Effect of 2,4,6-trinitrobenzenesulphonic acid (TNBS)-induced ileitis on the motor function of non-inflamed rat gastric fundus

Colonic motility adjustments in acute and chronic DSS-induced colitis

AIMS

Inflammatory bowel disease is recurrent inflammation that affects the gastrointestinal tract causing changes in intestinal motility. The evolution of these changes is not completely understood. The aim of this study was to evaluate anatomical and functional changes in the colon during the development of acute and chronic DSS-induced ulcerative colitis (UC) in C57Bl/6 mice.

MATERIALS AND METHODS

Mice were relocated into 5 groups: control (GC) and groups exposed to DSS 3 % for 2 (DSS2d), 5 (DSS5d) and 7 DSS7d) days (acute UC) or 3 cycles (DSS3C; Chronic UC). Mice were monitored daily. After euthanasia, colonic tissue was assessed with histological, immunofluorescence and colon manometry methods.

KEY FINDINGS

Ulcerative Colitis is a chronic disease characterized by overt inflammation of the colon. Here we investigate whether the morphological changes caused by UC in the colonic wall, in tuft cells and in enteric neurons also promote any alteration in colonic motility patterns. UC Promotes thickening in the colonic wall, fibrosis, reduction in the number of tuft cells and consequently goblet cells also, without promoting neuronal death however there is a change in the chemical code of myenteric neurons. All of these morphological changes were responsible for causing a change in colonic contractions, colonic migration motor complex, total time of gastrointestinal transit and therefore promoting dysmotility. Further studies stimulating a hyperplasia of tuft cells may be the way to try to keep the colonic epithelium healthy, reducing the damage caused by UC.

SIGNIFICANCE

Increasing disease pathology of DSS-induced UC induces structural and neuroanatomical changes and driven damage to cholinergic neurons causes colonic dysmotility, including increase of cholinergic myenteric neurons, followed by variations in the motility pattern of different regions of the colon that taking together characterize colonic dysmotility.

Homeoprotein OTX1 and OTX2 involvement in rat myenteric neuron adaptation after DNBS-induced colitis

BACKGROUND

Inflammatory bowel diseases are associated with remodeling of neuronal circuitries within the enteric nervous system, occurring also at sites distant from the acute site of inflammation and underlying disturbed intestinal functions. Homeoproteins orthodenticle OTX1 and OTX2 are neuronal transcription factors participating to adaptation during inflammation and underlying tumor growth both in the central nervous system and in the periphery. In this study, we evaluated OTX1 and OTX2 expression in the rat small intestine and distal colon myenteric plexus after intrarectal dinitro-benzene sulfonic (DNBS) acid-induced colitis.

METHODS

OTX1 and OTX2 distribution was immunohistochemically investigated in longitudinal muscle myenteric plexus (LMMP)-whole mount preparations. mRNAs and protein levels of both OTX1 and OTX2 were evaluated by qRT-PCR and Western blotting in LMMPs.

RESULTS

DNBS-treatment induced major gross morphology and histological alterations in the distal colon, while the number of myenteric neurons was significantly reduced both in the small intestine and colon. mRNA levels of the inflammatory markers, TNFα, pro-IL1β, IL6, HIF1α and VEGFα and myeloperoxidase activity raised in both regions. In both small intestine and colon, an anti-OTX1 antibody labeled a small percentage of myenteric neurons, and prevalently enteric glial cells, as evidenced by co-staining with the glial marker S100β. OTX2 immunoreactivity was present only in myenteric neurons and was highly co-localized with neuronal nitric oxide synthase. Both in the small intestine and distal colon, the number of OTX1- and OTX2-immunoreactive myenteric neurons significantly increased after DNBS treatment. In these conditions, OTX1 immunostaining was highly superimposable with inducible nitric oxide synthase in both regions. OTX1 and OTX2 mRNA and protein levels significantly enhanced in LMMP preparations of both regions after DNBS treatment.

CONCLUSIONS

These data suggest that colitis up-regulates OTX1 and OTX2 in myenteric plexus both on site and distantly from the injury, potentially participating to inflammatory-related myenteric ganglia remodeling processes involving nitrergic transmission.

