Symptom pattern and pathophysiological correlates of weight loss in tertiary-referred functional dyspepsia.

In patients with gastrointestinal symptoms, weight loss is an alarm symptom, indicative of organic disease. Recent studies reported weight loss in subsets of functional dyspepsia (FD) patients. The aim of this study was to analyse symptom patterns associated with weight loss in tertiary care FD. Six hundred and thirty-six FD patients (67% female, mean age 43 years) completed a dyspepsia questionnaire, and underwent gastric emptying and gastric barostat studies. After identifying independent symptom domains through orthogonal factor analysis, patients were clustered on the basis of symptom profile. Clusters were compared in terms of their association with weight loss and gastric emptying or sensorimotor function. Weight loss (4.2 kg on average) correlated most strongly with early satiety followed by nausea and vomiting (rho respectively 0.38, 0.28 and 0.23, all P < 0.0001). Factor analysis revealed three factors: Factor 1 characterized by nausea, vomiting and early satiety; factor 2 by early satiety, postprandial fullness and bloating; and factor 3 by pain, epigastric burning and belching. Subsequent cluster analysis revealed six patient clusters. The most severe cluster, which loaded high on all three factors, and a cluster dominated factor 2 were associated with the highest average weight loss (6.8 and 8.0 kg, respectively). The former cluster was also characterized by visceral hypersensitivity and delayed gastric emptying. The lowest weight loss occurred in the two clusters that had depressed scores for both early satiety associated factors (2.4 and 2.5 kg, respectively). In tertiary care FD, weight loss is strongly associated with two early satiety associated symptom clusters.

Endogenous and exogenous ghrelin enhance the colonic and gastric manifestations of dextran sodium sulphate-induced colitis in mice.

Ghrelin is an important orexigenic peptide that not only exerts gastroprokinetic but also immunoregulatory effects. This study aimed to assess the role of endogenous and exogenous ghrelin in the pathogenesis of colitis and in the disturbances of gastric emptying and colonic contractility during this process. Dextran sodium sulphate colitis was induced for 5 days in (i) ghrelin(+/+) and ghrelin(-/-) mice and clinical and histological parameters were monitored at days 5, 10 and 26 and (ii) in Naval Medical Research Institute non-inbred Swiss (NMRI) mice treated with ghrelin (100 nmol kg(-1)) twice daily for 5 or 10 days. Neural contractility changes were measured in colonic smooth muscle strips, whereas gastric emptying was measured with the (14)C octanoic acid breath test. Inflammation increased ghrelin plasma levels. Body weight loss, histological damage, myeloperoxidase activity and IL-1beta levels were attenuated in ghrelin(-/-) mice. Whereas absence of ghrelin did not affect changes in colonic contractility, gastric emptying in the acute phase was accelerated in ghrelin(+/+) but not in ghrelin(-/-) mice. In agreement with the studies in ghrelin knockout mice, 10 days treatment of NMRI mice with exogenous ghrelin enhanced the clinical disease activity and promoted infiltration of neutrophils and colonic IL-1beta levels. Unexpectedly, ghrelin treatment decreased excitatory and inhibitory neural responses in the colon of healthy but not of inflamed NMRI mice. Endogenous ghrelin enhances the course of the inflammatory process and is involved in the disturbances of gastric emptying associated with colitis. Treatment with exogenous ghrelin aggravates colitis, thereby limiting the potential therapeutic properties of ghrelin during intestinal inflammation.

Influence of buspirone on gastric sensorimotor function in man.

