Effects of morphine and atropine on motility and transit in the human ileum

An ingestible self-propelling device for intestinal reanimation

Postoperative ileus (POI) is the leading cause of prolonged hospital stay after abdominal surgery and is characterized by a functional paralysis of the digestive tract, leading to symptoms such as constipation, vomiting, and functional obstruction. Current treatments are mainly supportive and inefficacious and yield acute side effects. Although electrical stimulation studies have demonstrated encouraging pacing and entraining of the intestinal slow waves, no devices exist today to enable targeted intestinal reanimation. Here, we developed an ingestible self-propelling device for intestinal reanimation (INSPIRE) capable of restoring peristalsis through luminal electrical stimulation. Optimizing mechanical, material, and electrical design parameters, we validated optimal deployment, intestinal electrical luminal contact, self-propelling capability, safety, and degradation of the device in ex vivo and in vivo swine models. We compared the INSPIRE's effect on motility in models of normal and depressed motility and chemically induced ileus. Intestinal contraction improved by 44% in anesthetized animals and up to 140% in chemically induced ileus cases. In addition, passage time decreased from, on average, 8.6 days in controls to 2.5 days with the INSPIRE device, demonstrating significant improvement in motility. Luminal electrical stimulation of the intestine via the INSPIRE efficaciously restored peristaltic activity. This noninvasive option offers a promising solution for the treatment of ileus and other motility disorders.

Manometry of the Human Ileum and Ileocaecal Junction in Health, Disease and Surgery: A Systematic Review

Background: The terminal ileum and ileocaecal junction form a transition zone in a relatively inaccessible portion of the gastrointestinal tract. Little is known about the motility of this region with few detailed studies, indicating the need for a robust synthesis of current knowledge. This review aimed to evaluate the quantitative and qualitative data on the manometry findings of the terminal ileum and ileocaecal junction during the fasting and post-prandial periods in healthy individuals and patients with motility disorders or patients after bowel surgery.

Methods: A systematic search of five databases (Medline, Pubmed, Embase, Scopus, and Cochrane Library) was performed. Studies that presented manometry data from the human ileum or ileocaecal junction were included.

Results: Forty-two studies met the inclusion criteria. The main motility patterns reported in the terminal ileum during fasting were the migrating motor complex, discrete clustered contractions, prolonged propagated contractions and phasic contractions. Post-prandial motility featured irregular, intense contractions. Some studies found a region of sustained increased pressure at the ileocaecal junction while others did not. Patients with motility disorders showed differences in manometry including retrograde propagation of phase III. Patients post-bowel surgery showed differences including higher incidence of phase III.

Conclusion: Motility patterns of the terminal ileum differ between fasting and fed states. Large variability existed in manometry recordings of the terminal ileum. Technical challenges and lack of standardized definitions may reduce accuracy of manometry assessment. Further research is needed to understand how this key portion of the gut physiologically functions.

Utility of animal gastrointestinal motility and transit models in functional gastrointestinal disorders

Alteration in the gastrointestinal (GI) motility and transit comprises an important component of the functional gastrointestinal disorders (FGID). Available animal GI motility and transit models are to study symptoms (delayed gastric emptying, constipation, diarrhea) rather than biological markers to develop an effective treatment that targets the underlying mechanism of altered GI motility in patients. Animal data generated from commonly used methods in human like scintigraphy, breath test and wireless motility capsule may directly translate to the clinic. However, species differences in the control mechanism or pharmacological responses of GI motility may compromise the predictive and translational value of the preclinical data to human. In this review we aim to provide a summary on animal models used to mimic GI motility alteration in FGID, and the impact of the species differences in the physiological and pharmacological responses on the translation of animal GI motility and transit data to human.

Effects of naloxegol on whole gut transit in opioid-naïve healthy subjects receiving codeine: A randomized, controlled trial

BACKGROUND

Nausea, vomiting, and constipation (OIC) are common adverse effects of acute or chronic opioid use. Naloxegol (25 mg) is an approved peripherally active mu-opiate opioid receptor antagonist.

AIM

To compare the effects on pan-gut transit of treatment with codeine, naloxegol, or combination in healthy volunteers.

METHODS

We conducted a randomized, double-blind, placebo-controlled, single-center, parallel-group study in 72 healthy opioid-naïve adults, randomized to: codeine (30 mg q.i.d.), naloxegol (25 mg daily), codeine and naloxegol, or matching placebo. During 3 days of treatment, we measured gastric emptying (GE) T1/2 , colonic filling at 6 hours (CF6), colonic geometric center at 24 and 48 hours, and ascending colon emptying (ACE) T1/2 .

KEY RESULTS

Participants were 59.7% women, median BMI 25.0 kg/m2 , and median age 33.8 years. Codeine significantly retarded GE T1/2, CF6, overall colonic transit, and ACE T1/2 . There was significant difference (P = .026) in GE T1/2 between codeine (144.0 min [IQR 110.5-238.6]) and naloxegol (95.5 min [89.1-135.4]). There was a significant overall group difference in CF6 (P = .023), with significant difference (P = .019) between codeine (11.0% [0.0-45.0]) and naloxegol (51% [18.8-76.2]). However, no significant differences were found between codeine-treated participants concomitantly receiving placebo or naloxegol.

CONCLUSIONS AND INFERENCES

Short-term administration of naloxegol (25 mg) in healthy, opioid-naïve volunteers does not reverse the retardation of gastric, small bowel, or colonic transit induced by acute administration of codeine. Further studies with naloxegol at higher dose are warranted to assess the ability to reverse the retardation of transit caused by acute administration of codeine in opioid-naïve subjects.

Silkworm Sericin: Properties and Biomedical Applications

Silk sericin is a natural polymer produced by silkworm, Bombyx mori, which surrounds and keeps together two fibroin filaments in silk thread used in the cocoon. The recovery and reuse of sericin usually discarded by the textile industry not only minimizes environmental issues but also has a high scientific and commercial value. The physicochemical properties of the molecule are responsible for numerous applications in biomedicine and are influenced by the extraction method and silkworm lineage, which can lead to variations in molecular weight and amino acid concentration of sericin. The presence of highly hydrophobic amino acids and its antioxidant potential make it possible for sericin to be applied in the food and cosmetic industry. The moisturizing power allows indications as a therapeutic agent for wound healing, stimulating cell proliferation, protection against ultraviolet radiation, and formulating creams and shampoos. The antioxidant activity associated with low digestibility of sericin that expands the application in the medical field, such as antitumour, antimicrobial and anti-inflammatory agent, anticoagulant, acts in colon health, improving constipation and protects the body from obesity through improved plasma lipid profile. In addition, the properties of sericin allow its application as a culture medium and cryopreservation, in tissue engineering and for drug delivery, demonstrating its effective use, as an important biomaterial.

