Melatonin as a modulator of the ileal brake mechanism

OBJECTIVE: The gastrointestinal tract represents the most important extrapineal source of melatonin. Intestinal melatonin release is induced by the ileal passage of nutrients and could play a part in the control of postprandial gut motility. The specific aim of this study was to determine the putative role of melatonin in the "ileal brake" reflex, an important mechanism released by ileal lipids that regulates the gastric emptying of chyme. MATERIAL AND METHODS: Under general anaesthesia rats were fitted with ileal cannula exteriorized at the back of the neck. After a 1-week recovery, experiments were performed in conscious fasted animals. Rats were fed by gavage 1.5 ml casein hydrolyse plus 0.05% phenol red and either saline or Intralipid were continuously infused (2 ml/h) into the ileum. Gastric emptying was measured 50 min after ingestion by gastric lavage and determination of phenol red by spectrophotometry. The effects of melatonin (1 mg/kg) and melatonin antagonist S-22153 (dose-response study 0.2-25 mg/kg) were tested versus vehicle in paired experiments at 1-week intervals. RESULTS: Ileal infusion of lipids delayed gastric emptying. During ileal infusion of lipids, melatonin antagonist S-22153, but not melatonin, potentiated the delay in gastric emptying induced by the ileal brake mechanism. The inhibition of gastric emptying induced by S-22153 was dose related. Neither melatonin nor S-22153 had noticeable effects on gastric emptying during ileal infusion of saline. CONCLUSIONS: Our data suggest that melatonin, released in response to ileal lipids, exerts a modulatory influence that decreases the inhibitory effects of the ileal brake on gastric emptying of nutrients.     

Increased permeability occurs in rat ileum following induction of pancolitis

Acetic acid-induced pan colitis in rats leads not only to colonic injury but also to a bystander ileal injury, characterized by decreased fluid and electrolyte absorption without associated histological injury or infiltration of inflammatory cells. To examine the nature of this decreased ileal fluid and electrolyte absorption, we measured effect of acetic acid-induced pancolitis on ileal transmural sodium and chloride transport, as well as on ileal permeability to mannitol and inulin on mucosal sheets mounted in Ussing chambers. In addition, ileal tight junctional morphology was assessed by electron microscopy. In colitic animals, ileal serosal-to-mucosal sodium and chloride transmural fluxes were increased (P<0.05); compatible with the observed decrease in net fluid absorption. Mannitol and inulin ileal serosal-to-mucosal and mucosal-to-serosal ileal fluxes were similarly increased (P<0.05), suggesting that an increase in ileal permeability occurred during acetic acid-induced pancolitis. This increase in ileal permeability was not accompanied by changes in tight junctional ultrastructure. These results suggest that: (1) the decrease in ileal fluid and electrolyte absorption seen during acetic acid-induced rat pancolitis occurred in parallel with a rise in both transcellular and paracellular permeability, and (2) the ileal permeability changes were not accompanied by structural changes.     

The partial ileal bypass operation does not cause essential fatty acid deficiency

Recent studies have indicated that ileal resection may lead to essential fatty acid deficiency, as demonstrated by plasma fatty acid composition. In the present study the serum cholesterol ester fatty acid composition was determined in patients who had undergone a partial ileal bypass operation several years earlier. The mean length of ileal exclusion was 2.0 m (range, 1.4-2.5 m). The patients with ileal bypass had severe bile acid malabsorption and slight fat malabsorption (fecal fat, 16 g/day). The fatty acid composition of serum cholesterol esters in the patients with ileal exclusion was identical with that of matched controls; for example, linoleic acid comprised 58% of the C14-18 fatty acids in the control patients and 61% in the patients with ileal bypass. It is concluded that exclusion of the distal third of a healthy small bowel does not cause essential fatty acid deficiency.     

Meckel's verticulum Complicated by Megaloblastic Anemia

A case of Meckel's diverticulum is presented with a symptomatic duration of over 30 yr, eventually complicated by megaloblastic anemia. A severe ileal stenosis was associated and probably caused by the diverticulum. Dilatation and stasis in the obstructed ileal loop were the cause of bacterial overgrowth and vitamin B₁₂ deficiency. Resection of the involved ileal segment led to complete clinical and hematological recovery.     