BACKGROUND: Previous studies have suggested involvement of 5HT(1) receptors in the control of gastric tone. AIM: To study the effect of buspirone, a 5HT(1A) agonist, on gastric sensorimotor function in healthy volunteers. METHODS: Ten healthy volunteers (six males and four females, ages 20-29 years) participated in a barostat study evaluating the influence of single oral doses of buspirone (5, 10, 20, 30 and 40 mg) on tone and sensitivity of the proximal stomach. In addition, the effect of placebo or the three lowest doses of buspirone on gastric emptying was assessed using a solid and liquid gastric emptying breath test. RESULTS: Compared to preadministration volumes, buspirone increased proximal stomach volumes in a dose-dependent manner, with significant fundic relaxation after 30 and 40 mg doses (intra-balloon volume increases of respectively 258 +/- 80 mL and 273 +/- 49 mL, P < or = 0.05). Pressure thresholds during gastric distention were not altered, but corresponding intraballoon volumes were significantly increased after 30 and 40 mg doses (respective discomfort volumes 596 +/- 73 vs. 791 +/- 87 mL and 630 +/- 73 vs.741 +/- 60 mL, both P < 0.05). Buspirone significantly slowed solid and liquid gastric emptying at the 20-mg dose. CONCLUSION: Buspirone dose-dependently relaxes the proximal stomach in the fasting state and decreases the gastric emptying rate in healthy volunteers.

Reproducibility and symptomatic predictors of a slow nutrient drinking test in health and in functional dyspepsia.

Impaired accommodation to a meal has been recognized as a pathophysiological mechanism in functional dyspepsia (FD). Based on observations in tertiary care patients, the drinking test has been proposed as a non-invasive tool to estimate accommodation. Our aim was to assess the reproducibility of the drinking test and its correlation with demographic, symptomatic and pathophysiological parameters in secondary care FD patients and healthy controls. Thirty-four healthy controls and 78 FD patients completed a drinking test (3 respectively 2 times), a gastric emptying study and an FD symptom questionnaire. Factors influencing maximal volume and gastric emptying were determined, and the reproducibility of the drinking test was investigated. The maximal satiety was reached at a lower volume in patients (489 +/- 276 and 503 +/- 248 mL for first and second test respectively vs 937 +/- 428 and 1048 +/- 421 mL, P < 0.0001). The ingested amount depended on age, sex and baseline FD symptom score. Patients' sex, final satiety score, total score for stomach complaints at screening and total symptom score before test accounted for the total symptom score after the test. The slow nutrient drinking test confirms its possible role as an attractive non-invasive and reproducible tool for the diagnosis of impaired accommodation and for the assessment of treatment responsiveness.

Activation of the cannabinoid 2 (CB2) receptor inhibits murine mesenteric afferent nerve activity.

Abstract Cannabinoid 2 (CB2) receptors have both antinociceptive and antihypersensitivity effects, although the precise mechanisms of action are still unclear. In this study, the modulatory role of CB2 receptors on the mesenteric afferent response to the endogenous immunogenic agent bradykinin (BK) was investigated. Mesenteric afferent recordings were obtained from anaesthetized wild-type and CB2(-/-) mice using conventional extracellular recording techniques. Control responses to BK were obtained in all experiments prior to administration of either CB2 receptor agonist AM1241, or AM1241 plus the CB2 receptor antagonist AM630. Bradykinin consistently evoked activation of mesenteric afferents (n = 32). AM1241 inhibited the BK response in a dose dependent manner. In the presence of AM630 (10 mg kg(-1)), however, AM1241 (10 mg kg(-)1) had no significant effect on the BK response. Moreover, AM1241 had also no significant effect on the BK response in CB2(-/-) mice. Activation of the CB2 receptor inhibits the BK response in mesenteric afferents, demonstrating that the CB2 receptor is an important regulator of neuroimmune function. This may be a mechanism of action for the antinociceptive and antihypersensitive effects of CB2 receptor agonists.

Sumatriptan is an agonist at 5-HT receptors on myenteric neurones in the guinea-pig gastric antrum.

Sumatriptan, a 5-hydroxytryptamine(1D) (5-HT(1D))-receptor agonist used in the treatment in migraine, inhibits gastric motility via the enteric nervous system. As no studies have reported enteric neuronal 5-HT(1D) receptors, we used conventional intracellular recordings to characterize the actions of sumatriptan on 145 guinea-pig antral myenteric neurones. In 24 of 29 neurones with a 5-HT(1P) receptor-mediated depolarizing response to 5-HT, application of sumatriptan caused a dose-dependent depolarization, accompanied by increased membrane resistance and enhanced excitability. Depolarizing responses to sumatriptan occurred both in cholinergic and in nitrergic neurones. Sumatriptan did not mimic the 5-HT(3) receptor-mediated fast-depolarizing responses or 5-HT(1A) receptor-mediated inhibitory responses to 5-HT. Sumatriptan had no effect on neurones not responding to 5-HT. The depolarizing response to sumatriptan was inhibited by renzapride, but not by 5-HT(1-7) receptor antagonists. We conclude that sumatriptan behaves as an agonist at the 5-HT(1P) receptor on myenteric neurones in the guinea-pig gastric antrum. The actions of sumatriptan on gastric motility seem to be attributable to a direct action on enteric neurones.

