Influence of a new 5-HT4 receptor partial agonist, YKP10811, on visceral hypersensitivity in rats triggered by stress and inflammation

BACKGROUND

Adverse effects of previously developed 5-HT4 receptor agonists to treat functional constipation (FC) and constipation IBS (IBS-C) patients have limited their use but have given rise to new and more selective 5-HT4 receptor agonists. This work was aimed to evaluate the influence of YKP10811, a new potent 5-HT4 receptor partial agonist, on rat models of colorectal hypersensitivity to distension.

METHODS

Male and female rats were submitted to colorectal distension (CRD) before and after trinitrobenzene sulfonic acid (TNBS) infusion, acute (PRS) or chronic (water avoidance -10 days - WAS) stress. Electromyographic (EMG) response of abdominal muscles to CRD (15-60 mmHg) was used to measure pain. Changes of colonic tone were also evaluated. The influence of YKP10811 was compared to that of tegaserod with or without exposure of rats to a 5-HT4 receptor antagonist in TNBS treated rats and to both tegaserod and CP-154,526, a corticotropine releasing factor-R1 antagonist in WAS. We tested a possible pharmacological tachyphylaxis of YKP10811 in TNBS-induced hypersensitivity.

KEY RESULTS

YKP10811 (30 mg/kg) had no effect on basal sensitivity and tone in male and female rats but suppressed TNBS-induced hypersensitivity, an effect blocked by the 5-HT4 receptor antagonist GR113808 (10 mg/kg, SC). YKP10811 attenuated acute PRS-induced but not chronic WAS-induced colonic hypersensitivity. In addition, YKP10811 but not tegaserod reduced TNBS-induced colorectal hypersensitivity after 7 days of treatment.

CONCLUSIONS & INFERENCES

YKP10811exhibits antinociceptive activity in inflammation and acute stress-induced colonic hypersensitivity through 5-HT4 receptors but unlike tegaserod, YKP10811 maintains its activity after repeated administrations and may represent a new candidate to treat IBS-C 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

BACKGROUND

  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.

METHODS

  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.

KEY RESULTS

  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.

CONCLUSIONS & INFERENCES

  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.

Proteinase-activated receptor-4 evoked colorectal analgesia in mice: an endogenously activated feed-back loop in visceral inflammatory pain

BACKGROUND

Activation of proteinase-activated receptor-4 (PAR-4) from the colonic lumen has an antinociceptive effect to colorectal distension (CRD) in mice in basal conditions. We aimed to determine the functional localization of the responsible receptors and to test their role in two different hyperalgesia models.

METHODS

Mice received PAR-4 activating peptide (PAR-4-AP, AYPGKF-NH(2)) or vehicle intraperitoneally (IP), and abdominal EMG response to CRD was measured. The next group received PAR-4-AP intracolonically (IC) with or without 2,4,6-triaminopyrimidine, a chemical tight junction blocker, before CRD. The SCID mice were used to test the role of lymphocytes in the antihyperalgesic effect. The effects of PAR-4-AP and PAR-4-antagonist (P4pal-10) were evaluated in water avoidance stress (WAS) model and low grade 2,4,6-trinitrobenzene sulfonic acid (TNBS) colitis. Spinal Fos protein expression was visualized by immunohistochemistry.

KEY RESULTS

The antinociceptive effect of PAR-4-AP disappeared when was administrered IP, or with the blockade of colonic epithelial tight junctions, suggesting that PAR-4-AP needs to reach directly the nerve terminals in the colon. The CRD-induced spinal Fos overexpression was reduced by 43% by PAR-4-AP. The PAR-4-AP was antihyperalgesic in both hyperalgesia models and in mice with impaired lymphocytes. The PAR-4-antagonist significantly increased the TNBS, but not the WAS-induced colonic hyperalgesia.

