tetrodotoxin and Colitis

Chronic visceral pain is a defining feature of irritable bowel syndrome (IBS). IBS patients often show alterations in innate and adaptive immune function which may contribute to symptoms. Immune mediators are known to modulate the activity of viscero-sensory afferent nerves, but the focus has been on the innate immune system. Interleukin-2 (IL-2) is primarily associated with adaptive immune responses but its effects on colo-rectal afferent function in health or disease are unknown.. Myeloperoxidase (MPO) activity determined the extent of inflammation in health, acute trinitrobenzene-sulfonic acid (TNBS) colitis, and in our post-TNBS colitis model of chronic visceral hypersensitivity (CVH). The functional effects of IL-2 on high-threshold colo-rectal afferents and the expression of IL-2R and NaV 1.7 mRNA in colo-rectal dorsal root ganglia (DRG) neurons were compared between healthy and CVH mice.. MPO activity was increased during acute colitis, but subsided to levels comparable to health in CVH mice. IL-2 caused direct excitation of colo-rectal afferents that was blocked by tetrodotoxin. IL-2 did not affect afferent mechanosensitivity in health or CVH. However, an increased proportion of afferents responded directly to IL-2 in CVH mice compared with controls (73% vs 33%; p < 0.05), and the abundance of IL-2R and NaV 1.7 mRNA was increased 3.5- and 2-fold (p < 0.001 for both) in colo-rectal DRG neurons.. IL-2, an immune mediator from the adaptive arm of the immune response, affects colo-rectal afferent function, indicating these effects are not restricted to innate immune mediators. Colo-rectal afferent sensitivity to IL-2 is increased long after healing from inflammation.

Topics: Adaptive Immunity; Afferent Pathways; Animals; Colitis; Disease Models, Animal; Ganglia, Spinal; Hyperalgesia; Interleukin-2; Irritable Bowel Syndrome; Mice; NAV1.7 Voltage-Gated Sodium Channel; Neurons, Afferent; Peroxidase; Real-Time Polymerase Chain Reaction; Receptors, Interleukin-2; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sodium Channel Blockers; Tetrodotoxin; Trinitrobenzenesulfonic Acid; Visceral Pain

We have previously shown that neurokinin-1 (NK1) receptors predominantly mediate substance P-induced secretion of the non-inflamed rat colonic mucosa in vitro with a gradient in the magnitude of these responses. The aim of this study was to examine the effects of chronic inflammation on the contributions of different neurokinin receptor subtypes to colonic mucosal secretion. Colitis was induced by the intracolonic administration of 2,4,6-trinitrobenzene sulfonic acid in rats, reactivated 6 weeks later. Segments of proximal, mid- and distal colon were stripped of muscularis propria and mounted in Ussing chambers for measurement of short-circuit current. Use of selective agonists suggests that in the chronically inflamed rat colon NK1 receptors play a greater role in neurokinin-mediated mucosal secretion than do either NK2 or NK3. Selective antagonism implies that this is region-specific, with the inflammatory process altering the relative contribution of the neurokinin receptor subtypes within each region of the rat colon.

Topics: Anesthetics, Local; Animals; Anti-Inflammatory Agents, Non-Steroidal; Antipsychotic Agents; Benzamides; Colitis; Disease Models, Animal; Indomethacin; Intestinal Mucosa; Male; Neurokinin A; Neurokinin-1 Receptor Antagonists; Neurotransmitter Agents; Piperidines; Quinuclidines; Rats; Rats, Sprague-Dawley; Receptors, Neurokinin-1; Receptors, Neurokinin-2; Receptors, Neurokinin-3; Receptors, Tachykinin; Stereoisomerism; Substance P; Tetrodotoxin; Trinitrobenzenesulfonic Acid