Systematic review with meta-analysis: post-infectious functional dyspepsia

BACKGROUND

The prevalence of functional dyspepsia (FD) following infectious gastroenteritis has not been systematically reviewed.

AIM

To conduct a systematic review and calculate the summary odds ratio (OR) for the development of FD following infectious gastroenteritis, as compared to a control population.

METHODS

Published studies in PubMed, EmBASE, and Cochrane Database and abstracts from standard sources were screened for eligible studies. Data from studies meeting inclusion criteria were pooled for meta-analysis.

RESULTS

Nineteen studies were eligible for inclusion. The mean prevalence of FD following acute gastroenteritis (AGE) was 9.55% (FD, n = 909; AGE, n = 9517) in adult populations. The summary OR for the development of post-infectious FD was 2.54 (95% CI = 1.76-3.65) at more than 6 months after AGE, as compared to the prevalence in controls within the same population. This is compared with the summary OR (3.51; 95% CI = 2.05-6.00) for the development of post-infectious irritable bowel syndrome (IBS) in the same population at more than 6 months after AGE. There was significant statistical heterogeneity with an I(2) of 72.8% for the summary OR of post-infectious FD. Several pathogens, including Salmonella spp., Escherichia coli O157, Campylobacter jejuni, Giardia lamblia and Norovirus have been shown to be associated with post-infectious FD symptoms.

CONCLUSIONS

Infectious gastroenteritis is associated with an increased risk for subsequent dyspepsia as well as for irritable bowel syndrome. Post-infectious FD and post-infectious irritable bowel syndrome may represent different aspects of the same pathophysiology. Further studies will be needed to determine this.

Neuroplasticity and dysfunction after gastrointestinal inflammation

The gastrointestinal tract is innervated by several distinct populations of neurons, whose cell bodies either reside within (intrinsic) or outside (extrinsic) the gastrointestinal wall. Normally, most individuals are unaware of the continuous, complicated functions of these neurons. However, for patients with gastrointestinal disorders, such as IBD and IBS, altered gastrointestinal motility, discomfort and pain are common, debilitating symptoms. Although bouts of intestinal inflammation underlie the symptoms associated with IBD, increasing preclinical and clinical evidence indicates that infection and inflammation are also key risk factors for the development of other gastrointestinal disorders. Notably, a strong correlation exists between prior exposure to gut infection and symptom occurrence in IBS. This Review discusses the evidence for neuroplasticity (structural, synaptic or intrinsic changes that alter neuronal function) affecting gastrointestinal function. Such changes are evident during inflammation and, in many cases, long after healing of the damaged tissues, when the nervous system fails to reset back to normal. Neuroplasticity within distinct populations of neurons has a fundamental role in the aberrant motility, secretion and sensation associated with common clinical gastrointestinal disorders. To find appropriate therapeutic treatments for these disorders, the extent and time course of neuroplasticity must be fully appreciated.

A prospective population-based study of triggers of symptomatic flares in IBD

OBJECTIVES

We aimed to determine whether any of the nonsteroidal anti-inflammatory drugs (NSAIDs), antibiotics, infections, and stress trigger symptomatic flares of inflammatory bowel diseases (IBDs).

METHODS

Participants drawn from a population-based IBD research registry were surveyed every 3 months for 1 year. They simultaneously tracked the use of NSAIDs, antibiotics, infections, major life events, mood, and perceived stress. Social networks, childhood socioeconomic status, and smoking were assessed at baseline. Disease flare was identified using the Manitoba Inflammatory Bowel Disease Index, a validated disease activity index. Across any two consecutive survey periods, participants were categorized as having a flare (inactive/active), having no flare (inactive/inactive), or remaining active (active/active). Potential triggers were evaluated for the first 3-month period to determine predictive rather than concurrent relationships. Data from only one pair of 3-month periods from an individual were analyzed.