CONCLUSIONS & INFERENCES

The antinociceptive effect of PAR-4-AP depends on its penetration to the colonic mucosa. The PAR-4 activation is endogenously involved as a feedback loop to attenuate inflammatory colonic hyperalgesia to CRD.

Guanylate cyclase C-mediated antinociceptive effects of linaclotide in rodent models of visceral pain

BACKGROUND Linaclotide is a novel, orally administered investigational drug currently in clinical development for the treatment of constipation-predominant irritable bowel syndrome (IBS-C) and chronic idiopathic constipation. Visceral hyperalgesia is a major pathophysiological mechanism in IBS-C. Therefore, we investigated the anti-nociceptive properties of linaclotide in rodent models of inflammatory and non-inflammatory visceral pain and determined whether these pharmacological effects are linked to the activation of guanylate cyclase C (GC-C). METHODS Orally administered linaclotide was evaluated in non-inflammatory acute partial restraint stress (PRS) and acute water avoidance stress (WAS) models in Wistar rats, and in a trinitrobenzene sulfonic acid (TNBS)-induced inflammatory model in Wistar rats and GC-C null mice. KEY RESULTS In TNBS-induced colonic allodynia, linaclotide significantly decreased the number of abdominal contractions in response to colorectal distension without affecting the colonic wall elasticity change in response to distending pressures after TNBS. However, linaclotide had no effect on visceral sensitivity under basal conditions. In addition, linaclotide significantly decreased colonic hypersensitivity in the PRS and WAS models. In wild type (wt) and GC-C null mice, the instillation of TNBS induced similar hyperalgesia and allodynia. However, in post-inflammatory conditions linaclotide significantly reduced hypersensitivity only in wt mice, but not in GC-C null mice. CONCLUSIONS & INFERENCES These findings indicate that linaclotide has potent anti-nociceptive effects in several mechanistically different rodent models of visceral hypersensitivity and that these pharmacological properties of linaclotide are exerted through the activation of the GC-C receptor. Therefore, linaclotide may be capable of decreasing abdominal pain in patients suffering from IBS-C.

Lactobacillus farciminis treatment attenuates stress-induced overexpression of Fos protein in spinal and supraspinal sites after colorectal distension in rats

Abstract Irritable bowel syndrome (IBS), frequently associated with psychological distress, is characterized by hypersensitivity to gut wall distension. Some probiotics are able to alleviate IBS symptoms and reduce visceromotor response to mechanical stimuli in animals. Moreover, we have previously shown that Lactobacillus farciminis treatment abolished the hyperalgesia to colorectal distension (CRD) induced by acute stress. The aims of the present study were to determine whether (i) stress-induced visceral hyperalgesia modifies the expression of Fos, a marker of general neuronal activation, induced by CRD, (ii) this activation can be modulated by L. farciminis treatment. Female rats were treated by L. farciminis and CRD was performed after partial restraint stress (PRS) or sham-PRS. The expression of Fos protein was measured by immunohistochemistry. After CRD or PRS, Fos expression was increased in spinal cord section (S1), nucleus tractus solitarius (NTS), paraventricular nucleus (PVN) of the hypothalamus, and in the medial nucleus of the amygdala (MeA). The combination of both stimuli, PRS and CRD, markedly increased this Fos overexpression in the sacral spinal cord section, PVN and MeA, but not in NTS. By contrast, a pretreatment with L. farciminis significantly reduced the number of Fos positive cells in these area. This study shows that PRS enhances Fos protein expression induced by CRD at the spinal and supraspinal levels in rats. Lactobacillus farciminis treatment inhibited this enhancing effect, suggesting that the antinociceptive effect of this probiotic strain results from a decrease of the stress-induced activation/sensitization of sensory neurons at the spinal and supraspinal level.