Influence of delaying gastric emptying on meal-related symptoms in healthy subjects.

BACKGROUND: Although delayed gastric emptying is often found in functional dyspepsia, a causal role for delayed emptying in inducing symptoms has not been demonstrated. AIM: To investigate the influence of delaying gastric emptying rate in healthy volunteers on the occurrence of meal-related symptoms. METHODS: Fourteen healthy subjects (six men, mean age 23 +/- 1) underwent gastric emptying studies twice using the 14C octanoic acid and 13C glycin breath test after pre-treatment with saline or sumatriptan 6 mg s.c. Breath samples were taken before meal and at 15-min intervals for a period of 360 min postprandially. At each breath sampling, the subject was asked to grade the intensity (0-6) of four dyspeptic symptoms. RESULTS: Sumatriptan pre-treatment significantly delayed solid but not liquid gastric emptying (t1/2 respectively 159 +/- 11 vs. 112 +/- 9 min, P < 0.005 and 134 +/- 11 vs. 116 +/- 12 min, N.S.). Sumatriptan significantly decreased the mean cumulative symptom score (21.3 +/- 5.5 vs. 8.0 +/- 2.6, P = 0.01), as well as scores for each individual symptom. CONCLUSION: A moderate delay in gastric emptying in health is not associated with an increase of meal-related symptoms. This observation argues against a causal role for delayed gastric emptying in the pathogenesis of dyspeptic symptoms.

Mapping slow waves and spikes in chronically instrumented conscious dogs: implantation techniques and recordings.

Myoelectric recordings from the intestines in conscious animals have been limited to a few electrode sites with relatively large inter-electrode distances. The aim of this project was to increase the number of recording sites to allow high-resolution reconstruction of the propagation of myoelectrical signals. Sets of six unipolar electrodes, positioned in a 3x2 array, were constructed. A silver ring close to each set served as the reference electrodes. Inter-electrode distances varied from 4 to 8 mm. Electrode sets, to a maximum of 4, were implanted in various configurations allowing recording from 24 sites simultaneously. Four sets of 6 electrodes each were implanted successfully in 11 female Beagles. Implantation sites evaluated were the upper small intestine (n=10), the lower small intestine (n=4) and the stomach (n=3). The implants remained functional for 7.2 months (median; range 1.4-27.3 months). Recorded signals showed slow waves at regular intervals and spike potentials. In addition, when the sets were positioned close together, it was possible to re-construct the propagation of individual slow waves, to determine their direction of propagation and to calculate their propagation velocity. No signs or symptoms of interference with normal GI-function were observed in the tested animals. With this approach, it is possible to implant 24 extracellular electrodes on the serosal surface of the intestines without interfering with its normal physiology. This approach makes it possible to study the electrical activities of the GI system at high resolution in vivo in the conscious animal.

Electrical activity in the rectum of anaesthetized dogs.

There is limited data available on the electrical activity of the rectum. An in vivo canine model was developed to record 240 extracellular electrograms simultaneously from the serosal surface of the rectum thereby enabling an off-line reconstruction of the behaviour of the electrical signals. Serosal rectal electrical activity is characterized by brief bursts of action potentials (=spikes) with a frequency of 22 cycles min(-1). High-resolution mapping of these signals revealed predominant propagation of these spikes in the longitudinal direction, originating from any site and conducted for a limited time and length before stopping spontaneously, thereby describing a patch of activity. The dimension of the patches in the longitudinal direction was significantly longer than the transversal width (13.6 vs 2.4 mm; P < 0.001). Spike propagation could occur in the aboral (46% of cases), in the oral (34%) or in both directions (20%). A bolus of betanechol (i.v., 0.5 mg kg(-1)) increased the frequency of the spikes without affecting size, shape or orientation of the patches. As in other parts of the gastrointestinal system, individual spike propagation in the rectum is limited to small areas or patches. The contractile activity of the organ could possibly reflect this underlying pattern of electrical behaviour.

