[Probiotic prophylaxis in patients with predicted severe acute pancreatitis: a randomised, double-blind, placebo-controlled trial]. / Probioticaprofylaxe bij voorspeld ernstige acute pancreatitis: een gerandomiseerde, dubbelblinde, placebogecontroleerde trial.

OBJECTIVE: To evaluate whether enteral prophylaxis with probiotics in patients with predicted severe acute pancreatitis prevents infectious complications. DESIGN: Multicentre, randomised, double-blind, placebo-controlled trial. METHOD: A total of 296 patients with predicted severe acute pancreatitis (APACHE II score > or = 8, Imrie score > or = 3 or C-reactive protein concentration > 150 mg/l) were included and randomised to one of two groups. Within 72 hours after symptom onset, patients received a multispecies preparation of probiotics or placebo given twice daily via a jejunal catheter for 28 days. The primary endpoint was the occurrence of one of the following infections during admission and go-day follow-up: infected pancreatic necrosis, bacteraemia, pneumonia, urosepsis or infected ascites. Secondary endpoints were mortality and adverse reactions. The study registration number is ISRCTN38327949. RESULTS: Treatment groups were similar at baseline with regard to patient characteristics and disease severity. Infections occurred in 30% of patients in the probiotics group (46 of 152 patients) and 28% of those in the placebo group (41 of 144 patients; relative risk (RR): 1.1; 95% CI: 0.8-1.5). The mortality rate was 16% in the probiotics group (24 of 152 patients) and 6% (9 of 144 patients) in the placebo group (RR: 2.5; 95% CI: 1.2-5.3). In the probiotics group, 9 patients developed bowel ischaemia (of whom 8 patients died), compared with none in the placebo group (p = 0.004). CONCLUSION: In patients with predicted severe acute pancreatitis, use of this combination of probiotic strains did not reduce the risk of infections. Probiotic prophylaxis was associated with a more than two-fold increase in mortality and should therefore not be administered in this category of patients.

The use of animal models to study bacterial translocation during acute pancreatitis.

Infection of pancreatic necrosis with intestinal flora is accepted to be a main predictor of outcome during severe acute pancreatitis. Bacterial translocation is the process whereby luminal bacteria migrate to extraintestinal sites. Animal models were proven indispensable in detecting three major aspects of bacterial translocation: small bowel bacterial overgrowth, mucosal barrier failure, and disturbed immune responses. Despite the progress made in the knowledge of bacterial translocation, the exact mechanism, origin and route of bacteria, and the optimal prophylactic and treatment strategies remain unclear. Methodological restrictions of animal models are likely to be the cause of this uncertainty. A literature review of animal models used to study bacterial translocation during acute pancreatitis demonstrates that many experimental techniques per se interfere with intestinal flora, mucosal barrier function, or immune response. Interference with these major aspects of bacterial translocation complicates interpretation of study results. This paper addresses these and other issues of animal models most frequently used to study bacterial translocation during acute pancreatitis.

A new intelligent distension system for hollow organs.

Controlled distension of hollow organs is an accepted technique for generating reproducible visceral stimuli. We have constructed a new, flexible and intelligent distension system in which discomfort, pain and autonomic responses are recorded online. These responses can be fed back into the system in a regulatory loop and be used to shape the distension paradigm. Consequently, it is possible to take all subjects to a state of equal, although subjective, level of discomfort or pain, even though pressure, tension and volume might be totally different. By using a variable airflow, this new distension system can be effectively used in all kinds of paradigms, e.g. phasic, tonic, or ramp distensions or customized combinations of them. The system can be used to control pressure, volume or tension. A refinement of the system is that it is possible to automatically change the controlled entity during a distension, e.g. from an isobaric ramp directly into an isovolumetric tonic phase. Furthermore, the distension device allows double distensions with independent distension paradigms.

[Potential role for probiotics in the prevention of infectious complications during acute pancreatitis]. / Potentiële rol voor probiotica bij de preventie van infectieuze complicaties tijdens acute pancreatitis.

