Stress-induced Visceral Hypersensitivity Research Articles

Importance of epigenetic mechanisms in visceral pain induced by chronic water avoidance stress

Epigenetic molecular mechanisms, which include DNA methylation and histone deacetylation, are implicated in the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Previously, we demonstrated that repeated water avoidance stress (WAS), a validated model of chronic psychological stress, induces heightened visceral pain behaviors in rodents that resemble irritable bowel syndrome (IBS) sequelae. However, the involvement of epigenetic molecular mechanisms in the pathophysiology of stress-induced visceral pain has not been explored. Our hypothesis is that epigenetic mechanisms within the central nervous system (CNS) are important to chronic stress-induced visceral hypersensitivity. Adult male F-344 rats with intracerebroventricular (i.c.v.) cannulae were exposed to 7 days of repeated WAS. Controls received a SHAM stress. Following the daily 1h stressor, trichostatin A (TSA; 100 ng/ml), a potent histone deacetylase inhibitor, or vehicle (VEH; 0.1% DMSO/saline,) as control was administered via the i.c.v. cannula. Visceral sensitivity was assessed 24h after the final WAS and quantified the visceromotor response (VMR) by recording the number of abdominal contractions in response to graded pressures (20-60 mmHg) of colorectal distensions (CRD). From a separate group of rats that were exposed to repeated WAS or SHAM stress, the amygdala was isolated to assess the methylation status of glucocorticoid receptor (GR) and corticotropin releasing-factor (CRF) genes via bisulfite sequencing and verified by pyrosequencing. GR and CRF gene expression was quantified via qRT-PCR. Stressed rats exhibited visceral hypersensitivity that was significantly attenuated by TSA. Compared to SHAM controls, methylation of the GR gene was increased following WAS while expression of the GR gene was decreased. Methylation of the CRF promoter was decreased with WAS with a concomitant increase in CRF expression. This study demonstrates the involvement of central epigenetic mechanisms in regulating stress-induced visceral hypersensitivity and provides a foundation for exploring the epigenetic mechanisms that may contribute to IBS-like symptomatology.

Novel insights about the mechanism of visceral hypersensitivity in maternally separated rats

Visceral hypersensitivity (VHS) is one of the most important characteristics of functional gastrointestinal disorders, including irritable bowel syndrome (IBS). Stress, whether physical or psychological, is known to be a crucial factor for inducing and maintaining visceral sensitivity in humans and rodents, but how stress induces VHS is not fully understood. In a recent study published in Neurogastroenterology and Motility, Wouters et al. demonstrate, for the first time, that maternal separation induces activation of periaqueductal gray (PAG), the hippocampus and the somatosensory cortex concomitantly with increased deactivation of the pre-frontal cortex. The findings provide insight on the role of maternal separation in inducing regional cerebral blood flow changes and cerebral plasticity. These novel insights on the role of central activation in the modulation of stress-induced VHS add to our growing understanding of the mechanisms that underlie VHS and suggest potential new drug development targets in stress-related diseases, including IBS.

Novel insights in the role of peripheral corticotropin‐releasing factor and mast cells in stress‐induced visceral hypersensitivity

Visceral hypersensitivity is one of the hallmarks in irritable bowel syndrome (IBS) pathophysiology. Stress is well known to affect visceral sensitivity in humans and rodents, an effect which is associated in part with alterations of intestinal epithelial permeability in rodents. Although the pathophysiology of visceral hypersensitivity is still unclear, two key factors have been identified as playing a major role in its modulation, namely peripheral corticotropin-releasing factor (CRF) and mast cells. In a recent study in Neurogastroenterology and Motility, van den Wijngaard et al. demonstrate that the mast-cell dependent visceral hypersensitivity observed in maternally separated rats after an acute exposure to a psychological stress can be prevented but not reversed by the peripherally restricted CRF receptor antagonist, α-helical CRF(9-41). They further show that the preventive effect of the CRF receptor antagonist is linked to a stabilization of mast cells and maintenance of the epithelial barrier at the colonic level. These data suggest that post stress mast cell activation and subsequent visceral hypersensitivity are not targeted by peripheral CRF receptor antagonists. These novel insights in the role of peripheral CRF in the modulation of stress-induced visceral hypersensitivity add to our growing understanding of the mechanisms that may lie at the origin of visceral pain disturbances following stress and will contribute to enhance the development of drugs that may have potential therapeutic benefits for IBS patients.

