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The use of superoxide dismutases (SODs) in inflammatory diseases is hampered by their short circulatory half-life. To determine whether a bacterial supply of SOD into the colon might improve an experimental colitis, the effects of oral treatment with live recombinant lactic acid bacteria producing different amounts of SOD and those of colonic infusion of SOD were compared. Wistar rats were fitted with a catheter in the proximal colon through which TNBS was administered to induce colitis. Animals received a continuous intracolonic infusion of bovine SOD (40 U per rat per day) for 4 days after TNBS or were treated orally with live recombinant Lactococcus lactis or Lactobacillus plantarum strains (10 colony-forming units (CFU)/d), producing or not producing SOD, for 4 days before and after TNBS. SOD activity of bacterial extracts was 0, 26, 74, and 624 units/10 CFU for L. plantarum, L. lactis, L. lactis SOD, and L. plantarum SOD, respectively. Four days after TNBS, macroscopic and microscopic damage, myeloperoxidase (MPO) activity, and nitrotyrosine immunostaining were evaluated. TNBS induced macroscopic and microscopic damages, an increase in MPO activity, and intense immunostaining for nitrotyrosine. Macroscopic damage and MPO activity were reduced by bovine SOD. These parameters and microscopic damages also were reduced by L. lactis, L. lactis SOD, and L. plantarum SOD, but not by L. plantarum. Nitrotyrosine immunostaining was attenuated after treatment with the 4 bacterial strains. Although not all of the anti-inflammatory effects could be attributed directly to SOD, our results suggest that SOD-producing lactic acid bacteria open a novel approach in inflammatory bowel disease treatment.

Activation of cannabinoid CB1 and CB2 receptors is known to attenuate nociception and hyperalgesia in somatic inflammatory conditions. The aim of this study was to determine whether cannabi- noids modulate colonic sensitivity in basal and in- flammatory conditions. The effects of CB1 and CB2 receptor agonists and antagonists on the abdominal contractile response to colorectal distension (CRD) in basal conditions and after 2,4,6-trini- trobenzenesulphonic acid-induced colitis were investigated. As previously described, colitis triggered a hypersensitivity to CRD. In basal conditions, both CB1 (WIN 55212-2) and CB2 (JWH 015) agonists reduced the abdominal response to CRD at a dose of 1m g kg )1 , i.p. Both compounds were active at a lower dose (0.1 mg kg )1 ) abolishing the hypersensitivity induced by colitis. Administered alone, CB1 (Rimonabant) and CB2 (SR 144528) receptor antago- nists (10 mg kg )1 ) had no effect on basal sensitivity. In contrast, the CB1, but not the CB2, receptor antagonist enhanced colitis-induced hyperalgesia. It is concluded that colonic inflammation enhances the antinociceptive action of CB1 and CB2 receptor agonists, and activates an endogenous, CB1 receptor mediated, antinociceptive pathway.

Alcohol hepatic toxicity in heavy drinkers is associated with high endotoxin blood levels and increased intestinal permeability. Because endotoxins can cross damaged mucosa, we investigated the mechanisms through which ethanol impairs the colonic epithelium of rats submitted to acute alcohol intake. Colonic permeability to (51)Cr-ethylenediamintetraacetic acid was increased 24 hours after 3.0 g/kg ethanol intake (3.2 +/- 0.2% versus 2.2 +/- 0.2%) and was associated with significant endotoxemia. Antibiotics and doxantrazole (a mast cell membrane stabilizer) significantly inhibited the effect of ethanol. Two hours after intake, plasma concentrations of ethanol were twofold higher in antibiotic-treated rats than in controls (155.8 +/- 9.3 mg/dl versus 75.7 +/- 7.6 mg/dl, P0.001). Lumenal concentrations of acetaldehyde were markedly increased after ethanol intake (132.6 +/- 31.6 micromol/L versus 20.8 +/- 1.4 micromol/L, P0.05) and antibiotics diminished this increase (86.2 +/- 10.9 micromol/L). In colonic samples mounted in Ussing chambers, acetaldehyde but not ethanol increased dextran flux across the mucosa by 54%. Doxantrazole inhibited the effect of acetaldehyde. This study demonstrates that an acute and moderate ethanol intake alters the epithelial barrier through ethanol oxidation into acetaldehyde by the colonic microflora and downstream mast cell activation. Such alterations that remain for longer periods could result in excessive endotoxin passage, which could explain the subsequent endotoxemia frequently observed in patients with alcoholic liver disease.

Background: Stress induced increase in colonic paracellular permeability results from epithelial cell cytoskeleton contraction and is responsible for stress induced hypersensitivity to colorectal distension (CRD). The probiotic Lactobacillus farciminis releases spontaneously nitric oxide (NO) in the colonic lumen in vivo and exerts anti-inflammatory effects. This study aimed: (i) to evaluate the effects of L farciminis on stress induced hypersensitivity to CRD and increase in colonic paracellular permeability; and (ii) to ascertain whether these effects are NO mediated and related to changes in colonocyte myosin light chain phosphorylation (p-MLC). Methods: Female Wistar rats received either 10 11 CFU/day of L farciminis or saline orally over 15 days before partial restraint stress (PRS) or sham-PRS application. Visceral sensitivity to CRD and colonic paracellular permeability was assessed after PRS or sham-PRS. Haemoglobin was used as an NO scavenger. Western blotting for MLC kinase, MLC, and p-MLC were performed in colonic mucosa from L farciminis treated and control rats after PRS or sham-PRS. Results: PRS significantly increased the number of spike bursts for CRD pressures of 30–60 mm Hg as well as colonic paracellular permeability. L farciminis treatment prevented both effects, while haemoglobin reversed the protective effects of L farciminis . p-MLC expression increased significantly from 15 to 45 minutes after PRS, and L farciminis treatment prevented this increase. Conclusion: L farciminis treatment prevents stress induced hypersensitivity, increase in colonic paracellular permeability, and colonocyte MLC phosphorylation. This antinociceptive effect occurs via inhibition of contraction of colonic epithelial cell cytoskeleton and the subsequent tight junction opening, and may also involve direct or indirect effects of NO produced by this probiotic.

Over the past 30 years, the main treatment of irritable bowel syndrome has aimed to normalize gastrointestinal transit using either laxatives or antidiarrheal agents, with or without the concurrent use of spasmolytics. The recent introduction of serotonin-related drugs has stimulated investigations into the pathophysiology of irritable bowel syndrome, including an evaluation of visceral sensitivity. At the same time, more information has been acquired on the status of the local immune system as a possible cause for sensitization of nerve terminals. Such investigations have stimulated the emergence of new concepts and original candidate drugs for the treatment of this functional disorder. Particular attention is devoted to the correction of visceral hyperalgesia.

Neonatal stress is known to alter immune responses in adults and parasitic infection is modulated by the immune status of the host. The present study aimed to establish whether neonatal maternal deprivation affects the time course of Nippostrongylus brasiliensis infection and associated intestinal alterations in adult rats. Rat pups were separated from their dam 3 h daily during postnatal days 2–14, or left undisturbed. At 12 weeks of age, N. brasiliensis infection was induced by subcutaneous administration of 3000 L3 larvae. At 7 and 12 days after primary infection, the number of intestinal adult worms, fecal egg output, jejunal paracellular permeability, and myeloperoxidase (MPO) activity were measured. On days 7 and 12 after a secondary infection, numbers of adult worms and egg production were determined. Maternal deprivation increased the number of jejunal adult worms and fecal eggs and larvae on day 7 after primary infection, and exacerbated the increase in jejunal MPO activity induced by the infection. On day 12, adult worms were only observed in deprived rats. N. brasiliensis infection did not potentiate the increase in jejunal paracellular permeability induced by maternal deprivation. After the second infection, no egg was detected in both control and deprived rats. In conclusion, maternal deprivation in rats facilitates primary infection by N. brasiliensis and enhances the inflammatory response of the jejunum, but does not induce severe breakdown of immunity to N. brasiliensis .