Acute pancreatitis has a high mortality in case of secondary infection of (peri-)pancreatic necrosis. Bacterial translocation is held responsible for the majority of these infectious complications of severe acute pancreatitis. Prophylactic strategies should therefore be directed at the three most important pathophysiological mechanisms of bacterial translocation: disturbed small-bowel motility and bacterial overgrowth, failure of the mucosal barrier function and a disturbed response of the immune system. In-vitro studies and research in experimental animals have shown that specially selected probiotics exert an effect on these mechanisms and can prevent bacterial translocation. Recently, several randomised, double-blind, placebo-controlled trials evaluating prophylactic treatment with enteral probiotics have shown good results. A Dutch multicentre trial, 'Probiotics in pancreatitis trial' (PROPATRIA), is currently underway.

Relationships between air swallowing, intragastric air, belching and gastro-oesophageal reflux.

BACKGROUND: With each swallow a certain amount of air is transported to the stomach. The stomach protects itself against excessive distention by swallowed air through belching (gas reflux). The mechanism of belching (transient lower oesophageal sphincter relaxation) is also one of the mechanisms underlying gastro-oesophageal reflux. AIM: To investigate whether swallowing of air leads to an increase in size of the intragastric air bubble and to gastro-oesophageal reflux. METHODS: Multichannel intraluminal impedance measurement was used to quantify the incidence of swallowing of air in 20 healthy volunteers before and after a meal. Radiography was used to measure the size of the intragastric air bubble. Gastro-oesophageal reflux was assessed by concurrent impedance and pH measurement. RESULTS: The rate of air swallowing was correlated to the size of the intragastric air bubble postprandially and to the rate of gaseous gastro-oesophageal reflux. The number of air swallows and the size of the intragastric air bubble did not correlate with the number of liquid acid and non-acid reflux episodes. CONCLUSIONS: In healthy subjects, air swallowing promotes belching but does not facilitate acid reflux.

Relationship between the mechanism of gastro-oesophageal reflux and oesophageal acid exposure in patients with reflux disease.

This study investigated the relationship between the oesophageal acid exposure time and the underlying manometric motor events in patients with gastro-oesophageal reflux disease (GORD). In 31 patients, 3-hour oesophageal motility and pH were measured after a test meal. Ten patients underwent 24-hour ambulatory manometry and pH recording. In the 3-hour postprandial study, of 367 reflux episodes 79% was associated with a transient lower oesophageal sphincter relaxation (TLOSR), 14% with absent basal lower oesophageal sphincter (LOS) pressure and the remaining 7% with other mechanisms, representing 62, 28 and 10% of the acid exposure time, respectively. Acid reflux duration per motor mechanism was longer for absent basal LOS pressure than for TLOSR (189 +/- 23 s and 41 +/- 5 s, respectively, P < 0.001). In the 24-hour ambulatory study, the contribution of TLOSRs to reflux frequency vs acid exposure time were 65 vs 54% interprandially and 74 vs 53% after the meal. During the night, absence of basal LOS pressure accounted for 36% of reflux events representing 71% of acid exposure time. In conclusion, the duration of oesophageal acid exposure following a TLOSR is shorter than reflux during absent basal LOS pressure. TLOSRs are, the major contributor to oesophageal acid exposure during the day. At night, however, reflux during absent basal LOS pressure is the major contributor to acid exposure.

Abnormalities of antroduodenal motility in type I diabetes.