Outcome of primary and secondary ileal pouch-anal anastomosis and ileorectal anastomosis in patients with familial adenomatous polyposis

PURPOSE: The aim of this study was to present Swedish experiences of the ileal pouch-anal anastomosis in patients with familial adenomatous polyposis from the introduction in 1984. The study also compared the surgical and functional outcome of different anal continence preserving procedures: ileal pouch-anal anastomosis as primary surgery, ileal pouch-anal anastomosis as secondary surgery after colectomy and ileorectal anastomosis, and ileorectal anastomosis alone. METHODS: The material comprises all 120 patients with familial adenomatous polyposis reported to the Swedish Polyposis Registry who had undergone prophylactic colorectal surgery, including those operated on because of colorectal cancer from 1984 until the end of 1996. Anal continence preserving surgery was performed on 102 patients: 20 had ileal pouch-anal anastomosis as primary surgery at a median age of 24.5 years, 39 had ileal pouch-anal anastomosis as secondary surgery at a median age of 34 years, and 43 had ileorectal anastomosis alone, at a median age of 26 years, because 6 of the initially ileorectal anastomosis-operated patients were converted to ileal pouch-anal anastomosis as secondary surgery. Surgical outcome was assessed on the basis of hospital records. A questionnaire was used to evaluate the functional outcome. Fisher's exact probability test was used for statistical analysis. RESULTS: Complications occurred in 51 percent of the patients after ileal pouch-anal anastomosis: 40 percent after ileal pouch-anal anastomosis as primary surgery and 56 percent after ileal pouch-anal anastomosis as secondary surgery. When the previous ileorectal anastomosis was taken into account 67 percent of the patients suffered complications which was significantly more compared with ileal pouch-anal anastomosis as primary surgery. After ileorectal anastomosis, 26 percent had complications which was significantly less compared with all other procedures but ileal pouch-anal anastomosis as primary surgery. No cancer occurred after ileal pouch-anal anastomosis, either in the ileal pouch or in retained rectal mucosa, but two of the patients who had an ileorectal anastomosis developed rectal cancer. One pouch excision was performed compared with ten rectal excisions. Functional outcome did not differ between ileal pouch-anal anastomosis as primary surgery and ileal pouch-anal anastomosis as secondary surgery. However, ileorectal anastomosis-operated patients had significantly better bowel function with regard to nighttime stool frequency, continence and perianal soreness. CONCLUSION: These findings indicate that major advantages of ileal pouch-anal anastomosis are the low excision rate and, so far, no cancer in the ileal pouch. Moreover, the surgical outcome of ileal pouch-anal anastomosis as primary surgery is not significantly different from that of ileorectal anastomosis. However, the good surgical and functional outcome of ileorectal anastomosis, despite the long-range prognosis including rectal cancer and excision risks, has to be taken into consideration when selecting patients with familial adenomatous polyposis for primary surgery.Parts of the functional outcome part of the study were presented at the Leeds Castle Polyposis Group meeting in Noordwijk, the Netherlands, June 4 to 7, 1997.Supported by the Cancer Society in Stockholm and the Karolinska Institute.     

Acute necrotizing enterocolitis of preterm piglets is characterized by dysbiosis of ileal mucosa-associated bacteria

Investigation of bacteria involved in pathogenesis of necrotizing enterocolitis (NEC) is limited by infant fragility, analysis restricted to feces, use of culture-based methods, and lack of clinically-relevant animal models. This study used a unique preterm piglet model to characterize spontaneous differences in microbiome composition of NEC-predisposed regions of gut. Preterm piglets (n=23) were cesarean-delivered and nurtured for 30 hours over which time 52% developed NEC. Bacterial DNA from ileal content, ileal mucosa, and colonic mucosa were PCR amplified, subjected to terminal restriction fragment length polymorphism (TRFLP) analysis and targeted 16S rDNA qPCR. Preterm ileal mucosa was specifically bereft in diversity of bacteria compared to ileal content and colonic mucosa. Preterm ileum was restricted to representation by only Proteobacteria, Firmicutes, Cyanobacteria and Chloroflexi. In piglets with NEC, ileal mucosa was uniquely characterized by increases in number of Firmicutes and diversity of phyla to include Actinobacteria and uncultured bacteria. Five specific TRFLP profiles, corresponding in closest identity to Clostridium butyricum, C. neonatale, C. proteolyticum, Streptomyces spp., and Leptolyngbya spp., were significantly more prevalent or observed only among samples from piglets with NEC. Total numbers of Clostridium spp. and C. butyricum were significantly greater in samples of NEC ileal mucosa but not ileal content or colonic mucosa. These results provide strong support for ileal mucosa as a focus for investigation of specific dysbiosis associated with NEC and suggest a significant role for Clostridium spp., and members of the Actinobacteria and Cyanobacteria in the pathogenesis of NEC in preterm piglets.     