The impact of colitis on uterine contractility and estrous cycle was investigated after intracolonic administration of 2,4,6-trinitrobenzenesulfonic acid (TNBS) in rats. Colitis severity was assessed by macroscopic damage scoring (MDS) 4 days after TNBS, and myeloperoxidase (MPO) activity was measured in both colon and uterus of control and colitic rats. Estrous cycle stages were determined by vaginal smears and histology, and uterine contractility was assessed in vitro on longitudinal and circular strips. In control rats, uterine MPO activity varied markedly during the cycle and peaked around estrus. In rats with moderate colitis [MDS < 5, 3.1 ± 0.2 (mean ± SE)], uterine MPO decreased by 61% compared with estrus control, without disruption of the cycle. Frequency of spontaneous contractions was reduced by 32% in circular muscle. Contractile responses to KCl and carbachol were not affected, whereas maximal response to oxytocin decreased by 47% in the longitudinal muscle. In rats with severe colitis (MDS > 5, 6.0 ± 0.2), uterine MPO was reduced by 96% and estrous cycle was disrupted. Spontaneous contractility was impaired in circular strips, and a 39% decrease in the contraction frequency occurred in the longitudinal strips. Circular strips did not contract to KCl or carbachol; however, longitudinal strips had maximal responses to KCl, carbachol, and oxytocin reduced by 36%, 27%, and 46%, respectively. Estrogen replacement protected the uterine responses to carbachol in colitic rats, whereas oxytocin responses remained depressed. These data indicate that colonic inflammation can influence both spontaneous and evoked uterine contractility, in relation to estrous cycle disturbances, impaired estradiol production, and functional alterations of myometrial cells.

Hypersensitivity to rectal or colonic distension characterizes most patients with IBS and increased gut permeability has been described in post-dysenteric IBS patients. However, no link has been established between these two events. The aim of this study was to determine (i) whether chemical blockade of stress-induced increase of colonic paracellular permeability by 2,4,6 triaminopyrimidine (TAP) affects the concomitant hypersensitivity to colonic distension, (ii) the role of epithelial cell contraction in the stress-induced increased permeability and hyperalgesia, using a myosin light chain kinase inhibitor (ML-7). The effect of acute partial restraint stress (PRS) on visceral sensitivity to colorectal distension (RD) was assessed by abdominal muscle electromyography. Colonic paracellular permeability was determined by measuring percentage of urinary 51Cr-EDTA recovery after intracolonic infusion. The effect of stress on both parameters was evaluated after TAP, ML-7 or vehicle pretreated animals. PRS significantly increased colonic paracellular permeability and the number of spike bursts for all volumes of RD applied compared to sham. TAP suppressed the stress-induced increase of colonic paracellular permeability and sensitivity to colonic distension. Similarly, ML-7 blocked the stress-induced increase of colonic paracellular permeability and sensitivity. Neither ML-7 nor TAP had any effect on both permeability and sensitivity in absence of stress. The increase of colonic permeability induced by PRS results from epithelial cell cytoskeleton contraction through myosin light chain kinase activation and this increase is responsible for stress-induced rectal hypersensitivity.

International audience; Although annexin l exerts extracellular anti-inflammatory properties, little is known about its release in inflammatory diseases. Here, we characterized annexin 1 secretion in ulcerative colitis (UC) patients. Annexin 1 was detected by immunoblotting, in tissue homogenates and supernatants of colonic biopsies incubated in culture media, and in luminal colonic perfusates of UC patients. Annexin 1 was released by inflamed colonic biopsies from patients having severe UC but not by biopsies from healthy colon of the same patient or by biopsies from non-UC patients or from patients with slight or moderate UC. Annexin 1 was detected in luminal colonic perfusates of patients having moderate or slight UC but not in perfusates from control patients. The level of annexin 1 expression and secretion was unrelated to long-term glucocorticoid treatment, but annexin 1 secretion in perfusates was induced, in some patients, by short-term glucocorticoid exposure. These results show that annexin 1 is secreted endogenously in the colon of patients with UC. This secretion, which occurs both in vitro and in vivo, depends on the severity of inflammation. Given the anti-inflammatory effects of annexin 1, this protein may serve to down-regulate the inflammatory response in the course of inflammatory bowel disease.

Activation of colonic proteinase-activated receptor-2 (PAR(2)) caused inflammation and increased mucosal permeability in mouse colon. The present study was aimed at characterizing the possible links between these two phenomena. We evaluated the effects of intracolonic infusion of PAR(2)-activating peptide, SLIGRL, on colonic paracellular permeability and inflammation at two different doses, 5 and 100 microg per mouse, in an attempt to discriminate between both PAR(2)-mediated effects. We further investigated the possible involvement of interferon gamma (IFN-gamma) and calmodulin-dependent activation of myosin light chain kinase (MLCK), and alterations of zonula occludens-1 (ZO-1) localization in PAR(2)-induced responses. Thus, at the lower dose, SLIGRL increased colonic permeability without causing inflammation. Western blotting showed phosphorylation of mucosal myosin light chain (MLC) expression after both doses of SLIGRL. Moreover, while the MLCK inhibitor, ML-7, abolished the permeability effects of the low dose of SLIGRL, it only partially inhibited that of the high dose. In IFN-gamma-deficient mice (B6 ifng(-/-)), the increases in permeability were similar for both doses of SLIGRL and prevented by ML-7. In addition, MLCK immunoprecipitation revealed an increase of calmodulin binding to MLCK in the mucosa of mice treated with either dose of SLIGRL. Finally, we have shown that direct activation of PAR(2) on enterocytes is responsible for increased permeability and ZO-1 disruption. Moreover, SLIGRL at a dose that does not produce inflammation increases permeability via calmodulin activation, which binds and activates MLCK. The resulting tight junction opening does not depend upon IFN-gamma secretion, while the increased permeability in response to the high dose of PAR(2) agonist involves IFN-gamma secretion.

Background: Stressful events in the early period of life (for example, maternal deprivation) have been shown to modify adult immune and gastrointestinal tract functions. The present study aimed to establish whether maternal deprivation affects colonic epithelial barrier and the development of an experimental colitis in adult rats. Methods: Male Wistar rat pups were separated during postnatal days 2–14 or left undisturbed with their dam. At 12 weeks of age, we assessed colonic paracellular permeability, bacterial translocation, myeloperoxidase (MPO) activity, mucosal mast cell density, cytokine (interleukin (IL)-1β, IL-2, IL-4, IL-10, and interferon γ (IFN-γ)) mRNA expression, and macroscopic damage. Total gut permeability, MPO activity, and macroscopic damage were also assessed four days after intracolonic administration of 2,4,6-trinitrobenzenesulphonic acid (TNBS). Results: Maternal deprivation triggered a significant increase in colonic permeability associated with bacterial translocation into the mesenteric lymph nodes, liver, and spleen. These alterations were associated with some macroscopic damage and an increase in colonic MPO activity, mucosal mast cell density, and cytokine mRNA expression. Intracolonic infusion of TNBS induced a significantly higher inflammatory reaction in separated animals, as judged by enhanced MPO colonic levels, total gut permeability, and macroscopic lesions. Conclusions: Maternal deprivation promotes long term alterations in the colonic epithelial barrier associated with an exaggerated immune response to an external immune stimulus. This suggests a role for early psychological factors in the regulation of colonic mucosal barrier in later life.

