The Role of Brain-Derived Neurotrophic Factor in Irritable Bowel Syndrome.

Several studies have implied a role of brain-derived neurotrophic factor (BDNF) in abdominal pain modulation in irritable bowel syndrome (IBS). The aim of this study was to establish BDNF protein expression in human colonic biopsies and to show variation in IBS compared to controls. BDNF protein and mRNA levels were correlated with IBS symptom severity based on the IBS-symptom severity score (IBS-SSS). Biopsies from the descending colon and IBS-SSS were obtained from 10 controls and 20 IBS patients. Total protein of biopsies was extracted and assessed by ELISA and Western Blot. Total mRNA was extracted and gene expression measured by nCounter analysis. In IBS patients, symptom severity scores ranged from 124 to 486 (mean ± sem: 314.2 ± 21.2, >300 represents severe IBS) while controls ranged from 0 to 72 (mean ± sem: 27.7 ± 9.0, <75 represents healthy subjects, p < 0.001). IBS patients reported significantly more food malabsorption, former abdominal surgery and psychiatric comorbidities. BDNF protein was present in all samples and did not differ between IBS and controls or sex. Subgroup analysis showed that female IBS patients expressed significantly more BDNF mRNA compared to male patients (p < 0.05) and male IBS-D patients had higher IBS symptom severity scores and lower BDNF mRNA and protein levels compared to male controls (p < 0.05). Scatter plot showed a significant negative correlation between IBS-SSS and BDNF mRNA levels in the cohort of male IBS-D patients and their male controls (p < 0.05). We detected a high proportion of gastrointestinal surgery in IBS patients and confirmed food intolerances and psychiatric diseases as common comorbidities. Although in a small sample, we demonstrated that BDNF is detectable in human descending colon, with higher BDNF mRNA levels in female IBS patients compared to males and lower mRNA and protein levels in male IBS-D patients compared to male controls. Further research should be directed toward subgroups of IBS since their etiologies might be different.

[Interpretation und performance of high-resolution esophageal manometry: Recommendations of the German Association of Neurogastroenterology and Motility (DGNM) and the German Association of Gastroenterology, Digestive and Metabolic Diseases (DGVS)]. / Interpretation und Durchführung der hochauflösenden Ösophagusmanometrie: Empfehlungen der Deutschen Gesellschaft für Neurogastroenterologie und Motilität (DGNM) sowie der Deutschen Gesellschaft für Gastroenterologie, Verdauungs- und Stoffwechselerkrankungen (DGVS).

Esophageal manometry provides a detailed evaluation of esophageal contractility and, therefore, represents the reference method for diagnosis of esophageal motility disorders. Significance and clinical relevance have been further increased by implementation of high-resolution esophageal manometry (HRM), which reveals the functional anatomy of the esophagus in a visually-intuitive manner. The current 3 rd version of the international Chicago Classification (CC v3.0) gives standardized recommendations on performance and interpretation of HRM and serves as the basis for much of this expert consensus document. However, CC v3.0 gives only limited information with regards to the function of the lower and upper esophageal sphincters, the use of adjunctive tests including solid test meals and long-term ambulatory HRM measurements. In this expert consensus, we describe how to perform and interpret HRM on the basis of the CC v3.0 with additional recommendations based on the results of recent, high-quality clinical studies concerning the use of this technology to assess the causes of esophageal symptoms in a variety of clinical scenarios.

MRI-guided percutaneous transhepatic cholangiodrainage: feasibility study in a porcine model.

BACKGROUND AND STUDY AIMS: MRI-guided procedures combine high-quality imaging with lack of radiation. Percutaneous transhepatic cholangiodrainage under real-time MRI guidance (MRI-PTCD) seems promising, allowing targeted puncture and avoiding multiple blind passes and use of contrast, which are associated with standard PTCD's heaviest complications. PATIENTS AND METHODS: Aim of this study was to investigate the feasibility of MRI-PTCD in three outbred piglets. Obstructive cholestasis was induced by common bile duct ligation. Two days later, MRI-PTCD was performed (open MRI, 1.0 Tesla) with prototype MRI-compatible accessories. Visualization was achieved with a balanced steady-state free precession real-time sequence (bSSFP: 0.75 frames/s, TR/TE [ms]: 7.2/3.6; flip angle: 45°; 200 × 200 matrix size; resolution: 1.3 × 1.3 mm(2), slice thickness: 7 mm). Cannulation of the bile ducts was followed by placement of Yamakawa drainages. RESULTS: Twelve punctures were performed (four per animal, 10/12 successful); in 2/10 the bile ducts could not be cannulated. Animal survival was 100% and no significant complications occurred. CONCLUSIONS: Initial data show that MRI-PTCD can be successfully performed. This may lead to establishment of a new optimized PTCD technique compared to the standard approach under fluoroscopy.