Role of the longitudinal smooth muscle coat in the ileal motile activity: evidence of ileo-ileal inhibitory reflex

BACKGROUND: All gut movements are claimed to be activated essentially by the concentric contraction of the circular muscle, moving the chyme aborally. The role of the longitudinal smooth muscle of the small intestine in gut motility is poorly understood; this point was investigated in the current study. METHODS: The abdomens of 14 crossbreed dogs (eight dogs, six bitches) were opened. A segment of the small intestine was distended by a balloon in increments of 2 mL of saline, and the pressure and electrical activity were recorded proximally and distally to the balloon. The gut wall around the balloon was anesthetized and the test was repeated. The longitudinal muscle coat of the small intestine segment was then excised, and the pressure response and electrical activity were recorded on ileal distension. RESULTS: Two milliliter ileal distension produced pressure decrease (P < 0.05) proximally and distally to the balloon and caused balloon movement. Four, 6 and 8 mL distension effected similar pressure response, while 10 mL showed no response. Electrical waves were recorded from the three electrodes applied to the ileal segment. Upon ileal distension, electrical activity increased over the distended area, with no activity proximally and distally to it. Balloon distension of the anesthetized ileal segment produced no pressure response or electrical activity. After longitudinal myectomy, no electrical activity was recorded at rest or upon ileal distension, and the balloon did not move. CONCLUSION: Ileal distension initiated circular muscle contraction only in the presence of the overlying longitudinal muscle, which appears to transmit the electrical activity to the circular muscle upon ileal distension. Ileal contraction is suggested to initiate ileal hypotonia in the proximal and distal ileal segments mediated through an 'ileo-ileal inhibitory reflex' that leads to aboral progress of the proximally and distally located chyme.     

Vagotomy inhibits the jejunal fluid secretion activated by luminal ileal Escherichia coli STa in the rat in vivo

BACKGROUND: Escherichia coli heat stable enterotoxin (STa) is a major cause of secretory diarrhoea in humans. AIMS: To assess the effects of instilling STa into the ileum on remote fluid secretion in the jejunum and colon in rats in vivo by a gravimetric technique. METHODS AND RESULTS: Ileal STa (55 ng/ml) stimulated fluid secretion in both ileal and jejunal loops but not in the colon. The fluid secretion induced by ileal STa was inhibited by L-NAME (Nomega-nitro-L-arginine methyl ester, 40 mg/kg intraperitoneally) but not by D-NAME (Nomega-nitro-D-arginine methyl ester). Ileal carbachol (183 mg/ml) instilled into the lumen stimulated ileal secretion but not jejunal secretion, and was unaffected by L-NAME. Capsaicin (10 microM), instilled luminally with STa in the ileum, blocked both the ileal and jejunal fluid secretion. Acute bilateral vagotomy prevented luminal ileal STa from inducing jejunal fluid secretion but not from activating ileal fluid secretion. CONCLUSION: Ileal E coli STa stimulates remote secretion in the rat jejunum but not in the colon, probably by a nitrinergic, vagal reflex mediated by C fibres. This neural pathway will amplify the action of the toxin in its generation of secretory diarrhoea.     

Multiple ileal ulcers and an ileal Dieulafoy's lesion induced by loxoprofen sodium

Loxoprofen sodium is one of the non‐steroidal anti‐inflammatory drugs (NSAIDs) that is a prodrug. Several adverse effects of the drug have been described, but ileal ulcer has not been reported so far. We experienced an 87‐year‐old male patient with disk herniation complicated with loxoprofen sodium‐induced multiple ileal ulcers and an ileal Dieulafoy's lesion that caused massive intestinal bleeding. The patient was saved by wedge resection of the Dieulafoy's lesion and discontinuance of the NSAID. ^99mTc‐red blood cell scintigraphy and intraoperative enteroscopy of the small bowel were useful in the diagnosis. This is the first case of multiple ileal ulcers with an ileal Dieulafoy's lesion induced by loxoprofen sodium.     