OBJECTIVE: In the present study, a recently developed manometric technique was used to study antroduodenal motility in ambulant type I diabetic subjects. RESEARCH DESIGN AND METHODS: In 12 patients with type I diabetes, antroduodenal manometry was performed for 20 h during the fasting period and the postprandial period after a standardized dinner and breakfast. All patients had evidence of cardiac autonomic neuropathy and complained of dyspeptic symptoms. During the manometric study, the blood glucose levels were frequently monitored and kept close to euglycemia in the diabetic patients. The results were compared with 12 healthy control subjects. RESULTS: The migrating motor complex cycles observed in the diabetic subjects were longer than in the control subjects, 118.9 +/- 46.0 vs. 87.0 +/- 21.6 min (P < 0.05). This increase was attributable to a prolonged phase II, 78.0 +/- 35.5 vs. 37.7 +/- 18.5 min (P < 0.05). In the diabetic subjects, antral phase III was seen significantly less than in the control subjects, 16.7 vs. 43.3% (P < 0.005). In 50% of the diabetic patients, total absence of antral phase III was observed-this phenomenon was not seen in the healthy control subjects. After dinner, the antral motility index was less in diabetic subjects compared with the healthy volunteers, indicating antral hypomotility (P < 0.01). Six diabetic patients showed abnormal duodenal activity such as early recurrence of phase III and bursts after dinner. No significant differences in antral motility index or in duodenal motility patterns were observed after breakfast. Six diabetic patients complained of dyspeptic symptoms after dinner, whereas none had dyspeptic symptoms after breakfast. In 67% of the patients, nausea was reported after an early phase III or a burst. CONCLUSIONS: This study shows that prolonged ambulatory antroduodenal manometry is a feasible technique in patients. Recording multiple migrating motor complexes showed that interdigestive motor abnormalities of the stomach and duodenum are common in diabetic patients. Furthermore, it shows the occurrence of antral hypomotility and abnormal duodenal motility patterns after a high-calorie meal, with dyspeptic symptoms in diabetic patients being related to the composition of the meal.

Effects of oral erythromycin on fasting and postprandial antroduodenal motility in patients with type I diabetes, measured with an ambulatory manometric technique.

OBJECTIVE: The aim of this double-blind crossover study was to evaluate the effects of oral erythromycin (250 mg t.i.d.) on fasting and postprandial gastrointestinal motility and gastrointestinal symptoms in patients with type I diabetes. RESEARCH DESIGN AND METHODS: Antroduodenal motility was recorded with an ambulatory manometric technique for a 20-h period, including a high-caloric high-fat dinner and a low-caloric low-fat breakfast and a long fasting period, after 2 weeks erythromycin and placebo treatment in 12 patients with type I diabetes. During the manometric study, plasma glucose concentrations were assessed by frequent self-testing. Gastrointestinal symptoms were scored daily to assess the severity of the symptoms (range 0-3). RESULTS: Oral erythromycin decreased the migrating motor complex cycle length from 118.9 +/- 46.0 to 86.2 +/- 25.3 min (P = 0.03) by shortening phase II from 68.7 +/- 23.5 to 48.5 +/- 19.4 min (P < 0.05). The total number of duodenal phase III increased from 48 to 62 (P = 0.075). However, the degree of antral participation to duodenal phase III did not increase. Erythromycin significantly decreased the duration of the postprandial period after dinner (from 417.0 +/- 137.9 to 348.8 +/- 93.8 min, P = 0.04). During this shorter postprandial period, the number of antral contractions (P < 0.01) and the antral motility index increased (P < 0.03), and early phase III activity at the level of the duodenum was abolished. In diabetic patients with antral hypomotility, after dinner, the mean symptom score improved significantly, from 2.07 +/- 0.86 to 1.52 +/- 0.63 (P = 0.018). CONCLUSIONS: This ambulatory antroduodenal manometric study showed that oral erythromycin (250 mg t.i.d.) improves both fasting and postprandial antroduodenal motor activity after a high-caloric meal in patients with type I diabetes. Furthermore, in diabetic subjects with postprandial antral hypomotility, erythromycin reduces dyspeptic symptoms.

Somal size and location within the ganglia for electrophysiologically identified myenteric neurons of the guinea pig ileum.

