosed with achalasia (using conventional criteria) between January 1994 and June 1998 were reviewed. A total of 51 cases of achalasia were identified. Thirteen patients were excluded because they either did not have contrast radiography before a manometric diagnosis or had their x-rays performed more than six months previously. Of the remaining 38 patients, achalasia was stated as a diagnostic possibility in the radiologists report in only 22 (58%) of those patients. Achalasia was not considered in the remaining 16 patients: two were reported as normal, four as having stenosis/narrowing in distal esophagus, two as having presbyesophagus, one as having mild gastroesophageal reflux and seven as having nonspecific dysmotility. To determine the reason for the diagnostic failure of the barium x-ray, an expert gastrointestinal radiologist reviewed 12 of the nondiagnostic x-rays in a blinded fashion, interspersed with 10 randomly selected esophageal-contrast radiographs from control subjects to avoid bias. Of these initially nondiagnostic x-rays in achalasia patients, typical radiological features of achalasia were deemed to be present in 50%. The present study indicates that contrast radiography lacks sensitivity in the diagnosis of achalasia. This is not only due to radiologist oversight but also because of the absence of the characteristic radiological features in many cases. This reinforces the important role of esophageal manometry in patients with persistent nonstructural dysphagia.

Stress increases descending inhibition in mouse and human colon.

BACKGROUND: A relationship between stress and the symptoms of irritable bowel syndrome (IBS) has been well established but the cellular mechanisms are poorly understood. Therefore, we investigated effects of stress and stress hormones on colonic descending inhibition and transit in mouse models and human tissues. METHODS: Stress was applied using water avoidance stress (WAS) in the animal model or mimicked using stress hormones, adrenaline (5 nM), and corticosterone (1 µM). Intracellular recordings were obtained from colonic circular smooth muscle cells in isolated smooth muscle/myenteric plexus preparations and the inhibitory junction potential (IJP) was elicited by nerve stimulation or balloon distension oral to the site of recording. KEY RESULTS: Water avoidance stress increased the number of fecal pellets compared to control (p < 0.05). WAS also caused a significant increase in IJP amplitude following balloon distension. Stress hormones also increased the IJP amplitude following nerve stimulation and balloon distension (p < 0.05) in control mice but had no effect in colons from stressed mice. No differences were observed with application of ATP between stress and control tissues, suggesting the actions of stress hormones were presynaptic. Stress hormones had a large effect in the nerve stimulated IJP in human colon (increased >50%). Immunohistochemical studies identified alpha and beta adrenergic receptor immunoreactivity on myenteric neurons in human colon. CONCLUSIONS & INFERENCES: These studies suggest that WAS and stress hormones can signal via myenteric neurons to increase inhibitory neuromuscular transmission. This could lead to greater descending relaxation, decreased transit time, and subsequent diarrhea.

Alteration of swallowing and oesophageal peristalsis by different initiators of deglutition.

It has long been believed that once initiated, the involuntary phase of deglutition follows a stereotypical pattern, that is modified only by ongoing sensory input from the transported bolus. To test the hypothesis that the mode of sensory activation of deglutition can modify the motor response irrespective of bolus characteristics, the mylohyoid, lower oesophageal sphincter (LES) and oesophageal body response to swallows induced in anaesthetized opossums by pharyngeal stroking or superior laryngeal nerve (SLN) stimulation (unilateral and bilateral) were compared. In comparison with unilateral SLN stimulation, swallows triggered by pharyngeal stroking resulted in a greater mylohyoid spike burst and LES relaxation. There was no significant difference in the oesophageal and LES motor response to pharyngeal stroking vs bilateral SLN stimulation, although the mylohyoid response was of greater magnitude with pharyngeal stroking. These studies demonstrate that the motor component of deglutition can be altered by different sensory initiators of swallowing, and provides a possible link between oropharyngeal and oesophageal motor disorders.

Etiology and pathogenesis of achalasia.

The primary pathophysiologic abnormality in achalasia is loss of intrinsic inhibitory innervation of the lower esophageal sphincter and smooth muscle segment of the esophageal body. Disease of the extrinsic (vagal) nervous system and esophageal musculature may also be present, but these are less consistent findings and could represent secondary phenomena. Inflammation within the esophageal myenteric plexus is pathognomonic of the disease, but the cause of this inflammation is uncertain. Autoimmunity and previous viral infection have been hypothesized, but remain unproven.

Extraesophageal complications of gastroesophageal reflux disease.

With the widespread availability of ambulatory esophageal pH monitoring, there has been recently renewed interest in the so-called 'extraesophageal' complications of gastroesophageal reflux disease (GERD). There are two proposed mechanisms by which reflux can cause extraesophageal symptoms or disease: refluxed acid may reach the oropharynx and/or respiratory tract and cause direct irritation; or acid contact with the esophageal mucosa may trigger neural reflexes, which, in turn, produce symptoms. Evidence is most compelling for an association between GERD and unexplained dental erosions, posterior laryngitis, chronic unexplained cough and intrinsic asthma. The clinician should be aware of these associations, and patients with these conditions should be questioned carefully about associated GERD symptoms. When GERD and any of these conditions coexist, intensive medical antireflux therapy is indicated. Twenty-four hour pH monitoring may be required in selected patients to document the relationship between reflux and the extraesophageal complication or to ensure that the medical therapy provided has eliminated acid reflux.

Management of complicated gastroesophageal reflux disease: atypical chest pain.