Functional changes induced by inflammation persist following recovery from the inflammatory response, but the mechanisms underlying these changes are not well understood. Our aim was to investigate whether the excitability and synaptic properties of submucosal neurons remained altered 8 wk post-trinitrobenzene sulfonic acid (TNBS) treatment and to determine whether these changes were accompanied by alterations in secretory function in submucosal preparations voltage clamped in Ussing chambers. Mucosal serotonin (5-HT) release measurements and 5-HT reuptake transporter (SERT) immunohistochemistry were also performed. Eight weeks after TNBS treatment, colonic inflammation resolved, as assessed macroscopically and by myeloperoxidase assay. However, fast excitatory postsynaptic potential (fEPSP) amplitude was significantly increased in submucosal S neurons from previously inflamed colons relative to those in control tissue. In addition, fEPSPs from previously inflamed colons had a hexamethonium-insensitive component that was not evident in age-matched controls. AH neurons were hyperexcitable, had shorter action potential durations, and decreased afterhyperpolarization 8 wk following TNBS adminstration. Neuronally mediated colonic secretory function was significantly reduced after TNBS treatment, although epithelial cell signaling, as measured by responsiveness to both forskolin and bethanecol in the presence of tetrodotoxin, was comparable with control tissue. 5-HT levels and SERT immunoreactivity were comparable to controls 8 wk after the induction of inflammation, but there was an increase in glucagon-like peptide 2-immunoreactive L cells. In conclusion, sustained alterations in enteric neural signaling occur following the resolution of colitis, which are accompanied by functional changes in the absence of active inflammation.

Topics: Action Potentials; Animals; Bethanechol; Body Weight; Cell Count; Colforsin; Colitis; Colon; Enteric Nervous System; Enteroendocrine Cells; Excitatory Postsynaptic Potentials; Glucagon-Like Peptide 2; Guinea Pigs; Male; Membrane Potentials; Neurons; Peptide YY; Peroxidase; Serotonin; Serotonin Plasma Membrane Transport Proteins; Submucous Plexus; Tetrodotoxin; Trinitrobenzenesulfonic Acid; Veratridine

Recent studies suggest that altered neural regulation of the gastrointestinal microvasculature contributes to the pathogenesis of inflammatory bowel disease. Therefore, we employed video microscopy techniques to monitor nerve-evoked vasoconstrictor responses in mouse colonic submucosal arterioles in vitro and examined the effect of 2,4,6-trinitrobenzene sulphonic acid (TNBS) colitis. Nerve stimulation (2-20 Hz) caused frequency-dependent vasoconstrictor responses that were abolished by tetrodotoxin (300 nm) and guanethidine (10 microm). The P2 receptor antagonist suramin (100 microm) or the alpha(1)-adrenoceptor antagonist prazosin (100 nm) reduced the vasoconstriction and the combination of suramin and prazosin completely abolished responses. Nerve-evoked constrictions of submucosal arterioles from mice with TNBS colitis were inhibited by prazosin but not suramin. Superfusion of ATP (10 microm) resulted in large vasoconstrictions in control mice but had no effect in mice with colitis whereas constrictions to phenylephrine (3 microm) were unaffected. P2X(1) receptor immunohistochemistry did not suggest any alteration in receptor expression following colitis. However, Western blotting revealed that submucosal P2X(1) receptor expression was increased during colitis. In contrast to ATP, alphabeta-methylene-ATP (1 microm), which is resistant to catabolism by nucleotidases, constricted control and TNBS arterioles. This indicates that reduced purinergic transmission to submucosal arterioles may be due to increased degradation of ATP during colitis. These data comprise the first description of the neural regulation of mouse submucosal arterioles and identify a defect in sympathetic regulation of the GI vasculature during colitis due to reduced purinergic neurotransmission.

Topics: Adenosine Triphosphate; Adrenergic Agents; Adrenergic alpha-Agonists; Adrenergic alpha-Antagonists; Animals; Arterioles; Colitis; Colon; Disease Models, Animal; Electric Stimulation; Enteric Nervous System; Guanethidine; Intestinal Mucosa; Male; Mice; Microscopy, Video; Norepinephrine; Phenylephrine; Prazosin; Purinergic P2 Receptor Antagonists; Receptors, Adrenergic, alpha-1; Receptors, Purinergic P2; Receptors, Purinergic P2X; Suramin; Sympathetic Nervous System; Tetrodotoxin; Time Factors; Trinitrobenzenesulfonic Acid; Up-Regulation; Vasoconstriction

