Impaired nitrergic innervation in rat colitis induced by dextran sulfate sodium

BACKGROUND & AIMS: The pathophysiological role of neuronal nitric oxide synthase (nNOS) in colitis remains unknown. METHODS: We investigated colonic transit, nonadrenergic, noncholinergic (NANC) relaxation, nNOS activity, and nNOS synthesis in the myenteric plexus in dextran sulfate sodium (DSS)-induced colitis in rats. RESULTS: Oral administration of 5% DSS for 7 days induced predominant distal colitis and delayed colonic transit. In the proximal colon, carbachol-, sodium nitroprusside-, and electrical field stimulation (EFS)-induced responses were not different between control and DSS-treated rats. In the distal colon, EFS-evoked cholinergic contraction, NANC relaxation, and orphanin FQ-induced contraction were significantly impaired in DSS-treated rats compared with those in control rats, but carbachol- and sodium nitroprusside-induced responses remained intact in DSS-treated rats. The number of nNOS-immunopositive cells, catalytic activity of NOS, and nNOS synthesis in the colonic wall were significantly reduced in the distal colon of DSS-treated rats. In contrast, the number of PGP 9.5-immunopositive cells and PGP 9.5 synthesis in the colonic wall remained intact in the distal colon of DSS-treated rats. CONCLUSIONS: These results suggest that impaired NANC relaxation in the distal colon is associated with reduced activity and synthesis of nNOS in the myenteric plexus in DSS-induced colitis.     

Altered colonic transit in TNBS-induced experimental colitis in guinea pig and distribution of nitric oxide synthase in the colonic wall]

BACKGROUND/AIMS: Inflammation-induced alterations in smooth muscle contractility may be due to the effects on smooth muscle itself, neurotransmitters or enteric nerves. In dextran sulfate sodium-induced colitic rat, the delay in colonic transit was caused by decreased activity and production of neuronal nitric oxide synthase (nNOS) in the myenteric plexus of the distal colon. The aim of this study was to investigate the relationship between the delay in colonic transit and the distribution of inducible NOS (iNOS) and nNOS immunoreactive cells in the myenteric plexus of trinitrobenzene sulfonic acid (TNBS)-induced colitic guinea pig. METHODS: Sacrificed and their colonic tissues of forty-five TNBS-induced colitic guinea pigs were used to measure the colonic transit, and analyzed by immunohistochemistry. RESULTS: Colonic transit was delayed significantly at 3, 7 and 14 days after administration of TNBS. In control, nNOS immunoreactivity was present in the mucosa, submucosa, lamina propria, and ganglion cells of the myenteric plexus, while after TNBS treatment, reduced nNOS cells were found. However, the number of nNOS ganglion cells in the myenteric plexus was similar to those seen in controls. After administration of TNBS, iNOS immunoreactivity was increased in the mucosa and submucosa, but the number of iNOS positive ganglion cells in the myenteric plexus was not changed compared to control. CONCLUSIONS: It is suggested that in TNBS-induced guinea pig colitis, delayed colonic transit is not associated with the expression of nNOS nor iNOS in the myenteric plexus.     

应激对大鼠结肠神经系统nNOS表达的影响

目的:探讨应激对大鼠结肠神经系统nNOS表达的影响. 方法:SD大鼠30只随机分为对照组,应激组和L-NAME 组,采用水浸-束缚应激(WRS)动物模型,用免疫组织化学ABC法检测nNOS在大鼠结肠黏膜下神经丛和肌间神经丛的表达,应用计算机图像分析系统对其表达进行定量分析．结果:与对照组比较,应激组黏膜下神经丛和肌间神经丛的nNOS阳性神经元的灰度值明显减少(P=0．02或P =0．005),阳性神经元细胞数的平均密度增加(P=0．04 或P=0．01),表达增强,且在黏膜上皮细胞、固有层淋巴细胞也有nNOS表达．L-NAME组黏膜下神经丛和肌间神经丛的nNOS阳性神经元的灰度值较应激组增加 (P=0．04),平均密度下降(P=0．04或P=0．03),表达减弱,而与对照组比较均无明显差异(P>0．05)．结论:应激可引起大鼠结肠神经系统nNOS表达增强, 提示一氧化氮(NO)在应激所致的结肠功能失调中可能起重要作用．     

Interstitial cells of Cajal are involved in the afferent limb of the rectoanal inhibitory reflex