RESULTS

A total of 704 participants completed the baseline survey; 552 (78.3%) returned all 5 surveys. In all, 174 participants who had a flare were compared with 209 who had no flare. Perceived stress, negative affect (mood), and major life events were the only trigger variables significantly associated with flares. There were no differences between those who flared and those who did not, in the use of NSAIDs, antibiotics, or in the presence of infections. Multivariate logistic regression analyses indicated that only high-perceived stress (adjusted odds ratio=2.40 (1.35, 4.26)) was associated with an increased risk of flare.

CONCLUSIONS

This study adds to the growing evidence that psychological factors contribute to IBD symptom flares. There was no support for differential rates of use of NSAIDS, antibiotics, or for the occurrence of (non-enteric) infections related to IBD flares.

Prolonged IL-1beta exposure alters neurotransmitter and electrically induced Ca(2+) responses in the myenteric plexus

BACKGROUND Infection and inflammatory diseases of the gut results in profound changes of intestinal motor function. Acute administration of the pro-inflammatory cytokine interleukin-1beta (IL-1beta) was shown to have excitatory and neuromodulatory roles in the myenteric plexus. Here we aimed to study the effect of prolonged IL-1beta incubation on the response of myenteric neurones to different stimuli. METHODS Longitudinal muscle myenteric plexus preparations (LMMP's) of the guinea pig jejunum were incubated for 24 h in medium with or without IL-1beta. After loading with Fluo-4, calcium imaging was used to visualize activation of neurones. The response to application of serotonin (5-HT), substance P (SP) and ATP or to electrical fibre tract stimulation (eFTS) was tested. Expression of nNOS, HuD, calbindin and calretinin was compared by immunohistochemistry. KEY RESULTS IL-1beta concentration-dependently influenced the neuronal responsiveness and duration of the [Ca(2+)](i) rises to 5-HT and ATP, while it also affected the Ca(2+)-transient amplitudes induced by 5-HT, ATP and SP. Ca(2+)-transients in response to eFTS were observed in significantly more neurones per ganglion after IL-1beta (10(-10) and 10(-11) mol L(-1)). Peak [Ca(2+)](i) rise after eFTS was concentration-dependently decreased by IL-1beta. The duration of the [Ca(2+)](i) rise after eFTS was prolonged after IL-1beta 10(-12) mol L(-1). IL-1beta (10(-9) mol L(-1)) incubation did not affect the number of nNOS, calretinin and calbindin expressing neurones, nor did it induce neuronal loss (HuD). CONCLUSIONS & INFERENCES In this study, IL-1beta differentially modulates the neuronal response to eFTS and neurotransmitter application in the myenteric plexus of guinea pigs. This cytokine could be implicated in the motility disturbances observed during gastrointestinal inflammation.

Schistosoma mansoni proteins attenuate gastrointestinal motility disturbances during experimental colitis in mice

AIM: To investigate the therapeutic effect of Schistosoma mansoni (S. mansoni) soluble worm proteins on gastrointestinal motility disturbances during experimental colitis in mice.

METHODS: Colitis was induced by intrarectal injection of trinitrobenzene sulphate (TNBS) and 6 h later, mice were treated ip with S. mansoni proteins. Experiments were performed 5 d after TNBS injection. Inflammation was quantified using validated inflammation parameters. Gastric emptying and geometric center were measured to assess in vivo gastrointestinal motility. Peristaltic activity of distal colonic segments was studied in vitro using a modified Trendelenburg set-up. Cytokine profiles of T-lymphocytes isolated from the colon were determined by real time reverse transcriptase-polymerase chain reaction.

RESULTS: Intracolonic injection of TNBS caused severe colitis. Treatment with S. mansoni proteins significantly ameliorated colonic inflammation after 5 d. TNBS did not affect gastric emptying but significantly decreased the geometric center and impaired colonic peristaltic activity 5 d after the induction of colitis. Treatment with S. mansoni proteins ameliorated these in vivo and in vitro motility disturbances. In addition, TNBS injection caused a downregulation of effector T cell cytokines after 5 d, whereas a S. mansoni protein effect was no longer observed at this time point.