The main goal of the present study was to examine the possibility of electrophysiologically identifying the excitable enteric S and AH neurons by use of one single criterion. Intracellular recordings were made from 189 cells of 64 ganglia in isolated preparations of the myenteric plexus of the guinea pig distal ileum. The recordings were made under visual control of the cells by using Hoffman Modulation Contrast optics at high magnification (600x). From photomicrographs, the soma size and the location within the ganglion of the individual (unstained) cells were determined. The cells were classified into three types according to their electrical excitability and the shape of the action potential. Excitable cells were classified as AH cells (n = 84) if the action potential showed a shoulder on the falling phase, otherwise as S cells (n = 56). Cells in which no action potential could be evoked by current injection were classified as nonspiking (NS) cells (n = 49). The three classes of cells showed significant differences with respect to membrane potential, input resistance and fast synaptic input. The AH cells had significantly larger somata (P < 0.01) than the S cells. The NS cells were significantly smaller than the AH and S cells (P < 0.01). AH and S cells were found to be randomly located in the ganglia, whereas the NS cells clustered (P < 0.008) in close proximity to the onsets of internodal strands. We conclude that the shoulder of the action potential can be used as a single criterion to distinguish "on line" S and AH neurons unequivocally.

Effects of erythromycin on gastric emptying, alcohol absorption and small intestinal transit in normal subjects.

The effects of erythromycin on gastric emptying and intragastric distribution of a mixed solid/liquid meal, alcohol absorption and small intestinal transit were examined in eight male volunteers. Each subject received, in double-blind randomized order, either erythromycin as the lactobionate (3 mg.kg-1 i.v. over 20 min) or saline immediately before the consumption of a radioisotopically labeled test meal, which consisted of 330 g minced beef and 400 ml of orange juice containing ethanol (0.5 g.kg-1 body weight) and 10 g lactulose. Erythromycin increased the rate of total stomach emptying and proximal stomach emptying of both the solid and liquid components of the meal (p < 0.001), but slowed small intestinal transit (p < 0.01). Peak blood alcohol concentrations (p < 0.01) were higher after erythromycin, with a mean increase of 40%. There was a significant inverse relationship between peak blood alcohol concentrations and the 50% emptying time for the liquid component of the meal after saline (r = -0.70, p < 0.05), but not after erythromycin (r = -0.57, p < 0.1). The total area under the venous blood alcohol concentration time curve (i.e., total absorption) was greater (p < 0.01) after erythromycin. These results suggest that: faster emptying from the proximal stomach contributes to more rapid gastric emptying induced by erythromycin, erythromycin retards small intestinal transit and that erythromycin increases the total amount of alcohol absorbed as well as the rate of alcohol absorption. These latter effects are likely to reflect more rapid delivery of alcohol to the small intestine and reduced metabolism of alcohol by the gastric mucosa.

Nitric oxide is involved in 5-HT-induced relaxations of the guinea-pig colon ascendens in vitro.

1. In the guinea-pig colon ascendens, 5-hydroxytryptamine (5-HT) induces contractions, mediated by 5-HT2, 5-HT3 and 5-HT4 receptors, and relaxations, through a 5-HT1 receptor subtype, that triggers the release of an inhibitory neurotransmitter. Nitric oxide (NO) is one of the main candidates of NANC inhibitory neurotransmission in the gut. The aim of this study was to establish whether NO is involved in 5-HT-induced relaxations of the guinea-pig colon ascendens. 2. Antagonists to block the contractile responses to 5-HT via 5-HT2, 5-HT3 and 5-HT4 receptors were present throughout the experiments and methacholine was administered to precontract the strips. Under these conditions, 5-HT concentration-dependently induced relaxations from 10 nM onwards (EC50 = 258 (172-387) nM). The relaxations were inhibited by metergoline (10 nM) and methiothepine (100 nM) and abolished by tetrodotoxin (TTX, 320 nM). Guanethidine (3.2 microM) did not affect them. 3. NG-nitro-L-arginine (L-NNA) inhibited the responses to 5-HT (IC50 = 18.7 (13.3-26.3) microM); at the highest 5-HT concentration a maximum inhibition of about 75% was observed with 320 microM L-NNA. This inhibition was reversed with L-arginine. Relaxations to glyceryl trinitrate (GTN) were not inhibited by L-NNA. 4. Haemoglobin (32 microM) inhibited the relaxations to 5-HT and GTN, but not those to isoprenaline (Iso). Methylene blue (10 microM) inhibited the relaxations to 5-HT but did not affect those caused by GTN or Iso. 5. It is concluded that 5-HT induces relaxations that involve NO.We also confirmed that 5-HT induces these relaxations via (a) 5-HT, receptor subtype(s), located on neurones.