A marketed fermented dairy product containing Bifidobacterium lactis CNCM I‐2494 suppresses gut hypersensitivity and colonic barrier disruption induced by acute stress in rats

Fermented milk (FM) containing Bifidobacterium lactis CNCM I-2494 and yogurt strains improves irritable bowel syndrome (IBS) symptoms in constipated IBS patients. In rats, stressful events exacerbate IBS symptoms and result in the alteration of gut sensitivity and permeability via epithelial cell cytoskeleton contraction. In a stress model, we aimed at evaluating the effect of B. lactis CNCM I-2494 as a pure strain or contained in an FM product on visceral sensitivity and the impact of this FM on intestinal barrier integrity. Visceral sensitivity was analyzed in rats subjected to partial restraint stress (PRS). Rats received during 15 days the B. lactis as a pure strain (10(6) to 10(10) CFU mL(-1)), B. lactis in an FM product (10(8) CFU g(-1), diluted or not), or a control product. Gut paracellular permeability, colonic occluding and Jam-A proteins, and blood endotoxin levels were determined in rats receiving B. lactis in an FM product submitted or not to a PRS. The FM product showed a dose-dependent inhibitory effect on stress-induced visceral hypersensitivity. A similar antihyperalgesic effect was observed at 10(10) CFU mL(-1) of pure B. lactis administration. The FM product prevented the increase in intestinal permeability induced by PRS and restored occludin and JAM-A expressions to control levels. The FM product abolished the increase concentration of blood endotoxin induced by PRS. This study illustrates that a probiotic food containing B. lactis CNCM I-2494 strain reduces visceral hypersensitivity associated with acute stress by normalizing intestinal epithelial barrier via a synergistic interplay with the different probiotic strains and/or metabolites contained in this product.

Electroacupuncture alleviates stress-induced visceral hypersensitivity through an opioid system in rats

To investigate whether stress-induced visceral hypersensitivity could be alleviated by electroacupuncture (EA) and whether EA effect was mediated by endogenous opiates. Six to nine week-old male Sprague-Dawley rats were used in this study. Visceral hypersensitivity was induced by a 9-d heterotypic intermittent stress (HIS) protocol composed of 3 randomly stressors, which included cold restraint stress at 4°C for 45 min, water avoidance stress for 60 min, and forced swimming stress for 20 min, in adult male rats. The extent of visceral hypersensitivity was quantified by electromyography or by abdominal withdrawal reflex (AWR) scores of colorectal distension at different distention pressures (20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg). AWR scores either 0, 1, 2, 3 or 4 were obtained by a blinded observer. EA or sham EA was performed at classical acupoint ST-36 (Zu-San-Li) or BL-43 (Gao-Huang) in both hindlimbs of rats for 30 min. Naloxone (NLX) or NLX methiodide (m-NLX) was administered intraperitoneally to HIS rats in some experiments. HIS rats displayed an increased sensitivity to colorectal distention, which started from 6 h (the first measurement), maintained for 24 h, and AWR scores returned to basal levels at 48 h and 7 d after HIS compared to pre-HIS baseline at different distention pressures. The AWR scores before HIS were 0.6 ± 0.2, 1.3 ± 0.2, 1.9 ± 0.2 and 2.3 ± 0.2 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg distention pressures, respectively. Six hours after termination of the last stressor, the AWR scores were 2.0 ± 0.1, 2.5 ± 0.1, 2.8 ± 0.2 and 3.5 ± 0.2 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg distention pressures, respectively. EA given at classical acupoint ST-36 in both hindlimbs for 30 min significantly attenuated the hypersensitive responses to colorectal distention in HIS rats compared with sham EA treatment [AWRs at 20 mmHg: 2.0 ± 0.2 vs 0.7 ± 0.1, P = 4.23,711 E-4; AWRs at 40 mmHg: 2.6 ± 0.2 vs 1.5 ± 0.2, P = 0.00,163; AWRs at 60 mmHg: 3.1 ± 0.2 vs 1.9 ± 0.1, P = 0.003; AWRs at 80 mmHg: 3.6 ± 0.1 vs 2.4 ± 0.2, P = 0.0023; electromyographic (EMG) at 20 mmHg: 24 ± 4.7 vs 13.8 ± 3.5; EMG at 40 mmHg: 60.2 ± 6.6 vs 30 ± 4.9, P = 0.00,523; EMG at 60 mmHg: 83 ± 10 vs 39.8 ± 5.9, P = 0.00,029; EMG at 80 mmHg: 94.3 ± 10.8 vs 49.6 ± 5.9, P = 0.00,021]. In addition, EA at the acupuncture point BL-43 with same parameters did not alleviate visceral hypersensitivity in HIS rats. EA in healthy rats also did not have any effect on AWR scores to colorectal distention at distention pressures of 20 and 40 mmHg. The EA-mediated analgesic effect was blocked by pretreatment with NLX in HIS rats [AWR scores pretreated with NLX vs normal saline (NS) were 2.0 vs 0.70 ± 0.20, 2.80 ± 0.12 vs 1.50 ± 0.27, 3 vs 2.00 ± 0.15 and 3.60 ± 0.18 vs 2.60 ± 0.18 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg; P = 0.0087, 0.0104, 0.0117 and 0.0188 for 20, 40, 60 and 80 mmHg, respectively]. Furthermore, EA-mediated analgesic effect was completely reversed by administration of m-NLX, a peripherally restricted opioid antagonist (EMG pretreated with m-NLX vs NS were 30.84 ± 4.39 vs 13.33 ± 3.88, 74.16 ± 9.04 vs 36.28 ± 8.01, 96.45 ± 11.80 vs 50.19 ± 8.28, and 111.59 ± 13.79 vs 56.42 ± 8.43 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg; P = 0.05,026, 0.00,034, 0.00,005, 0.000,007 for 20 mmHg, 40 mmHg, 60 mmHg and 80 mmHg, respectively). EA given at classical acupoint ST-36 alleviates stress-induced visceral pain, which is most likely mediated by opioid pathways in the periphery.