CONCLUSION: Treatment with S. mansoni proteins attenuated intestinal inflammation and ameliorated motility disturbances during murine experimental colitis.

Persistent gut motor dysfunction in a murine model of T-cell-induced enteropathy

BACKGROUND

Inflammatory bowel disease (IBD) patients in remission often experience irritable bowel syndrome (IBS)-like symptoms. We investigated the mechanism for intestinal muscle hypercontractility seen in T-cell-induced enteropathy in recovery phase.

METHODS

BALB/c mice were treated with an anti-CD3 antibody (100 microg per mouse) and euthanized at varying days post-treatment to investigate the histological changes, longitudinal smooth muscle cell contraction, cytokines (Th1, Th2 cytokines, TNF-alpha) and serotonin (5-HT)-expressing enterochromaffin cell numbers in the small intestine. The role of 5-HT in anti-CD3 antibody-induced intestinal muscle function in recovery phase was assessed by inhibiting 5-HT synthesis using 4-chloro-DL-phenylalanine (PCPA).

KEY RESULTS

Small intestinal tissue damage was observed from 24 h after the anti-CD3 antibody injection, but had resolved by day 5. Carbachol-induced smooth muscle cell contractility was significantly increased from 4 h after injection, and this muscle hypercontractility was evident in recovery phase (at day 7). Th2 cytokines (IL-4, IL-13) were significantly increased from 4 h to day 7. 5-HT-expressing cells in the intestine were increased from day 1 to day 7. The 5-HT synthesis inhibitor PCPA decreased the anti-CD3 antibody-induced muscle hypercontractility in recovery phase.

CONCLUSIONS & INFERENCES

Intestinal muscle hypercontractility in remission is maintained at the smooth muscle cell level. Th2 cytokines and 5-HT in the small intestine contribute to the maintenance of the altered muscle function in recovery phase.

Colitis affects the smooth muscle and neural response to motilin in the rabbit antrum

BACKGROUND AND PURPOSE

The underlying mechanisms of gastric dysfunction during or after an episode of intestinal inflammation are poorly understood. This study investigated the effects of colitis on the contractile effects of motilin, an important endocrine regulator of gastric motility, in the antrum.

EXPERIMENTAL APPROACH

Myeloperoxidase (MPO) activity, NF-kappaB activity and motilin receptor density were determined in the antrum of rabbits 5 days after the induction of 2,4,6-trinitrobenzenesulphonic acid colitis. Smooth muscle and neural responses to motilin were studied in antral smooth muscle strips in vitro.

KEY RESULTS

Colitis did not affect MPO activity, but increased NF-kappaB activity in the antrum. Motilin receptor density in the antrum was not affected. Under control conditions, motilin induced a slowly developing tonic smooth muscle contraction. Five days post-inflammation, tonic contractions to motilin were reduced and preceded by a rapid initial contraction. Other kinases were recruited for the phosphorylation of myosin light chain (MLC) (a multi-functional MLC kinase), and for the inhibition of MLC phosphatase (Rho kinase in addition to protein kinase C) to mediate the motilin-induced contractions during inflammation. Colitis potentiated the cholinergic neural on-contractions in the antrum. This was associated with a hyper-reactivity to motilin and an increased muscle response to ACh.

CONCLUSIONS AND IMPLICATIONS

Colitis altered the course of the motilin-induced smooth muscle contraction in the antrum. This involved changes in the kinases phosphorylating MLC. Increased cholinergic excitability to motilin in the antrum may play a role in the pathogenesis of inflammation-associated gastric motility disorders.