Percutaneous transhepatic cholangiodrainage under real-time MRI guidance: initial experience in an animal model.

AIMS: To assess percutaneous transhepatic cholangiodrainage (PTCD) under real-time MRI-guidance and compare it to procedures performed under fluoroscopy. METHODS: We developed an in vitro model for MRI-guided and conventional PTCD, using an animal organ set including liver and bile ducts placed in an MRI-compatible box and tested it in a 1.0-Tesla open MRI-scanner. Prototype 18G needles and guide wires, standard guide wires, dilatation bougies, and drainages were used (MRI-compatible). MRI-visualization was by means of a bFFE real-time sequence using a surface coil (Flex-L). Outcome measurements were success rates and time needed for bile duct puncture using real-time MRI-guidance versus conventional radiologic methods in the model. Cannulation and drainage placement were also analysed. RESULTS: Fifty MRI-guided experiments were performed, leading to rapid (mean: 43s, range: 15-72s) and successful puncture and cannulation in 96% of procedures. Median drainage placement time was 321.5s (range: 241-411s). In 35 control experiments under fluoroscopy, puncture success was 69%, whereas times were significantly longer (mean 273s, range 45-631s). CONCLUSIONS: Initial in vitro experience shows that PTCD can be successfully and rapidly performed under real-time MRI-guidance and demonstrates improved performance compared to the conventional radiologic approach.

Initial results of MR-guided liver resection in a high-field open MRI.

BACKGROUND: The goal of this study was to evaluate high-field open magnetic resonance imaging (MRI) for intraoperative real-time imaging during hand-assisted laparoscopic liver resection. MR guidance has several advantages compared to ultrasound and may represent a future technique for abdominal surgery. Various MRI-safe and -compatible instruments were developed, tested, and applied to realize minimally invasive liver surgery under MR guidance. As proof of the concept, liver resection was performed in a porcine model. METHODS: All procedures were conducted in a 1.0-T open MRI unit. Imaging quality and surgical results were documented during three cadaveric and two live animal procedures. A nonferromagnetic hand port was used for manual access and the liver tissue was dissected using a Nd:YAG laser. RESULTS: The intervention time ranged from 126 to 145 min, with a dissection time from 11 to 15 min. Both live animals survived the intervention with a blood loss of 250 and 170 ml and a specimen weight of 138 and 177 g. A dynamic T2W fast spin-echo sequence allowed real-time imaging (1.5 s/image) with good delineation of major and small hepatic vessels. The newly developed MR-compatible instruments and camera system caused only minor interferences and artifacts of the MR image. CONCLUSION: MR-guided liver resection is feasible and provides additional image information to the surgeon. We conclude that MR-guided laparoscopic liver resection improves the anatomical orientation and may increase the safety of future minimally invasive liver surgery.

Serotonin transporter activity and serotonin concentration in platelets of patients with irritable bowel syndrome: effect of gender.

BACKGROUND: In the past decade, a strong argument has been built for the role of serotonin (5HT) and the serotonin transporter (SERT) in irritable bowel syndrome (IBS). However, it is still not clear how SERT contributes to this clinically heterogeneous disease. The present study addressed this issue by implementing platelet (plt) markers of SERT activity in the assessment protocol. METHODS: Fasting blood samples of 149 (51 male/98 female) subjects with Rome II and III defined IBS subtypes, and 163 healthy control subjects (CSs; 75 male/88 female) were analyzed for platelet 5HT concentration and 5HT uptake activity [maximum uptake rate (V (max)) and affinity constant (K (m))]. RESULTS: Gender had a significant impact on platelet markers of SERT activity. Male IBS patients showed significantly lower median V (max) and K (m) values than the male CS (V (max) 1.706 vs. 2.148 nmol/10(9) plts x min, P < 0.001; K (m) 346 vs. 410 nmol, P = 0.008) without any significant reduction in platelet 5HT concentration (362 vs. 394 ng/10(9) plts). On the other hand, V (max) values were not different between female IBS patients and female CS (1.642 vs. 1.741 nmol/10(9) plts x min), but platelet 5HT concentration was significantly lower in females with diarrhea-predominant IBS (363 vs. 435 ng/10(9) plts, P < 0.05). CONCLUSION: Although an absolute extrapolation from platelets to the gastrointestinal tissue does not appear to be justified, our findings demonstrated that the contribution of disturbed SERT activity to IBS is not uniform and is possibly gender-specific. The results suggest that an assessment of SERT function in platelets may help to elucidate the differences between IBS patients in response to drugs affecting the 5HT system.