Background & Aims: Stressful life events are supposed to be involved in various diseases such as inflammatory bowel diseases and irritable bowel syndrome. Impairment of the intestinal epithelial barrier function is a suspected consequence of stress, but the underlying mechanisms remain unclear. This study aimed to determine the mechanisms through which stress modulates the colonic epithelial barrier. Methods: Cytokine messenger RNA (mRNA) expression was evaluated in murine colon, liver, and spleen by competitive reverse-transcription polymerase chain reaction after 1–4 days of daily 2-hour stress sessions. Colonic paracellular permeability was measured as the in vivo lumen-to-blood ratio of 51 Cr-ethylenediaminetetraacetic acid. The effect of a myosin light chain (MLC) kinase inhibitor (ML-7) was assessed on stress-induced interferon (IFN)-γ mRNA expression and colonic epithelial barrier impairment, and MLC phosphorylation was determined by immunoblot. Finally, the incidence of repeated stress sessions on bacterial translocation was determined. Results: Repeated stress induced an overexpression of colonic IFN-γ. In the liver, higher levels of IFN-γ, interleukin (IL)-4, and IL-10 mRNAs were detected and were associated with bacterial translocation, inflammation, and apoptosis. Stress increased colonic permeability of control mice, but not of SCID and IFN-γ-deficient mice. ML-7 inhibited the stress-induced increased permeability, bacterial translocation, and cytokine overexpression in the liver and restored a normal histology. Larger amounts of phosphorylated MLC were detected in stressed animals. Conclusions: Repeated stress sessions drive organ-specific cytokine expression patterns and alter colonic mucosal barrier functions associated with bacterial translocation. This effect depends on the presence of CD4 + T cells and requires IFN-γ production and MLC phosphorylation.

Capsaicin-sensitive afferent nerves are described as being protective against gastric inflammation; their destruction leads to an exacerbation of inflammatory processes. However, these nerves have been shown to exert a pro-inflammatory action on stress-induced gastritis in rats. Our study aimed to investigate the role of capsaicin-sensitive afferent nerves in different experimental models of gastritis in rats. Functional ablation of sensory nerves was achieved by systemic capsaicin treatment (100 mg/kg). Gastritis was induced by mild (iodoacetamide, diquat, surgical duodeno-gastric reflux [DGR]) and strong (70% ethanol, indomethacin) inflammatory agents. Antagonists of the CGRP1 and NK1 receptors, hCGRP8-37 and SR140333, were administered in rats treated with iodoacetamide and ethanol. Macroscopic damage scores (MDS), myeloperoxidase (MPO) activity and malondialdehyde (MDA) concentration were evaluated after sacrifice. Macroscopic lesions appeared only in ethanol and indomethacin gastritis and were enhanced by capsaicin treatment. Gastric MPO activity was significantly increased by all agents compared to controls. Capsaicin treatment did not have any effect on MPO activity in indomethacin-treated rats or in rats submitted to surgery for duodeno-gastric reflux. However, it abolished the increase in MPO induced by iodoacetamide and diquat, and significantly enhanced that induced by ethanol. hCGRP8-37 and SR140333 abolished the increase in MPO activity and MDA concentration in iodoacetamide treated rats. In ethanol-treated rats, SR140333 diminished MPO activity. These results indicate that, depending upon the nature and duration of the experimental inflammation, capsaicin-sensitive afferent nerves may act differently to control gastric inflammatory processes, suggesting the involvement of a neurogenic component in some forms of gastric inflammation.

Hormonal cycling may be related to a higher incidence of pain syndrome in female. As tachykinins are pivotal in stress-induced colonic dysfunction, we investigated whether ovarian steroids influence stress-induced visceral hypersensitivity to rectal distension (RD) in female rats and further, whether this influence involves NK1 receptors. Female Wistar rats, either intact or ovariectomized (OVX), were equipped for abdominal muscle electromyography and submitted to 2-h partial restraint stress (PRS) or sham-PRS. First, the effect of PRS was evaluated in intact rats. Second, abdominal response to RD was recorded in OVX rats treated with either, progesterone, 17beta-estradiol, 17beta-estradiol-plus-progesterone, or vehicle, in both basal and PRS conditions. Third, the NK1 receptor-antagonist, SR140333, was tested in PRS-intact and PRS-OVX rats under 17beta-estradiol or 17beta-estradiol-plus-progesterone treatment. PRS induced visceral hypersensitivity to RD and this effect was prevented by ovariectomy. OVX rats treated with 17beta-estradiol or 17beta-estradiol-plus-progesterone, but not progesterone alone, exhibited visceral hypersensitivity after PRS similar to that of intact rats. Both stress-induced visceral hypersensitivity in intact rats and the hormonally-restored visceral hyper-responsiveness of OVX rats were antagonized by SR140333. It is concluded, therefore, that stress-induced visceral hypersensitivity in female rats is estrogens-dependent and mediated through NK1 receptor activation.

Proteinase-activated receptor-2 (PAR2) activation induces colonic inflammation by an unknown mechanism. We hypothesized that PAR2 agonists administered intracolonically in mice induce inflammation via a neurogenic mechanism. Pretreatment of mice with neurokinin-1 and calcitonin-gene-related peptide (CGRP) receptor antagonists or with capsaicin showed attenuated PAR2-agonist-induced colitis. Immunohistochemistry demonstrated a differential expression of a marker for the type-1 CGRP receptor during the time course of PAR2-agonist-induced colitis, further suggesting a role for CGRP. We conclude that PAR2-agonist-induced intestinal inflammation involves the release of neuropeptides, which by acting on their receptors cause inflammation. These results implicate PAR2 as an important mediator of intestinal neurogenic inflammation.Key words: trypsin, proteinase-activated receptor-2, colitis, neurogenic inflammation, substance P, neurokinin-1 receptors, calcitonin-gene-related peptide.

In rats, the nematode Nippostrongylus brasiliensis induces an intestinal inflammation, but after the inflammation had resolved and the worm burden eliminated, morphological alterations of the intestinal wall, mainly consisting of mast cell hyperplasia and enteric nerve remodeling, persist for several weeks. Intestinal signals reaching the brain through the vagus nerve and involving neuropeptides such as CCK, play a role in the control of food intake. Our hypothesis was that neuroimmune alterations of the intestine may alter this control. This work was aimed to evaluate whether post-infection alterations of the intestinal wall may affect the satiety effects of CCK and further, the role of mast cells and their mediators, histamine and serotonin, in post- N. brasiliensis -infected rats. In basal conditions, food intake was not different in control and post-infected groups of rats. Post-infected rats were characterized by prolonged satiety effects of both CCK and histamine but not serotonin. The prolonged effect of CCK was reduced when mast cells were previously stabilized by ketotifen, which had no effect per se on food intake. No difference was observed in the increase of food intake induced by CCK-A and CCK-B receptor antagonists in both control and post-infected rats. Mast cell degranulation with compound 48/80 induced severe anorectic effects that lasted for less than 24 h in post-infected rats and as long as 6 days in controls. Thus, in our experimental conditions, i.e., within 30–50 days post- N. brasiliensis infection, we observed an enhancement of the anorectic effect of exogenous CCK involving mast cell degranulation and histamine.