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

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

TRPV1 receptors on unmyelinated C-fibres mediate colitis-induced sensitization of pelvic afferent nerve fibres in rats

Patients with inflammatory bowel disease often suffer from gastrointestinal motility and sensitivity disorders. The aim of the current study was to investigate the role of transient receptor potential of the vanilloid type 1 (TRPV1) receptors in the pathophysiology of colitis-induced pelvic afferent nerve sensitization. Trinitrobenzene sulphate (TNBS) colitis (7.5 mg, 30% ethanol) was induced in Wistar rats 72 h prior to the experiment. Single-fibre recordings were made from pelvic nerve afferents in the decentralized S1 dorsal root. Fibres responding to colorectal distension (CRD) were identified in controls and rats with TNBS colitis. The effect of the TRPV1 antagonist N-(4-tertiarybutylphenyl)-4-(3-chlorophyridin-2-yl)tetrahydropyrazine-1(2H)carboxamide (BCTC; 0.25-5 mg kg(-1)) or its vehicle (hydroxypropyl-beta-cyclodextrin) was tested on the afferent response to repetitive distensions (60 mmHg). Immunocytochemical staining of TRPV1 and NF200, a marker for A-fibre neurons, was performed in the dorsal root ganglia L6-S1. TNBS colitis significantly increased the response to colorectal distension of pelvic afferent C-fibres. BCTC did not significantly affect the C-fibre response in controls, but normalized the sensitized response in rats with colitis. TNBS colitis increased the spontaneous activity of C-fibres, an effect which was insensitive to administration of BCTC. TNBS colitis had no effect on Adelta-fibres, nor was their activity modulated by BCTC. TNBS colitis caused an immunocytochemical up-regulation of TRPV1 receptors in the cell bodies of pelvic afferent NF200 negative neurons. TRPV1 signalling mediates the colitis-induced sensitization of pelvic afferent C-fibres to CRD, while Adelta-fibres are neither sensitized by colitis nor affected by TRPV1 inhibition.

Review article: gastrointestinal sensory and motor disturbances in inflammatory bowel disease - clinical relevance and pathophysiological mechanisms

BACKGROUND

It is well known that inflammation has a profound impact on the neuromuscular apparatus of the gastrointestinal tract during the inflammatory insult and in periods of remission, at the site of inflammation and at distance from this site. The importance of this interaction is illustrated by the higher prevalence of functional gut disorders in patients with inflammatory bowel disease.

AIMS

To document the epidemiological and clinical significance of functional alterations of gut motility and sensitivity in patients with inflammatory bowel disease and to formulate potential pathophysiological mechanisms.

RESULTS AND CONCLUSIONS

Functional gut disorders occur frequently in patients with inflammatory bowel disease, both during inflammatory episodes and in periods of remission, and have a major impact on their quality of life. The clinical manifestations of these motility and sensitivity disorders vary and are often difficult to treat, mainly because therapeutic guidelines and specific diagnostic tests to distinguish inflammatory bowel disease from functional gut disorders are lacking. Chronic bowel inflammation results in a complicated interaction between neuroendocrine serotonin-predominant cells of the mucosa, inflammatory cells (particularly mast cells) in the submucosa, the intrinsic and extrinsic innervation and the muscular apparatus including the interstitial cells of Cajal. The outcome of this interaction is a perturbation of gastrointestinal motor function, both locally and at distance from the site of inflammation and during both acute inflammation and remission.

Gastrointestinal dysmotility in 5-fluorouracil-induced intestinal mucositis outlasts inflammatory process resolution

AIM

To evaluate gastrointestinal motility during 5-fluorouracil (5-FU)-induced intestinal mucositis.

MATERIALS AND METHODS

Wistar rats received 5-FU (150 mg kg(-1), i.p.) or saline. After the 1st, 3rd, 5th, 15th and 30th day, sections of duodenum, jejunum and ileum were removed for assessment of epithelial damage, apoptotic and mitotic indexes, MPO activity and GSH concentration. In order to study gastrointestinal motility, on the 3rd or 15th day after 5-FU treatment, gastric emptying in vivo was measured by scintilographic method, and stomach or duodenal smooth muscle contractions induced by CCh were evaluated in vitro.

RESULTS

On the third day of treatment, 5-FU induced a significant villi shortening, an increase in crypt depth and intestinal MPO activity and a decrease in villus/crypt ratio and GSH concentration. On the first day after 5-FU there was an increase in the apoptosis index and a decrease in the mitosis index in all intestinal segments. After the 15th day of 5-FU treatment, a complete reversion of all these parameters was observed. There was a delay in gastric emptying in vivo and a significant increase in gastric fundus and duodenum smooth muscle contraction, after both the 3rd and 15th day.