BACKGROUND AND AIMS: Interstitial cells of Cajal (ICC) have been shown to be involved in nitrergic neurotransmission of the lower oesophageal sphincter and pylorus. Here we studied the role of ICC and nitric oxide (NO) in the inhibitory neurotransmission of the murine internal anal sphincter (IAS). METHODS: The rectoanal inhibitory reflex, rectal compliance, and relaxation of the isolated IAS to electrical stimulation were measured in controls, KIT (W)/KIT (Wv) mice, and neuronal NO synthase (nNOS) deficient mice. In addition, we evaluated the effect of blockade of nNOS using N-nitro-L-arginine methyl ester. Distribution of nNOS positive neurones and ICC in the IAS was assessed immunohistochemically. RESULTS: KIT positive ICC were present in a dense network in the IAS of controls but not in KIT (W)/KIT(Wv) mice. Relaxation of IAS muscle strips induced by electrical stimulation was diminished in nNOS-/- mice but not in KIT (W)/KIT (Wv) mice. Blockade of NOS reduced the relaxation of IAS muscle strips in both mice. Relaxation of the IAS to rectal distension was significantly diminished in KIT (W)/KIT (Wv) mice and nNOS deficient mice. In concert, in vivo blockade of NOS attenuated the relaxation of the IAS in controls. No significant difference in compliance was found. CONCLUSION: The inhibitory innervation of the IAS and the rectoanal inhibitory reflex are mediated by NO and the rectoanal inhibitory reflex requires an intact network of ICC in the IAS. Thus both loss of nitrergic innervation and deficiency of ICC lead to impaired anal relaxation and may play an important role in rectal evacuation disorders.     

Acupuncture for functional gastrointestinal disorders

Functional gastrointestinal (GI) symptoms are common in the general population. Especially, motor dysfunction of the GI tract and visceral hypersensitivity are important. Acupuncture has been used to treat GI symptoms in China for thousands of years. It is conceivable that acupuncture may be effective in patients with functional GI disorders because it has been shown to alter acid secretion, GI motility, and visceral pain. Acupuncture at the lower limbs (ST-36) causes muscle contractions via the somatoparasympathetic pathway, while at the upper abdomen (CV-12) it causes muscle relaxation via the somatosympathetic pathway. In some patients with gastroesophageal reflux disease (GERD) and functional dyspepsia (FD), peristalsis and gastric motility are impaired. The stimulatory effects of acupuncture at ST-36 on GI motility may be beneficial to patients with GERD or FD, as well as to those with constipation-predominant irritable bowel syndrome (IBS), who show delayed colonic transit. In contrast, the inhibitory effects of acupuncture at CV-12 on GI motility may be beneficial to patients with diarrhea-predominant IBS, because enhanced colonic motility and accelerated colonic transit are reported in such patients. Acupuncture at CV-12 may inhibit gastric acid secretion via the somatosympathetic pathway. Thus, acupuncture may be beneficial to GERD patients. The antiemetic effects of acupuncture at PC-6 (wrist) may be beneficial to patients with FD, whereas the antinociceptive effects of acupuncture at PC-6 and ST-36 may be beneficial to patients with visceral hypersensitivity. In the future, it is expected that acupuncture will be used in the treatment of patients with functional GI disorders.     

Nitric oxide not carbon monoxide mediates nonadrenergic noncholinergic relaxation in the murine internal anal sphincter

BACKGROUND & AIMS: Inhibitory reflexes in the internal anal sphincter (IAS) are controlled by inhibitory nonadrenergic, noncholinergic innervation (i-NANC). We investigated the roles of 3 different neurohumoral agonists as possible i-NANC neurotransmitters: carbon monoxide (CO), nitric oxide (NO), and vasoactive intestinal peptide (VIP). METHODS: IAS smooth muscle strips were isolated from wild-type (WT), heme oxygenase (HO)-2 knockout (HO-2-/-) and neuronal NO synthase (nNOS) knockout (nNOS-/-) mice. Relaxation of IAS was induced by CO, NO, VIP, and electrical field stimulation (EFS) in the presence and absence of neurohumoral inhibitors (tin protoporphyrin IX [SnPP IX] for CO synthesis, N(omega)-nitro-L-arginine [L-NNA] for NO synthesis, and VIP(10-28) for VIP receptor). Western blot and immunohistochemistry were used to test the presence and localization of HO (for CO synthesis) types 1 (HO-1) and 2 (HO-2), neuronal NO synthase (nNOS, for NO synthesis), and VIP. RESULTS: All 3 neurohumoral agonists produced relaxation (with no difference between WT and HO-2-/- IAS), but CO was over 100 times less potent than NO and VIP. EFS produced relaxation in WT and HO-2-/- IAS with the same intensity. L-NNA and nNOS deletion (approximately 80%) and VIP(10-28) (approximately 15%) significantly inhibited the relaxations, whereas SnPP IX had no effect. Positive immunoreactivities for HO-2, nNOS, and VIP were found in the myenteric plexus of WT IAS. HO-2-/- IAS did not express immunoreactivity for HO-2. CONCLUSIONS: i-NANC relaxations of mouse IAS are primarily mediated via NO (by nNOS activity) and partly via VIP. CO directly relaxes the mouse IAS but does not play any significant role in the i-NANC relaxation.     