Synthetic nitric oxide donors are known to protect the gastric mucosa from damage and dietary nitrate is known to release NO in the stomach. Mast cells have been found to be involved in gastric mucosal damage in humans or in rodents, and recent studies have pointed out the possibility of nitric oxide from endogenous or exogenous origin to modulate mast cell reactivity. This study aimed to determine whether the protective effect afforded by dietary nitrate against gastric mucosal damage was linked to mast cell stabilization. Mast cell involvement in iodoacetamide-induced gastritis was investigated in rats receiving oral administration of iodoacetamide together with the mast cell stabilizer doxantrazole (ip) or its solvent. The effects of dietary nitrate on mast cells during gastritis were investigated in rats receiving iodoacetamide orally, associated or not with KNO3. Control groups were given water instead of iodoacetamide either with or without KNO3, doxantrazole or its solvent. After sacrifice, blood samples were taken to determine RMCP II serum level and the stomach was resected in order to determine myeloperoxidase (MPO) activity and mucosal mast cell (MMC) number. Iodoacetamide significantly increased gastric MPO activity but did not modify RMCP II serum level or MMC number. Doxantrazole and KNO3 significantly reduced iodoacetamide-induced increase in gastric MPO activity, increased MMC number, and decreased RMCP II serum level in basal conditions. Only doxantrazole was able to modify all parameters under inflammatory conditions. These results suggest that nitric oxide released by dietary nitrate in the stomach stabilizes mast cells in basal conditions but exerts its protective effect against experimental gastritis through other pathways.

Nitrates have long been considered as harmful dietary components and judged responsible for deleterious effects on human health, leading to stringent regulations concerning their levels in food and water. However, recent studies demonstrate that dietary nitrate may have a major role in human health as a non-immune mechanism for host defence, through its metabolism to NO in the stomach. NO is a versatile molecule and although evidence exists showing that administration of low doses of exogenous NO protects against gastrointestinal inflammation, higher NO doses have been shown to exacerbate injury. So, the effect of an ingestion of nitrates in doses corresponding to a normal diet in human consumers on an experimental gastritis induced by iodoacetamide in rats was investigated. During gastritis one of the following compounds was given orally: water; KNO3; the NO donor sodium nitroprusside; the NO scavenger haemoglobin given with either water or KNO3. N(G)-nitro-L-arginine methyl ester (L-NAME), a non-specific NO synthase inhibitor, was administered with either water, iodoacetamide alone, or combined with KNO3. After killing, the stomach was resected and microscopic damage scores, myeloperoxidase and NO synthase activities were determined. Iodoacetamide-induced gastritis was significantly reduced by KNO3administration, an effect which was reproduced by sodium nitroprusside and reversed by haemoglobin. L-NAME induced gastric mucosal damage in itself, and KNO3did not prevent the gastritis induced by iodoacetamide associated with L-NAME. In conclusion, dietary nitrate exerts a protective effect against an experimental gastritis in rats by releasing NO in the stomach but such an effect requires the production of endogenous NO.

Stress results in activation of the hypothalamic pituitary adrenal axis and affects illnesses such as neuroinflammatory syndrome. In vivo acute stress (restraint stress) induces gastrointestinal function disturbances through colonic mast cell activation. This study investigated the effect of acute stress in histamine content of colonic mast cells, and the central role of interleukin-1 (IL-1) and corticotropin-releasing factor (CRF) in this effect. After a restraint stress session colonic segments were isolated and submitted to three protocols: (i) determination of histamine levels by radioimmunoassay (RIA) after incubation with 48/80 compound, (ii) evaluation by histology of mucosal mast cell (MMC) number and (iii) determination of histamine immunoreactivity of MMC. These procedures were conducted (1) in sham or stressed rats, (2) in stressed rats previously treated with intracerebroventricular (I.C.V.) IL-1ra or alpha-helical CRF9-41, (3) in naive rats pretreated with I.C.V. rhIL-1beta or CRF and (4) in rats treated with central IL-1beta and CRF plus alpha-helical CRF and IL-1ra, respectively (cross-antagonism reaction). Acute stress increases histamine content in colonic mast cells, without degranulation. I.C.V. pretreatment with IL-1ra or alpha-helical CRF9-41 blocked stress-induced mast cell histamine content increase. Both I.C.V. rhIL-1beta and CRF injections reproduced the stress-linked changes. I.C.V. treatment with CRF antagonist blocked I.C.V. rhIL-1beta-induced mast cell histamine content increase, whereas central IL-1ra did not affect stress events induced by I.C.V. CRF administration. These results suggest that in rats acute stress increases colonic mast cell histamine content. This effect is mediated by the release in cascade in the brain first of IL-1 and secondly of CRF.

Chronic gut inflammation is associated with radical oxygen species (ROS) genesis. ROS may activate certain transcription factors such as nuclear factor kappa beta (NF-kappaB), which regulates cyclooxygenase-2 (COX-2). Diquat, a food contaminant, is responsible for oxidative stress. This work aimed to establish the involvement of ROS and prostanoids on diquat-induced gastrointestinal inflammation and mast cell hyperplasia. Diquat increased gastrointestinal MPO activity and mast cell number. Its effect on gastric MPO activity was reversed by PD 138,387 (a COX-2 selective inhibitor) and PDTC (an inhibitor of NF-kappaB activation) but not by DMSO (a hydroxyl radical scavenger) and allopurinol (a xanthine oxidase inhibitor). In contrast, increased jejunal MPO activity was blocked by both DMSO, PD 138,387, and PDTC, while allopurinol enhanced it. PD 138,387 and PDTC reduced gastrointestinal mast cell number while DMSO and allopurinol did not Diquat-induced inflammation involves a gastrointestinal NF-kappaB activation and COX-2 dependent proinflammatory prostanoid synthesis. Furthermore, the hydroxyl radical is involved in intestinal but not gastric inflammation.

PAR-2s are highly expressed throughout the gastrointestinal tract. These receptors are cleaved by trypsin and mast cell tryptase and can be activated by peptides corresponding to the tethered ligand of the receptor (SLIGRL-NH2 for rat). The aim of this study was to determine whether colonic administration of PAR-2 agonists affects visceral sensitivity to rectal distention in conscious rats.Abdominal contractions (a criteria of visceral pain) were recorded in rats equipped with intramuscular electrodes. Rectal distention was performed at various times after intracolonic infusion of SLIGRL-NH2 and trypsin. Inflammation parameters and permeability were followed in the colon after the intracolonic injections. Fos expression at a spinal level (L4-L6) was also studied 2 hours after intracolonic injection of SLIGRL-NH2.Rectal distention significantly increased abdominal contractions starting at the RD volume of 0.8 mL. Intracolonic injection of SLIGRL-NH2 (200 microg/rat) and trypsin (200 U/rat), but not vehicle, LRGILS-NH2 (control peptide), boiled trypsin, or SLIGRL-NH2 injected IP, significantly increased (P0.05) abdominal contractions for high volumes of distention, 10- and 24-hour postinfusion. SLIGRL-NH2-induced hyperalgesia was inhibited by a NK1 receptor antagonist (SR 140333) but not by indomethacin. Intracolonic injection of SLIGRL-NH2 elevated spinal Fos expression and caused increased intestinal permeability but did not cause detectable inflammation.Intracolonic infusion of subinflammatory doses of PAR-2 agonists activated spinal afferent neurons and produced a delayed rectal hyperalgesia that involves changes in intestinal permeability and the activation of NK1 receptors. These results identify a possible role for proteinases and PAR-2 in the genesis of visceral hyperalgesia.