CONCLUSION

5-FU-induced gastrointestinal dysmotility outlasts intestinal mucositis.

Experimental pancreatitis disturbs gastrointestinal and colonic motility in mice: effect of the prokinetic agent tegaserod

Acute pancreatitis remains a potentially life-threatening disease associated with gastrointestinal motility disturbances. Prokinetic agents may be useful to overcome these motility disturbances. In this study, we investigated the effect of acute necrotizing pancreatitis (ANP) on gastrointestinal motility in female mice and evaluated the effect of tegaserod, a prokinetic 5-hydroxytryptamine-4 (5HT4) receptor agonist. ANP was induced by feeding mice a choline-deficient ethionine-supplemented diet during 72 h. In vivo intestinal motility was measured as the geometric centre (GC) of 25 glass beads 30-120-360 min after gavage. Colonic peristaltic activity was studied using a modified Trendelenburg set-up. ANP significantly decreased GC 30-120-360 min after bead gavage, associated with a significant increase of myeloperoxidase in the proximal small intestine and colon, but not in the stomach or distal small intestine. Tegaserod significantly ameliorated GC 360 min after bead gavage in control and pancreatitis mice. In isolated colonic segments, ANP significantly decreased the amplitude of peristaltic waves and increased the interval between peristaltic contractions. Tegaserod normalized the disturbed interval. In conclusion, ANP impairs gastric, small intestinal and colonic motility in mice. Tegaserod improves ANP-induced motility disturbances in vivo and in vitro, suggesting a therapeutic benefit of prokinetic 5HT4 receptor agonists in the treatment of pancreatitis-induced ileus.

Neural mechanisms of early postinflammatory dysmotility in rat small intestine

Although human postinflammatory dysmotility is known, so far animal studies have primarily investigated changes during inflammation. Here, we focused on postinflammatory changes in rat jejunal myenteric plexus and jejunal motility. Evolution of ethanol/2,4,6-tri-nitrobenzene sulphonic acid (TNBS)-induced inflammation was assessed histologically and by measuring myeloperoxidase activity (MPO). Electromyography and immunohistochemistry were performed 1 week after ethanol/TNBS and also after N(G)-nitro-L-arginine methyl ester (L-NAME) administration. Ethanol/TNBS induced a transient inflammation, with normalization of MPO and histological signs of an early phase of recovery after 1 week. The number of cholinergic neurones was not altered, but myenteric neuronal nitric oxide synthase (nNOS)-immunoreactivity was significantly lower in the early phase of recovery after TNBS compared with water (1.8 +/- 0.2 vs 3.5 +/- 0.2 neurones ganglion(-1), P < 0.001). Interdigestive motility was disrupted with a loss of phase 1 quiescence, an increase of migrating myoelectric complex cycle length, a higher number of non-propagated activity fronts and a decrease of adequately propagated phase 3 s after TNBS. Administration of L-NAME resulted in a similar disruption of interdigestive motility patterns. In the early phase of recovery after ethanol/TNBS-induced jejunal inflammation, a loss of motor inhibition occurs due to a decrease of myenteric nNOS activity. These observations may provide a model for early postinflammatory dysmotility syndromes.

Individual reactivity to the open-field predicts the expression of cardiovascular and behavioural sensitisation to novel stress