A Case of Stercoral Perforation Detected on CT Requiring Proctocolectomy in a Heroin-Dependent Patient

Stercoral perforation of the colon is rare but carries with it significant morbidity and mortality. Stercoral perforation usually occurs in elderly, immobile patients with chronic constipation. In this manuscript, we report the case of stercoral perforation in a patient due to chronic heroin dependence. We report the case of a 56-year-old male patient with stercoral perforation, diagnosed by computed tomography, secondary to heroin dependence, requiring proctocolectomy and an end ileostomy. There are very few reports in the literature describing cases of stercoral perforation and questions have been asked about the importance of preoperative cross-sectional imaging. In our case, the diagnosis of stercoral perforation was made only on CT. Although this is not the first such case to be reported, it is significant as preoperative CT imaging was influential not only in determining the aetiology of the abdominal distension seen on the plain film, but also in detecting the pneumoperitoneum which was not evident clinically or on plain radiographs.

Opioid-induced bowel dysfunction: epidemiology, pathophysiology, diagnosis, and initial therapeutic approach

Opioids affect motor and sensory function throughout the gastrointestinal tract, and are frequently associated with a number of gastrointestinal symptoms including constipation, which impairs the quality of life and may limit the dose of opioid or result in discontinuation altogether. Patients with opioid-induced constipation should be assessed by careful history and physical examination, and in some cases where the diagnosis is unclear with select diagnostic tests. Few clinical studies have been conducted to assess the efficacy of various treatments. However, it is generally recommended that first-line therapy begin with opioid rotation, as well as with low-cost and low-risk approaches such as lifestyle changes, consumption of fiber-rich food, stool softeners, and laxatives.

Gastrointestinal Safety Pharmacology in Drug Discovery and Development

Although the basic structure of the gastrointestinal tract (GIT) is similar across species, there are significant differences in the anatomy, physiology, and biochemistry between humans and laboratory animals, which should be taken into account when conducting a gastrointestinal (GI) assessment. Historically, the percentage of cases of drug attrition associated with GI-related adverse effects is small; however, this incidence has increased over the last few years. Drug-related GI effects are very diverse, usually functional in nature, and not limited to a single pharmacological class. The most common GI signs are nausea and vomiting, diarrhea, constipation, and gastric ulceration. Despite being generally not life-threatening, they can greatly affect patient compliance and quality of life. There is therefore a real need for improved and/or more extensive GI screening of candidate drugs in preclinical development, which may help to better predict clinical effects. Models to identify drug effects on GI function cover GI motility, nausea and emesis liability, secretory function (mainly gastric secretion), and absorption aspects. Both in vitro and in vivo assessments are described in this chapter. Drug-induced effects on GI function can be assessed in stand-alone safety pharmacology studies or as endpoints integrated into toxicology studies. In silico approaches are also being developed, such as the gut-on-a-chip model, but await further optimization and validation before routine use in drug development. GI injuries are still in their infancy with regard to biomarkers, probably due to their greater diversity. Nevertheless, several potential blood, stool, and breath biomarkers have been investigated. However, additional validation studies are necessary to assess the relevance of these biomarkers and their predictive value for GI injuries.

Localization of muscarinic receptors M1R, M2R and M3R in the human colon

BACKGROUND

Muscarinic acetylcholine receptors (MR) are involved in multiple intestinal reflexes. The cellular localization of subtypes of MRs within enteric circuits mediating muscle and mucosal reflexes remains to be demonstrated. This study aimed to localize the three functionally significant subtypes of MRs in human colon.

METHODS

Reverse transcriptase-PCR was used to determine expression levels of muscarinic receptor subtype (MRs) M1Rs, M2Rs and M3Rs in human colon. Indirect immunofluorescence and confocal microscopy was used to localize MRs in cryostat-cut sections of human colon. Sections were double labeled for multiple cellular and neurochemical markers. Western blotting was used to confirm specificity of the muscarinic antisera used.

KEY RESULTS

All three MR subtypes were expressed in human colon. Immunoreactivity (IR) for M2Rs and M3Rs was most abundant in circular and longitudinal muscle. M1R-IR was most abundant on myenteric and submucosal nerve cells, both cholinergic and nitrergic. M3R-IR was also present on populations on myenteric nerve cell bodies. Immunoreactivity for all three receptors was present on nerve fibers in the circular muscle.

CONCLUSIONS & INFERENCES

In the human colon, subtypes of MRs were present on multiple cell types within the enteric circuits underlying motility, secretory and vasoactive reflexes. The cellular distribution for MRs found in this study agrees with data from functional studies, providing insight into the role MRs have in mediating enteric cholinergic neurotransmission.

Comparison of selective M3 and nonselective muscarinic receptor antagonists on gastrointestinal transit and bowel habits in humans

Although in vitro studies show that muscarinic M(3) receptors primarily mediate the effects of acetylcholine on gastrointestinal contractility, the muscarinic receptor subtypes regulating gastrointestinal motor activity and transit in humans in vivo are unclear. We hypothesized that muscarinic M(3)-specific but not nonspecific receptor antagonists would delay gastrointestinal and colonic transit in humans. In this parallel-group study, gastric emptying, small intestinal transit, and colonic transit were assessed by scintigraphy on days 4-6 in 72 healthy subjects (49 women) who received placebo (n = 16), the M(3) antagonist darifenacin ER [7.5 mg (n = 20) or 15 mg daily (n = 17)], or the nonspecific antagonist tolterodine [4 mg daily (n = 19)] for 6 days. Bowel habits were recorded by daily diaries. Both doses of darifenacin substantially delayed [P < 0.01 vs. placebo (for both doses), P < 0.01 vs. tolterodine (for 15 mg)] small intestinal transit, i.e., colonic filling at 6 h (placebo [59.6 +/- 6.4%, mean +/- SE], 7.5 mg ER [34.4 +/- 6.1%], 15 mg ER [20.4 +/- 6.3%)]. Darifenacin (15 mg) also delayed (P < 0.01 vs. placebo and tolterodine) half-time for ascending colonic emptying [placebo (12.0 +/- 1.5 h), 7.5 mg (18.6 +/- 1.9 h), 15 mg (22.9 +/- 2.6 h)] and colonic transit (geometric center) at 24 [placebo (2.8 +/- 0.2), 7.5 mg (2.4 +/- 0.2), 15 mg (1.9 +/- 0.2)] but not 48 h. Darifenacin did not affect gastric emptying and tolterodine did not affect bowel habits or gastrointestinal transit. With muscarinic antagonists used at clinically approved doses, these findings demonstrate that muscarinic M(3) receptors regulate small intestinal and colonic transit in humans; colonic effects are more pronounced in the right than left colon. At doses that affect small and large intestinal transit, M(3) antagonists do not affect gastric emptying in humans. The efficacy of darifenacin in diarrhea-predominant irritable bowel syndrome should be evaluated.