Colitis induced by Trichinella spiralis in rat induces alterations in the spontaneous motor pattern displayed by circular colonic muscle [Auli, M., Fernandez, E., 2005. Characterization of functional and morphological changes in a rat model of colitis induced by T. spiralis. Digestive Diseases and Sciences 50(8), 1432-1443]. We examined the temporal relationship between the severity of inflammation and the altered contractility of the underlying circular muscle as well as the role of NANC inhibitory pathways in the disruption of the motility pattern. Colitis was induced by intrarectal administration of T. spiralis larvae. Responses to acetylcholine (ACh) and increased extracellular potassium as well as the effect of tetrodotoxin (TTX, 1 microM), N-nitro-l-arginine (L-NOARG, 1 mM) and apamin (1 microM) were determined in vitro in the organ bath with circular muscle strips from sham-infected and infected rats at days 2-30 postinfection (PI). Microelectrode recordings were performed to study the putative changes in electrical activity of colonic smooth muscle cells. Responses to ACh and KCl were decreased at all days PI compared to sham. Intracellular calcium depletion had a greater inhibitory effect in inflamed tissue (6-14 PI). The effect of TTX, L-NOARG and apamin on the spontaneous contractions was found to be altered in all infected rats, i.e. their effects were transient and milder. Inflamed tissue showed lower resting membrane potential and a decreased duration of inhibitory junction potentials induced by electrical stimulation. These data suggest that the decreased contractility of colonic circular smooth muscle induced by the intrarectal T. spiralis infection results from the impairment of the excitation-contraction coupling, from a persistent hyperpolarization of smooth muscle cells and from impaired NANC inhibitory neurotransmission.

Topics: Acetylcholine; Animals; Apamin; Colitis; Disease Models, Animal; Disease Progression; Electric Stimulation; Enteric Nervous System; Gastrointestinal Motility; Inflammation; Intestines; Male; Muscle Contraction; Muscle, Smooth; Nitroarginine; Rats; Rats, Sprague-Dawley; Signal Transduction; Synaptic Transmission; Tetrodotoxin; Time Factors; Trichinella spiralis; Trichinellosis

Impairment of small intestinal absorption has been described in patients with ulcerative colitis and in animal models of experimental colitis. The pathophysiology of this dysfunction has not been elucidated. The aim of this study was to investigate the effect of chemical colitis on jejunal fluid absorption and determine the role of the enteric nervous system and some putative neurotransmitters. In a rat model of iodoacetamide-induced colitis, jejunal net fluid absorption was evaluated by the in vivo single-pass perfusion technique. The effects of 1) tetrodotoxin (TTX), 2) benzylalkonium chloride (BAC), 3) capsaicin, 4) vasoactive intestinal polypeptide (VIP) antagonism, 5) nitric oxide (NO) synthase (NOS) inhibition, and 6) 5-hydroxytryptamine type 3 and 4 (5-HT(3) and 5-HT(4)) receptor antagonism on the changes in fluid movement were investigated. A significant decrease in jejunal net fluid absorption was found 2 and 4 days after colitis induction: 26 (SD 14) and 28 (SD 19) microl x min(-1) x g dry intestinal wt(-1), respectively [P < 0.0002 compared with sham rats at 61 (SD 6.5) microl x min(-1) x g dry intestinal wt(-1)]. No histological changes were evident in jejunal sections. TTX and BAC reversed this decrease in fluid absorption: 54 (SD 13) and 44 (SD 14) microl x min(-1) x g dry intestinal wt(-1) (P = 0.0005 and P = 0.019, respectively, compared with colitis). Ablation of capsaicin-sensitive primary afferent fibers had a partial effect: 45 (SD 5) microl x min(-1) x g dry intestinal wt(-1) (P = 0.001 and P = 0.003 compared with colitis and sham, respectively). Constitutive and neuronal NOS inhibition and VIP antagonism returned jejunal net fluid absorption to normal values: 66 (SD 19), 61 (SD 5), and 56 (SD 14) microl x min(-1) x g dry intestinal wt(-1), respectively. 5-HT(3) and 5-HT(4) receptor antagonism had no effect. Chemical colitis is associated with a significant decrease in jejunal net fluid absorption. This decrease is neurally mediated and involves VIP- and NO-related mechanisms.