Osteochondral lesions of the talus: retrograde drilling with high-field-strength MR guidance.

The institutional review board approved the use of cadaveric specimens, and informed consent was obtained from all volunteers. The authors performed and assessed a magnetic resonance (MR)-assisted navigation method for minimally invasive retrograde drilling of talar osteochondral lesions. For this method, a single imaging plane is sufficient for navigation during intervention. To accomplish this objective, a passive MR navigation device was used to evaluate 16 cadaveric ankle joints. Use of this interactive MR-assisted navigation method in combination with a passive aiming device allowed precise and rapid retrograde drilling of talar osteochondral lesions.

First evidence for an association of a functional variant in the microRNA-510 target site of the serotonin receptor-type 3E gene with diarrhea predominant irritable bowel syndrome.

Diarrhea predominant irritable bowel syndrome (IBS-D) is a complex disorder related to dysfunctions in the serotonergic system. As cis-regulatory variants can play a role in the etiology of complex conditions, we investigated the untranslated regions (UTRs) of the serotonin receptor type 3 subunit genes HTR3A and HTR3E. Mutation analysis was carried out in a pilot sample of 200 IBS patients and 100 healthy controls from the UK. The novel HTR3E 3'-UTR variant c.*76G>A (rs62625044) was associated with female IBS-D (P = 0.033, OR = 8.53). This association was confirmed in a replication study, including 119 IBS-D patients and 195 controls from Germany (P = 0.0046, OR = 4.92). Pooled analysis resulted in a highly significant association of c.*76G>A with female IBS-D (P = 0.0002, OR = 5.39). In a reporter assay, c.*76G>A affected binding of miR-510 to the HTR3E 3'-UTR and caused elevated luciferase expression. HTR3E and miR-510 co-localize in enterocytes of the gut epithelium as shown by in situ hybridization and RT-PCR. This is the first example indicating micro RNA-related expression regulation of a serotonin receptor gene with a cis-regulatory variant affecting this regulation and appearing to be associated with female IBS-D.

Peripheral injection of ghrelin induces Fos expression in the dorsomedial hypothalamic nucleus in rats.

Peripheral ghrelin has been shown to act as a gut-brain peptide exerting a potent orexigenic effect on food intake. The dorsomedial nucleus of the hypothalamus (DMH) is innervated by projections from other brain areas being part of the network of nuclei controlling energy homeostasis, among others NPY/AgRP-positive fibers arising from the arcuate nucleus (ARC). The aim of the study was to determine if peripherally administered ghrelin affects neuronal activity in the DMH, as assessed by Fos expression. The number of Fos positive neurons was determined in the DMH, paraventricular nucleus of the hypothalamus (PVN), ARC, ventromedial hypothalamic nucleus (VMH), nucleus of the solitary tract (NTS) and in the area postrema (AP) in non-fasted Sprague-Dawley rats in response to intraperitoneally (ip) injected ghrelin (3 nmol/rat) or vehicle (0.15 M NaCl). Peripheral ghrelin induced a significant increase in the number of Fos-ir positive neurons/section compared with vehicle in the ARC (mean+/-SEM: 49+/-2 vs. 23+/-2 neurons/section, p=0.001), PVN (69+/-5 vs. 34+/-3, p=0.001), and DMH (142+/-5 vs. 83+/-5, p<0.001). Fos-ir positive neurons were mainly localized within the ventral part of the DMH. No change in Fos expression was observed in the VMH (53+/-8 vs. 48+/-6, p=0.581), NTS (42+/-2 vs. 40+/-3, p=0.603), and in the AP (7+/-1 vs. 5+/-1, p=0.096). Additional double-labelling with anti-Fos and anti-AgRP revealed that Fos positive neurons in the DMH were encircled by a network of AgRP-ir positive fibers. These data indicate that peripheral ghrelin activates DMH neurons and that NPY-/AgRP-positive fibers may be involved in the response.