Current and novel therapeutic options for irritable bowel syndrome management

Irritable bowel syndrome is a functional gastrointestinal disorder affecting up to 3-15% of the general population in western countries. It is characterised by unexplained abdominal pain, discomfort, and bloating in association with altered bowel habits. The pathophysiology of irritable bowel syndrome is multifactorial involving disturbances of the brain-gut axis. The pathophysiology provides the rationale for pharmacotherapy: abnormal gastrointestinal motor functions, visceral hypersensitivity, psychosocial factors, autonomic dysfunction, and mucosal immune activation. Understanding the mechanisms, and their mediators or modulators including neurotransmitters and receptors have led to several therapeutic approaches including agents acting on the serotonin receptor or serotonin transporter system, antidepressants, novel selective anticholinergics, alpha-adrenergic agonists, opioid agents, cholecystokinin-antagonists, neurokinin-antagonists, somatostatin receptor agonists, corticotropin releasing factor antagonists, chloride channel activators, guanylate cyclase-c agonists, melatonin, atypical benzodiazepines, antibiotics, immune modulators and probiotics. The mechanisms and current evidence regarding efficacy of these agents are reviewed.

Influence of naloxone on rectal sensorimotor function in health

Abnormal rectal motor physiology and visceral hypersensitivity are implicated in the pathogenesis of irritable bowel syndrome. Endogenous opioids are involved in both the regulation of gut motility and the processing of sensory information. Our aim was to study the effect of suppression of endogenous opioid function by naloxone on rectal sensorimotor function in health. Eighteen healthy subjects participated in a rectal barostat study. Sensorimotor function was evaluated during two consecutive stepwise distensions separated by 30 min of basal tone recording, and with perception scoring on a 0-6 graded scale. Naloxone was administered, after 15 min of basal tone measurements, as an intravenous bolus (0.4 mg), followed by continuous infusion (20 microg kg(-1) h(-1)) in a placebo-controlled, single-blinded and randomized fashion. Naloxone did not alter rectal sensitivity. Comparison of visual analogue scale scores between naloxone and saline did not reveal altered intensities of pain or discomfort. Compared to the baseline distension, a significant adaptive increase in compliance occurred during the second distension after saline (7.8 +/- 0.7 vs 11.0 +/- 0.6 mL mmHg(-1), P = 0.0016). This dynamic change in rectal compliance did not occur after naloxone administration (8.8 +/- 0.7 vs 10.1 +/- 0.8 mL mmHg(-1), ns). Low intensity tonic distension induced a rectal adaptive relaxation, which was absent after naloxone. Naloxone does not alter rectal sensitivity but abolishes rectal adaptation in response to repeated balloon distention. These observations suggest that the endogenous opioid system is involved in control of rectal tone rather than rectal sensitivity.

Challenges to the therapeutic pipeline for irritable bowel syndrome: end points and regulatory hurdles

Recent advances in our understanding of basic neuroenteric mechanisms and the role of effectors and transmitters in the brain-gut axis have provided opportunities to develop new therapeutic agents for irritable bowel syndrome (IBS). Furthermore, human pharmacodynamic studies utilizing transit, colonic, or rectal sensitivity and brain imaging have been useful in determining therapeutic efficacy (particularly for drugs that act on motor function). This review provides an overview of medications that have not yet been approved for treatment of patients with IBS yet have shown promise in phase IIB trials. These include drugs that act on the serotonin receptor and transporter system: antidepressants, norepinephrine reuptake inhibitors, opioids, cholecystokinin antagonists, neurokinin-antagonists, chloride channel activators, guanylate cyclase C agonists, atypical benzodiazepines, probiotics, and antibiotics. The changing landscape in the regulatory approval process has impacted the development of IBS drugs. Guidance documents from regulatory agencies in Europe and the United States have focused on patients' reported outcomes and associated quality of life. After a decade of experience with different end points that have generated some data on psychometric validation and unprecedented information about responsiveness of the binary or global end points to drug therapy, it is necessary to pursue further validation studies before or during pivotal phase IIB or III trials. The hope of providing relief to patients should galvanize all parties to achieve these goals.

Role of endogenous opioids in the control of gastric sensorimotor function

Endogenous opioids have been implicated not only in the process of feeding but also in the control of gastric sensitivity and gastric motor responses, and impairment of antinociceptive opioid pathways has been hypothesized to contribute to the pathogenesis of functional dyspepsia. Our aim was to study the effect of suppression of endogenous opioid action by naloxone on gastric sensorimotor function in healthy volunteers. During intravenous administration of saline or naloxone (0.4 mg intravenous bolus followed by continuous infusion 20 microg kg(-1) h(-1)), sensitivity to gastric distension, gastric accommodation and fundic phasic contractility were evaluated by barostat in 15 subjects. Nutrient tolerance and meal-related symptoms were assessed using a satiety drinking test (n = 13), and solid and liquid gastric emptying were evaluated by breath test (n = 14). Naloxone did not influence gastric compliance and sensitivity. No effect on preprandial gastric tone was found but meal-induced accommodation was significantly inhibited by naloxone (P = 0.031). Subjects receiving naloxone demonstrated a higher motility index before (20.8 +/- 2.4 vs 28.0 +/- 1.9 mL s(-1), P = 0.007) and after (15.2 +/- 2.0 vs 22.7 +/- 1.5 mL s(-1), P = 0.0006) the meal. Naloxone significantly decreased the amount of food ingested at maximum satiety (715.4 +/- 77.7 vs 617.3 +/- 61.3 mL, P = 0.03). No effect of naloxone on gastric emptying was observed and intensity of postprandial symptoms was unchanged. These observations suggest that endogenous opioids are involved in the control of gastric accommodation and phasic contractility but not in the control of sensitivity to gastric distension or gastric emptying in healthy volunteers.