Topics: Animals; Benzalkonium Compounds; Capsaicin; Colitis; Enteric Nervous System; Enzyme Inhibitors; Intestinal Absorption; Iodoacetamide; Jejunum; Male; Myenteric Plexus; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Perfusion; Rats; Rats, Sprague-Dawley; Serotonin; Serotonin Antagonists; Sulfhydryl Reagents; Tetrodotoxin; Ulcer; Vasoactive Intestinal Peptide

Protease activated receptors (PARs) have been postulated to play a role during intestinal inflammation. The presence and role played by PAR(4) in gastrointestinal functions have not been fully clarified. The aims of this study were: (i) to examine expression of PAR(4) in rat proximal colon; (ii) to determine the mechanical effects induced by PAR(4) activation in longitudinal muscle; and (iii) to characterise the underlying mechanisms.. PAR(4) expression was determined by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. Mechanical activity was recorded as changes in isometric tension.. A PCR product corresponding to the predicted size of the PAR(4) signal was amplified from RNA prepared from the colon of rats, showing the presence of PAR(4) in those tissues. Immunohistochemistry revealed that PAR(4) protein was expressed on epithelial surfaces and submucosa. PAR(4) activating peptides, GYPGKF-NH(2) and AYPGKG-NH(2), produced concentration dependent contractile effects on longitudinal muscle. Tetrodotoxin (TTX) or atropine significantly reduced the contractile responses to AYPGKG-NH(2), and atropine after TTX did not cause any further reduction. NK(1) receptor antagonist, SR140333, or NK(2) receptor antagonist, SR48968, alone or in combination, produced a reduction in PAR(4) induced contractile effect, and when coadministered with TTX abolished it. Capsaicin markedly reduced the contractions evoked by AYPGKG-NH(2).. The present results suggest that PAR(4) is functionally expressed in rat colon and its activation induces contraction of the longitudinal muscle both through TTX sensitive release of acetylcholine and release of tachykinins, probably from sensory nerves. These actions may contribute to motility disturbances during intestinal trauma and inflammation.

Topics: Animals; Atropine; Benzamides; Capsaicin; Colitis; Colon; Dose-Response Relationship, Drug; Gastrointestinal Motility; Immunohistochemistry; Male; Muscle Contraction; Muscle, Smooth; Neurokinin-1 Receptor Antagonists; Oligopeptides; Piperidines; Quinuclidines; Rats; Rats, Wistar; Receptors, Neurokinin-2; Receptors, Thrombin; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tetrodotoxin

The composition of Na+ currents in dorsal root ganglia (DRG) neurons depends on their neuronal phenotype and innervation target. Two TTX-resistant (TTX-R) Na+ currents [voltage-gated Na channels (Nav)] have been described in small DRG neurons; one with slow inactivation kinetics (Nav1.8) and the other with persistent kinetics (Nav1.9), and their modulation has been implicated in inflammatory pain. This has not been studied in neurons projecting to the colon. This study examined the relative importance of these currents in inflammation-induced changes in a mouse model of inflammatory bowel disease. Colonic sensory neurons were retrogradely labeled, and colitis was induced by instillation of trinitrobenzenesulfonic acid (TNBS) into the lumen of the distal colon. Seven to ten days later, immunohistochemical properties were characterized in controls, and whole cell recordings were obtained from small (<40 pF) labeled DRG neurons from control and TNBS animals. Most neurons exhibited both fast TTX-sensitive (TTX-S)- and slow TTX-R-inactivating Na+ currents, but persistent TTX-R currents were uncommon (<15%). Most labeled neurons were CGRP (79%), tyrosine kinase A (trkA) (84%) immunoreactive, but only a small minority bind IB4 (14%). TNBS-colitis caused ulceration, thickening of the colon and significantly increased neuronal excitability. The slow TTX-R-inactivating Na current density (Nav1.8) was significantly increased, but other Na currents were unaffected. Most small mouse colonic sensory neurons are CGRP, trkA immunoreactive, but not isolectin B4 reactive and exhibit fast TTX-S, slow TTX-R, but not persistent TTX-R Na+ currents. Colitis-induced hyperexcitability is associated with increased slow TTX-R (Nav1.8) Na+ current. Together, these findings suggest that colitis alters trkA-positive neurons to preferentially increase slow TTX-R Na+ (Nav1.8) currents.

Topics: Anesthetics, Local; Animals; Calcitonin Gene-Related Peptide; Colitis; Colon; Female; Ganglia, Spinal; Kinetics; Lectins; Male; Membrane Potentials; Mice; Mice, Inbred Strains; NAV1.8 Voltage-Gated Sodium Channel; NAV1.9 Voltage-Gated Sodium Channel; Neurons, Afferent; Neuropeptides; Nociceptors; Receptor, trkA; Sodium; Sodium Channels; Tetrodotoxin