Stressful life events are frequently associated with outward signs of irritable bowel syndrome (IBS). Increasing evidence suggests that acute and chronic stress stimuli implicate different physiological mechanisms and neuroendocrine responses. Therefore, we investigated the influence of acute and chronic stress on visceral nociception in female rats and the involvement of colonic mast cells in this effect. The effect of acute and chronic partial restraint stress (PRS) on visceral sensitivity to rectal distension (RD) was assessed by abdominal muscle electromyography. Colonic mast cell activation was determined by measuring histamine release after in vitro stimulation with substance P (SP) in colonic samples from rats experiencing RD vs. controls. Acute PRS significantly enhanced abdominal response to RD compared with sham PRS for all volumes of distension. In contrast, chronic PRS induced a hyperalgesic response for the highest volumes of distension (0.8 and 1.2 mL), but did not affect the number of abdominal contractions for the lowest volume (0.4 mL) compared with controls. Both acute and chronic PRS increased in vitro SP-induced histamine release without affecting mast cell numbers. RD induced similar in vitro histamine release from colonic samples from both acute and chronic PRS rats; this release, however, was significantly higher than that measured in sham-PRS rats. Acute and chronic PRS differently influence visceral sensitivity in response to RD in female rats. This difference, however, cannot be attributed to a different effect of either stress paradigm on mast cell histamine release.

Serotonin (5-HT) is considered as a major mediator causing hyperalgesia and is involved in inflammatory reactions and irritable bowel syndrome. Alverine citrate may possess visceral antinociceptive properties in a rat model of rectal distension-induced abdominal contractions. This study was designed to evaluate the pharmacological properties of alverine citrate in a rat model of rectal hyperalgesia induced by 5-HTP (5-HT precursor) and by a selective 5-HT1A agonist (8-OH-DPAT) and to compare this activity with a reference 5-HT1A antagonist (WAY 100635). At 4 h after their administration, 5-HTP and 8-OH-DPAT increased the number of abdominal contractions in response to rectal distension at the lowest volume of distension (0.4 mL). When injected intraperitoneally before 8-OH-DPAT and 5-HTP, WAY 100635 (1 mg kg−1) blocked their nociceptive effect, but also reduced the response to the highest volume of distension (1.6 mL). Similarly, when injected intraperitoneally, alverine citrate (20 mg kg−1) suppressed the effect of 5-HTP, but not that of 8-OH-DPAT. However, when injected intracerebroventricularly (75 μg/rat) alverine citrate reduced 8-OH-DPAT-induced enhancement of rectal distension-induced abdominal contractions. In-vitro binding studies revealed that alverine citrate had a high affinity for 5-HT1A receptors and a weak affinity for 5-HT3 and 5-HT4 subtypes. These results suggest that 5-HTP-induced rectal hypersensitivity involves 5-TH1A receptors and that alverine citrate acts as a selective antagonist at the 5-HT1A receptor subtype to block both 5-HTP and 8-OH-DPAT-induced rectal hypersensitivity.

Background Rectal sensory thresholds are lowered in patients with irritable bowel syndrome (IBS), reflecting visceral hyperlagesia, which might be related to subclinical inflammation. Aim To evaluate the effects of an intraluminal injection of glycerol, a mucosal irritant, on rectal tone and perception of distension in 12 healthy subjects. Methods Rectal tone was evaluated with a barostat. First sensation, need to defecate and pain thresholds were evaluated during isobaric phasic distensions, before and 20 and 120 min after injection of 10 ml glycerol in the rectum. Results Baseline bag volume (97.9 +/- 56.2 ml) significantly decreased 20 min (49.7 +/- 42.2 ml; P= 0.026) and 120 min (66.5 +/- 38.3 ml; P= 0.050) after injection of glycerol, indicating its hypertonic effect. The pressure defining sensory thresholds was decreased significantly 20 min after glycerol injection: first sensation, 14.6 +/- 2.9 versus 18.3 +/- 7.2 mm Hg (P = 0.01); need to defecate, 19.6 +/- 3.7 versus 26.0 +/- 6.9 mm Hg; pain, 23.8 +/- 4.5 versus 35.6 +/- 9.5 mm Hg (P = 0.001). This effect was maintained for 120 min after injection of glycerol. Slopes of the compliance curves did not differ before and after injection of glycerol. Conclusions Intraluminal injection of glycerol significantly increases rectal tone and sensitizes healthy volunteers to rectal distension, since they show significantly lower thresholds after glycerol. This could constitute a model of visceral hypersensitivity in healthy volunteers.

Activation of Proteinase-Actvated Receptor-2 by the Peptide SLIGRL or Trypsin Induces Inflammation of Mouse Colon. Digestive Disease Week / 102nd Annual meeting of the AGA

Dietary factors can modulate visceral sensitivity and are suggested to interact with neuroimmune pathways. To determine whether daily low-level exposure to a food contaminant (diquat) alters sensitivity to gastric distension (GD) and the role of mast cells and tachykinin receptors activation, two series of experiments were conducted in eight groups of eight male Wistar rats (200–250 g) receiving daily doses of either diquat (0.1 mg/kg per day orally) or water for 21 days. In the first series, rats were sacrificed at the end of treatments and the gastric mucosal mast cell (MMC) number was histologically quantified. In the second series, after 21 days of treatment the cardiovascular depressor (CVD) response and corresponding gastric volumes were recorded under GD (from 10 to 40 mmHg). Doxantrazole (5 mg/kg intraperitoneally (i.p.)), a mast cell stabilizer, and SR 140333 (1 mg/kg i.p.) and MEN 11420 (0.1 mg/kg intravenously), respectively NK1 and NK2 receptor antagonists, were administered before GD. Before and after GD, blood samples were taken to measure blood histamine and the gastric MMC number was determined after sacrifice. Diquat treatment increased the MMC number. In diquat-treated rats, GD increased the CVD response and blood histamine level and induced MMC degranulation. Doxantrazole did not modify the hypersensitivity to GD but prevented mast cell degranulation. Both NK1 and NK2 receptor antagonists blocked the enhanced CVD response induced by diquat and prevented mast cell degranulation. None of the drugs had any effect in control animals. Prolonged exposure to a food contaminant at doses possibly found in food increases gastric sensitivity to distension, activates tachykinin receptors and results in MMC degranulation after GD.