The effect of macronutrients on gastric volume responses and gastric emptying in humans: A magnetic resonance imaging study.

The effects of macronutrients on gastric volume changes, emptying, and gastrointestinal symptoms are incompletely understood. Three liquid meals of 500 ml (fat emulsion, 375 kcal; protein solution, 375 kcal; glucose solution, 400 kcal) were infused into the stomach of 12 healthy volunteers on three occasions. Studies were performed in seated body position using an open-configuration magnetic resonance imaging (MRI) system. MRI imaging sequences, assessing stomach and meal volumes, were performed prior to and at times t = 0, 3, 6, 9, 12, 15, 25, 35, 45, 60, 75, and 90 min after meal administration. Areas under the curve for the early emptying phase (0-15 and 0-45 min) were calculated, and characteristics of the volume curves were analyzed by a gastric emptying model. Gastrointestinal symptoms were assessed by a self-report scale. Initial (t = 0 min) and early postprandial gastric volumes were highest for glucose because of lower initial emptying. However, in the early emptying phase the characteristics of the volume curves for stomach and meal were uniform for all macronutrients. Perceptions of fullness and satiety were linearly associated with postprandial gastric volumes, but not with macronutrient composition. Isovolumic macronutrient meals modulate gastric volume response by initial meal emptying patterns. Macronutrient specific accommodation responses, as shown in barostat studies, are not reflected as gastric volume responses under noninvasive conditions.

Peripheral injection of CCK-8S induces Fos expression in the dorsomedial hypothalamic nucleus in rats.

Peripheral cholecystokinin (CCK) plays a physiological role in the regulation of food intake. The dorsomedial hypothalamic nucleus (DMH) has been implicated in the brain regulation of food intake and satiety. The aim of this study was to determine if peripherally administered CCK affects neuronal activity in the DMH, as assessed by Fos expression. Density of Fos-positive neurons was determined in the DMH, paraventricular nucleus of the hypothalamus (PVN), arcuate nucleus of the hypothalamus (ARC) and ventromedial hypothalamic nucleus (VMH) in non-fasted Sprague-Dawley rats in response to intraperitoneally (ip) injection of CCK-8S (2 microg/kg, n=6) or vehicle (0.15 M NaCl; n=6). CCK-8S increased Fos immunoreactivity in the DMH (mean+/-SEM; cells/section: 108+/-10 versus 54+/-6, p<0.001) and PVN (120+/-12 versus 20+/-3, p<0.001) compared to the vehicle group while not influencing Fos expression in the ARC and VMH. Double labeling showed that 27.4+/-6.4% (n=3) of Fos-positive neurons induced by CCK-8S were positive for corticotropin-releasing factor immunoreactivity, that were mainly localized in the ventral part of the DMH, and encircled in a network of tyrosine-hydroxylase-immunoreactive positive fibers. These data indicate that in addition of the PVN, peripheral CCK increases neuronal activity in the DMH suggesting a possible role in this hypothalamic nucleus in the satiating effect of the peptide.

Gastric electrical stimulation in gastroparesis: where do we stand?

Gastroparesis is a chronic disabling condition of impaired gastric motility that results in decreased quality of life. Currently available medical therapy consists of prokinetic and/or antiemetic therapy, dietary modifications, and nutritional supplementation. For patients with medication-resistant gastroparesis a non-pharmacological therapy, gastric electric stimulation, has evolved over the last decade. Based on the frequency of the electrical stimulus, gastric electric stimulation can be classified into low- and high-frequency gastric electric stimulation. The first method aims to normalize gastric dysrhythmia and entrain gastric slow waves and accelerates gastric emptying, whereas high-frequency gastric electric stimulation is unable to restore normal gastric emptying, but nevertheless stunningly reduces symptoms, such as nausea and vomiting, re-establishes quality of life, nutritional state in all patients, and metabolic control in patients with diabetic gastroparesis. Gastric electric stimulation presents a new possibility in the treatment of gastroparesis.

Cerebral processing of auditory stimuli in patients with irritable bowel syndrome.