Effect of tolterodine on gastrointestinal transit and bowel habits in healthy subjects

Clinical trials and observations suggest that constipation is an uncommon side effect of treating overactive bladder with the muscarinic receptor antagonist tolterodine. Because muscarinic antagonism inhibits gastrointestinal motor activity, we evaluated the effects of tolterodine on bowel habits, gastrointestinal and colonic transit in healthy subjects. In this double-blind study, 36 healthy subjects were randomized to tolterodine extended release (ER, 4 mg daily) or placebo for 6 days. Gastric emptying (GE), small bowel and colonic transit were assessed on days 4-6 by scintigraphy. Bowel habits were recorded by diaries. Tolterodine did not significantly affect half-time for GE (GE t(half)) [116 +/- 6 min (mean +/- SEM) for placebo vs 126 +/- 7 min for tolterodine], small bowel transit measured by colonic filling at 6 h (45 +/- 6% for placebo vs 36 +/- 6% for tolterodine) or the geometric center of colonic transit at 24 h (2.9 +/- 0.2 for placebo vs 2.6 +/- 0.3 for tolterodine). Subjects who received tolterodine had slightly fewer bowel movements (i.e. 1.34 +/- 0.1 stools per day for placebo vs 1.0 +/- 0.1 for tolterodine; P = 0.02 for treatment effect). Tolterodine did not significantly affect stool consistency or ease of defecation. At the therapeutic dose used to treat overactive bladder, tolterodine did not significantly affect gastrointestinal or colonic transit and had minor effects on bowel habits in healthy subjects. Further studies are necessary to elucidate whether these observations are explained by tolterodine effects at muscarinic receptors which stimulate and inhibit gastrointestinal motility.

New therapies in the treatment of postoperative ileus after gastrointestinal surgery

Postoperative ileus after gastrointestinal surgery results from many factors, including the effects of surgical trauma, anesthetic agents, hyperactivity of the sympathetic nervous system, local inflammatory reactions, and the use of opioids in the postoperative period. Postoperative ileus can lead to potential complications and may prolong patients' hospitalization, thereby leading to an increase in healthcare costs. There have been recent efforts to improve the understanding of the pathogenesis of postoperative ileus and to develop new treatments to prevent or minimize its occurrence. Here, we present a review of the factors related to the development of postoperative ileus and new therapies directed at its prevention.

Peripherally acting opioid antagonists in the treatment of opiate-related constipation: a systematic review

Many patients treated with opioids suffer from constipation. Opiate- or opioid-related constipation is not only a frequent but also a distressing symptom and difficult to treat. There is emerging evidence regarding a novel approach to the management of opiate-related constipation. The aim of this paper is to collect, critically appraise, and summarize the evidence on the effectiveness of recently developed peripherally acting micro-receptor antagonists in the treatment of opiate-related constipation. A comprehensive search of 11 computerized databases was conducted and efforts were made to identify unpublished and ongoing research. Twenty studies were identified; 13 were randomized controlled trials (RCTs) and 7 were Phase II studies assessing toxicity. Studies were mainly executed in healthy volunteers or members of methadone programs with opioid-induced constipation as a model to mimic the condition of patients on opioids. Two RCTs were conducted in hospice patients. Quality of study design and validity of the findings was assessed in all studies. Data show proof of concept but do not allow a definitive answer concerning the effectiveness of the peripherally acting micro-opioid antagonists methylnaltrexone and alvimopan in managing opiate-related constipation. Further research is needed. If future Phase III trials provide supportive data, opioid antagonists may become a standard therapeutic option for the treatment of opiate-related constipation in patients with advanced cancer.

Irritable bowel syndrome: recent and novel therapeutic approaches

Irritable bowel syndrome (IBS) is a highly prevalent functional gastrointestinal disorder affecting up to 3-15% of the general population in Western countries. It is characterised by unexplained abdominal pain, discomfort and bloating in association with altered bowel habits. The pathophysiology of IBS is considered to be multifactorial, involving disturbances of the brain-gut-axis: IBS has been associated with abnormal gastrointestinal motor functions, visceral hypersensitivity, psychosocial factors, autonomic dysfunction and mucosal inflammation. Traditional IBS therapy is mainly symptom oriented and often unsatisfactory. Hence, there is a need for new treatment strategies. Increasing knowledge of brain-gut physiology, mechanisms, and neurotransmitters and receptors involved in gastrointestinal motor and sensory function have led to the development of several new therapeutic approaches. This article provides a systematic overview of recently approved or novel medications that show promise for the treatment of IBS; classification is based on the physiological systems targeted by the medication. The article includes agents acting on the serotonin receptor or serotonin transporter system, novel selective anticholinergics, alpha-adrenergic agonists, opioid agents, cholecystokinin antagonists, neurokinin antagonists, somatostatin receptor agonists, neurotrophin-3, corticotropin releasing factor antagonists, chloride channel activators, guanylate cyclase-c agonists, melatonin and atypical benzodiazepines. Finally, the role of probiotics and antibacterials in the treatment of IBS is summarised.

The ileocolonic sphincter

The human ileocolonic sphincter (ICS) develops a sustained tone mainly due to propagated and not propagated phasic motor activity. The ileocaecocolonic segment is also able to behave, yet uncommonly, as a synchronized segment involving propagated contractions originating from the ileum and migrating to the proximal colon. The ICS motor activity alone has a limited role towards forward flow. On the contrary, the functional entity corresponding to the distal ileum and the ICS provides a clearance mechanism for reflux of colonic contents into the small intestine. The presence of short chain fatty acids (SCFA) in the distal ileum, sensed either by endocrine cells or chemo-sensitive vagal afferents, is an important actor in triggering this clearance mechanism. The ICS tone is in part myogenic but a neuronal nitrergic component is also involved. Reflex excitatory and inhibitory responses of the ICS originating from ileal or colonic distension involve primarily spinal nitrergic and adrenergic pathways.

Alvimopan, a selective peripherally acting mu-opioid antagonist

Alvimopan is a novel, peripherally acting mu-opioid antagonist that is being developed for the management of acute postoperative ileus and for the reversal of the delayed gastrointestinal and colonic transit that result in symptoms such as constipation, nausea and motility disorders in patients treated with opiate analgesics. There is a clinical need for effective medications for the treatment of postoperative ileus and opiate-induced constipation and other motility disorders. This review addresses the basic and applied pharmacology and current evidence for the use of the medication, alvimopan, in clinical gastroenterology.