BACKGROUND: Total anorectal reconstruction with dynamic graciloplasty is an alternative to a permanent colostomy; however, perfect continence cannot be achieved because of loss of sensitivity. This study was designed in dogs to determine whether monitoring of rectal electric impedance can give information about fullness or motility of the rectum. METHODS: Four adult female begale dogs underwent rectal electric impedance measurements using a bipolar electrode implanted on the rectal wall. An alternating current of 1µA at a frequency of 4 kHz was applied between the two wires. Variations of impedance (called impedance waves), defecations, and weight of stools were recorded and analyzed. RESULTS: The basal rectal impedance was 682±19 Ω. During the period of observation (n=4), 84 impedance waves (amplitude, 72±2 Ω; duration, 58±11 minutes) were observed and 33 defecations (weight of stools, 74±6 g) occurred. Four types of impedance waves were identified and classified into two groups: low-amplitude or short-duration waves (Types I, II, and III), and high-amplitude and long-duration waves (Type IV). Frequency of defecation was associated with the amplitude of the waves. The weight of stools was correlated with the duration of the waves (r=0.574, n=27,P=0.002). Types I, II, and III waves were correlated with eventual partial defecations, whereas Type IV waves were correlated with complete defecations. After defecation, no spontaneous new defecation occurred before recovering at least 80 percent of the basal impedance. CONCLUSIONS: Rectal impedance variations are correlated with defecation in a canine model, and single bipolar measurements provide a suitable evaluation of rectum fullness. This suggests the possible use of impedance signals to control electrostimulated graciloplasty after anorectal reconstruction.

Fecal Calprotectin and Transferrin as Markers of Gut Inflammation in Children and Rat. Digestive Disease Week / 102nd Annual AGA meeting

The effect of the tachykinin NK(2) receptor antagonist, nepadutant (MEN 11420 or (c[[(beta-D-GlcNAc)Asn-Asp-Trp-Phe-Dpr-Leu]c(2beta-5beta)])) was assessed on cardiovascular function (unanaesthetized rats and anaesthetized dogs) and gastrointestinal motor activity (fasted unanaesthetized dogs). The selective tachykinin NK(2) receptor agonist, [betaAla(8)]neurokinin A (4-10), up to 100 nmol/kg, i.v., did not produce changes on mean blood pressure or heart rate in unanaesthetized rats. Nepadutant did not affect blood pressure and heart rate up to 10 micromol/kg, whereas saredutant (SR 48968 or ((S)-N-methyl-N[4-(4-acetylamino-4-phenyl piperidino)-2-(3,4-dichlorophenyl)butyl] benzamide), a nonpeptide antagonist, produced a transient reduction of mean blood pressure and heart rate. Nepadutant up to 20 micromol/kg, i.v. neither caused changes of cardiovascular and respiratory parameters in anaesthetized dogs nor induced any changes in left ventricular systolic pressure, left ventricular dP/dt or of electrocardiogram (lead II) waveforms. Intravenous administration of neurokinin A (9 nmol/kg) in unanaesthetized dogs stimulated gastrointestinal motility for 20-25 min. Nepadutant at 0.1 micromol/kg suppressed the stimulant effects of neurokinin A but, up to a dose of 10 micromol/kg, did not produce significant changes in the basal migrating motor complexes. We conclude that tachykinin NK(2) receptors do not participate in the physiologic regulation of resting cardiovascular and respiratory functions and that they do not regulate the fasted pattern of gastrointestinal motility. The cardiovascular changes induced by the nonpeptide tachykinin NK(2) receptor antagonist, saredutant, likely arise from nonspecific effects unrelated to tachykinin NK(2) receptor blockade.

Evidence exists to support the concept that ovarian hormones influence mast cell functioning and related events. Here, we evaluated the constitutive gender difference and the influence of ovarian status on rat mast cell (MC) distribution in jejunum and colon, histamine synthesis and / or its release elicited by Substance P (SP). Higher mast cell (MC) number and histamine release were found in female compared with male. In female rats, hormonal status did not affect the density of resident MC neither in the jejunum nor in the colon. Interestingly, histamine levels released after SP stimulation of jejunal segment was reduced in ovariectomized (OVX) compared with sham OVX rats, and restored in OVX female receiving progesterone. In the colon, OVX resulted in a significant increase in histamine levels released after SP stimulation and a treatment with progesterone did not restore basal histamine levels. Thus, ovarian steroid hormones do not affect jejunal and colonic mast cell number. However, the hormonal status differently influences jejunal and colonic MC sensitivity to SP.

Only recently has it been considered that numerous interactions between the enteric nervous system and local immunocytes are responsible for adaptive functional changes, including motility and secretion (fig 1). Several neuropeptides such as tachykinins, vasoactive intestinal peptide, somatostatin, and opioids are involved in both intrinsic and extrinsic innervation but can also affect immune reactions directly. They exert a dual role in the regulation of local and peripheral motor and secretory reflexes and affect the release of cytokines and proinflammatory mediators. On the other hand, proinflammatory mediators such as eicosanoids and cytokines may activate intrinsic neurones directly or stimulate extrinsic neurones indirectly, releasing neuropeptides which act on intrinsic neurones, smooth muscle cells, or enterocytes. These acute immediate neuroimmune reactions are often followed by long term changes in the number of receptors at the presynaptic or postsynaptic level as well as phenotypic changes of the effector cells, as evidenced for smooth muscle cells and enteric neurones which can synthetise cytokines. Figure 1 Interaction between the central nervous system and the immune system. VIP, vasoactive intestinal peptide; SP, substance P; SOM, somatostatin; G, ganglion; GALT, gut associated lymphoid tissue; MLN, mesenteric lymph node. (From Ottaway.20) There are at least three major target cells affected by the presence of inflammatory mediators: smooth muscle cells, glial cells, and neurones. Both intrinsic enteric neurones and terminals of extrinsic afferent and efferent nerves are affected …

Intraperitoneal lipopolysaccharide (LPS) produces somatic hyperalgesia, releases interleukin (IL)-1beta and tumor necrosis factor-alpha (TNF-alpha), and activates vagal afferents. The aim of this study was to evaluate the effect of peripheral LPS on rectal sensitivity and to specify the mechanisms involved. Abdominal muscle contractions were recorded in conscious rats equipped with intramuscular electrodes. Rectal distension (RD) was performed at various times after LPS or experimental treatments. In controls, RD significantly increased the number of abdominal contractions from a threshold volume of distension of 0.8 ml. At the lowest volume (0.4 ml), this number was increased after administration of LPS (3, 9, and 12 h later), recombinant human IL-1beta (from 3 to 9 h), recombinant bovine TNF-alpha (from 6 to 9 h), and BrX-537A (from 6 to 12 h), a mast cell degranulator. The effect of LPS was reduced by doxantrazole, Lys-D-Pro-Thr, and soluble recombinant TNF receptor. Vagotomy selectively amplified the response to LPS. We conclude that, in vivo, intraperitoneal LPS lowers visceral pain threshold (allodynia) through a mechanism involving mast cell degranulation and IL-1beta and TNF-alpha release and that the vagus nerve may exert a tonic protective role against LPS-induced rectal allodynia.