A deficiency of gastric interstitial cells of Cajal accompanied by decreased expression of neuronal nitric oxide synthase and substance P in patients with type 2 diabetes mellitus

Background Gastrointestinal motility is impaired in patients with diabetes mellitus (DM). Interstitial cells of Cajal (ICC) in the gastrointestinal tract play a central role in gastrointestinal motility. The present study examined whether ICC density, or expression of neuronal nitric oxide synthase (nNOS)- and substance P (SP)-containing nerves in the gastric antrum, were altered in patients with type 2 DM. Methods Paraffin-embedded gastric specimens from 51 controls and 36 male DM patients with gastric cancer were used for immunohistochemistry. Serial sections were stained with Kit and mast cell tryptase-specific antibodies. Fresh-frozen gastric specimens from patients with gastric cancer were used for immunofluorescence. The specimens were stained with antibodies to Kit, nNOS, and SP, and levels of expression of these three markers were compared between controls and DM patients. Results ICC density in the inner circular muscle layer, but not in the myenteric plexus, was lower in patients with severe DM than in controls in paraffin-embedded specimens. In addition, decreased expression of nNOS and SP accompanied by reduced ICC density was observed in frozen specimens from patients with DM. Conclusions These results suggest that lower gastric ICC, nNOS, and SP densities in patients with DM may be associated with the pathogenesis of diabetic gastroparesis.     

An enteric occult reflex underlies accommodation and slow transit in the distal large bowel

BACKGROUND & AIMS: Transit of fecal material through the human colon takes > or =30 hours, whereas transit through the small intestine takes 24 hours. The mechanisms underlying colonic storage and slow transit have yet to be elucidated. Our aim was to determine whether an intrinsic neural mechanism underlies these phenomena. METHODS: Recordings were made from circular muscle (CM) cells and myenteric neurons in the isolated guinea pig distal colon using intracellular recordings and Ca(2+) imaging techniques. Video imaging was used to determine the effects of colonic filling and pellet transit. RESULTS: Circumferential stretch generated ongoing oral excitatory and anal inhibitory junction potentials in the CM. The application of longitudinal stretch inhibited all junction potentials. N-omega-nitro-L-arginine (100 micromol/L) completely reversed the inhibitory effects of longitudinal stretch suggesting that nitric oxide (NO) inhibited interneurons controlling peristaltic circuits. Ca(2+) imaging in preparations that were stretched in both axes revealed ongoing firing in nNOS +ve descending neurons, even when synaptic transmission was blocked. Inhibitory postsynaptic potentials were evoked in mechanosensitive interneurons that were blocked by N-omega-nitro-L-arginine (100 micromol/L). Pellet transit was inhibited by longitudinal stretch. Filling the colon with fluid led to colonic elongation and an inhibition of motility. CONCLUSIONS: Our data support the novel hypothesis that slow transit and accommodation are generated by release of NO from descending (nNOS +ve) interneurons triggered by colonic elongation. We refer to this powerful inhibitory reflex as the intrinsic occult reflex (hidden from observation) because it withdraws motor activity from the muscle.     

CCK1 antagonists: are they ready for clinical use?