5-HT(4) receptors on cholinergic nerves involved in contractility of canine and human large intestine longitudinal muscle.

5-HT(4) receptors mediate circular muscle relaxation in both human and canine large intestine, but this phenomenon alone can not explain the improvement in colonic motility induced by selective 5-HT(4) receptor agonists in vivo. We set out to characterize 5-HT(4) receptor-mediated effects in longitudinal muscle strips of canine and human large intestine. Electrical field stimulation (EFS) was applied providing submaximal isotonic contractions. L-NOARG (0.1 mM) was continuously present in the organ bath to preclude nitric oxide-induced relaxation to EFS. The selective 5-HT(4) receptor agonist prucalopride (0.3 microM) enhanced EFS-evoked contractions, that were antagonized in both preparations by the selective 5-HT(4) receptor antagonist GR 113808 (0.1 microM). The prucalopride-induced increase was present in canine ascending and descending colon, but absent in rectum. Regional differences in response to prucalopride were not observed in human ascending and sigmoid colon and rectum. Incubation with atropine (1 microM) or tetrodotoxin (0.3 microM) inhibited EFS-induced contractions, which were then unaffected by prucalopride (0.3 microM) in both tissues. In the presence of methysergide (3 microM; both tissues) and granisetron (0.3 microM; only human tissues), 5-HT (0.3 microM) enhanced EFS-induced contractions, an effect that was antagonized by GR 113808 (0.1 microM). In the presence of atropine or tetrodotoxin, EFS-induced contractions were inhibited, leaving 5-HT (0.3 microM) ineffective in both preparations. This study demonstrates for the first time that in human and canine large intestine, 5-HT(4) receptors are located on cholinergic neurones, presumably mediating facilitating release of acetylcholine, resulting in enhanced longitudinal muscle contractility. This study and previous circular muscle strip studies suggest that 5-HT(4) receptor agonism facilitates colonic propulsion via a coordinated combination of inhibition of circumferential resistance and enhancement of longitudinal muscle contractility.

5-HT(4) receptors mediating enhancement of contractility in canine stomach; an in vitro and in vivo study.

We aimed to study 5-HT(4) receptors in canine stomach contractility both in vivo and in vitro. In anaesthetized Beagle dogs, the selective 5-HT(4) receptor agonist prucalopride (i.v.) induced dose-dependent tonic stomach contractions under isobaric conditions, an effect that was antagonized by the selective 5-HT(4) receptor antagonist GR 125487 (10 microg kg(-1), i.v.). Electrical field stimulation (EFS) of corpus longitudinal muscle strips resulted in atropine- and tetrodotoxin-sensitive contractions (L-NOARG (0.1 mM) present in all organ bath solutions). Prucalopride increased these contractions (maximal response after single-dose addition (0.3 microM): 165% of initial value, or after cumulative addition: 188%). In the presence of methysergide (3 microM), 5-HT also increased EFS-contractions (after single-dose addition (0.3 microM): increase to 192%, after cumulative addition: 148%). The selective 5-HT(4) receptor antagonists GR 113808 (0.1 microM) or GR 125487 (10 nM) antagonized the prucalopride (0.3 microM)-induced contraction increments. When EFS-induced contractions were blocked by atropine or tetrodotoxin, prucalopride was ineffective. In the presence of methysergide (3 microM), the contraction increases to 5-HT (0.3 microM) were prevented by GR 113808 (0.1 microM). The prucalopride curve (pEC(50) 7.9) was shifted in parallel to the right by GR 113808 3 nM (pA(2) 9.4). In the presence of methysergide (3 microM), the curve to 5-HT (pEC(50) 8.1) was competitively antagonized by GR 113808, yielding a Schild slope of 0.8+/-0.2 (pK(B) of 9.1 with unit Schild slope). In corpus circular muscle strips, the prucalopride (0.3 microM)-induced augmentation of EFS-contractions (258%) was also prevented by GR 113808 (0.1 microM) (124%). In conclusion, the effects of 5-HT(4) receptor agonists on proximal stomach motor activity in vivo can be explained by an effect on 5-HT(4) receptors on cholinergic nerves within the gastric muscle wall.