Secondary pouchitis in a post-operative patient with ulcerative colitis, successfully treated by salvage surgery

We report a case of secondary pouchitis, defined as a mucosal inflammatory lesion in the ileal reservoir provoked by pouch-related complication following total colectomy and pouch anal anastomosis, which was successfully treated by salvage surgery- A 20-year-old woman with ulcerative colitis developed acute severe bloody diarrhea following proctocolectomy, ileal pouch-anal anastomosis and diverting ileostomy. She was diagnosed as having a secondary pouchitis mainly caused by a peripouch abscess and partly concerned with the abnormal pouch formation. The remnant rectum and ileal pouch were excised and ileal pouch-anal anastomosis and diverting ileostomy were constructed. The postoperative course was uneventful with no sign of pouchitis. Salvage surgery may be indicated to treat secondary pouchitis when caused by surgery-related complications.     

Ileal Varices Revealed by Recurrent Hematuria in a Patient with Portal Hypertension and Mekong Schistosomiasis

This present report describes a unique case of a patient with ileal varices revealed by recurrent bleeding from vesical varicosities. Ileal varices were associated with portal hypertension secondary to portal thrombosis. An unusual ileovesical shunt was demonstrated by the venous phase of the superior mesenteric arteriogram. This shunt was favored by adhesions between an abnormal ileal loop, which was infiltrated with ova of schistosome mekongi, and the superior vesical wall. The patient was treated successively by lysis of adhesions and ileal resection. No portacaval shunt was performed.     

Effect of rectal distension on the small intestine with evidence of a recto-enteric reflex

BACKGROUND/AIMS: To study the effect of rectal distension on jejunal and ileal motility aiming at the assessment of the possible role of rectal distension induced by constipation on the transport of the material in the gut. METHODOLOGY: The rectum of 16 healthy volunteers (mean age: 38.6 +/- 11.7 years, 10 men, and 6 women) was distended by a balloon filled with water in increments of 50 mL up to 200 mL and the response of the jejunal and ileal pressures was recorded. The test was repeated distending the anesthetized rectum 20 min and 3 hours after anesthetization. RESULTS: Rectal distension with 50 mL of water effected no jejunal or ileal pressure changes (P > 0.05). One hundred-mililitre (100-mL) rectal distension produced decrease of jejunal and ileal pressures (P < 0.05) which lasted as long as distension was maintained. Rectal distension with 150 and 200 mL caused jejunal and ileal pressure response similar to that of the 100 mL distension (P > 0.05). Distension of the anesthetized rectum effected no significant jejunal or ileal pressure changes. CONCLUSIONS: The results were reproducible in the individual subject. The decline of the intestinal pressure upon rectal distension postulates a reflex relationship between the 2 conditions. This reflex nature is evidenced by reproducibility and by its absence on distension of the anesthetized rectum. We termed this reflex relation: "recto-enteric reflex". It is suggested that under normal physiologic conditions the reflex inhibits the intestinal transit, thus giving the rectum time to evacuate itself. Continuous rectal distension, as occurs in inertia constipation, appears to effect enteric hypotonia, a hypothesis which requires further studies.     

Collagenous pouchitis

Collagenous colitis is characterised by watery diarrhoea, normal colonic mucosa on endoscopy, diffuse colitis with surface epithelial injury, and a distinctive thickening of the subepithelial collagen table on histology. Some patients can develop medically refractory collagenous colitis, in which case they may require surgical intervention. This is the first report of collagenous pouchitis in a collagenous colitis patient with proctocolectomy and ileal pouch-anal anastomosis. A patient with medically refractory collagenous colitis who underwent a total proctocolectomy and ileal pouch-anal anastomosis was sequentially evaluated with an endoscopy and histology of the colon, distal small intestine, and ileal pouch. A 58-year-old female had a 10-year history of collagenous colitis before having a total proctocolectomy and ileal pouch-anal anastomosis for medically refractory disease. The histologic features of collagenous colitis were present in all colon and rectum biopsy or resection specimens, but were absent in the distal ileum specimen. The post-operative course was complicated by persistent increase of stool frequency, abdominal cramps, and incontinence. A pouch endoscopy was performed 3 years after ileal pouch-anal anastomosis which showed the histologic features of collagenous colitis in the ileal pouch, collagenous pouchitis, while the pre-pouch neo-terminal ileum had no pathologic changes. After antibiotic therapy, the histologic changes of collagenous pouchitis resolved. This is the first reported case of collagenous pouchitis. Since the abnormal collagen table and its associated features were only present in the pouch and absent in the neo-terminal ileum, and the patient had histologic improvement after antibiotic therapy, it would suggest that faecal stasis and bacterial load may play a role in the pathogenesis.     