Posttraumatic stress disorder (PTSD) is the fourth most common psychiatric disorder. It is associated with cardiovascular disorders and irritable bowel syndrome (IBS). Besides stressful life-events, a prior history of gastrointestinal infection is a predisposing factor for the development of IBS. Only a proportion of persons exposed to traumatic events develop PTSD. Several factors, like genetic predisposition, stressor intensity, cognitive appraisal mechanisms and coping processes influence the likelihood of developing PTSD after exposure to a trauma. We used a single session of footshocks in rats, an animal model with a high degree of validity for PTSD, to study whether transient colonic inflammation alters local and distal visceral sensitivity, and whether reactivity to the open-field (low (LA) or high (HA) active) predicts long-term stress-induced behavioural and cardiovascular sensitisation and altered visceral pain sensitivity. A distention series and noise challenge were given 2 weeks after foot-shocks, followed by a transient colonic inflammation period and a second distention series and noise challenge 4 weeks after foot-shocks. During exposure to noise, both before and after inflammation, footshocked rats showed increased immobility compared to controls, which was significantly greater in LA rats than in HA rats. LA preshocked rats also showed a greater blood pressure response to the noise test, but this only became evident in the second noise-test. Neither footshocks nor colonic inflammation affected duodenal pain sensitivity. The results provide additional evidence for long-lasting cardiovascular hyperresponsivity after a stressful event and indicate that its degree is predicted by personality traits or coping style.

Role of nitric oxide in the impairment of circular muscle contractility of distended, uninflamed mid-colon in TNBS-induced acute distal colitis in rats

AIM: To evaluate the role of nitric oxide (NO) in the motor disorders of the dilated uninflamed mid-colon (DUMC) from trinitrobenzene sulfonic acid (TNBS)-induced acute distal colitis in rats.

METHODS: Colitis was induced in male Sprague-Dawley rats by a single intracolonic administration of TNBS. Control rats received an enema of 0.9% saline. The rats were killed 48 h after TNBS or saline administration. Macroscopic and histologic lesions of the colon were evaluated. Myeloperoxidase (MPO) and nitric oxide synthase (NOS) activity were measured on the colonic tissue. In TNBS rats, we evaluated spontaneous and evoked contractile activity in circular muscle strips derived from DUMC in comparison to the same colonic segment of control rats, both in the presence and in the absence of a non-selective NOS isoforms inhibitor N-nitro-L-arginine (L-NNA). Pharmacological characterization of electric field stimulation (EFS)-evoked contractile responses was also performed.

RESULTS: In TNBS rats, the distal colon showed severe histological lesions and a high MPO activity, while the DUMC exhibited normal histology and MPO activity. Constitutive NOS activity was similar in TNBS and control rats, whereas inducible NOS activity was significantly increased only in the injured distal colon of TNBS rats. Isometrically recorded mechanical activity of circular muscle strips from DUMC of TNBS rats showed a marked reduction of the force and frequency of spontaneous contractions compared to controls, as well as of the contractile responses to a contracting stimulus. In the presence of L-NNA, the contractile activity and responses displayed a significantly greater enhancement compared to controls. The pharmacological characterization of EFS contractile responses showed that a cooperative-like interaction between cholinergic muscarinic and tachykinergic neurokinin 1 and 2 receptors mediated transmission in DUMC of TNBS rats vs a simple additive interaction in controls.

CONCLUSION: The results of this study show that, during TNBS-induced acute distal colitis, circular muscle intrinsic contractile mechanisms and possible enteric neural excitatory activity are inhibited in the distended uninflamed mid-colon. Suppression of NO synthesis markedly improves spontaneous and evokes muscle contractions, in spite of any evident change in local NO activity.

Plasticity of the enteric nervous system during intestinal inflammation

Inflammation of the bowel causes structural and functional changes to the enteric nervous system (ENS). While morphological alterations to the ENS are evident in some inflammatory conditions, it appears that relatively subtle modifications to the neurophysiology of enteric microcircuits may play a role in gastrointestinal (GI) dysfunction. These include changes to the excitability and synaptic properties of enteric neurones. The response of the ENS to inflammation varies according to the site and type of inflammation, with the functional consequences depending on the nature of the inflammatory stimulus. It has become clear that inflammation at one site can produce changes that occur at remotes sites in the GI tract. Immunohistochemical data from patients with inflammatory bowel disease (IBD) and animal models indicate that inflammation alters the neurochemical content of some functional classes of enteric neurones. A growing body of evidence supports an active role for enteric glia in neuronal and neuroimmune communication in the GI tract, particularly during inflammation. In conclusion, plasticity of the ENS is a feature of intestinal inflammation. Elucidation of the mechanisms whereby inflammation alters enteric neural control of GI functions may lead to novel treatments for IBD.