Validation of 16S rDNA sequencing in microdissected bowel biopsies from Crohn's disease patients to assess bacterial flora diversity.

The bowel flora is implicated in Crohn's disease (CD) pathogenesis but its precise role is still unclear. Several non-mutually exclusive hypotheses have been proposed: an unidentified persistent pathogen; excessive bacterial translocation; an immune system abnormality in response to normal bacteria; or a breakdown in the balance between protective and harmful bacteria. These hypotheses can be tested by identifying bacteria in specific microscopic bowel structures or lesions. The present paper describes a novel technique to assess bacterial flora diversity in bowel biopsies, by combining laser capture microdissection with broad-range 16S rDNA sequencing. Fifty-four samples comprising histologically normal and pathological mucosa, MALT, ulcers, submucosal lymphangiectasias, epithelioid granulomas, and lymph nodes were microdissected out of 30 bowel biopsies from five CD patients. Bacterial 16S rDNA was successfully amplified by PCR in all samples, and PCR products from 15 samples were selected for cloning and sequence analysis. A total of 729 bacterial DNA sequences were analysed, which could be attributed to six different phyla (Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Fusobacteria, and Planctomycetes). DNA from typical bowel bacteria (Enterobacteriaceae, Clostridiales, Bacteroidetes, Fusobacteria) was detected in all microdissected areas. It was thus convincingly demonstrated that 16S rDNA sequencing can be combined with microdissection to study the bowel flora. However, no specific persistent pathogen causal for CD was identified. The results suggest that Enterobacteriaceae may initiate or colonize ulcers in CD. Translocation of bacteria through established mucosal lesions or as a result of increased permeability may be involved in the evolution towards chronic inflammation and in the establishment of persistent lesions. Further study is needed to confirm these preliminary findings.

Role of endogenous ghrelin in the hyperphagia of mice with streptozotocin-induced diabetes.

Ghrelin is an orexigenic peptide involved in the regulation of energy homeostasis. To investigate the role of ghrelin in the hyperphagia associated with uncontrolled streptozotocin-induced diabetes, food intake was followed in diabetic ghrelin knockout (ghrelin(-/-)) and control wild-type (ghrelin(+/+)) mice and diabetic Naval Medical Research Institute noninbred Swiss mice treated with either saline or the ghrelin receptor antagonist, D-Lys3-GH-releasing peptide-6 (D-Lys3-GHRP-6) for 5 d. In diabetic ghrelin(-/-) mice, hyperphagia was attenuated, and the maximal increase in food intake was 50% lower in mutant than in wild-type mice. The increased food intake observed during the light period (1000-1200 h) in ghrelin(+/+) mice was abolished in mutant mice. Diabetic ghrelin(-/-) mice lost 12.4% more body weight than ghrelin(+/+) mice. In diabetic ghrelin(+/+) mice, but not in ghrelin(-/-) mice, the number of neuropeptide Y (NPY)-immunoreactive neurons was significantly increased. Diabetic Naval Medical Research Institute noninbred Swiss mice were hyperphagic and had increased plasma ghrelin levels. Treatment with D-Lys3-GHRP-6 reduced daily food intake by 23% and reversed the increased food intake observed during the light period. The change in the number of NPY- (2.4-fold increase) and alpha-MSH (1.7-fold decrease)-immunoreactive hypothalamic neurons induced by diabetes was normalized by D-Lys3-GHRP-6 treatment. Our results suggest that enhanced NPY and reduced alpha-MSH expression are secondary to the release of ghrelin, which should be considered the underlying trigger of hyperphagia associated with uncontrolled diabetes.

Ghrelin gastrokinetic action in patients with neurogenic gastroparesis.