Visceral sensation and irritable bowel syndrome; with special reference to comparison with functional abdominal pain syndrome

Stress-induced visceral hypersensitivity may play an important role in the pathogenesis of irritable bowel syndrome (IBS) but not in functional abdominal pain syndrome (FAPS). We examined rectal sensation in those patients. Experiment 1: Rectal thresholds of pain (PT) and maximum tolerance were assessed by barostat with ramp distention before and after repetitive rectal painful distention (RRD). Experiment 2, PT was measured in basal state and after intravenous CRF (100 µg) or vehicle, together with or without RRD. Experiment 3: Three phasic distentions at physiological range were randomly loaded. The subjects were asked to mark the visual analogue scale (VAS) in reference to subjective intensity of sensation. Experiment 1: Majority of IBS patients showed rectal hypersensitivity before RRD in contrast to FAPS. All IBS patients developed hypersensitivity after RRD, however, none of the FAPS patients did. RRD significantly reduced both thresholds in IBS (n=7) but did not change in controls (n=14) and FAPS (n=6). Experiment 2: PT was not modified by RRD in placebo group (n=6), while it was significantly reduced in CRF-treated group (n=5). On the other hand, CRF (n=5) or vehicle (n=5) without RRD did not alter PT. Experiment 3: The VAS ratings were increased in IBS (n=7) but significantly decreased in FAPS (n=6) as compared to controls (n=14). RRD-induced rectal hypersensitivity seems to be reliable marker for IBS, and CRF may contribute to this response. FAPS patients may have hyposensitivity to non-noxious physiological distention, suggesting FAPS has different pathogenesis from IBS.

A protease inhibitor against acute stress-induced visceral hypersensitivity and paracellular permeability in rats

In the present study, we investigated the effects of camostat mesilate (CM), a synthetic protease inhibitor, on visceral sensitivity and paracellular permeability induced by the acute restraint stress. We also explored the possible mechanisms underlying these effects. The acute restraint stress was induced by wrapping the fore shoulders, upper forelimbs and thoracic trunk of Sprague–Dawley rats for 2 h. Either CM (30, 100 and 300 mg/kg) or saline was intragastrically administrated to the rats 30 min before the acute restraint stress. Visceral perception was quantified as visceral motor response with an electromyography in a subset of rats. Paracellular permeability was determined in another subset of rats. We found that the visceral sensitivity and paracellular permeability were significantly reduced in the CM-treated rats. Moreover, the fecal protease activity was decreased in the CM-treated rats. The ZO-1 protein expression was markedly reduced by the stress treatment, but this decrease was suppressed by CM administration. Our data indicated that CM could efficiently inhibit visceral sensitivity and paracellular permeability induced by the acute restraint stress in rats. Therefore, CM might be an effective drug for the treatment of irritable bowel syndrome.