Impaired gastric motility in the gastroesophageal reflux rat model: an in vitro study

PURPOSE

The present study investigated the effects of acid and mixed reflux on the responsiveness of gastric smooth muscle in the gastroesophageal reflux (GER) rat model.

MATERIAL AND METHODS

Three groups of rat were studied encompassing acid reflux, mixed reflux and sham operation. Acid reflux was induced by pyloric ligation (AR group) and mixed reflux was induced by jejunal ligation 1 cm distal to Treitz ligament (MR group). Similar surgical manipulations were carried out in the sham operated rats (SO group). Carbachol-, serotonin-, KCl-induced contractile response and nicotine-, sodium nitroprusside-, papaverine-induced relaxant response in isolated gastric fundus smooth muscle strips were determined using in vitro muscle technique 24 h after surgery.

RESULTS

Isolated gastric fundus smooth muscle contractility to serotonin, carbachol or KCl was significantly reduced in the AR and MR groups with decreased Emax and pD(2) values compared with the SO group. Relaxant responses to nicotine was significantly increased in the AR and MR groups with increased Emax and pD(2) values compared with the SO group. Sodium nitroprusside and papaverine-induced-relaxant responses were similar in all of the groups and there was no change in agonist potency.

CONCLUSION

The present study indicates that decreased contractile and increased nicotine-induced relaxant response of the gastric smooth muscle in the surgically created GER model. These findings suggest that impaired gastric smooth muscle reactivity at least in part may play a role in gastric dysmotility in GER.

Altered prejunctional modulation of intestinal cholinergic and noradrenergic pathways by alpha2-adrenoceptors in the presence of experimental colitis

1 This study investigates the influence of intestinal inflammation on: (1) the control of intestinal neurotransmission and motility by prejunctional alpha(2)-adrenoceptors and (2) the expression of intestinal alpha(2)-adrenoceptors. Experimental colitis was induced by intrarectal administration of 2,4-dinitrobenzenesulphonic acid (DNBS) to rats. 2 UK-14,304 inhibited atropine-sensitive electrically evoked contractions of ileal and colonic longitudinal muscle preparations. UK-14,304 acted with similar potency, but higher efficacy, on tissues from DNBS-treated animals; its effects were antagonized with greater potency by phentolamine than rauwolscine. 3 Electrically induced [(3)H]noradrenaline release from ileal preparations was reduced in the presence of colitis. Tritium outflow was decreased by UK-14,304 and stimulated by rauwolscine or phentolamine: these effects were enhanced in preparations from animals with colitis. 4 Reverse transcription-polymerase chain reaction and Western blot assay demonstrated the protein expression of alpha(2A)-adrenoceptors in mucosal and muscular tissues isolated from ileum and colon. The induction of colitis increased alpha(2A)-adrenoceptor expression in both ileal and colonic muscular layers, without concomitant changes in mucosal tissues. 5 Induction of colitis reduced gastrointestinal propulsion of a charcoal suspension in vivo. In this setting, the gastrointestinal transit was inhibited by intraperitoneal (i.p.) UK-14,304 and stimulated by i.p. rauwolscine. After pretreatment with guanethidine, the stimulant action of rauwolscine no longer occurred, and UK-14,304 exerted a more prominent inhibitory effect that was antagonized by rauwolscine. 6 The present results indicate that, in the presence of intestinal inflammation, prejunctional alpha(2)-adrenoceptors contribute to an enhanced inhibitory control of cholinergic and noradrenergic transmission both at inflamed and noninflamed distant sites. Evidence was obtained that such modulatory actions depend on an increased expression of alpha(2A)-adrenoceptors within the enteric nervous system.

Small bowel motility

The publications relevant to small bowel motility have been concentrated during the past year in several main areas: further characterization of normal patterns of small bowel motor activity and transit, physiologic control mechanisms, visceral hypersensitivity, inflammation and motility, disease processes and dysmotility, and novel pharmacologic approaches to altered sensorimotor activity.