The 'ileal brake' after ileal pouch-anal anastomosis

The aim of this study was to assess if infusion of oleic acid into the ileal pouch would slow gastric emptying and small-bowel transit, delay defecation, and increase plasma levels of enteroglucagon, neurotensin, or peptide YY in patients with colectomy and ileal pouch-anal anastomosis. Eight subjects with chronic ulcerative colitis who had undergone the operation were studied on 2 consecutive days. On 1 day, saline (154 mM NaCl) was infused into the ileal pouch, and on the other day emulsified oleic acid (152 mM) was infused. The subjects ate a 300-kcal mixed meal containing liquid labelled with 99mTc-DTPA. To assess small-bowel transit concurrently with gastric emptying, a second marker, 111In-DTPA, was instilled through a tube into the duodenum at the end of the meal. Transit of both markers was monitored scintigraphically. Infusion of oleic acid into the ileal pouch slowed gastric emptying and small-bowel transit, and delayed the time to defecation compared with saline infusion. Neither the ileal pouch infusion alone or the meal alone altered plasma levels of enteroglucagon, neurotensin, or peptide YY, but the combination of the oleic acid infusion and the meal increased the levels of all 3 hormones. It was concluded that an "ileal brake" on gastrointestinal transit is functional following ileal pouch-anal anastomosis. Oleic acid placed into the ileal pouch slowed gastrointestinal transit and delayed defecation, effects which may have clinical application. The mechanism mediating the ileal brake may in part be hormonal.     

Study of the effect of jejuno-ileal distension on the motor activity of the stomach with evidence of "entero-gastric inhibitory reflex"

BACKGROUND/AIMS: In chronic constipation due to delayed colonic transit, stasis of the ileal contents with resulting ileal distension may occur. The current study investigated the effect of ileal and jejunal distension on the gastric motility, aiming at elucidating the possible existence of a relationship and its role in the flow through the gut. METHODOLOGY: The response of the gastric pressure to ileal and jejunal balloon distension in increments of 2 mL of saline was recorded in 12 mongrel dogs. The test was repeated after separate local anesthetization of the ileum, jejunum and stomach. RESULTS: 2- and 4-mL ileal balloon distension produced no significant gastric pressure response, while 6- and up to 10-mL distension effected decrease of the antral and corporeal pressures (p < 0.05, p < 0.05, respectively). Jejunal distension produced a gastric pressure decline (p < 0.05) with 4 and up to 10 mL of saline. The gastric pressure decrease did not show significant changes with the various distending volumes. It was maintained as long as ileal or jejunal distension was continued. Distension of the anesthetized ileum or jejunum caused no gastric pressure changes, nor did ileal or jejunal distension produce pressure changes in the anesthetized stomach. CONCLUSIONS: The gastric pressure decline and presumably hypotonia upon ileal or jejunal distension with big volumes postulate a reflex relationship which we call "entero-gastric inhibitory reflex". The small intestine is suggested to slow down gastric emptying through this reflex. A balance is thus created between chyme delivery from the stomach and chyme processing by the small intestine. Reflex derangement in neurogenic and myogenic diseases may result in gastrointestinal disorders, a point that needs to be investigated.     

Direct measurement of first-pass ileal clearance of a bile acid in humans

The purpose of this study was to develop and validate a method of directly measuring ileal bile acid absorption efficiency during a single enterohepatic cycle (first-pass ileal clearance). This has become feasible for the first time because of the availability of the synthetic gamma-labeled bile acid 75Selena-homocholic acid-taurine (75SeHCAT). Together with the corresponding natural bile acid cholic acid-taurine (labeled with 14C), SeHCAT was infused distal to an occluding balloon situated beyond the ampulla of Vater in six healthy subjects. Completion of a single enterohepatic cycle was assessed by obtaining a plateau for 75SeHCAT activity proximal to the occluding balloon, which prevented further cycles. Unabsorbed 75SeHCAT was collected after total gut washout, which was administered distal to the occluding balloon. 75SeHCAT activity in the rectal effluent measured by gamma counter was compared with that of absorbed 75SeHCAT level measured by gamma camera and was used to calculate first-pass ileal clearance. This was very efficient (mean value, 96%) and showed very little variation in the six subjects studied (range, 95%-97%). A parallel time-activity course in hepatic bile for 14C and 75Se during a single enterohepatic cycle, together with a ratio of unity for 14C/75Se in samples obtained at different time intervals, suggests that 75SeHCAT is handled by the ileum like the natural bile acid cholic acid-taurine. Extrapolation of 75SeHCAT first-pass ileal clearance to that of the natural bile acid therefore seems justifiable. In a subsidiary experiment, ileal absorption efficiency per day for 75SeHCAT was also measured by scanning the gallbladder area on 5 successive days after the measurement of first-pass ileal clearance. In contrast with absorption efficiency per cycle, absorption efficiency per day varied widely (49%-86%), implying a possible wide variation in recycling frequency per day.     