195 Free Immunoglobulin Light Chains May Be Involved in Stress-Induced Visceral Hypersensitivity in Maternal Separated Rats

195 Free Immunoglobulin Light Chains May Be Involved in Stress-Induced Visceral Hypersensitivity in Maternal Separated Rats

8 Kit Low Interstitial Cell of Cajal Stem Cells are a Cell of Origin of Gastrointestinal Stromal Tumors

BACKGROUND: We previously showed that the mast cell stabilizer ketotifen reduces IBS symptoms and increases the threshold of discomfort in hypersensitive IBS-patients. However, as ketotifen also has Histamine 1-receptor antagonistic properties and is known to penetrate the blood-brain barrier, its beneficial effect observed in this trial could also result from H1 receptor blockade, either at the peripheral or central level. AIM: To establish whether fexofenadine, a peripherally restricted 2nd generation Histamine 1-receptor antagonist, can mimic the effect of ketotifen and A) reverse stress-induced, mast cell dependent visceral hypersensitivity in a rat model of maternal separation (MS), and B) modulate gastrointestinal transit in MS and non-handled (NH) rats. METHODS: Adult MS and NH rats (n=9 in all groups) were subjected to acute stress (1 hr water avoidance,WA). The visceromotor response (VMR) to colorectal distension (1, 11⁄2, 2ml) was established preand 24 hours post-WA and expressed as area-under-curve (AUC, volume-vs-response, significant difference when P<0.05: Wilcoxon). Rats were then treated with fexofenadine (1,8 mg/kg or 18 mg/kg) or vehicle and re-evaluated 48 hrs post-WA. Pre-WA transit was measured in NH (n=4) and MS (n=5) rats treated with fexofenadine or vehicle by evaluating the transit (geometric centre or GC) of orally administered fluorescein-labeled dextran (MW=70.000) (1 is stomach, 2 most proximal small bowel, 11 most distal, 12 cecum, 13-15 colon). RESULTS: WA induced an increased VMR to distension in MS rats (pre-WA vs post-WA, 64±4 vs 98±6 (mean±SEM), P=0.012) which was reversed by 1.8 mg/kg fexofenadine (post-WA vs post-fexofenadine, 98±6 vs 69±5, P=0.012). High concentration fexofenadine (18 mg/kg) showed similar results (pre-WA vs post-WA, 72±4 vs 97±6, P=0.012 and post-WA vs post fexofenadine 97±6 vs 60±6, P=0.008). NH rats remained normo-sensitive under all conditions. Baseline pre-WA transit times of NH and MS were equal (10±0.2 vs 9.6±0.4). Administration of high-dose fexofenadine decreased transit time in NH (vehicle vs fexofenadine, 10±0.2 vs 6.4±1.1, P= 0.028) and MS-rats (9.6±0.4 vs 6.9±0.2, P=0.008). CONCLUSION: The peripheral H1 receptor antagonist fexofenadine effectively reverses stress-induced visceral hypersensitivity and decreases intestinal transit. As low dose fexofenadine does not cross the blood brain barrier, these data justify future IBS patient trials with 2nd generationH1-receptor antagonists.