Characterization of the receptors involved in the 5-HT-induced excitation of canine antral longitudinal muscle.

1. We aimed to characterize the 5-HT receptors involved in the 5-HT-induced effect on electrically induced contractions of dog antrum longitudinal muscle in vitro. 2. In the presence of L-NOARG (0.1 mM), electrical field stimulation (EFS) induced atropine- and tetrodotoxin-sensitive contractions. Tetrodotoxin or atropine left any agonist tested ineffective. These EFS-induced contractions were on average enhanced by 5-HT (0.3 microM), however, pronounced variation in the response to 5-HT was observed. There were non-significant trends of the selective 5-HT3 receptor antagonist granisetron (1 microM), and methysergide (1 microM; preventing interactions of 5-HT with 5-HT1, 5-HT2, 5-ht5, 5-HT6 and 5-HT7 receptors) to increase the response to 5-HT. The selective 5-HT4 receptor antagonist GR 113808 (0.1 microM) displayed a non-significant trend to inhibit the 5-HT-induced increase. 3. Combination experiments with methysergide (1 microM), granisetron (1 microM) and GR 113808 (0.1 microM) revealed that the 5-HT (0.3 microM)-induced response consisted of (1) an excitatory component blocked by GR 113808, (2) excitatory and inhibitory components both blocked by methysergide. 4. The selective 5-HT4 receptor agonist prucalopride (0.3 microM) increased EFS-induced contractions, an effect prevented by GR 113808 (0.1 microM). 5. The increase of EFS-induced contractions by the preferential 5-HT2 receptor agonist alpha-Me-5-HT (0.3 microM) was antagonized by 5-HT2B receptor antagonists. 6. The 5-HT1/5-HT7 receptor agonist 5-carboxamidotryptamine (5-CT; 0.3 microM) inhibited EFS-induced contractions. This was prevented by methysergide (1 microM), the 5-HT7 receptor antagonist mesulergine (0.3 microM) and the selective 5-HT7 receptor antagonist SB-269970 (0.3 microM). 7. In the presence of GR 113808 (0.1 microM), alpha-Me-5-HT (1 microM) increased EFS-induced contractions. The 5-HT (0.3 microM)-induced inhibition of the stimulation by alpha-Me-5-HT was prevented by SB-269970 (0.3 microM). 8. In conclusion, dog antral longitudinal muscle is endowed with (1) excitatory neuronal 5-HT4 receptors and 5-HT2B receptors and (2) inhibitory smooth muscle 5-HT7 receptors.

Evidence for 5-HT7 receptors mediating relaxation of human colonic circular smooth muscle.

5-HT4 receptors mediate relaxation of human colon circular muscle. However, after 5-HT4 receptor blockade (SB 204070 10 nM), 5-HT still induced a relaxation (pEC50 6.3). 5-HT4 receptors were sufficiently blocked, as the curves to 5-HT obtained in the presence of 10 and 100 nM SB 204070 were indistinguishable. This 5-HT-induced relaxation was tetrodotoxin-insensitive, indicative of a smooth muscle relaxant 5-HT receptor. This, and the rank order of potency (5-CT=5-MeOT=5-HT) suggested involvement of 5-HT1 or 5-HT7 receptors. Mesulergine, a 5-HT7 receptor antagonist at nanomolar concentrations, and a 5-HT1 receptor antagonist at micromolar concentrations, competitively antagonized the 5-HT-induced relaxation (pKB 8.3) and antagonized the relaxation to 5-CT. Methysergide antagonized the 5-HT-induced relaxation (pA2 7.6). It is concluded that the profile of the smooth muscle inhibitory 5-HT receptor resembles that of the 5-HT7 receptor. These data provide the first evidence for functional human 5-HT7 receptors.

An improved in vitro bioassay for the study of 5-HT(4) receptors in the human isolated large intestinal circular muscle.