Increased faecal serine protease activity in diarrhoeic IBS patients: a colonic lumenal factor impairing colonic permeability and sensitivity

OBJECTIVES

Diarrhoea-predominant irritable bowel syndrome (IBS-D) is characterised by elevated colonic lumenal serine protease activity. The aims of this study were (1) to investigate the origin of this elevated serine protease activity, (2) to evaluate if it may be sufficient to trigger alterations in colonic paracellular permeability (CPP) and sensitivity, and (3) to examine the role of the proteinase-activated receptor-2 (PAR-2) activation and signalling cascade in this process.

PATIENTS AND METHODS

Faecal enzymatic activities were assayed in healthy subjects and patients with IBS, ulcerative colitis and acute infectious diarrhoea. Following mucosal exposure to supernatants from control subjects and IBS-D patients, electromyographic response to colorectal balloon distension was recorded in wild-type and PAR-2(-/-) mice, and CPP was evaluated on colonic strips in Ussing chambers. Zonula occludens-1 (ZO-1) and phosphorylated myosin light chain were detected by immunohistochemistry.

RESULTS

The threefold increase in faecal serine protease activity seen in IBS-D patients compared with constipation-predominant IBS (IBS-C) or infectious diarrhoea is of neither epithelial nor inflammatory cell origin, nor is it coupled with antiprotease activity of endogenous origin. Mucosal application of faecal supernatants from IBS-D patients in mice evoked allodynia and increased CPP by 92%, both of which effects were prevented by serine protease inhibitors and dependent on PAR-2 expression. In mice, colonic exposure to supernatants from IBS-D patients resulted in a rapid increase in the phosphorylation of myosin light chain and delayed redistribution of ZO-1 in colonocytes.

CONCLUSIONS

Elevated colonic lumenal serine protease activity of IBS-D patients evokes a PAR-2-mediated colonic epithelial barrier dysfunction and subsequent allodynia in mice, suggesting a novel organic background in the pathogenesis of IBS.

Lactobacillus farciminis treatment suppresses stress induced visceral hypersensitivity: a possible action through interaction with epithelial cell cytoskeleton contraction

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.

LPS-induced lung inflammation is linked to increased epithelial permeability: role of MLCK

The respiratory system is directly exposed to low levels of lipopolysaccharide (LPS), present as a contaminant on airborne particles. In cystic fibrosis, the prevailing data identify structural changes of the airway epithelium, as well as tight junction dilatation. This study was aimed at determining the contribution of myosin light chain kinase to maintaining airway epithelium barrier integrity in the lung inflammatory response to LPS in rats. The effects of the selective myosin light chain kinase inhibitor, 5-iodonaphthalene-1-sulphonyl-homopiperazine (ML-7), were evaluated: 1) on pulmonary inflammation and airway epithelium barrier permeability alterations induced by intra-tracheal LPS from Pseudomonas aeruginosa; and 2) on levels of the phosphorylated form of the myosin light chain, which is increased in a human airway epithelial cell line (NCI-H292) and tracheal tissue after LPS exposure. The results show that LPS increased airway epithelium barrier paracellular permeability and lung inflammation, and that pre-treatment with ML-7 inhibited both effects. This effect of ML-7 was associated with the inhibition of phosphorylated myosin light chain in both NCI-H292 cells and tracheal tissue. The data, obtained using in vivo and in vitro approaches, demonstrate a key role for myosin light chain kinase in lung inflammation, and suggest that myosin light chain kinase could be a potential target for novel drugs intended for relief of lung injury.

Antidiarrhoeal properties of a novel sigma ligand (JO 2871) on toxigenic diarrhoea in mice: mechanisms of action

BACKGROUND AND AIMS

Sigma ligands display antisecretory activity against various secretagogues, suggesting antidiarrhoeal properties. In this study, we evaluated: (i) the antidiarrhoeal effect of JO 2871, a high affinity sigma ligand, in three models of toxigenic diarrhoea in mice; and (ii) the site and mechanism of action of this compound.