7 The Peripheral Histamine 1-Receptor Antagonist Fexofenadine Effectively Reverses Stress-Induced Visceral Hypersensitivity in a Rat Model of Maternal Separation

BACKGROUND: We previously showed that the mast cell stabilizer ketotifen reduces IBS symptoms and increases the threshold of discomfort in hypersensitive IBS-patients. However, as ketotifen also has Histamine 1-receptor antagonistic properties and is known to penetrate the blood-brain barrier, its beneficial effect observed in this trial could also result from H1 receptor blockade, either at the peripheral or central level. AIM: To establish whether fexofenadine, a peripherally restricted 2nd generation Histamine 1-receptor antagonist, can mimic the effect of ketotifen and A) reverse stress-induced, mast cell dependent visceral hypersensitivity in a rat model of maternal separation (MS), and B) modulate gastrointestinal transit in MS and non-handled (NH) rats. METHODS: Adult MS and NH rats (n=9 in all groups) were subjected to acute stress (1 hr water avoidance,WA). The visceromotor response (VMR) to colorectal distension (1, 11⁄2, 2ml) was established preand 24 hours post-WA and expressed as area-under-curve (AUC, volume-vs-response, significant difference when P<0.05: Wilcoxon). Rats were then treated with fexofenadine (1,8 mg/kg or 18 mg/kg) or vehicle and re-evaluated 48 hrs post-WA. Pre-WA transit was measured in NH (n=4) and MS (n=5) rats treated with fexofenadine or vehicle by evaluating the transit (geometric centre or GC) of orally administered fluorescein-labeled dextran (MW=70.000) (1 is stomach, 2 most proximal small bowel, 11 most distal, 12 cecum, 13-15 colon). RESULTS: WA induced an increased VMR to distension in MS rats (pre-WA vs post-WA, 64±4 vs 98±6 (mean±SEM), P=0.012) which was reversed by 1.8 mg/kg fexofenadine (post-WA vs post-fexofenadine, 98±6 vs 69±5, P=0.012). High concentration fexofenadine (18 mg/kg) showed similar results (pre-WA vs post-WA, 72±4 vs 97±6, P=0.012 and post-WA vs post fexofenadine 97±6 vs 60±6, P=0.008). NH rats remained normo-sensitive under all conditions. Baseline pre-WA transit times of NH and MS were equal (10±0.2 vs 9.6±0.4). Administration of high-dose fexofenadine decreased transit time in NH (vehicle vs fexofenadine, 10±0.2 vs 6.4±1.1, P= 0.028) and MS-rats (9.6±0.4 vs 6.9±0.2, P=0.008). CONCLUSION: The peripheral H1 receptor antagonist fexofenadine effectively reverses stress-induced visceral hypersensitivity and decreases intestinal transit. As low dose fexofenadine does not cross the blood brain barrier, these data justify future IBS patient trials with 2nd generationH1-receptor antagonists.

Riluzole Normalizes Early-Life Stress-Induced Visceral Hypersensitivity in Rats: Role of Spinal Glutamate Reuptake Mechanisms

The molecular basis underlying visceral hypersensitivity in functional irritable bowel syndrome remains elusive, resulting in poor treatment effectiveness. Because alterations in spinal non-neuronal (astrocytic) glutamate reuptake are suspected to participate in chronic pain, we asked whether such processes occur in visceral hypersensitivity. Visceral hypersensitivity was induced in Sprague-Dawley rats by maternal separation. Separated adults were given a systemic administration of riluzole (5 mg/kg), an approved neuroprotective agent activating glutamate reuptake. Visceral hypersensitivity was assessed using colorectal distension (40 mm Hg). Somatic nociception was quantified using Hot Plate, Randall-Sellito, and Hargreaves tests. Spinal proteins were quantified using immunofluorescence and Western blot. The dependence of visceral sensory function upon spinal glutamate transport was evaluated by intrathecal injection of glutamate transport antagonist DL-threo-beta-benzyloxyaspartate (TBOA). For in vitro testing of riluzole and TBOA, primary cultures of astrocytes were used. We show that riluzole counteracts stress-induced visceral hypersensitivity without affecting visceral response in nonseparated rats or altering nociceptive responses to somatic pain stimulation. In addition, maternal separation produces a reduction in glial excitatory amino acid transporter (EAAT)-1 with no change in EAAT-2 or gamma-amino butyric acid transporters. Stress was not associated with changes in glial fibrillary acidic protein or astrocytic morphology per se. Furthermore, visceral normosensitivity relies on spinal EAAT, as intrathecal TBOA is sufficient to induce hypersensitivity in normal rats. We identify spinal EAAT as a therapeutic target, and establish riluzole as a candidate to counteract gastrointestinal hypersensitivity in disorders such as irritable bowel syndrome.