Cholecystokinin (CCK) is a peptide hormone which is found both in the gastrointestinal tract throughout the human small intestine and nerves in the myenteric plexus of the enteric nervous system and in the central nervous system. This dual location constitutes the anatomical basis for this in functions as a hormone and a neurotransmitter implicated in the regulation of both systems. CCK regulates not only motor functions in the gastrointestinal tract like lower oesophageal sphincter relaxation, gastric secretion and emptying, gall bladder contractility and bile secretion into the duodenum, intestinal and colonic motility, but also sensory functions and plays a role in the regulation of food intake. These effects are mediated through selective receptors CCK1 and CCK2. Over the last few years, research has focused on understanding the role of CCK, its receptors with antagonists at the biological, pharmacological, clinical and therapeutic level. As far as the CCK1 antagonists is concerned, important inroads have been made in the potential role of these antagonists in the treatment of GERD, IBS and pancreatitis. They have also shown encouraging results in sphincter of Oddi dysfunction and some gastrointestinal cancers. This review focuses on the recent ad vances of the biological role of CCK and their CCK1 antagonists: their current basic and clinical status in gastroenterology, with particular emphasis on the potential therapeutic role of the CCK1 antagonists and future research directions.     

应激大鼠幽门区一氧化氮和神经元型一氧化氮合酶与胃内胆汁反流的关系

背景：幽门区一氧化氮（NO）与幽门括约肌舒张功能密切相关，但从形态学上探讨神经元型一氧化氮合酶（nNOS）与胃内胆汁反流关系的研究却较少。目的：探讨应激大鼠幽门区NO和nNOS含量变化对胃内胆汁反流的影响。方法：55只大鼠随机分为正常对照组（n=10）、实验组（n=30）和免疫组化组（n=15），后两组以水浸束缚应激诱导应激性溃疡模型。实验组于应激开始后2、4、5、6、8和10h各取5只大鼠，分别检测胃内胆汁酸浓度和胃黏膜溃疡指数（UI，Guth评分），以生化试剂盒检测幽门区NO含量。免疫组化组于应激开始后0、4和6h各取5只大鼠，以免疫组化SP法结合图像分析检测幽门区nNOS免疫反应阳性产物的平均光密度值。结果：应激性溃疡大鼠幽门区NO含量于应激结束后lh达到峰值（P〈0．01）；应激结束后2h，胃内胆汁酸浓度达到峰值（P〈0．01）；胃黏膜UI于应激结束后4h达到峰值（P〈0．01）。免疫组化染色显示应激性溃疡大鼠胃内胆汁反流增加时，幽门区肌间神经丛nNOS免疫反应阳性产物平均光密度值显著增高（P〈0．01）。结论：NO能促进应激大鼠胃内胆汁反流，NO和nNOS参与了幽门括约肌舒张功能的调控。     

Deficiency of interstitial cells of Cajal in the small intestine of patients with Crohn''s disease

OBJECTIVE: Interstitial cells of Cajal are critical for the generation of electrical slow waves that regulate the phasic contractile activity of the tunica muscularis of the GI tract. Under certain pathophysiological conditions loss of interstitial cells of Cajal may play a role in the generation of certain motility disorders. The aim of the present study was to determine if there is an abnormality in the density or distribution of interstitial cells of Cajal from patients with Crohn's disease. METHODS: Small intestines from control subjects and patients with Crohn's disease were examined using immunohistochemistry and antibodies against the Kit receptor, which is expressed in interstitial cells of Cajal within the tunica muscularis of the GI tract. The density and distribution of interstitial cells of Cajal were assessed in the longitudinal and circular muscle layers and in the myenteric and deep muscular plexus regions of Crohn's and control tissues. RESULTS: Tissues from Crohn's disease patients showed an almost complete abolition of interstitial cells of Cajal within the longitudinal and circular muscle layers and a significant reduction in numbers at the level of the myenteric and deep muscular plexuses. CONCLUSIONS: In tissues from Crohn's disease patients, the density of interstitial cells of Cajal was reduced throughout the tunica muscularis in comparison to control small intestines. The disturbance of intestinal motility that occurs in patients with Crohn's disease may be a consequence of the loss of or defects in specific populations of interstitial cells of Cajal within the tunica muscularis.     