We used the trinitrobenzenesulphonic acid (TNBS) rat model of experimental colitis to study the alterations in electrogenic ion transport in the inflamed distal colon. The distal colon exhibited decreased basal transport and reduced short-circuit current responses to carbachol and isobutylmethylxanthine (IBMX). The concentration/response curve for IBMX was also shifted to the right. Ion substitution experiments indicated that electrogenic transport was attributable chiefly to Cl(-) secretion. The mucosal layer of the inflamed distal colon (devoid of the submucosa) exhibited normal maximal responses to carbachol and IBMX, although the concentration/response curve for the latter was again shifted to the right. Tetrodotoxin markedly increased the response of the normal distal colon to both secretagogues and nullified the inhibition of the response to carbachol, but not that to IBMX, in the inflamed colon. The response of the mucosal preparation to 8-bromoadenosine 3',5'-cyclic monophosphate was similar in the normal and inflamed intestine, while the G protein activator NaF had a greater effect in the latter. The expression of the cystic fibrosis transmembrane conductance regulator (CFTR), as assessed by Northern blotting, was unchanged. cAMP levels in isolated colonocytes were markedly reduced by inflammation. We conclude that colonic inflammation produces disturbances of the enteric nervous system resulting in defective mucosal cAMP production and inhibition of ionic secretion.

Topics: 1-Methyl-3-isobutylxanthine; Anesthetics, Local; Animals; Biological Transport; Carbachol; Cholinergic Agonists; Colitis; Colon; Cyclic AMP; Cystic Fibrosis Transmembrane Conductance Regulator; Enteric Nervous System; Female; Gene Expression; Intestinal Mucosa; Ions; Phosphodiesterase Inhibitors; Rats; Rats, Wistar; Tetrodotoxin; Trinitrobenzenesulfonic Acid

We investigated the effects of experimental colitis on the muscarinic signaling properties and contractile behavior of canine colonic circular smooth muscle. The hypotheses that inflammation 1) inhibits in vivo muscarinic receptor mediated contractions, and 2) alters receptor density or receptor-binding affinities were tested. Muscarine was infused close-intra-arterially in seven conscious dogs during normal and experimental colitis states. Colonic circular muscle contractions were recorded via surgically attached strain gauge transducers. Muscarine stimulated phasic contractions in a dose-dependent manner, whereas colitis was inhibited. The inhibitory concentration 50% dose of M(3) receptor inhibitor was several times lower than that of M(1), M(2), and M(4) inhibitors during normal and colitis. However, inflammation induced a significant leftward shift in the circular muscle inhibitory dose-response curve of M(2) inhibitor. Muscarinic receptor density and binding analyses in isolated circular muscle cells was done in normal and colitis states. Inflammation significantly decreased maximum binding from 4082 fmol/mg to 2708 fmol/mg, whereas affinity constant remained unaffected. The conclusions were that 1) spontaneous and muscarine-activated in vivo phasic contractile activity of colonic circular muscle cells is primarily mediated by M(3) receptors; 2) inflammation was associated with a shift in M(2) receptor potency, due chiefly to a decrease in receptor density; and 3) this inhibitory effect was seen in normal and inflamed states, suggesting the importance of M(2) receptor. These findings suggest that changes in muscarinic response during colitis may contribute to the abnormal motility seen with inflammatory bowel disease.

Topics: Animals; Cholinergic Agents; Colitis; Dogs; Female; Ganglionic Blockers; Hexamethonium; Infusions, Intra-Arterial; Male; Muscarine; Muscarinic Antagonists; Muscle Contraction; Muscle, Smooth; Peroxidase; Receptors, Muscarinic; Tetrodotoxin

1. Neuronal cholinergic input is an important regulator of epithelial electrolyte transport and hence water movement in the gut. 2. In this study, colitis was induced by treating mice with 4% (w v(-1)) dextran sodium-sulphate (DSS)-water for 5 days followed by 3 days of normal water. Mid-colonic segments were mounted in Ussing chambers and short-circuit current (Isc, indicates net ion movement) responses to the cholinergic agonist, carbachol (CCh; 10(-4) M)+/-tetrodotoxin, atropine (ATR), hexamethonium (HEX), naloxone or phenoxybenzamine were assessed. 3. Tissues from mice with DSS-induced colitis displayed a drop in Isc in response to CCh (-11.3+/-3.3 microA/cm(2)), while those from control mice showed a transient increase in Isc (76.3+/-13.0 microA/cm(2)). The DeltaIsc in colon from DSS-treated mice was tetrodotoxin-sensitive, atropine-insensitive and was reversed by hexamethonium (HEX+CCh=16.7+/-7.8 microA/cm(2)), indicating involvement of a nicotinic receptor. 4. CCh induced a drop in Isc in tissues from controls only when they were pretreated with the cholinergic muscarinic receptor blocker, atropine: ATR+CCh=-21.3+/-7.0 microA/cm(2). Nicotine elicited a drop in Isc in Ussing-chambered colon from both control and DSS-treated mice that was TTX-sensitive. 5. The drop in Isc evoked by CCh challenge of colonic tissue from DSS-treated mice or ATR+CCh challenge of control tissue was not significantly affected by blockade of opiate or alpha-adrenergic receptors by naloxone or phenoxybenzamine, respectively. 6. The data indicate that DSS-colitis reveals a nicotinic receptor that becomes important in cholinergic regulation of ion transport.