METHODS

Faeces were collected after toxin or vehicle administration in male DBA2 or NMRI mice. Diarrhoea was determined by cumulative stool weight (mg) over a 120 minute period. Diarrhoea was induced by intravenous administration of Salmonella enteriditis lipopolysaccharide (LPS), or oral administration of Escherichia coli heat stable (E coli-sta) or Clostridium difficile toxins. Two sigma ligands, igmesine and JO 2871, were administered either orally or intravenously, 60 and 30 minutes before the toxins, respectively. JO 2871 was also given orally 30 minutes after E coli-sta. In addition, JO 2871 was administered intracerebroventricularly five minutes before LPS and E coli-sta. BMY 14802 (1000 microg/kg orally), a sigma receptor antagonist, or cyclosomatostatin (CSS 1 microg/kg intravenously), a somatostatin antagonist, were given five minutes prior to JO 2871 in LPS, E coli-sta, and C difficile toxin treated mice. Gastric emptying and intestinal transit were evaluated after oral JO 2871 and BMY 14802 and intravenous CSS.

RESULTS

Stool weight measured 120 minutes after administration of the toxins was significantly increased. Oral JO 2871 and igmesine dose dependently inhibited toxigenic diarrhoea in all models. ED(50) values obtained using JO 2871 (1-20 microg/kg) were more than 40 times lower than those obtained with igmesine. Oral JO 2871 given after E coli-sta also inhibited diarrhoea in a dose dependent manner (ED(50) 50 microg/kg). Both sigma ligands were active by the intravenous route on LPS and E coli-sta induced stool weight increases. JO 2871 administered intracerebroventricularly failed to block this effect at any dose tested. Both BMY 14802 and CSS reversed the antidiarrhoeal effect of oral JO 2871. JO 2871, BMY 14802, and CSS did not affect transit parameters.

CONCLUSIONS

JO 2871 exerts a potent oral antidiarrhoeal effect, acting peripherally through sigma sites and somatostatin release.

Acute restraint stress activates functional NK1 receptor in the colon of female rats: involvement of steroids

BACKGROUND AND AIMS

Psychological factors have been implicated in the aetiology of irritable bowel syndrome characterised by intestinal altered motility and visceral hypersensitivity. Similar disorders have been found in rats under stressful conditions. The role of tachykinins in bowel dysfunctions caused by stress is not fully documented. Therefore, we investigated the influence of stress on NK1 receptor activation at the colonic level in female rats.

METHODS

The stress procedure used consisted of two hours of partial restraint. Histamine release was measured from colonic samples of control and stressed animals and the effect of SR140333, a NK1 receptor antagonist, on substance P induced histamine release was determined. Involvement of steroids has been evaluated in this response.

RESULTS

NK1 receptor antagonist was found to inhibit substance P induced histamine release in samples from stressed female rats but not in samples from control animals. Previous treatment of female rats with RU 486 abolished this effect observed in stressed animals. Similarly, in samples from stressed female rats previously ovariectomised, SR140333 failed to inhibit substance P induced histamine release but previous treatment with both progesterone and oestrogen restored its effect.

CONCLUSIONS

Stress induces NK1 receptor activation in the colon, and ovarian steroids are involved in this response.

Acute and chronic stress differently affect visceral sensitivity to rectal distension in female rats

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.

Effect of ovarian hormones on intestinal mast cell reactivity to substance P

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.

Antinociceptive effect of pregabalin in septic shock-induced rectal hypersensitivity in rats