单核细胞趋化蛋白-1与急性胰腺炎肠屏障功能呈负相关

背景:急性胰腺炎(AP)时可发生全身性炎症反应综合征,肠屏障功能障碍是导致重症急性胰腺炎(SAP)并发多器官功能衰竭的重要因素之一。目的:检测大鼠AP模型单核细胞趋化蛋白-1(MCP-1)表达和肠屏障功能指标的变化,探讨MCP-1在AP肠屏障功能障碍中的作用。方法:分别以0.5%和5%牛磺胆酸钠逆行胰胆管注射制备大鼠急性水肿性胰腺炎(AEP)和急性坏死性胰腺炎(ANP)模型,行胰腺组织病理学评分,电子显微镜观察回肠组织超微结构,免疫组化染色、RT-PCR和蛋白质印迹法检测回肠组织中紧密连接蛋白occludin和MCP-1的表达。结果:与假手术(SO)组相比,AP模型大鼠尤其是ANP组大鼠胰腺组织病理学评分显著升高,回肠绒毛高度和柱状细胞指数降低,occludin表达下调(P0.05)。SO组和AEP组回肠组织中无MCP-1表达,ANP组MCP-1表达随时间延长而上调(P0.05)。回肠组织MCP-1表达与胰腺组织病理学评分呈正相关,与肠屏障功能指标(绒毛高度、柱状细胞指数和occludin表达)呈负相关。结论:ANP大鼠回肠组织中MCP-1表达上调,MCP-1在AP肠屏障功能障碍中发挥重要作用。     

Ileal schwannoma developing into ileocolic intussusception

Intussusception is rare in adults. We describe a 47-yearold man with ileal schwannoma that led to ileocolic intussusception. Abdominal ultrasonography, abdominal CT scan and barium enema confirmed an ileal tumor. Colonoscopy revealed a peduncular submucosal tumor （SMT） 75 mm long with an ulcerated apex at the ascending colon. The provisional diagnosis was a gastrointestinal stromal tumor of the terminal ileum. Ileocecal resection was carried out and the tumor was histologically diagnosed as schwannoma. Abdominal pain resolved postoperatively. This case reminds us that ileal schwannoma should be included in the differential diagnosis of intussusception caused by an SMT in the intestine.     

Effect of dopamine and bromocriptine on rat ileal and colonic transport. Stimulation of absorption and reversal of cholera toxin-induced secretion

Water and electrolyte transport were determined in rat ileum and colon using the single-pass perfusion technique. Intraperitoneal dopamine caused prompt stimulation of both ileal and colonic water absorption. The dopamine effect was mediated by both specific dopamine and alpha 2-adrenergic receptors. Haloperidol, a specific dopamine antagonist, and yohimbine, an alpha 2-adrenergic antagonist, inhibited the effect of dopamine in ileal absorption; both antagonists alone had no effect on basal water transport. Bromocriptine (intravenous and intraluminal) stimulated ileal and colonic water absorption, which was inhibited by haloperidol and yohimbine, and reversed cholera toxin-induced ileal secretion. Magnitude and time-courses of the increased water absorption in ileal loops, inoculated with saline, were the same as in loops, inoculated with saline, suggesting that bromocriptine acted to reverse cholera toxin-induced secretion by stimulating absorption. Bromocriptine had no effect on the cyclic adenosine monophosphate increase caused by cholera toxin. We conclude (a) dopamine stimulates water absorption in vivo in rat ileum and colon; (b) this dopamine effect is via specific dopamine and alpha 2-receptors; (c) bromocriptine stimulates water absorption in ileum and colon and also acts by dopamine and alpha 2-receptors; and (d) bromocriptine reverses cholera toxin-induced secretion.