Although most patients with gastroesophageal reflux disease (GERD) present with the classic symptoms of heartburn and acid regurgitation, many complain of atypical chest pain suggestive of cardiac disease. Once cardiac ischemia has been excluded, it is important to consider GERD because this may be established as the cause of pain in 10% to 50% of such patients. If GERD is suspected or documented, vigorous antireflux treatment, preferably with proton pump inhibitory therapy, is indicated.

Acid-induced esophageal shortening in humans: a cause of hiatus hernia?

BACKGROUND: Hiatus hernia and gastroesophageal reflux disease commonly coexist, and there is pathophysiological evidence that the presence of a hiatus hernia contributes to abnormal acid reflux. However, the cause of hiatus hernia remains unclear. In an animal model, it has been shown that acute acid injury to the esophagus results in esophageal shortening, raising the possibility that reflux esophagitis per se can contribute to the formation of hiatus hernia by inducing esophageal shortening. AIM: To determine whether luminal acid produces esophageal shortening in humans. METHODS: Twelve volunteers were each studied on two occasions, one week apart, in a double-blind, crossover trial. The location of the lower esophageal sphincter (LES), as well as the LES resting pressure and axial length were determined at baseline and then again after 20 min of either acid or saline perfusion. RESULTS: Acid perfusion did not induce significant changes in resting LES pressure but resulted in proximal migration of the LES (ie, esophageal shortening) by an average of 0.5 cm, with the largest proximal migration being 1.8 cm. In contrast, saline perfusion resulted in slight distal migration of the LES (ie, esophageal lengthening). CONCLUSIONS: Intraluminal acid perfusion causes longitudinal axis shortening of the esophagus and suggests that gastroesophageal acid reflux may contribute to the cause of hiatus hernia.

Esophagitis as the outcome of progressive failures of the defensive repertoire.

Pre-epithelial defences include the coordinated actions of the lower esophageal sphincter and the esophageal muscles, which minimize reflux of gastric contents and promote clearance of refluxed material. The esophageal epithelium also possesses innate resistance to luminal damaging agents and may be protected luminally by a mucus or 'mucus bicarbonate' barrier and possibly a layer of hydrophobic surfactants. These components are derived from submucosal glands located in the submucosal connective tissue and from salivary secretions that may bind to the esophageal surface. Epithelial defences include the glycocalyx, permeability properties of the epithelial cell plasma membrane, junctional barriers to proton permeation through the paracellular pathway and ion transport processes for regulation of intracellular pH. Subepithelial defences involve mainly regulation of blood supply via responses of nerves, mast cells and blood vessels to influxing protons. Although the epithelium can withstand prolonged exposure to physiologically relevant concentrations of acid, the presence of pepsin or bile salts may overcome the permeability barrier, which probably resides in the superficial layers of epithelial cells. Focal destruction of these cells allows access of luminal acid and other aggressive agents to the vulnerable basolateral cell membranes and to the submucosa. The result is lesion production, although an efflux of alkaline plasma may protect the underlying submucosa and allow healing. Salivary-derived epidermal growth factor (EGF) is present in the luminal fluid, and lesion development may also provide access of EGF to receptors within the epithelium and in the underlying vasculature. Accelerated cell proliferation would then contribute to healing. Inflammation and healing should also be viewed as defensive responses, as can the development of Barrett's esophagus, in which the stratified squamous epithelium is replaced by a potentially acid-resistant columnar epithelium. Chronic inflammation and esophagitis only result when this multilayered set of defences is overcome. The challenge for research is to identify those components of the defensive repertoire that are defective in individuals who suffer from chronic esophagitis.

The pathogenesis of amniotic fluid embolism with particular reference to transabdominal amniocentesis.

A fatal case of amniotic fluid embolism is presented. Several amniocenteses had been performed during the pregnancy. A review is presented of definite and probable examples of amniotic fluid embolism following amniocentesis.

TREK-1 channels do not mediate nitrergic neurotransmission in circular smooth muscle from the lower oesophageal sphincter.

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.

Proteinase-activated receptor-2 activation evokes oesophageal longitudinal smooth muscle contraction via a capsaicin-sensitive and neurokinin-2 receptor-dependent pathway.

BACKGROUND: Intraluminal acid evokes sustained oesophageal longitudinal smooth muscle (LSM) contraction and oesophageal shortening, which may play a role in oesophageal pain and the aetiology of hiatus hernia. In the opossum model, this reflex has been shown to involve mast cell activation and release of neurokinins from capsaicin-sensitive neurons. The aim of this study was to determine whether proteinase-activated receptor-2 (PAR-2) activation evokes reflex LSM contraction via similar mechanisms. METHODS: Tension recording studies were performed using opossum oesophageal LSM strips in the presence and absence of pharmacological agents. In addition, the effect of trypsin on single isolated LSM cells was determined using videomicroscopy, and the expression of PAR-2 in oesophageal tissue was examined using immunohistochemistry. KEY RESULTS: The PAR-2 agonist trypsin evoked sustained, concentration-dependent contraction of LSM muscle strips, but had no effect on isolated LSM cells. The trypsin-induced contraction was blocked by capsaicin desensitization, substance P (SP) desensitization or application of the selective neurokinin-2 (NK-2) receptor antagonist MEN 10376. Immunohistochemistry revealed co-localization of SP, calcitonin gene-related peptide and PAR-2 in axons of opossum oesophageal LSM. CONCLUSIONS & INFERENCES: Longitudinal smooth muscle contraction induced by trypsin involves capsaicin-sensitive neurons and subsequent activation of NK-2, which is identical to the pathway involved in acid-induced LSM contraction and oesophageal shortening. This suggests that acid-induced LSM contraction may involve mast cell-derived mediators that activate capsaicin-sensitive neurons via PAR-2.