Protective effect of intraluminal nitric oxide in experimental colitis in rats. Digestive Disease Week / 101th Annual meeting of the AGA

Jejunal contractility responses to bradykinin and neurokinin A are altered after nematode exposure-induced intestinal mastocytosis in rats. Digestive Disease Week / 101th Annual AGA meeting

Mast cells and afferent nerves are involved in the development and sequels of intestinal inflammation in post-Nippostrongylus brasiliensis-infected rats. Digestive Disease Week / 101th Annual AGA meeting

Objectives: To determine whether intestinal mast cells and capsaicin-sensitive afferent nerves are involved in the development and sequels of Nippostrongylus brasiliensis-induced intestinal inflammation in rats. Methods: Two series of experiments were performed. In the first series, six groups of 8 rats were used to study the effects of mast cell stabilization by ketotifen. In the second series, six groups of 6 rats were used to study the effects of gut extrinsic sensory neuron depletion by capsaicin. For each series, four groups of rats were infected with N. brasiliensis and two groups were not infected. Results: Infection with N. brasiliensis resulted in an increase of myeloperoxidase (MPO) activity and mast cell numbers at day 12 postinfection; MPO returned to preinfection levels by day 35 while mast cell numbers remained elevated at that time. In ketotifen-treated infected rats, the increase of MPO at day 12 was less pronounced, but MPO activity remained elevated and mast cell numbers were increased at day 35. In capsaicin-treated infected rats, the MPO increase at day 12 was augmented, and MPO was still not returned to preinfection values by day 35; in contrast, the increase of mast cell numbers at days 12 and 35 was not modified by afferent nerve depletion. Conclusion: Mast cell stabilization decreased jejunal inflammation during the acute stage (day 12), but prolonged the inflammatory process until at least day 35 postinfection. The data also confirmed the protective role of gut extrinsic sensory neurons against intestinal inflammation in a model of nematode infection and revealed that these afferent nerves do not seem crucial for the development of nematode-induced hypermastocytosis.

Hypersensitivity to rectal distension is frequently observed in patients with irritable bowel syndrome (IBS). However, few data are available about the influence of age on rectal sensory thresholds and tone. The aim of this study was to measure rectal sensory thresholds and tone with a barostat in 12 healthy subjects (aged 86 +/- 4 years, eight females, four males) as compared with 12 young healthy male controls (26 +/- 1 years). Isobaric phasic distensions were performed in the fasted state (increment of 4 mmHg, steps of 5 min, interval of 5 min). Rectal tone changes were then measured as changes in volume of the barostat bag, the pressure being kept constant. After a baseline recording of 1 h, a 1000-kcal meal was served and the tone recorded until return to baseline. Rectal sensory thresholds were significantly higher in aged subjects. First sensation, sensation of urge to defaecate and sensation of pain were triggered at 21.1 +/- 3.2 mmHg, 30.4 +/- 5.4 mmHg and 40.5 +/- 5.0 mmHg, respectively, in aged subjects, vs 13.3 +/- 4.6 mmHg (P < 0.05), 20.7 +/- 1.0 mmHg (P < 0.001) 31.3 +/- 1.7 mmHg (P < 0.001) in controls. Rectal compliance was not significantly different between the two groups. Mean barostat bag volume was 104 +/- 13 mL in fasting aged subjects and 125 +/- 23 mL in controls (NS). After the meal, the barostat bag volume decreased by 69 +/- 11% during 85 +/- 17 min in aged subjects and 75 +/- 14% during 89 +/- 15 min in young controls (NS). Rectal sensory thresholds triggered by distension are increased in aged healthy subjects while compliance and tone are not different. Age should be considered as a confounding factor when studying rectal sensitivity and further studies in aged patients with IBS should include a group of control subjects within the same range of age as studied patients.

Background & Aims: Tachykinins contribute to the control of gastrointestinal motility and modulation of somatic and visceral pain. The role of neurokinin (NK) B and NK3 receptors in visceral pain and gastrointestinal disorders has not been determined. Methods: Using electromyographic recordings of both abdominal and colonic muscle and electrophysiological recordings of pelvic nerve afferent fibers, we studied drug effects on responses to colorectal distention. Results: In awake rats, intraperitoneal administration of the NK3-receptor antagonist SR 142,801 reduced, whereas the NK3-receptor agonist senktide increased, both the rectocolonic inhibitory reflex and abdominal contractions produced by colorectal distention. In contrast, intracerebroventricular administration of SR 142,801 increased the number of abdominal contractions without affecting the rectocolonic inhibitory reflex produced by colorectal distention. In a similar manner, intracerebroventricular injection of senktide diminished the number of abdominal contractions. In electrophysiological experiments, SR 142,801 decreased responses of pelvic nerve afferent fibers to colorectal distention. Responses of pelvic nerve fibers to urinary bladder distention, however, were unaffected by SR 142,801. Conclusions: These results suggest that peripheral NK3 receptors are involved in the mediation of both visceral nociception and gastrointestinal disorders. Also, central NK3 receptors seem to play a role in the modulation of visceral nociception.

The effect of synthetic sorbin derivatives was determined on cholera toxin-stimulated jejunal secretion in anesthetized rats in vivo, using both perfused and ligated loop. An inhibitory effect on water secretion induced by cholera toxin was shown with C-terminal sorbin peptides: C20 (YEPGKSSILQHERPVTKPQA-amide), C10 and Dala 7 heptapeptide-amide of sorbin, given by subcutaneous (SC) or intraduodenal administration. When perfused intravenously, C20-sorbin inhibited the cholera-induced stimulation of net flux of water, Na + and K + , in the jejunum and at the same time the net flux of water and Cl − in the duodenum, which was not in contact with the toxin. 5-hydroxytryptamine was not significantly changed in plasma or fluid. Prostaglandin E 2 release in jejunal as well as duodenal fluid was significantly stimulated by cholera toxin, but was not significantly different from basal value after C20 administration.

The effects of trimebutine and its major metabolite, N-desmethyltrimebutine on inflammation- and stress-induced rectal hyperalgesia have been evaluated in rats fitted with electrodes implanted in the longitudinal striated muscle of the abdomen. Intermittent rectal distension was performed before and 3 days after induction of rectal inflammation by local infusion of trinitrobenzenesulphonic acid (in ethanol). Stress consisted of 2 h partial restraint and rectal distension was performed before and 30min after the end of the partial restraint session. The animals were treated intraperitoneally with trimebutine or desmethyltrimebutine (5, 10 or 20mgkg−1) or vehicle 15min before rectal distension. Naloxone (1mgkg−1) or saline was injected subcutaneously before trimebutine and desmethyltrimebutine. Before treatment trimebutine at the highest dose (20 mgkg−1) reduced the abdominal response to rectal distension for the highest volume of distension (1·6mL) whereas desmethyltrimebutine was inactive. After rectocolitis the abdominal response to rectal distension was enhanced and trimebutine at 5mgkg−1 reduced and at 10mgkg−1 suppressed inflammation-induced hyperalgesia, an effect reversed by naloxone. Desmethyltrimebutine was inactive. Stress-induced hypersensitivity was attenuated or suppressed, or both, by trimebutine and desmethyltrimebutine at doses of 5, 10 or 20mgkg−1; greater efficacy was observed for desmethyltrimebutine and the effects were not reversed by naloxone. It was concluded that trimebutine and desmethyltrimebutine are active against inflammation- and stress-induced rectal hyperalgesia but act differently. The effect of trimebutine on inflammation-induced hyperalgesia is mediated through opioid receptors.

Previous studies have shown tachykinins implicated in gut inflammation. The aim of this work was to evaluate the effect of treatments with tachykinin NK1, NK2, and NK3 selective receptor antagonists on the development of gut inflammation induced by trinitrobenzenesulfonic acid (TNBS) in rats and guinea-pigs. On day 0, rats and guinea-pigs received an intraluminal instillation of TNBS/ethanol (40 mg kg ). Each group was daily treated with intraperitoneally injected NK1 (SR 140333; 0.3 mg/kg/day), NK2 (SR 48968; 5 mg/kg/day), or NK3 (SR 142801; 1, 5, or 10 mg/kg/day) receptor antagonists or their vehicle. On day 4, inflammatory levels were evaluated by measuring gut permeability, myeloperoxidase activity, macro- and microscopic damage scores. In TNBS treated rats, daily administration of SR 140333 (0.3 mg/kg/day) and SR 48968 (5 mg/kg/day) reduced colonic inflammation. In TNBS treated guinea-pigs, daily administration of SR 48968 (5 mg/kg/day) and SR 142801 (at 5 and 10 mg/kg/day) attenuated significantly ileal injury. These results suggest that non-peptide tachykinin receptor antagonists are potent anti-inflammatory agents on gut inflammation in rats and guinea-pigs. However, their activity depends upon the animal species and type of receptor considered.