Distribution of constitutive nitric oxide synthase in the jejunum of adult rat

AIM：To study the distribution of the constitutive nitric oxide synthase(NOS) in the jejunom of adult rat.METHODS:The distribution of endothelial NOS(eNOS) was detected by immunohistochemistry.Immunofluorescence histochemical dual stainging technique were used for studying the distribution of neuronal NOS( nNOS) and eNOS,The dual stained slides were observed under a confocal laser scanning microscope.RESULTS:Positive neuronal NOS(nNOS) and endothelial NOS(eNOS) cells were found to be distributed in lamina propria of villi,and the epithelial cell was not stained,eNOS was mainly located in submucosal vascular endothelia while nNOS was mainly sityated in myenteric plexus.Some cells in the villi had both nNOS and eNOS.More than 80% of the cells were positive for both nNOS and eNOS,the rest cells were positive either for nNOS or for eNOS.CONCLUSION:The two constitutive nitric oxide synthases are distributed differently in the jejunum of rat.nNOS distributed in myenteric plexus is a neurotransmitter in the non-adrenergic non-cholinergic(NANC)inhibitory nerves eNOS distributed in endothelial and smooth muscle cells of blood vessels plays vasodilator role .eNOS and nNOS are coexpressed in some cells of lamina propria of villi.NO genearted y those NOS is very important in the physiological and pathological process of small intestine.     

A review of the L-arginine - nitric oxide - guanylate cyclase pathway as a mediator of lower urinary tract physiology and symptoms

Lower urinary tract symptoms (LUTS) are common and costly conditions that affect millions of men and women worldwide. A focal area of research into the cause and potential treatment of LUTS is the nitric oxide pathway, which is involved in nerve-induced relaxation in the lower urinary tract. Isoforms of NOS, including nNOS, eNOS, and iNOS, have been identified in the lower urinary tract of both animals and humans. Nerves that are immunoreactive to nitric oxide synthase (NOS) mainly serve the bladder outlet region, but some serve the detrusor. Pathology of the l-arginine-nitric oxide-cGMP pathway involving nNOS and eNOS may lead to impaired relaxation of the urethral outlet, increased bladder afferent activity, and detrusor smooth muscle overactivity. Such pathology has been implicated in the conditions of detrusor instability, urinary incontinence and outlet obstruction. iNOS may play an important role in inflammatory and infectious conditions of the bladder. Strategic manipulation of nitric oxide (NO), or interventions that address its mechanisms of action, possibly by pharmacological means or with gene therapy, may restore function or produce desired functional effects in the lower urinary tract.     

Nitric Oxide Synthase (NOS) Expression in the Myenteric Plexus of Streptozotocin-Diabetic Rats

Nitric oxide (NO) is an important inhibitoryneurotransmitter in the gut. Alterations in NO mediatedresponses have been described in diabetic animals. Thepresence of nitric oxide synthase (NOS) reflects the potential for NO synthesis and is found inneurons in the myenteric plexus. The aim of this studywas to determine changes in nitric oxide synthase (NOS)expression in the myenteric plexus of thegastrointestinal tract of diabetic rats at three months ofstreptozotocin-induced diabetes, compared to age matchedcontrols, using immunohistochemistry. Diabetic animalsshowed a decrease in NOS expression in the antrum, with 59.1 ± 7.3% of neurons beingpositive for NOS in diabetes compared to 81.2 ±4.7% in controls (P < 0.05). NOS expression induodenum, ileum, and colon of diabetic animals was notstatistically different from controls. Decreased expression of NOS inantrum may contribute to altered gastric emptyingobserved in diabetics.     

Gastroesophageal sphincter pressure and histological changes in distal esophagus in patients with achalasia of the esophagus

A prospective study was performed in 17 patients with achalasia of the esophagus determining the manometric characteristics of the gastroesophageal sphincter, correlating in with hisotological analysis by biopsies taken during surgery at the distal narrowed segment of the esophagus, at the location of the sphincter. The histological findings were compared to 10 control cases. Presence or absence of ganglion cells at the Auerbach's plexuses and appearance of smooth muscle fibers were evaluated. Only one case (6%) had Chagas' disease. The mean sphincter pressure was 41 mm Hg, with incomplete relaxation in all patients. Histological analysis showed a complete disappearance of ganglion cells in 94% of the cases and a decrease in the number of neurons with marked chronic inflammatory cells in one case (6%). In all control cases, the ganglion cells were normal. Smooth muscle fibers were normal on light microscopy. No relationship was found between resting gastroesophageal sphincter pressure, length and relaxation, and histological findings at the distal esophagus. These findings suggest that the denervation in the majority of cases is located in the Auerbach plexus, with complete absence of ganglion cells and, therefore, absence of postganglionic nerve fibers.     