Pregabalin [S-(+)-3-isobutylgaba] is a novel compound under development for its analgesic, anxiolytic, and anticonvulsant properties, and its interaction with the alpha(2)delta-subunit of voltage-dependent Ca(2+) channels. In this study, we investigate the antinociceptive activity of pregabalin in a rat model of delayed visceral hyperalgesia induced by i.p. lipopolysaccharide (LPS) administration. LPS (Escherichia coli, serotype O111:B4) leads to a delayed lowering threshold (9-12 h) of abdominal contractions in response to rectal distension (RD) in awake rats surgically prepared for electromyography of abdominal muscles. This allodynic effect of LPS was blocked by morphine (0.3 mg/kg s.c.), and the action of morphine was antagonized by naloxone (2.5 mg/kg s.c.). A single i.p. (10, 30 mg/kg) and oral (1, 3, 10 and 30 mg/kg) treatment of pregabalin dose dependently suppressed LPS-induced rectal hypersensitivity. When administered 2 h before RD (but preceded 12 h by LPS injection), the oral dose of 10 mg/kg was effective both in the allodynic response induced by LPS and in the intensity of the nociceptive response related to RD. Pretreatment by either naloxone or bicuculline (a GABA(A) antagonist, 0.5 mg/kg i.p.) did not affect the antiallodynic effect of pregabalin. We conclude that pregabalin is a therapeutic candidate in the treatment of gut hypersensitivity not acting through GABA(A) and opiate receptors.

Chronic ingestion of a potential food contaminant induces gastrointestinal inflammation in rats: role of nitric oxide and mast cells

Chronic ingestion of xenobiotics could be pathogenic in the gastrointestinal tract. Recently, we showed that acute low administration of a food contaminant (diquat) induced intestinal secretion involving mast cells and nitric oxide. This work aimed to determine in rats: (1) the influence of a low level (0.1 mg/kg/day per os) chronic ingestion of diquat on gastrointestinal immune cells, and (2) the participation of nitric oxide synthases (NOS) in these effects. Diquat increased both gastric and jejunal myeloperoxidase activities, tissue histamine in vitro release after stimulation by 48/80, and mast cell numbers. Diquat did not alter gastric NOS but increased intestinal inducible NOS (iNOS) activity. L-NAME prevented diquat-induced gastric and intestinal mastocytosis and gastric but not intestinal inflammation. L-NAME reduced gastric constitutive NOS (cNOS) activity and reestablished control iNOS activity. Chronic low level ingestion of diquat induces a low-grade gastric and intestinal inflammation with mastocytosis and enhancement of intestinal iNOS activity.

Involvement of interleukin-1, prostaglandins and mast cells in rectal distension-induced colonic water secretion in rats

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.

Stress-induced visceral hypersensitivity to rectal distension in rats: role of CRF and mast cells

BACKGROUND

Psychological factors have long been implicated in the aetiology of irritable bowel syndrome often associated with abdominal pain. This work was designed to study, in rats, the influence of partial restraint stress on the abdominal cramps induced by rectal distension and to determine the role of corticotropin releasing factor (CRF) and mast cells degranulation in this response.

METHODS

Abdominal contractions were electromyographically recorded. Thirty minutes after stress or intracerebroventricular CRF, rectal distension was performed by inflation of a balloon (0.4-1.2 mL). alpha-helical CRF9-41 or doxantrazole were administered centrally (15 min) and intraperitoneally (30 min), respectively, before stress. Histamine release and the number of mast cells were determined in colonic pieces from stressed and control rats.

RESULTS

Stress and CRF enhanced the number of abdominal cramps evoked by rectal distension without affecting rectal compliance. alpha-helical CRF9-41 and doxantrazole antagonized the stress and CRF-induced enhancement of abdominal cramps. Stress increased the colonic histamine content whereas the number of colonic mast cells was unchanged.

CONCLUSIONS

Stress enhances abdominal contractions in response to rectal distension in rats via pathways involving central CRF and intestinal mast cells.

Rectal distention-induced colonic net water secretion in rats involves tachykinins, capsaicin sensory, and vagus nerves

BACKGROUND & AIMS

Distention of the intestine induces neural anion secretion in vitro. Both substance P and neurokinin A modify water and ion transport in vivo. This study investigated in vivo (1) the effect of rectal distention (RD) on proximal colonic net water flux, (2) the role of tachykinins, and muscarinic and nicotinic connections, and (3) the influence of capsaicin-sensitive nerves and vagotomy in this effect.