Distension of the rat intestine causes a depressor response which is predictive of nociception. This study investigated the effects of previous infection with Nippostrongylus (N.) brasiliensis on the sensitivity to intestinal distension and the role of tachykinin NK 2 receptors. The tachykinin NK 2 receptor antagonist, SR48968 ( S )- N -methyl- N [4-(4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl)butyl]benzamide) inhibited the nociceptive response (ED 50 =0.7 mg/kg) in control rats. In post- N. brasiliensis -infected rats sensitivity to intestinal distension was increased which was accompanied by an increase in the apparent potency value of SR48968 (ED 50 =0.1 mg/kg). The hypersensitivity was limited to areas of hypermastocytosis. It is concluded that the post-inflammatory changes that occur in post-infected rats increase visceral sensitivity and the apparent potency of tachykinin NK 2 receptor antagonists.

Influence of chronic ingestion of nitrates ans nitrites on gastrointestinal neutrophils and mast cells in rats. Digestive Disease Week / 99th Annual AGA meeting

Effects of chronic treatment with antidepressants on in vitro jejunal contractility in rats. Digestive Disease Week / 99th Annual AGA meeting

Diquat, a nonselective desiccant herbicide, induces a significant secretion of fluid into the lumen of the gastrointestinal tract of rats at sublethal doses (from 0.5 to 50 mg/kg). This study investigated the effect of an acute low-level exposure to diquat (0. 1, 0.5, and 1 mg/kg) on intestinal net water flux and the mechanisms involved. In anesthetized rats, an intestinal loop (7 cm) was infused with Ringer's buffer containing [14C]-polyethylene glycol 4000. After equilibration, diquat (0.1, 0.5, and 1 mg/kg) was added to Ringer's buffer during 60 min. Net water flux was calculated according to [14C] activity determined in the effluent collected at 15-min intervals. Infused in the intestinal loop for 60 min at doses of 0.5 and 1 mg/kg but not at 0.1 mg/kg, diquat induced an intestinal net water secretion during 180 min with a maximal effect at the highest dose used and during the first hour following the end of diquat infusion. Diquat-induced (1 mg/kg) intestinal net water secretion was blocked by a neurotoxin, tetrodotoxin (5 micrograms/kg iv), doxantrazole (5 mg/kg ip), a mast cell stabilizer, and two inhibitors of NO synthases: l-NAME (25 mg/kg ip) and aminoguanidine (2 mg/kg ip). It is concluded that a single low-level (0.5 and 1 mg/kg) intrajejunal administration of diquat induces a net water intestinal secretion and that this secretory effect is nerve-mediated, implying mast cell degranulation and NO release.

1. In vivo rectal distension (RD) induces a neurally mediated colonic net water hypersecretion in rats. Interleukin-1 beta (IL-1 beta) also induces neural colonic water hypersecretion involving the release of prostaglandins (PGs) and a mast cell degranulation in rats. This study investigated in vivo the role of IL-1, PGs and mast cells in RD-induced colonic hypersecretion. 2. Proximal colonic net water flux was determined using [14C]polyethylene glycol (PEG) 4000 (mol. wt. 4000) in anaesthetized rats. On strips taken from the distal colon: (i) a histological analysis was performed to determine the number of mucosal mast cells (MMC); and (ii) histamine levels were measured by radioimmunoassay after stimulation with compound 48/80. 3. RD induced a net colonic water secretion that was blocked by i.c.v. administration of IL-1ra (an IL-1 receptor antagonist) and indomethacin, and by systemic treatment with doxantrazole and indomethacin. RD decreased the number of resident mast cells and the release of histamine from the distal colonic strips. Moreover, using SDS-PAGE immunoblotting the expression of IL-1 beta was detected in the brain. 4. These results suggest that, in rats, RD induces colonic net water hypersecretion by the activation of a neuro-immunological reflex pathway, involving IL-1 beta, PG release and peripheral mast cell degranulation.

The effect of calcitonin on meal-stimulated gallbladder emptying (GBE) was examined after intravenous (i.v.) and intracerebroventricular (i.c.v.) administration in six mongrel dogs. The gallbladder contraction was surveyed by means of real-time ultrasonography in conscious dogs. Calcitonin given i.v. elicited an immediate and strong inhibition of postprandial GBE-the integrated 0- to 120-min gallbladder response was 118.1 +/- 8.0%.h after placebo, whereas it was 91.8 +/- 2.1%.h, 59.4 +/- 17.9%.h (P0.001), and 14.2 +/- 20.5%.h (P0.001) after 3.6, 18.0, and 90.0 pmol.kg-1 calcitonin, respectively. After i.c.v. administration (1.8 and 18.0 pmol.kg-1), only the higher calcitonin dose exerted a moderate inhibitory effect on postprandial GBE. The calcitonin doses required to evoke a 50% inhibition of meal-stimulated GBE were 15- to 10-fold lower after i.v. than i.c.v. application. Peripherally given calcitonin brought about a dose-dependent increase in the interdigestive gallbladder volume-the linear regression of the relative gallbladder volume versus calcitonin dose was y = 11.60 [ln(dose + 1)] + 97.02 (r = 0.864, P0.001). Intravenous application of calcitonin did not affect caerulein-induced GBE. The results obtained imply that: (i) calcitonin exerts an inhibitory influence on meal-induced GBE and that this effect is more pronounced after i.v. than after i.c.v. administration, and (ii) peripherally given calcitonin does not inhibit caerulein-induced gallbladder contraction in the dog.

Intestinal motility disorders are often associated with gut inflammation. We evaluated, in vitro under isometric conditions, changes in contractility of longitudinal and circular muscle layers from guinea pig ileum after 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced ileitis. TNBS treatment did not modify length-active tension relationships for both muscle layers, whereas a significant increase in passive tension was observed in the circular muscle response to stretching. Moreover, in both control and inflamed strips at optimal stretch, concentration-response curves to KCl were similar for both layers. In contrast, contractile responses to receptor agonists were differentially altered in both layers in comparison with controls. Thus, in longitudinal strips from TNBS-treated ileum, there was a twofold increase in maximal response (Emax) induced by carbachol and histamine without modification of 50% effective concentration (EC50) values; responses to 5-hydroxytryptamine (5-HT) were not modified; both alpha 1- and alpha 2-adrenoceptor-mediated responses to epinephrine were abolished. In circular strips, inflammation did not affect the Emax induced by carbachol and histamine but led to increased EC50 values; Emax to 5-HT was reduced without change in EC50 values. Moreover, in the dose range used (0.1 nM to 0.1 mM), a maximal response to carbachol was not obtained in inflamed circular strips. The results indicate that in the guinea pig model of TNBS-induced ileitis, the in vitro contractile responses of circular and longitudinal smooth muscle to the stimulation of various receptors are differentially altered, whereas non-receptor-mediated contraction to KCl depolarization is not modified.