Ghrelin has been shown to accelerate gastric emptying in animals where its effect appeared mediated through the vagus nerve. We aimed to verify the gastrokinetic capacity of ghrelin in human. Patients with gastroparesis attributed to a neural dysregulation by diabetes (n = 5) or surgical vagotomy (n = 1) were evaluated. The emptying of a test meal (420 kcal) was determined by the C13 octanoic acid breath test. Saline or synthetic ghrelin 1-4 microg/kg were given in 1 min bolus at the end of the meal. T-lag and T-1/2 were shorter during ghrelin than during saline administration [33 +/- 5 min versus 65 +/- 14 min (p < 0.01) and 119 +/- 6 min versus 173 +/- 38 min (p < 0.001)]. Ghrelin injection therefore accelerated gastric emptying of a meal in humans even in presence of a deficient gastric innervation.

Influence of ghrelin on interdigestive gastrointestinal motility in humans.

BACKGROUND: Recent studies in animals have shown that ghrelin stimulates upper gastrointestinal motility through the vagus and enteric nervous system. The aim of the present study therefore was to simultaneously investigate the effect of administration of ghrelin on upper gastrointestinal motility and to elucidate its mode of action by measuring plasma levels of gastrointestinal hormones in humans. MATERIALS AND METHODS: Nine healthy volunteers (four males; aged 22-35 years) underwent combined antroduodenal manometry and proximal stomach barostat study on two separate occasions at least one week apart. Twenty minutes after the occurrence of phase III of the migrating motor complex (MMC), saline or ghrelin 40 mug was administered intravenously over 30 minutes in a double blind, randomised, crossover fashion. Ghrelin, motilin, pancreatic polypeptide, glucagon, and somatostatin were measured by radioimmunoassay in blood samples obtained at 15-30 minute intervals. The influence of ghrelin or saline on MMC phases, hormone levels, and intraballoon volume was compared using paired t test, ANOVA, and chi(2) testing. RESULTS: Spontaneous phase III occurred in all subjects, with a gastric origin in four. Administration of ghrelin induced a premature phase III (12 (3) minutes, p<0.001; gastric origin in nine, p<0.05), compared with saline (95 (13) minutes, gastric origin in two). Intraballoon volumes before infusion were similar (135 (13) v 119 (13) ml; NS) but ghrelin induced a longlasting decrease in intraballoon volume (184 (31) v 126 (21) ml in the first 60 minutes; p<0.05). Administration of ghrelin increased plasma levels of pancreatic polypeptide and ghrelin but motilin, somatostatin, and glucagon levels were not altered. CONCLUSIONS: In humans, administration of ghrelin induces a premature gastric phase III of the MMC, which is not mediated through release of motilin. This is accompanied by prolonged increased tone of the proximal stomach.

Energy homeostasis and gastric emptying in ghrelin knockout mice.

To elucidate the role of endogenous ghrelin in the regulation of energy homeostasis and gastric emptying, ghrelin knockout mice (ghrelin(-/-)) were generated. Body weight, food intake, respiratory quotient, and heat production (indirect calorimetry), and gastric emptying ((14)C breath test) were compared between ghrelin(+/+) and ghrelin(-/-) mice. In both strains, the effect of exogenous ghrelin on gastric emptying and food intake was determined. Ghrelin(-/-) mice showed some subtle phenotypic changes. Body weight gain and 24-h food intake were not affected, but interruption of the normal light/dark cycle triggered additional food intake in old ghrelin(+/+) but not in ghrelin(-/-) mice. Exogenous ghrelin increased food intake in both genotypes with a bell-shaped dose-response curve that was shifted to the left in ghrelin(-/-) mice. During the dark period, young ghrelin(-/-) mice had a lower respiratory quotient, whereas their heat production was higher than that of the wild-type littermates, inferring a leaner body composition of the ghrelin(-/-) mice. Absence of ghrelin did not affect gastric emptying, and the bell-shaped dose-response curves of the acceleration of gastric emptying by exogenous ghrelin were not shifted between both strains. In conclusion, ghrelin is not an essential regulator of food intake and gastric emptying, but its loss may be compensated by other redundant inputs. In old mice, meal initiation triggered by the light/dark cue may be related to ghrelin. In young animals, ghrelin seems to be involved in the selection of energy stores and in the partitioning of metabolizable energy between storage and dissipation as heat.