Topics: Animals; Atropine; Carbachol; Cholinergic Agonists; Colitis; Dextran Sulfate; Disease Models, Animal; Hexamethonium; Intestinal Mucosa; Ion Transport; Male; Mice; Mice, Inbred BALB C; Narcotics; Nicotine; Receptors, Adrenergic, alpha; Receptors, Cholinergic; Receptors, Muscarinic; Tetrodotoxin

In inflammatory bowel disease, smooth muscle function reportedly varies with disease duration. The aim of these studies was to determine changes in the control of spontaneous contractions in a model of experimental colitis that included reinflammation of the healed area. The amplitude and frequency of spontaneous contractions in circular smooth muscle were determined after intrarectal administration of trinitrobenzenesulfonic acid in rat distal colon. With the use of a novel paradigm, rats were studied 4 h (acute) or 28 days (healed) after the initial inflammation. At 28 days, rats were studied 4 h after a second inflammation (reinflamed) of the colon. Colitis induced transient increases in the amplitude of spontaneous contractions coincident with a loss of nitric oxide synthase activity. The frequency of contractions was controlled by constitutive nitric oxide in controls. Frequency was increased in healed and reinflamed colon and was associated with a shift in the dominance of neural constitutive nitric oxide synthase control to that of inducible nitric oxide synthase (iNOS). The initial colitis induced a remodeling of the neural control of spontaneous contractions reflecting changes in their regulation by constitutive nitric oxide synthase and iNOS.

Topics: Animals; Colitis; Colon; Disease Models, Animal; Gastrointestinal Motility; Guanidines; In Vitro Techniques; Inflammation; Inflammatory Bowel Diseases; Male; Muscle Contraction; Muscle, Smooth; NADPH Dehydrogenase; Nitric Oxide Synthase; omega-N-Methylarginine; Rats; Rats, Sprague-Dawley; Tetrodotoxin; Time Factors; Trinitrobenzenesulfonic Acid

The receptor responsible for CGRP-induced ion transport and permeability was examined in tissues from animals treated 7 days previously with trinitrobenzenesulfonic acid to induce colitis or in controls. CGRP caused a concentration-dependent increase in short circuit current (I(sc), EC(50) 21 nM), which was abolished in chloride-free buffer but was not blocked by CGRP(8-37) or tetrodotoxin (TTX). Amylin and adrenomedullin caused only a modest increase in I(sc). The responses to the linear CGRP(2) receptor agonists [Cys(Et)(2,7)] hCGRPalpha and [Cys(Acm)(2,7)] hCGRPalpha were considerably smaller than the response to CGRP. These responses were abolished in chloride-free buffer and were TTX sensitive. Atropine, doxantrazole, and indomethacin did not block the effects of CGRP or the CGRP(2) agonists. The response to [Cys(Et)(2,7)] hCGRPalpha was not affected by prior desensitization of the CGRP receptor and vice versa. Inflamed rats had a similar secretory response to CGRP (I(sc), EC(50) 15 nM) and [Cys(Et)(2,7)] hCGRPalpha as control tissues, while being hyporesponsive to carbachol. CGRP application increased electrical conductance of inflamed preparations. Taken together, these data suggest that CGRP may play an important role in the maintenance of host defense in colitis through an apparently novel CGRP receptor located on the colonic enterocyte.