Recently, it was demonstrated that 5-HT induces relaxation of human colon circular muscle through activation of 5-HT(4) receptors and 5-HT(7) receptors. The aim of the current study was to develop a new in vitro bioassay of human colon that would facilitate the pharmacological analysis of 5-HT responses mediated solely by 5-HT(4) receptors. Contracting circular muscle strips with KCl (80 mM) yielded a stable contractile tension and, in contrast to muscarinic cholinoceptor agonists and histamine, a profound reduction of spontaneous contractility. This allowed the establishment of reproducible, fully-defined, agonist concentration-response curves by cumulative dosing. Under these conditions, 5-HT induced a concentration-dependent relaxation (pEC(50) 7.31, Hill slope 0.91). Neither methysergide (10 microM) nor granisetron (1 microM) affected the 5-HT-induced relaxation, suggesting that 5-HT(1), 5-HT(2), 5-HT(3), 5-ht(5), 5-HT(6) or 5-HT(7) receptors are not involved. The lack of effect of tetrodotoxin (0.3 microM) indicated a direct effect of 5-HT on the smooth muscle. The selective 5-HT(4) receptor antagonists GR 113808, GR 125487 and RS 39604 competitively antagonized the 5-HT-induced relaxation (pK(B) 9.43, 10.12 and 8.53, respectively). SB 204070 (1 nM) produced a rightward shift (pA(2) 10.34) and depression of the 5-HT curve. These affinity estimates are similar to those previously reported for 5-HT(4) receptors. The selective 5-HT(4) receptor agonists, prucalopride and R076186, induced relaxations (pEC(50) 7.50 and 7.57, respectively), that were blocked by GR 113808 (3 nM), yielding pA(2) estimates of 9.31 and 9.21, respectively. To summarise, in KCl (80 mM)-contracted muscle strips, 5-HT induces relaxation through activation of a homogeneous smooth muscle 5-HT(4) receptor population. This new bioassay allows the focused, pharmacological characterization of human colonic 5-HT(4) receptors in vitro.

Pharmacological characterization of 5-HT4 receptors mediating relaxation of canine isolated rectum circular smooth muscle.

This study aimed to characterize for the first time in vitro 5-HT4 receptors in the canine gastrointestinal tract. For this purpose, we used circular muscle strips of the canine isolated rectum. In the presence of methysergide (60 microM), 5-HT induced relaxation of methacholine (1 microM)-precontracted muscle strips, yielding a monophasic sigmoidal concentration-relaxation curve (pEC50 7.2+/-0.07). Tetrodotoxin (0.3 microM) did not affect the curve to 5-HT, suggesting the inhibitory 5-HT receptor is located on the smooth muscle. Granisetron (0.3 microM) did also not affect the curve to 5-HT, which excludes the 5-HT3 receptor mediating the relaxation to 5-HT. The presence of methysergide rules out the involvement of 5-HT1, 5-HT2 or 5-HT7 receptors. 5-HT, the selective 5-HT4 receptor agonists R076186, prucalopride (R093877) and SDZ HTF-919 and the 5-HT4 receptor agonists cisapride and 5-MeOT relaxed the muscle strips with a rank order of potency R076186 = 5-HT > cisapride > prucalopride > or = SDZ HTF-919 > 5-MeOT. The selective 5-HT4 receptor antagonists GR 125487, RS 39604 and GR 113808 competitively antagonized the relaxations to 5-HT, yielding pK(B) estimates of 9.7, 7.9 and 9.1, respectively. The selective 5-HT4 receptor antagonist SB 204070 shifted the curve to 5-HT rightward and depressed the maximal response (apparent pA2 10.6). GR 113808 (10 nM) produced a parallel rightward shift of the curve to the selective 5-HT4 receptor agonists R076186 (pA2 8.8). It is concluded that 5-HT induces relaxation of the canine rectum circular muscle through stimulation of a single population of smooth muscle 5-HT4 receptors. For the first time, a nonhuman species was shown to exhibit relaxant 5-HT4 receptors in the large intestine.

The effect of cisapride on duodenal acid exposure in the proximal duodenum in healthy subjects.