Adrenergic Stimulation Mediates Visceral Hypersensitivity to Colorectal Distension Following Heterotypic Chronic Stress

Chronic stress exacerbates or causes relapse of symptoms such as abdominal pain and cramping in patients with irritable bowel syndrome. We investigated whether chronic stress increases plasma norepinephrine and sensitizes colon-specific dorsal root ganglion (DRG) neurons by increasing expression of nerve growth factor (NGF) in the colon wall. Heterotypic chronic stress (HeCS) was applied to male Wistar rats and neurologic and molecular responses were analyzed. Tissues were analyzed for NGF expression. HeCS significantly increased visceromoter response to colorectal distension; expression of NGF increased in colonic muscularis externa and mucosa/submucosa. Rheobase decreased, resting membrane potential was depolarized, and electrogenesis of action potentials increased in colon-specific thoracolumbar DRG neurons. Luminal administration of resiniferatoxin in distal colon, systemic administration of anti-NGF antibody, or inhibition of the NGF receptor trkA by k252a or antisense oligonucleotides in thoracolumbar DRG blocked the chronic stress-induced visceral hypersensitivity to colorectal distension. Blockade of alpha1/alpha2- and beta1/beta2-adrenergic receptors prevented the stress-induced visceral hypersensitivity and increased expression of NGF in the colon wall. HeCS did not induce any inflammatory response in the colon wall. The peripheral stress mediator norepinephrine induces visceral hypersensitivity to colorectal distension in response to HeCS by increasing the expression of NGF in the colon wall, which sensitizes primary afferents in the absence of an inflammatory response.

Essential role for TRPV1 in stress‐induced (mast cell‐dependent) colonic hypersensitivity in maternally separated rats

Irritable bowel syndrome is in part characterized by an increased sensitivity to colonic distension. Stress is an important trigger factor for symptom generation. We hypothesized that stress induces visceral hypersensitivity via mast cell degranulation and transient receptor ion channel 1 (TRPV1) modulation. We used the rat model of neonatal maternal separation (MS) to investigate this hypothesis. The visceromotor response to colonic distention was assessed in adult MS and non-handled (NH) rats before and after acute water avoidance (WA) stress. We evaluated the effect of the mast cell stabilizer doxantrazole, neutralizing antiserum against the mast cell mediator nerve growth factor (NGF) and two different TRPV1 antagonists; capsazepine (non-specific) and SB-705498 (TRPV1-specific). Immunohistochemistry was used to assess post-WA TRPV1 expression in dorsal root ganglia and the presence of immunocytes in proximal and distal colon. Retrograde labelled and microdissected dorsal root ganglia sensory neurons were used to evaluate TRPV1 gene transcription. Results showed that acute stress induces colonic hypersensitivity in MS but not in NH rats. Hypersensitivity was prevented by prestress administration of doxantrazole and anti-NGF. Capsazepine inhibited and SB-705498 reversed poststress hypersensitivity. In MS rats, acute stress induced a slight increase in colonic mast cell numbers without further signs of inflammation. Post-WA TRPV1 transcription and expression was not higher in MS than NH rats. In conclusion, the present data on stress-induced visceral hypersensitivity confirm earlier reports on the essential role of mast cells and NGF. Moreover, the results also suggest that TRPV1 modulation (in the absence of overt inflammation) is involved in this response. Thus, mast cells and TRPV1 are potential targets to treat stress-induced visceral hypersensitivity.

25 Supraspinal Activation Associated with Stress-Induced Visceral Hypersensitivity: A Neuroimaging Study in the Awake Rat

25 Supraspinal Activation Associated with Stress-Induced Visceral Hypersensitivity: A Neuroimaging Study in the Awake Rat

908 CRH-Receptor Antagonism Prevents the Development of Stress-Induced Visceral Hypersensitivity But Fails to Affect Established Hypersensitivity

908 CRH-Receptor Antagonism Prevents the Development of Stress-Induced Visceral Hypersensitivity But Fails to Affect Established Hypersensitivity

Sensory Denervation Reduces Visceral Hypersensitivity in Adult Rats Exposed to Chronic Unpredictable Stress: Evidences of Neurogenic Inflammation