METHODS

In anesthetized rats, colonic loops were infused with [14C]polyethylene glycol 4000 Ringer's buffer. Net water flux was calculated according to 14C activity in the effluent collected. RD was performed by inflation of a balloon (2 mL) in the rectum.

RESULTS

RD induced a colonic net water hypersecretion. This effect was blocked by previous systemic capsaicin, vagotomy, atropine, and hexamethonium treatment. Both neurokinin 1 (NK1) (SR-140,333; 1 mg/kg) and NK2 (MEN-10,627; 150 microg/kg) antagonists administered intraperitoneally suppressed the RD-hypersecretory effect, whereas NK2 (MEN-10,627; 1.5 microg/kg) and NK3 (SR-142,801; 0.01 mg/kg) antagonists are active when injected intracerebroventricularly.

CONCLUSIONS

In vivo, RD induces colonic net water secretion in rats, involving capsaicin-sensitive innervation and vagal nerves. This effect involves tachykininergic pathways at both peripheral and central levels.

Implication of NK1 and NK2 receptors in rat colonic hypersecretion induced by interleukin 1 beta: role of nitric oxide

BACKGROUND & AIMS

Interleukin (IL) 1 beta is known to induce a neurally mediated colonic water secretion in vivo. The aim of this study was to investigate the mechanism of action of IL-1 beta on colonic net water flux and the role of tachykinins and nitric oxide.

METHODS

In anesthetized rats, isolated colonic loops were infused with Ringer's buffer containing [14C]polyethylene glycol 4000. Net water flux was calculated according to 14C activity determined in the effluent that was collected at 15-minute intervals.

RESULTS

Recombinant human IL-1 beta induced a 30-minute colonic hypersecretion. This effect was blocked by NK1 and NK2 antagonists, tetrodotoxin, and NG-methyl-L-arginine (L-NMA). L-arginine reversed the antisecretory effect of L-NMA on IL-1 beta-induced hypersecretion but did not modify the IL-1 beta-induced hypersecretion. Both NK1 and NK2 agonists induced a colonic hypersecretion, and their effects were blocked by L-NMA and tetrodotoxin. The NK3 agonist had no effect on water movements. The NK2 antagonist abolished the secretory effect of NK1 agonist; in contrast, the NK1 antagonist had no effect on the NK2 agonist-induced secretion.

CONCLUSIONS

IL-1 beta-induced colonic hypersecretion in vivo involves NK1- and NK2-receptor activation in cascade, suggesting a release of substance P and neurokinin A acting through NO release.

Interleukin 1 induces a neurally mediated colonic secretion in rats: involvement of mast cells and prostaglandins

BACKGROUND/AIMS

Interleukin 1 beta (IL-1 beta) is known to regulate intestinal ion and water transport in vitro through prostaglandin release. This study investigated the effect of IL-1 beta on colonic net water flux in vivo to determine its nature (nerve mediation versus action on the epithelium), the mediators involved, and its relationship with mast cell degranulation.

METHODS

Isolated colonic loops of anesthetized animals were infused with Ringer's buffer containing [14C]polyethylene glycol 4000. Net water flux was calculated according to 14C activity determined in the effluent collected at 15-minute intervals. Histological analysis was used to identify intact mast cells in colonic sections and radioimmunoassay to determine histamine levels.

RESULTS

Both IL-1 beta and the calcium ionophore A23187 induced colonic hypersecretion during 30 minutes. This effect was blocked by tetrodotoxin, doxantrazole, and indomethacin but not chlorpheniramine. Recombinant human interleukin 1 beta decreased the number of intact mast cells. This effect was eliminated by doxantrazole but not tetrodotoxin or indomethacin. A23187 or IL-1 beta increased histamine levels in the effluent during 75 and 45 minutes, respectively.

CONCLUSIONS

In vivo, rhL-1 beta induces colonic hypersecretion in rats. This effect is nerve mediated but not H1 receptor mediated and involves mast cell degranulation and prostaglandin release.