Topics: Animals; Calcitonin Gene-Related Peptide; Colitis; Colon; Electric Conductivity; Humans; Ion Transport; Male; Rats; Rats, Wistar; Receptors, Calcitonin Gene-Related Peptide; Tetrodotoxin; Trinitrobenzenesulfonic Acid

This study was conducted to determine the ion transport mechanisms in the normal mouse cecum and compare them to an inbred mouse model of colitis. The Ussing chamber-voltage clamp technique was used to monitor the short circuit current (I(sc)). The basal I(sc) in the normal cecum was 82.6 +/- 5.8 microA/cm2. It was not affected by bumetanide, 9-anthracene carboxylate, amiloride, and phenamil or by removal of Cl- ions; but was abolished by the removal of Na+ ions. Flux measurements revealed the presence of neutral NaCl transport. In the colitic cecum, the basal current was significantly higher than the normal cecum. Basal current in the normal cecum was due primarily to Na+ absorption through a Na+ channel, while in the colitic cecum it was due to Cl- ion secretion. cAMP addition in colitic cecum did not increase Cl- secretion, further suggesting that the tissue is already secreting at a maximal rate.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Animals; Atropine; Cecum; Colitis; Electric Conductivity; Female; Ion Transport; Mice; Mice, Inbred C3H; Muscarinic Antagonists; Reference Values; Tetrodotoxin

The present study was designed to investigate inflammation-induced changes in smooth muscle responses to acetylcholine and the tachykinins that may contribute to the abnormal motility associated with inflammatory bowel disease. Colitis was induced in male Sprague-Dawley rats by intrarectal administration of trinitrobenzenesulphonic acid in ethanol. After either 4 h (acute) or 7 days (chronic) the distal colon was taken for in vitro measurement of smooth muscle tension and histological assessment. Acute colitis featured injury and neutrophilic infiltration confined to the mucosa while chronic inflammation showed marked injury, lymphocytic infiltration and muscle thickening. Acute inflammation increased responses to substance P and acetylcholine but decreased responses to neurokinin A. The enhanced response to substance P was dependent on nerves, while the decreased response to neurokinin A reflected a reduction in activity at the level of the smooth muscle. In the saline group, there was evidence of cholinergic interaction with substance P, but not neurokinin A. Substance P modulation of cholinergic nerves was absent in acute inflammation. Responses to all neurotransmitters were decreased in the chronic stage. These data demonstrate progressive changes in the smooth muscle function during acute and chronic colitis that may contribute to the abnormal motility associated with inflammatory bowel disease.

Topics: Acetylcholine; Animals; Atropine; Colitis; Dose-Response Relationship, Drug; Gastrointestinal Motility; Hexamethonium; Male; Muscle Contraction; Muscle, Smooth; Neurokinin A; Nicotinic Antagonists; Parasympatholytics; Potassium Chloride; Rats; Rats, Sprague-Dawley; Substance P; Tetrodotoxin; Trinitrobenzenesulfonic Acid; Vasodilator Agents

The present in vitro study was conducted to investigate possible alterations in the control of colonic electrolyte transport in an experimental model of colitis. Intrarectal administration of trinitrobenzenesulfonic acid induced a colitis-like inflammation in the rabbit distal colon. Responses to amiloride and residual short-circuit current after this treatment were unchanged, suggesting that the absorptive and secretory mechanisms remained intact. Electrical field stimulation and vasoactive intestinal polypeptide, a candidate secretomotor neurotransmitter, both elicited similar responses in control and colitic tissue. This suggests that communication at the neuroepithelial junction was unimpaired. In untreated tissue, the effects of prostaglandin E2 (PGE2) and of acetylcholine were attenuated by tetrodotoxin, suggesting, therefore, that both play a role in the modulation of secretomotor neurons. In addition, PGE2 had an appreciable direct epithelial effect. Responses to both of these agonists were absent in colitis. The effects of N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate were unchanged in colitis, suggesting that altered PGE2 responsiveness may involve changes in epithelial receptor number, affinity, or in their ability to mediate an increase in adenosine 3',5'-cyclic monophosphate levels. It is concluded that this rabbit model of colitis exhibits 1) defects in the modulation of secretomotor neurons by acetylcholine and PGE2 and 2) an attenuated epithelial response to PGE2.

Topics: Acetylcholine; Amiloride; Animals; Bucladesine; Colitis; Colon; Dinoprostone; Disease Models, Animal; Epithelium; Inflammation; Male; Membrane Potentials; Motor Neurons; Muscle, Smooth; Rabbits; Tetrodotoxin; Trinitrobenzenesulfonic Acid; Vasoactive Intestinal Peptide