A quantitative approach to recording peristaltic activity from segments of rat small intestine in vivo

We have developed methods that allow correlation of propulsive reflexes of the intestine with measurements of intraluminal pressure, fluid movement and spatio-temporal maps of intestinal wall movements for the first time in vivo. A segment of jejunum was cannulated and set up in a Trendelenburg recording system while remaining connected to the vascular and nerve supply of the anaesthetized rat. The resting intraluminal pressure in intact intestine was 2-4 mmHg. Hydrostatic pressures of 2, 4, 8 and 16 mmHg were imposed. At a baseline pressure of 4 mmHg, propulsive waves generated pressures of 9 +/- 1 mmHg, that progressed oral to anal at 2-5 mm s(-1). Individual propulsive waves propelled 0.8 +/- 0.4 mL of fluid. The frequency of propulsive waves increased with pressure, but peristaltic efficiency (mL per contraction) decreased with pressure increase between 4 and 16 mmHg. Atropine, as a bolus, transiently blocked peristalsis, but caused maintained block when infused. Hexamethonium blocked propulsive contractions. Inhibition of nitrergic transmission converted regular peristalsis to non-propulsive contractions. These studies demonstrate the utility of an adapted Trendelenburg method for quantitative investigation of motility and pharmacology of enteric reflexes in vivo.

Opioids and the gut: pharmacology and current clinical experience

This article reviews the pharmacology and physiology of opiate receptors and the current and potential uses of opioid agonists and antagonists in clinical gastroenterology. Mu-receptors are involved in motor and sensory functions, and their modulation is established for treatment of diarrhea. Mu-antagonists have potential to reverse endogenous (e.g., postoperative ileus) or iatrogenic dysmotility (e.g., opioid bowel dysfunction). Modulation of the function of kappa-receptors may be a novel approach to control visceral pain in functional gut disorders. Results of formal testing of novel opioid modulators are keenly awaited.

Intrinsic primary afferent neurons and nerve circuits within the intestine

Intrinsic primary afferent neurons (IPANs) of the enteric nervous system are quite different from all other peripheral neurons. The IPANs are transducers of physiological stimuli, including movement of the villi or distortion of the mucosa, contraction of intestinal muscle and changes in the chemistry of the contents of the gut lumen. They are the first neurons in intrinsic reflexes that influence the patterns of motility, secretion of fluid across the mucosal epithelium and local blood flow in the small and large intestines. In the guinea pig small intestine, where they have been characterized in detail, IPANs have Dogiel type II morphology, that is they are large round or oval neurons with multiple processes, some of which end close to the luminal surface of the intestine, and some of which form synapses with enteric interneurons, motor neurons and with other IPANs. The IPANs have well-defined ionic currents through which their excitability, and their functions in enteric nerve circuits, is determined. These include voltage-gated Na(+) and Ca(2+) currents, a long lasting calcium-activated K(+) current, and a hyperpolarization-activated cationic current. The IPANs exhibit long-term changes in their states of excitation that can be induced by extended periods of low frequency activity in synaptic inputs and by inflammatory mediators, either applied directly or released during an inflammatory challenge. The IPANs may be involved in pathological changes in enteric function following inflammation.

Model of rapid gastrointestinal transit in dogs: effects of muscarinic antagonists and a nitric oxide synthase inhibitor

Our aims were to establish a canine model of rapid gastrointestinal transit, and to test the effects of muscarinic receptor antagonists (atropine, pirenzepine, AF-DX116, and darifenacin), and an NOS inhibitor, L-nitro-N-arginine (L-NNA) in this model. For gastric emptying and small bowel transit, 99mTc-labelled DTPA were added to a meal of skimmed milk (236 mL) that contained 2.4 g of magnesium hydroxide. Regional colonic transit was measured by111In-labelled beads placed in a capsule that released isotope in the proximal colon. Scintiscans were taken at regular intervals and indices of transit were calculated. Drugs were administrated intravenously. Gastric emptying, small bowel and colonic transit were rapid. Atropine and darifenacin (a selective M3 antagonist) delayed gastric emptying and colonic transit, the selective M1 and M2 muscarinic antagonists did not. The muscarinic blockers did not slow small bowel transit. L-NNA delayed small bowel and colonic transit but did not slow gastric emptying. A model suitable for the preclinical study of antidiarrhoeals was established. M3 receptors are important in the control of gastric emptying and colonic transit, and NOS inhibition slowed small bowel and colonic transit.

Management of opioid-induced gastrointestinal effects in patients receiving palliative care

Opioid-induced gastrointestinal side effects, namely, nausea and constipation, are bothersome yet often easy to manage. Due to their widespread frequency, it is imperative that prophylactic and treatment modalities be understood. Although many pharmacotherapeutic agents are available with which to prevent or treat these side effects, few randomized, placebo-controlled studies have been conducted in terminally ill patients, thus limiting most treatment decisions to empiric therapies based on extrapolated data. A strong understanding of the pathophysiology of the sequelae is therefore paramount. Common agents administered for nausea are butyrophenones, phenothiazines, metoclopramide, and serotonin-receptor antagonists. Those given to manage constipation are stimulant laxatives and stool softeners, individually or in combination.

Investigation of the effects of YM-31636, a novel 5-HT3 receptor agonist, on defecation in normal and constipated ferrets

We examined the effects of YM-31636 (2-(1H-imidazol-4-ylmethyl)-8H-indeno[1,2-d]thiazole monofumarate), a newly synthesized 5-HT(3) receptor agonist, on defecation in normal and constipated ferrets, and evaluated it as an agent against constipation. YM-31636 facilitated defecation without inducing diarrhea or emetic episodes. This effect occurred within 1 h after oral administration, mostly within 30 min, whereas sodium picosulfate, a widely used laxative, tended to increase the frequency of defecation for several hours with much lower peak incidence than that of YM-31636, and induced diarrhea. UK14304 (brimonidine), an alpha2 receptor agonist, and morphine reduced the frequency of defecation and YM-31636 restored it. These effects of YM-31636 were antagonized by ramosetron, a 5-HT(3) receptor antagonist. These results suggest that YM-31636 could be promising in the treatment of constipation. Because of an early and reliable onset of action compared with sodium picosulfate, YM-31636 could make it easier to control the time of defecation.

Types of neurons in the enteric nervous system

This paper, written for the symposium in honour of more than 40 years' contribution to autonomic research by Professor Geoffrey Burnstock, highlights the progress made in understanding the organisation of the enteric nervous system over this time. Forty years ago, the prevailing view was that the neurons within the gut wall were post-ganglionic neurons of parasympathetic pathways. This view was replaced as evidence accrued that the neurons are part of the enteric nervous system and are involved in reflex and integrative activities that can occur even in the absence of neuronal influence from extrinsic sources. Work in Burnstock's laboratory led to the discovery of intrinsic inhibitory neurons with then novel pharmacology of transmission, and precipitated investigation of neuron types in the enteric nervous system. All the types of neurons in the enteric nervous system of the small intestine of the guinea-pig have now been identified in terms of their morphologies, projections, primary neurotransmitters and physiological identification. In this region there are 14 functionally defined neuron types, each with a characteristic combination of morphological, neurochemical and biophysical properties. The nerve circuits underlying effects on motility, blood flow and secretion that are mediated through the enteric nervous system are constructed from these neurons. The circuits for simple motility reflexes are now known, and progress has been made in analysing those involved in local control of blood flow and transmucosal fluid movement in the small intestine.