Effect of nitroblue tetrazolium on NO synthase and motor function of opossum esophagus

Nitric oxide mediates neuromuscular events in the opossum esophagus. The NADPH diaphorase stain is used to localize nitric oxide synthase-containing enteric neurons. Cells stain by the NADPH diaphorase technique because they reduce nitroblue tetrazolium to the visible formazan. The effects of nitroblue tetrazolium on neuromuscular function and nitric oxide synthase of esophageal muscle were studied. The NADPH diaphorase stain was performed. Nitroblue tetrazolium inhibited lower esophageal sphincter relaxation, abolished the latency gradient of the off response, and inhibited nitric oxide synthase. The NADPH diaphorase technique stained myenteric plexus nerve cell bodies and nerve processes. Nitroblue tetrazolium is not a nonspecific muscle or nerve toxin, as nerve-mediated cholinergic responses, responses to exogenous nitric oxide, and responses to myogenic stimulation were maintained after nitroblue tetrazolium abolished the off response and lower esophageal sphincter relaxation. Nitroblue tetrazolium inhibits nitric oxide-mediated events and nitric oxide synthase. It stains neurons in the esophageal myenteric plexus.This work was supported by a Merit Grant and a Research Career Development Award from the Department of Veterans Affairs, and NIH grant DK 11242.     

Effect of chagas' disease on nitric oxide-containing neurons in severely affected and unaffected intestine

PURPOSE: The pathophysiology of Chagas' disease is incompletely understood. Neuronal nitric oxide has been cited as a candidate neurotransmitter responsible for relaxation of the internal anal sphincter. Neuronal nicotinamide adenine dinucleotide phosphate diaphorase can be used as a marker for neuronal nitric oxide synthase. This study was designed to examine the alterations of the nitric oxidecontaining neurons in the enteric nervous system of the colon of patients who underwent resections for advanced megacolon and to compare these specimens with small-bowel specimens from the same patients and with specimens from control subjects. METHODS: Specimens from resected rectum and extramucosal small-bowel biopsy specimens from 11 patients with Chagas megacolon but no apparent small-bowel clinical involvement were compared with the uninvolved colon and jejunum of 10 control patients with colon cancer. Tissues were fixed in Zamboni solution and evaluated by histochemistry for nicotinamide adenine dinucleotide phosphate diaphorase-containing neurons. Reactivity was evaluated on a 0 to 4 scale in the longitudinal muscle, myenteric plexus, circular muscle, submucosal plexus, and mucosa. RESULTS: Specimens from control patients showed well-stained myenteric and submucosal neurons and an abundant network of terminal nerve fibers in the muscle layers. Chagasic specimens had decreased staining in all layers of the gut. Overall there was a statistically significant decrease in nicotinamide adenine dinucleotide phosphate diaphorase-containing neurons. Biopsy specimens from clinically uninvolved small bowel of patients with Chagas' disease also showed decreased reactivity, but to a lesser degree. CONCLUSIONS: Nicotinamide adenine dinucleotide phosphate diaphorase activity is decreased in patients with advanced megacolon. The alterations are more relevant in the myenteric plexus and the circular muscle. Reactivity is also diminished in the clinically uninvolved small bowel, but to a lesser extent.     

Differential expression of endothelin-2 along the mouse intestinal tract

Endothelin (ET)-2, an ET family peptide, is highly expressed in intestine. However, the specific distribution and function of ET-2 remain unknown. We elucidated the expression profile and localization of ET-2 in mouse gastrointestinal tract. Real-time PCR analysis revealed that ET-2 gene expression in the gastrointestinal tract of healthy animals was relatively high in the colon. Immunohistochemical analysis revealed ET-2-like immunoreactivity mainly in epithelial cells of the mucosa throughout the intestinal tract of healthy animals. Intracellularly, ET-2 was concentrated close to the basement membrane of intestinal epithelial cells. A weak ET-2-like immunoreactivity was also localized to some neurofibers and the myenteric plexus of the muscle layer, coexpressing with vasoactive intestinal peptide. ET-2-like immunoreactivity was also detected at Brunner's glands of the duodenum and follicle-associated epithelium of Peyer's patch. In contrast, ET-1-like immunoreactivity was uniformly distributed in epithelial cells. In dextran sulfate sodium (DSS)-induced colitis, colonic ET-2 was upregulated during the late stage of DSS treatment. These results suggest that in intestinal epithelial cells ET-2 could be secreted into the lamina propria and the dome region in Peyer's patch, and that it might modulate immune cells in these sites for mucosal defense.