AIM: To determine by brain functional magnetic resonance imaging (fMRI) whether cerebral processing of non-visceral stimuli is altered in irritable bowel syndrome (IBS) patients compared with healthy subjects. To circumvent spinal viscerosomatic convergence mechanisms, we used auditory stimulation, and to identify a possible influence of psychological factors the stimuli differed in their emotional quality. METHODS: In 8 IBS patients and 8 controls, fMRI measurements were performed using a block design of 4 auditory stimuli of different emotional quality (pleasant sounds of chimes, unpleasant peep (2000 Hz), neutral words, and emotional words). A gradient echo T2*-weighted sequence was used for the functional scans. Statistical maps were constructed using the general linear model. RESULTS: To emotional auditory stimuli, IBS patients relative to controls responded with stronger deactivations in a greater variety of emotional processing regions, while the response patterns, unlike in controls, did not differentiate between distressing or pleasant sounds. To neutral auditory stimuli, by contrast, only IBS patients responded with large significant activations. CONCLUSION: Altered cerebral response patterns to auditory stimuli in emotional stimulus-processing regions suggest that altered sensory processing in IBS may not be specific for visceral sensation, but might reflect generalized changes in emotional sensitivity and affective reactivity, possibly associated with the psychological comorbidity often found in IBS patients.

Bombesin, but not amylin, blocks the orexigenic effect of peripheral ghrelin.

The interaction between ghrelin and bombesin or amylin administered intraperitoneally on food intake and brain neuronal activity was assessed by Fos-like immunoreactivity (FLI) in nonfasted rats. Ghrelin (13 microg/kg ip) increased food intake compared with the vehicle group when measured at 30 min (g/kg: 3.66 +/- 0.80 vs. 1.68 +/- 0.42, P < 0.0087). Bombesin (8 microg/kg) injected intraperitoneally with ghrelin (13 microg/kg) blocked the orexigenic effect of ghrelin (1.18 +/- 0.41 g/kg, P < 0.0002). Bombesin alone (4 and 8 microg/kg ip) exerted a dose-related nonsignificant reduction of food intake (g/kg: 1.08 +/- 0.44, P > 0.45 and 0.55 +/- 0.34, P > 0.16, respectively). By contrast, ghrelin-induced stimulation of food intake (g/kg: 3.96 +/- 0.56 g/kg vs. vehicle 0.82 +/- 0.59, P < 0.004) was not altered by amylin (1 and 5 microg/kg ip) (g/kg: 4.37 +/- 1.12, P > 0.69, and 3.01 +/- 0.78, respectively, P > 0.37). Ghrelin increased the number of FLI-positive neurons/section in the arcuate nucleus (ARC) compared with vehicle (median: 42 vs. 19, P < 0.008). Bombesin alone (4 and 8 microg/kg ip) did not induce FLI neurons in the paraventricular nucleus of the hypothalamus (PVN) and coadministered with ghrelin did not alter ghrelin-induced FLI in the ARC. However, bombesin (8 microg/kg) with ghrelin significantly increased neuronal activity in the PVN approximately threefold compared with vehicle and approximately 1.5-fold compared with the ghrelin group. Bombesin (8 microg/kg) with ghrelin injected intraperitoneally induced Fos expression in 22.4 +/- 0.8% of CRF-immunoreactive neurons in the PVN. These results suggest that peripheral bombesin, unlike amylin, inhibits peripheral ghrelin induced food intake and enhances activation of CRF neurons in the PVN.

Megacolon in adulthood after surgical treatment of Hirschsprung's disease in early childhood.

Hirschsprung's disease (HD) is a disorder associated with congenital malformation of the enteric nervous system with segmental aganglionosis. Prevailing therapy includes a resection of the affected part of the bowel. However, patients often do not obtain complete functional improvement after surgical treatment. We present the case of a 25-year-old woman who had surgical treatment of HD in early childhood. After that procedure she had clinical features of constipation for years in the end, passing of stool once a week, requiring laxatives and enemas. We diagnosed an incomplete resection of the aganglionic bowel via rectal biopsy and resected the remaining aganglionic segment. Two months after surgery the patient's bowel function improved to a frequency of 1-4 stools per day. We conclude that regular follow-up is required to identify HD patients with persistent alterations of bowel function after surgery. In patients presenting with constipation, recognition of a remaining aganglionic segment or other alterations of the enteric nervous system should be aimed at in an early stage.

Gastric perception thresholds are low and sensory neuropeptide levels high in helicobacter pylori-positive functional dyspepsia.