Effect of atropine and sincalide on the intestinal uptake of F-18 fluorodeoxyglucose

PURPOSE

Variable diffuse intestinal uptake of F-18 fluorodeoxyglucose (FDG) is commonly seen in patients undergoing positron emission tomography (PET) imaging. Diffuse high uptake can obscure a lesion, whereas occasional high focal uptake can mimic a lesion. The cause of intestinal FDG uptake and the parameters that influence the level of uptake are unknown.

METHODS

We hypothesized that intestinal FDG uptake may result from smooth muscle peristalsis. We tested our hypothesis by comparing FDG uptake at baseline and after administration of two drugs (atropine and sincalide) that are known to affect intestinal motility. We performed FDG PET scans in random order in five healthy male volunteers without medication, after intramuscular administration of atropine, and after intravenous administration of sincalide.

RESULTS

Qualitative comparison of the images before and after both medications did not show any significant difference in the level of intestinal FDG uptake.

CONCLUSIONS

We conclude that intestinal FDG uptake is probably not caused by peristalsis. Mucosal uptake may be an alternative explanation.

Modeling intermittent digesta flow to calculate glucose uptake capacity of the bovine small intestine

To test the hypothesis that the uptake capacity of the bovine small intestine for glucose is upregulated to match or slightly exceed glucose delivery, glucose was continuously infused into the proximal duodenum of four cannulated holstein heifers. Every 3 days, infusion rates were increased by an average of 34 mmol/h. A model of glucose disappearance from multiple boluses of intestinal digesta was used to estimate the transporter maximum velocity and functional maximum uptake capacity for the entire small intestine from average ileal glucose flows during the third day of each period. Because of its intermittency, digesta flow remained independent of simulated transit time. For each unit increase in glucose infusion rate, uptake capacity increased by only 0.55 units. Excess capacity for glucose uptake was approximately twofold in forage-fed cattle and declined to below delivery at infusions of >208 mmol/h added glucose, approximately three times the normal load. Calculations for cattle, sheep, and rats indicate that the glucose transport capacity of the small intestine is typically underutilized because of a fraction of time that transporters are not in contact with digesta.

Muscarinic blockade inhibits gastric emptying of mixed-nutrient meal: effects of weight and gender

We compared the vagal contribution to gastric emptying in lean and obese subjects by monitoring gastric emptying of a meal during muscarinic blockade. Lean (n = 6) and obese subjects (n = 6) underwent two treatments: 1) saline infusion and 2) atropine infusion [0.4 mg/m2 bolus, 0.4 mg. (m2)-1. h-1] for 2 h, initiated 30 min before ingestion of a 600-kcal breakfast (64% carbohydrate, 23% fat, 13% protein) composed of orange juice (labeled with Indium-111), egg sandwich (labeled with Technetium-99m), cereal, milk, and banana. Anterior and posterior images were taken every 90 s for 90 min using a dual-headed camera. Atropine significantly delayed emptying of both solid (P < 0.007) and liquid (P < 0.002). Obese subjects exhibited a greater delay in liquid emptying during muscarinic blockade compared with lean subjects (P < 0.02). Female subjects exhibited a slower rate of gastric emptying and were less sensitive to atropine. These data suggest that obese subjects exhibit altered gastric cholinergic activity compared with lean subjects and that gender differences in gastric emptying rate may be due to differences in autonomic tone.

Basal pressure patterns and reflexive motor responses in the human ileocolonic junction

This study aimed to determine whether a sustained high-pressure zone exists at the human ileocolonic junction (ICJ) and whether the motor responses of ICJ are consistent with sphincteric function. In 10 subjects with temporary ileostomies, a high-pressure zone was identified using a manometric pull-through with a mean pressure of 9. 7 +/- 3.2 mmHg and length of 4.8 +/- 1.2 cm. Prolonged recordings using a sleeve sensor confirmed sustained tone in the ICJ and superimposed phasic pressure waves (4-8 counts/min) occupying 35% of fasted state. A meal increased ICJ tone (P = 0.0001) and the proportion of time occupied by phasic activity to 50% (P = 0.013). Terminal ileal propagating pressure wave sequences inhibited ICJ phasic activity, and sequences not extending to the cecum reduced ICJ tone (9.0 +/- 7.2 to 5.6 +/- 6.3 mmHg; P = 0.04). Cecal distension increased ICJ tone (8.9 +/- 4.4 mmHg to 11.7 +/- 4.9 mmHg; P = 0.005). The ICJ response to ileal distension was variable and depended on resting tone at the time of distension. We conclude that the human ICJ has sustained tone with superimposed phasic activity. Tone is augmented by cecal distension or a meal and is inhibited by ileal propagating pressure waves. Response to ileal distension is variable but suggests control by descending excitatory and inhibitory pathways.

The role of interdigestive small bowel motility in the regulation of gut microflora, bacterial overgrowth, and bacterial translocation in rats

OBJECTIVE

To clarify the role of the migrating motor complex (MMC) in the regulation of small intestinal microflora and bacterial translocation.

SUMMARY BACKGROUND DATA

The intestinal microflora may serve as a source of infectious microorganisms. Failure of regulatory mechanisms of the intestinal flora could therefore play an important role in the pathogenesis of gut-derived infections.

METHODS

Rats were fitted with small intestinal myoelectrodes. MMCs were measured on a control day and 3 consecutive days during continuous administration of morphine or placebo. Mesenteric lymph nodes, liver, spleen, peripheral blood, duodenum, and ileum samples were cultured quantitatively.

RESULTS

The mean MMC cycle length in placebo-treated animals was 15.1+/-0.5 minutes. MMCs were completely disrupted after morphine treatment. Total bacterial growth in the duodenum was 7.27+/-0.34 10log colony-forming units (CFU)/g with placebo and 8.28+/-0.27 CFU/g with morphine. In placebo-treated animals, the mean MMC cycle length the day before culturing correlated with total bacterial growth in the duodenum. Translocation incidences to the mesenteric lymph nodes, liver, spleen, and blood were 0/8, 1/8, 0/8, and 0/8 with placebo and 7/8, 6/8, 5/8, and 0/8 with morphine. The overall translocation incidence was 1/8 in placebo-treated animals and 8/8 in morphine-treated animals.