Divergent role for CRF1 and CRF2 receptors in the modulation of visceral pain.

Both anti- and pro-nociceptive effects of corticotropin-releasing factor (CRF) treatment on visceral pain have been reported. Here, this dual action of CRF was differentiated by selective (in)activation of the CRF1 and CRF2 receptor prior to a visceral pain stimulus. Visceral pain was evaluated out of behavioural and visceromotor (abdominal electromyogram) responses to duodenal distension in the freely moving rat. Intraperitoneal (i.p.) CRF (50 microg kg-1) increased the distension-induced visceromotor and behavioural pain response. The pro-nociceptive effects of CRF on the behavioural response were attenuated by a selective CRF1 (CP-154526; 20 mg kg-1) but not a selective CRF2 [antiSauvagine30 (aSVG30); 100 microg kg-1] antagonist. Selective activation of the CRF2 receptor by stresscopin-related peptide (SRP; i.p. 25 microg kg-1) reduced the distension-induced visceromotor and behavioural response. Intrathecal injection of CRF (2 microg 10 microL-1) or SRP (20 microg 10 microL-1) decreased the distension-induced visceromotor and behavioural response. The antinociceptive effects of intrathecal CRF on the behavioural response were attenuated by aSVG30 (20 microg 10 microL-1) but not with CP-154526 (10 microg 10 microL-1). These findings indicate that the CRF1 receptor is involved in pro-nociception of visceral pain, whereas the CRF2 receptor is mainly involved in antinociception. This divergent role of the CRF subreceptors may explain the bimodal effects of CRF treatment on visceral nociception.

Telemetric animal model to evaluate visceral pain in the freely moving rat.

Several research groups have measured the visceromotor response to visceral distension by electromyography (EMG) in the conscious restraint, wrapped or lightly anaesthetized rat. Our aim was to develop a more physiological and stress-free technique that enables the simultaneous measurement of duodenal distension-induced visceromotor and cardiovascular responses in the conscious, freely moving rat. A telemetry transmitter, consisting of a bipolar electrode pair and arterial catheter, was chronically implanted into the rat to measure abdominal EMG, mean arterial pressure (MAP) and heart rate (HR). Furthermore, a balloon catheter was chronically implanted in the duodenum to deliver volume-fixed staircase (0.1-0.6 ml) or phasic (0.1, 0.3, 0.5 ml) distensions. The area under the curve (AUC; mVs) and maximal amplitude (EMG(max); mV) during distension were analyzed. The model was validated by pre-treatment with morphine (0.3, 1.5 and 3 mg/kg, intraperitoneally). Staircase and phasic distension produced a volume-dependent increase in AUC and EMG(max), HR and MAP. Pre-treatment with morphine inhibited the distension-induced visceromotor response, i.e. abdominal contractions, increase in AUC and EMG(max). These findings indicate that telemetry is an adequate tool to measure visceromotor and cardiovascular responses to averse, noxious duodenal distension continuously and simultaneously in the rats home cage, without additional handling-related or restraint-induced stress. The presented animal visceral model is intended for studying acute and chronic analgesic properties of new pharmaceutical compounds.

Influence of the selective serotonin re-uptake inhibitor, paroxetine, on gastric sensorimotor function in humans.