BACKGROUND AND AIMS: In functional dyspepsia (FD) decreased perception levels can be shown on gastric distension. Substance P (SP) and calcitonin gene-related peptide (CGRP) are involved in the sensitization of afferent neuronal pathways due to chronic inflammation. The role of Helicobacter pylori-induced gastric mucosal inflammation in the pathogenesis of FD is controversial. The aim of this study was to assess whether FD patients have altered mucosal concentrations of CGRP and SP, and to investigate whether this is associated with visceral hypersensitivity or H. pylori infection. METHODS: Gastrointestinal symptoms, H. pylori status, perception thresholds at gastric balloon distension, and gastric mucosal concentrations of CGRP and SP were determined in 13 FD patients and 18 healthy controls (HC). RESULTS: In H. pylori-positive FD patients discomfort and pain thresholds on gastric distension were lower compared to other groups. Antral mucosal levels of CGRP and SP were higher in H. pylori-positive subjects. In FD significantly negative correlations between discomfort and pain thresholds and antral mucosal concentrations of CGRP and SP were observed. CONCLUSIONS: In FD low perception thresholds on gastric distension are associated with high levels of CGRP and SP in the antrum, suggesting that sensory neuropeptides are involved in FD pathophysiology.

CCK inhibits the orexigenic effect of peripheral ghrelin.

CCK and ghrelin exert antagonistic effects on ingestive behavior. The aim of the present study was to investigate the interaction between ghrelin and CCK administered peripherally on food intake and neuronal activity in specific hypothalamic and brain stem nuclei, as assessed by c-Fos-like immunoreactivity (c-FLI) in nonfasted rats. Ghrelin (13 microg/kg body wt) injected intraperitoneally significantly increased the cumulative food intake when measured at 30 min and 1 h after injection, compared with the vehicle group (2.9 +/- 1.0 g/kg body wt vs. 1.2 +/- 0.5 g/kg body wt, P < 0.028). Sulfated CCK octapeptide (CCK-8S) (2 or 25 microg/kg body wt) injected simultaneously blocked the orexigenic effect of ghrelin (0.22 +/- 0.13 g/kg body wt, P < 0.001 and 0.33 +/- 0.23 g/kg body wt, P < 0.0008), while injected alone, both doses of CCK-8S exerted a nonsignificant trend to reduce food intake. Ghrelin (13 microg/kg body wt ip) markedly increased the number of c-FLI-positive neurons per section in the arcuate nucleus (ARC) compared with vehicle (median: 31.35 vs. 9.86, P < 0.0001). CCK-8S (2 or 25 microg/kg body wt ip) had no effect on neuronal activity in the ARC, as assessed by c-FLI (median: 5.33 and 11.21 cells per section), but blocked the ghrelin-induced increase of c-fos expression in this area when both peptides were administered simultaneously (median: 13.33 and 12.86 cells per section, respectively). Ghrelin at this dose had no effect on CCK-induced stimulation of c-fos expression in the paraventricular nucleus of the hypothalamus and the nucleus of the solitary tract. These results suggest that CCK abolishes ghrelin-induced food intake through dampening increased ARC neuronal activity.

Expression and functional role of serine/threonine phosphatases in rat esophagus.

BACKGROUND: Smooth muscle contraction is due to phosphorylation, while relaxation results from dephosphorylation of regulatory proteins such as the light chains of myosin (MLC20). Dephosphorylation of MLC20 is catalyzed by protein phosphatases (PP) types 1 and 2A. While some data are available on the expression and functional importance of PP1 and PP2A in vascular smooth muscle preparations, little is known of the importance of PP for force regulation in the gastrointestinal tract. MATERIAL/METHODS: Here we address the expression and functional importance of PP1 and PP2A in the rat esophagus. We measured both the isometric force of contraction and PP activity and also performed Western and Northern blotting for PPs in the tunica muscularis mucosae (TMM) and the muscularis mucosae propria (MM). RESULTS: Cantharidin (0.01-100 microM) inhibited PP activity in homogenates from TMM (IC50=20 KM) in a concentration-dependent manner. The mRNAs of catalytic and regulatory subunits (PP1 alpha, PP1 beta, PP2A alpha and M110) were detectable at 1.8 kb, 3.2 kb, 2.0 kb and 5.7 kb in both TMM and MM. Western blot analysis revealed PP1 in TMM and MM. PP2A (protein) was more abundant in TMM than in TMM. Cantharidin increased muscular tone in isolated preparations of TMM (starting at 100 microM) to 164.6 (14.8 % of predrug force at 300 microM (the highest concentration studied). This increase in force of contraction was comparable to that of 10 microM carbachol. CONCLUSIONS: The results suggest that PP activity can play an important role in the regulation of esophageal tone.