AIM: To investigate the effect of the prokinetic drug, cisapride, on fasting and postprandial acid exposure in the proximal duodenum. METHODS: Using a double-blind, placebo-controlled crossover study design, 12 healthy male volunteers were studied. After 1 week of dosing (cisapride 20 mg b.d. orally or placebo), fasting and postprandial antroduodenal pH-and pressure-recordings were made. Using a small-caliber (4 mm) catheter, containing one antral and two duodenal pH electrodes, and two antral and three duodenal pressure recording sites. Transmucosal potential difference was measured to ensure proper catheter position. Infusions of 0.1 N HCl were given in the duodenal bulb. RESULTS: Endogenous acidification of the duodenal bulb occurred more frequently during phase II and postprandially, compared to phase I (P<0.001). During phase I, alkalinization of the antrum was observed. Cisapride significantly increased the postprandial number of duodenal acidic periods (P<0.02), but shortened their duration (P<0.04). The duodenal motor response elicited by exogenous acid was lower during phase I (P<0.05). CONCLUSIONS: Antral and proximal duodenal acidity vary with the phases of the interdigestive motor complex. Cisapride shortens the individual periods of duodenal acidification.

The effects of the specific 5HT(4) receptor agonist, prucalopride, on colonic motility in healthy volunteers.

BACKGROUND: Prucalopride is a selective and specific 5-hydroxytryptamine(4) receptor agonist that is known to increase stool frequency and to accelerate colonic transit. AIM: To investigate the effect of prucalopride on high-amplitude propagated contractions and segmental pressure waves in healthy volunteers. METHODS: After 1 week of dosing (prucalopride or placebo in a double-blind, randomized, crossover fashion), colonic pressures were recorded in 10 healthy subjects using a solid-state pressure catheter with six sensors spaced 10 cm apart. Subjects kept diary records of their bowel habits (frequency, consistency and straining). High-amplitude propagated contractions were analysed visually, comparing their total numbers and using 10-min time windows. Segmental pressure waves were analysed using computer algorithms, quantifying the incidence, amplitude, duration and area under the curve of all detected peaks. RESULTS: When taking prucalopride, stool frequency increased, consistency decreased and subjects strained less. Prucalopride just failed to increase the total number of high-amplitude propagated contractions (P=0.055). The number of 10-min time windows containing high-amplitude propagated contractions was increased by prucalopride (P=0.019). Prucalopride increased the area under the curve per 24 h (P=0.026). CONCLUSIONS: The 5-hydroxytryptamine(4) receptor agonist prucalopride stimulates high-amplitude propagated contractions and increases segmental contractions, which is likely to be the underlying mechanism of its effect on bowel habits in healthy volunteers.

The effect of omeprazole on gastro-oesophageal reflux and symptoms during strenuous exercise.

BACKGROUND: Strenuous exercise exacerbates gastro-oesophageal reflux and symptoms and this may be diminished by antisecretory medication with omeprazole. METHODS: Fourteen well-trained athletes (13 men, one woman), who indicated suffering from either heartburn, regurgitation or chest pain during competition running, performed two experimental trials at 2-week intervals using a randomized, double-blind, placebo-controlled crossover design. During the 6 days preceding the trial and on the trial day itself either 20 mg of omeprazole or a placebo was administered. Two hours after a low-fat breakfast and 1 h after the last study dose, the trial started with five successive 50-min periods: rest, three running periods on a treadmill, and recovery. Reflux (percentage time and number of periods oesophageal pH <4) was measured with an ambulant pH system during these periods. RESULTS: Compared to rest, reflux lasted significantly longer and occurred more frequently during the first running period, irrespective of the intervention, whereas during the second running period this effect was only observed with the placebo. Reflux occurred for longer and more frequently with the placebo than with omeprazole, but this was significant during the first two running periods only. Seven subjects reported heartburn, regurgitation and/or chest pain during exercise, irrespective of the intervention. Only a minority of the symptom periods was actually associated with acid reflux and in all cases this concerned periods with heartburn. CONCLUSIONS: Running-induced acid reflux, but not symptoms, were decreased by omeprazole, probably because most symptoms were not related to acid reflux.