The purpose of this study is to provide evidence of neurogenic inflammation in chronic unpredictable stressed rats with the changes of visceral sensitivity, number of mast cells, and close proximity among mast cell-nerve-blood vessels. We found that (1) capsaicin denervation blocked stress-induced increase of visceral sensitivity, while doxantrazole presented a partial blocking; (2) capsaicin denervation blocked stress-induced enhancement of the proximity of mast cell-nerve fiber-blood vessels and blood vessel damage, while doxantrazole showed no effects on these; (3) doxantrazole blocked stress-induced increases of the MPO activity, the number and the degranulation of mast cells in the colon; (4) sensory denervation and doxantrazole had no effects on stress-induced behavioral inhibition. These results suggest that capsaicin-sensitive sensory fibers play a key role in stress-induced visceral hypersensitivity and the ultrastructural changes, mast cells play an important role in the generation of stress-induced colon inflammation.

T1387 SSR149415, a V1b Receptor Antagonist, Inhibits Stress-Induced Visceral Hypersensitivity in Rats

T1387 SSR149415, a V1b Receptor Antagonist, Inhibits Stress-Induced Visceral Hypersensitivity in Rats

Pharmacological and Pharmacokinetic Aspects of Functional Gastrointestinal Disorders

Medications are commonly used for the treatment of patients with functional gastrointestinal disorders. The general goal of this report is to review the pharmacokinetics and pharmacology of medications used in functional gastrointestinal disorders. Methods included literature review, consensus evaluation of the evidence for each topic assigned originally to 1 or 2 authors, and broader review at a harmonization session as part of the Rome III process. This report reviews the animal models that have been validated for the study of effects of pharmacologic agents on sensation and motility; the preclinical pharmacology, pharmacokinetics, and toxicology usually required for introduction of novel therapeutic agents; the biomarkers validated for studies of sensation and motility end points with experimental medications in humans; the pharmacogenomics applied to these medications and disorders; and the pharmacology of agents that are applied or have potential for treatment of functional gastrointestinal disorders, including psychopharmacologic agents. Clinician and basic investigators involved in the treatment or investigation of functional gastrointestinal disorders or disease models need to have a comprehensive understanding of a vast range of medications. It is anticipated that the interaction between investigators of basic science, basic and applied pharmacology, and clinical trials will lead to better treatment of these disorders.

Corticotropin-releasing factor receptor 1 mediates acute and delayed stress-induced visceral hyperalgesia in maternally separated Long-Evans rats

In rodents, maternal pup interactions play an important role in programming the stress responsiveness of the adult organism. The aims of this study were 1) to determine the effect of different neonatal rearing conditions on acute and delayed stress-induced visceral sensitivity as well as on other measures of stress sensitivity of the adult animal; and 2) to determine the role of corticotropin-releasing factor receptor (CRF-R) subtype 1 (CRF(1)R) in mediating visceral hypersensitivity. Three groups of male Long-Evans rat pups were used: separation from their dam for 180 min daily from postnatal days 2-14 (MS180), daily separation (handling) for 15 min (H), or no handling. The visceromotor responses (VMR) to colorectal distension, stress-induced colonic motility, and anxiety-like behavior were assessed in the adult rats. The VMR was assessed at baseline, immediately after a 1-h water avoidance (WA) stress, and 24 h poststress. Astressin B, a nonselective CRF-R antagonist, or CP-154,526, a selective CRF(1)R antagonist, was administered before the stressor and/or before the 24-h measurement. MS rats developed acute and delayed stress-induced visceral hyperalgesia. In contrast, H rats showed hypoalgesia immediately after WA and no change in VMR on day 2. MS rats with visceral hyperalgesia also exhibited enhanced stress-induced colonic motility and increased anxiety-like behavior. In MS rats, both CRF-R antagonists abolished acute and delayed increases in VMR. Rearing conditions have a significant effect on adult stress responsiveness including immediate and delayed visceral pain responses to an acute stressor. Both acute and delayed stress-induced visceral hypersensitivity in MS rats are mediated by the CRF/CRF(1)R system.

Stress-induced visceral hypersensitivity in female rats is estrogen-dependent and involves tachykinin NK1 receptors

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, 17β-estradiol, 17β-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 17β-estradiol or 17β-estradiol-plus-progesterone treatment. PRS induced visceral hypersensitivity to RD and this effect was prevented by ovariectomy. OVX rats treated with 17β-estradiol or 17β-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.