CONCLUSIONS

The MMC is an important mechanism controlling bacterial growth in the upper small bowel. Its disruption with morphine promotes duodenal bacterial overgrowth and bacterial translocation.

Response to intraluminal gas in irritable bowel syndrome. Motility versus perception

Our aim was to evaluate the response to intraluminal gas in irritable bowel syndrome and to determine whether this response was consequent upon disordered motility or altered perception. We evaluated 10 patients who satisfied the clinical criteria for the diagnosis of irritable bowel syndrome and 10 healthy controls. An eight-lumen perfused catheter assembly was positioned to monitor motor activity in the duodenum and proximal jejunum; a separate side port in the distal duodenum permitted gas infusion. Subjects recorded symptoms of abdominal pain, bloating, and nausea throughout the study, using a visual analog scale. Following an overnight fast and a 60-min basal recording period in the fasted state, subjects ate a standard meal; 60 min later, "sham" gas was administered for 20 min, followed by the actual infusion of nitrogen gas at 40 ml/min. Subjects were randomized to receive atropine (7 micrograms/kg) or placebo intravenously during the period of actual gas infusion. Patients with irritable bowel syndrome described more pain (score, mean +/- SE, control versus irritable bowel: 0.22 +/- 0.16 vs 1.65 +/- 0.5, P < 0.01) and nausea (0.25 +/- 0.21 vs 1.45 +/- 0.64, P < 0.04) during sham gas; motility indices were similar in both groups. During active gas, irritable bowel syndrome patients reported more pain (0.40 +/- 0.39 vs 2.94 +/- 1.16, P < 0.03); motility indices at all sites were similar in both groups. Symptom severity in irritable bowel syndrome subjects randomized to receive atropine was similar to control subjects during active gas infusion; motility indices were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of a tricyclic antidepressant on small intestinal motility in health and diarrhea-predominant irritable bowel syndrome

Antidepressants are used in irritable bowel syndrome (IBS) and may have effects on the gut independent of improving mood. We have investigated the actions of a tricyclic antidepressant on small intestinal motor function in eight healthy volunteers and in six patients with diarrhea-predominant IBS. Fasting ambulatory motility was recorded from six small intestinal sites for 16-18 hr while on no drug (baseline) and while taking imipramine for five days. Orocecal transit time (OCTT) was measured by lactulose hydrogen breath test, during baseline and imipramine administration. Imipramine did not alter migrating motor complex periodicity, but slowed jejunal phase III propagation velocity in controls from 7.5 +/- 1.1 to 3.6 +/- 0.5 cm/min (P < 0.01) and in IBS from 7.8 +/- 0.6 to 4.4 +/- 0.5 cm/min (P < 0.0001). Phase III duration at each site was increased, and total recorded phase III was greater during imipramine than baseline studies. Imipramine increased the amplitude of phase III contractions. There was no effect of imipramine on non-phase-III motility index or discrete clustered contractions. Imipramine, prolonged OCTT from 73 +/- 6 min to 97 +/- 8 min in controls (P < 0.05) and from 61 +/- 9 min to 89 +/- 8 min in IBS (P < 0.05). Although OCTT was shorter in the IBS group, no motility differences were seen between controls and IBS. This demonstration that a tricylic antidepressant can modify small intestinal motor function in health and in IBS supports the view that these drugs may have therapeutic actions in IBS unrelated to mood improvement.

Neurogenic inhibition of duodenal and jejunal motility in the anaesthetized rat

Duodenal or jejunal motility (monitored as pressure changes in a saline-perfused intraluminal catheter) was studied in anaesthetized rats, vagotomized and pretreated with adrenergic blocking agents. In the duodenum (but not the jejunum), atropine or the selective muscarinic M1 and M3 receptor antagonists, pirenzepine and 4-diphenyl-acetoxy-N-methylpiperidine (4-DAMP), respectively, augmented the spontaneous contractile activity. This effect could be abolished either by nicotinic ganglionic receptor antagonism with hexamethonium, or with morphine. Moreover, blockade of the synthesis of nitric oxide by N omega-nitro-L-arginine elicited hypermotility both in the duodenum and the jejunum, and also this response was abolished by hexamethonium. It is proposed from the present results that the rat small is controlled by non-adrenergic, non-cholinergic inhibitory as well as excitatory motor neurons. The latter motor neurons seem to be modulated by muscarinic, nitroxergic or opioidergic mechanisms.

Differences between jejunal myoelectric activity after a meal and during phase 2 of migrating motor complexes in healthy humans

Using an intraluminal probe with six pairs of annular electrodes, the myoelectric activity of the proximal jejunum was recorded during 48-hr sessions in 16 healthy volunteers receiving evening and noon meals (1000 kcal) and breakfast (400 kcal). In 10 subjects receiving no drug, the characteristics of the migrating motor complexes (period, duration of each phase, velocity of propagation of phase 3, duration of the postprandial disruption) varied markedly between subjects but were relatively constant from the first to the second day of recording. Single spike bursts propagated at a rate of 2-5 cm/sec, clusters of 3-10 spike bursts propagated at a rate of 0.5-1 cm/sec, and similar clusters recurring repetitively each 1.5-2 min were observed after the meals and very rarely in the fasted state during phase 2 of nocturnal migrating motor complexes. In six subjects, oral administration of codeine (50 mg) 1 hr before a meal induced migrating motor complexes in the postprandial state, with characteristics similar to that observed in the fasted state except a longer duration of phase 2. Single spike bursts and isolated and repetitive clusters of spike bursts were observed during phase 2 of the codeine-induced migrating motor complexes and after meals preceded by placebo, but very rarely during the phase 2 of nocturnal (fasted state) migrating motor complexes. It is concluded that the patterns of jejunal contractions consisting of propagated single spike bursts and isolated or repetitive spike bursts characterize the postprandial state in healthy humans and are dependent upon digesta flow.

Contractile response of guinea pig ileum by repetitive application of morphine

1. The repetitive application of morphine gradually induced a contracture in the isolated guinea pig ileum. 2. The optimum conditions for induction of the contracture were as follows: the concentration, incubation time and washout time of morphine were 1 or 10 microM, 2 and 3 min, respectively. 3. Preincubation with naloxone or TTX blocked this morphine-induced contracture. 4. Among twitch-inhibiting drugs, only clonidine induced a contracture similar to that induced by morphine, while tetrodotoxin (TTX) and adenosine did not. 5. The contracture was also observed in the longitudinal muscle-myenteric plexus preparations. 6. These findings indicate that morphine has a dual inhibitory and excitatory action on the guinea pig ileum and that its repetitive application preferentially diminish the inhibitory one.