BACKGROUND: The role of 5-hydroxytryptamine in the control of gastric fundus tone in humans is still unknown. Selective 5-hydroxytryptamine re-uptake inhibitors act both centrally and peripherally to enhance the availability of physiologically released 5-hydroxytryptamine. AIM: To study the influence of a selective 5-hydroxytryptamine re-uptake inhibitor, paroxetine, on gastric fundus tone, on the perception to gastric distension and on gastric accommodation to a meal. METHODS: Sixteen healthy volunteers underwent a gastric barostat study on two occasions, after pre-treatment with placebo or paroxetine, 20 mg/day. Graded isobaric and isovolumetric distensions were performed and perception was scored by a questionnaire. Subsequently, the amplitude of the gastric accommodation to a mixed liquid meal was also measured. RESULTS: Pre-treatment with paroxetine did not alter the thresholds for perception and discomfort during isobaric (4.7 +/- 2.3 vs. 4.0 +/- 2.0 mmHg and 13.3 +/- 3.1 vs. 12.7 +/- 2.3 mmHg above the minimum intragastric distending pressure, N.S.) and isovolumetric (307 +/- 90 vs. 417 +/- 114 mL and 772 +/- 74 vs. 750 +/- 76 mL, N.S.) distensions. Paroxetine significantly enhanced the amplitude of the meal-induced fundus relaxation (136 +/- 51 vs. 255 +/- 43 mL, P < 0.05). CONCLUSIONS: Pre-treatment with paroxetine enhances gastric accommodation to a meal. These data suggest that the release of 5-hydroxytryptamine, probably at the level of the enteric nervous system, is involved in the control of the accommodation reflex in humans, and that paroxetine may be beneficial to patients with impaired post-prandial fundus relaxation.

Perception of changes in wall tension of the proximal stomach in humans.

BACKGROUND: Hypersensitivity to distension of the stomach is a frequent finding in functional dyspepsia. During gastric distension studies both wall tension and elongation are increased. AIM: We wished to distinguish changes in wall tension from changes in elongation in the genesis of perception of mechanical stimuli originating from the proximal stomach in healthy subjects. SUBJECTS AND METHODS: Twenty six volunteers were studied using gastric barostat and antroduodenal manometry. In 14 subjects, stepwise isobaric and isovolumetric distensions were performed before and during erythromycin infusion. In all volunteers, on a separate occasion, phasic contractions of the proximal stomach were detected as intraballoon pressure increases during fixed volume inflation. These contractions were matched with perception changes during two 10 minute periods, before and during administration of erythromycin. RESULTS: Erythromycin significantly lowered the perception and discomfort thresholds during stepwise gastric distension. During fixed volume inflation, erythromycin increased the number and amplitude of fundic contractions and enhanced their perception from 51.1 (7.4)% to 64.0 (4.7)%. The proportion of perception score increases coinciding with fundic contractions increased from 47.3 (0.7)% to 81.5 (0.5)%. The amplitude of correctly identified isolated fundic pressure waves was higher compared with non-identified waves. CONCLUSIONS: These results support the hypothesis that changes in gastric wall tension may be involved in the genesis of symptoms originating from the stomach.

Identification of peptide ligand-binding domains within the human motilin receptor using photoaffinity labeling.

The cDNA encoding the human motilin receptor was recently cloned and found to represent a G protein-coupled receptor that is structurally related to the growth hormone secretagogue receptors. Together, these represent a new Class I receptor family. Our aim in the present work is to gain insight into the molecular basis of binding of motilin to its receptor using photoaffinity labeling. To achieve this, we developed a Chinese hamster ovary cell line that overexpressed functional motilin receptor (CHO-MtlR; 175,000 sites per cell, with K(i) = 2.3 +/- 0.4 nm motilin and EC(50) = 0.3 +/- 0.1 nm motilin) and a radioiodinatable peptide analogue of human motilin that incorporated a photolabile p-benzoyl-l-phenylalanine (Bpa) residue into its pharmacophoric domain. This probe, [Bpa(1),Ile(13)]motilin, was a full agonist at the motilin receptor that increased intracellular calcium in a concentration-dependent manner (EC(50) = 1.5 +/- 0.4 nm). This photolabile ligand bound specifically and with high affinity to the motilin receptor (K(i) = 12.4 +/- 1.0 nm), and covalently labeled that molecule within its M(r) = 45,000 deglycosylated core. Cyanogen bromide cleavage demonstrated its covalent attachment to fragments of the receptor having apparent M(r) = 6,000 and M(r) = 31,000. These were demonstrated to represent fragments that included both the first and the large second extracellular loop domains, with the latter representing a unique structural feature of this receptor. The spatial approximation of the pharmacophoric domain of motilin with these receptor domains support their functional importance as well.