Perendoscopic manometry of the distal ileum and ileocecal junction in humans

Previous manometric studies of the ileocolonic junction were performed without assessing the precise spatial relationship between recording sensors and ileocolonic junction. In the present study, the motor activity of the ileocolonic junction was recorded using manometric sensors localized under direct colonoscopic control in 11 patients (4 men, 7 women; mean age, 55 years) referred for hematochezia with normal stool frequency. No medications were administered before and during endoscopy. A perfused catheter (OD 1.7 mm, with three side holes 4 mm apart and marked by evenly spaced black rings in the distal 6 cm) was passed through the biopsy channel of the endoscope and advanced through the ileocolonic junction and 6 cm into the ileum. The catheter was then withdrawn into the cecum by 1-cm steps, and motor activity was recorded for 4-6 minutes at each station. A single catheter taped to the endoscope continuously recorded cecal pressure. An ileocecal pressure gradient could not be identified in the majority of subjects; individual values ranged from -8 to +4 mm Hg, and gradients were maintained over the entire length of the ileum. In the distal ileum, tonic and phasic pressure waves were detected. Tonic variations were present for 70.1% of the recording time, either alone (44%) or together with phasic waves (56%). Phasic waves were present for 10.3% of the recording time and, according to their duration, were subdivided into those compatible with the rate of ileal slow waves and prolonged waves not compatible with the rate of ileal slow waves. Regular phasic waves could be either isolated or in clusters; prolonged waves were always isolated. A similar proportion of regular (27.9%) and prolonged (31.2%) phasic waves propagated aborally along the ileum or from ileum to cecum. Clusters presented an average of 8.7 +/- 0.6 peaks/min, and 44% of them propagated aborally. The manometric characteristics did not vary between the segments 5-3 cm and 2-0 cm proximal to the ileocecal junction. In conclusion, a powerful ileocecal sphincter was not detected at the human ileocecal junction, and motor activity of the distal ileum was characterized by tonic changes and rapid phasic contractions.

Long-term effects of jejunoileal autotransplantation on myoelectrical activity in canine small intestine

We studied the longitudinal effects of autotransplantation on the motor function of the jejunoileum. By performing the autotransplantation procedure in a manner similar to that employed for allotransplantation, we sought to examine the long-term effects of both extrinsic denervation and the operative procedure itself on small intestinal motor function. Although initially disrupted, interdigestive myoelectrical activity demonstrated progressive organization: 88% of migrating myoelectrical complexes in animals studied between 12 and 20 months following autotransplantation demonstrated each phase of the complex in normal sequence. Longitudinal studies of several parameters of myoelectrical activity provided further evidence of progressive organization and entrainment of motor functions within the denervated intestine. Several abnormal myoelectrical patterns were observed within the autotransplanted segment, however, and coordination of either slow wave or phase III activity with the proximal innervated intestine did not recover with time. The major component of the myoelectrical response to feeding was permanently impaired with a delayed onset and shortened duration of the fed response. We conclude that the extrinsically denervated intestine recovers the ability to generate and organize all phases of the MMC but demonstrates permanent impairment of the major motor response to food. However, anoxic and cooling damage to enteric nerves and muscle, incurred during the autotransplantation procedure, may explain the persistence of abnormal motor patterns and impaired myoelectrical conduction and could play an important role, additional to that of extrinsic denervation, in the long-term motor function of the allotransplanted intestine.

A comparison of metoclopramide and trimebutine on small bowel motility in humans

Trimebutine meleate and metoclopramide increase small bowel motility. The present manometric study of the human normal interdigestive duodeno-jejunal motility demonstrated two different pharmacological effects in 15 healthy volunteers. Trimebutine constantly induced a premature phase 3 activity (0.81 +/- 0.4 min after a 100-mg intravenous injection) with patterns similar to spontaneous phase 3. Metoclopramide increased the motility index (contractile activity) during phase 2 without inducing a premature phase 3. No significant variations in plasma motilin concentration were noticed after either trimebutine or metoclopramide. The pancreatic polypeptide concentration rose significantly after metoclopramide injection.

Orocecal transit delay in obese patients

Orocecal transit time was assessed with lactulose hydrogen breath test in 12 obese patients during intravenous infusion of placebo or naloxone 40 micrograms/kg/hr given in randomized order and in double-blind conditions. Transit time was also evaluated in 22 healthy controls. Orocecal transit was significantly (P less than 0.01) longer in the obese patients, during placebo treatment (median 130, range 100-200 min) than in the healthy controls (median 75, range 40-170 min). Compared with placebo, transit time in the obese subjects was delayed (P less than 0.05) during naloxone treatment (median 150, range 100-230 min).

Effect of ileal perfusion of carbohydrates and amylase inhibitor on gastrointestinal hormones and emptying

To determine if carbohydrates perfused into the ileum affect gastric emptying and circulating levels of gastrointestinal hormones, 18 healthy subjects were intubated with an oroileal tube. A 400-cal (60% carbohydrate, 20% protein, 20% fat) homogenized meal labeled with 111In-DTPA was then infused into the stomach over 10 min. Simultaneously, a test solution of normal saline (n = 6) or 12.5 (n = 4), 25 (n = 4), 50 (n = 2), or 100 (n = 2) mg/min of carbohydrates (75% rice starch, 25% glucose) containing a nonabsorbable marker, polyethylene glycol, was continuously perfused into the terminal ileum at 3 ml/min for 7 h. In one-half of the subjects the perfusate contained an amylase inhibitor (3.3 mg/ml) that reduced starch digestion and carbohydrate absorption. Gastric emptying was measured by a dual-headed gamma-camera. Plasma concentrations of hormones and the amount of carbohydrates passing the ileum were measured every 10 min. The amylase inhibitor significantly reduced the absorption of complex carbohydrates from the terminal ileum (p less than 0.05). Gastric emptying was significantly slowed by ileal perfusion of carbohydrates (p less than 0.01). This effect was enhanced by the amylase inhibitor (p = 0.06). Plasma concentrations of C-peptide, glucagon, motilin, gastrin, and human pancreatic polypeptide were not related to gastric emptying or ileal perfusates, but decreased concentrations of gastric inhibitory polypeptide and neurotensin and increased concentrations of peptide YY were significantly associated (p less than 0.05) with slowing of gastric emptying. Perfusing carbohydrates into the ileum was associated with nausea, abdominal pain, and vomiting, but we could detect no direct relationship between the onset of these symptoms and gastric emptying. Slowing of gastric emptying of a homogenized mixed meal by the entry of complex carbohydrates into the ileum may be partly mediated by peptide YY or nonvagally mediated neural mechanisms.