Search

Susan H Boklage,1 Allen W Mangel,2 Varun Ramamohan,2 Deirdre Mladsi,2 Tao Wang1 1Otsuka America Pharmaceutical, Inc, Princeton, NJ, 2RTI Health Solutions, Research Triangle Park, NC, USA Background: The treatment failure rate for Helicobacter pylori eradication therapy is ~20% due to poor patient compliance and increased antibiotic resistance. This analysis assessed the cost-effectiveness of universal post-treatment testing to confirm eradication of H. pylori infection in adults.Methods: Decision-analytic models evaluated the cost-effectiveness of universal post-treatment testing (urea breath test [UBT] or monoclonal fecal antigen test [mFAT]) vs no testing (Model 1), and UBT vs mFAT after adjusting for patient adherence to testing (Model 2) in adults who previously received first-line antimicrobial therapy. Patients testing positive received second-line quadruple therapy; no further action was taken for those testing negative or with no testing (Model 1) or for those nonadherent to testing (Model 2). In addition to testing costs, excess lifetime costs and reduced quality-adjusted life-years (QALYs) due to continuing H. pylori infection were considered in the model.Results: Expected total costs per patient were higher for post-treatment testing (UBT: US$325.76; mFAT: US$242.12) vs no testing (US$182.41) in Model 1 and for UBT (US$336.75) vs mFAT (US$326.24) in Model 2. Expected QALYs gained per patient were 0.71 and 0.72 for UBT and mFAT, respectively, vs no testing (Model 1), and the same was 0.37 for UBT vs mFAT (Model 2). The estimated incremental costs per QALY gained for post-treatment testing vs no testing were US$82.90–US$202.45 and, after adjusting for adherence, US$28.13 for UBT vs mFAT.Conclusion: Universal post-treatment testing was found to be cost-effective for confirming eradication of H. pylori infection following first-line therapy. Better adherence to UBT relative to mFAT was the key to its cost-effectiveness. Keywords: health-economic, decision-analytic modeling, infectious disease

Susan H Boklage,1 Allen W Mangel,2 Varun Ramamohan,2 Deirdre Mladsi,2 Tao Wang1 1Otsuka America Pharmaceutical Inc, Princeton, NJ, 2RTI Health Solutions, Research Triangle Park, NC, USA Objective: Previous US-based economic models of noninvasive tests for diagnosis of Helicobacter pylori infection did not consider patient adherence or downstream costs of continuing infection. This analysis evaluated the long-term cost-effectiveness of the urea breath test (UBT), fecal antigen test (FAT), and serology for diagnosis of H. pylori infection after incorporating information regarding test adherence.Materials and methods: A decision-analytic model incorporating adherence information evaluated the cost-effectiveness of the UBT, FAT, and serology for diagnosis of H. pylori infection. Positive test results led to first-line triple therapy; no further action was taken for nonadherence or negative results. Excess lifetime costs and reduced quality-adjusted life-years (QALYs) were estimated for patients with continuing H. pylori infection.Results: In the base-case scenario with estimated adherence rates of 86%, 48%, and 86% for the UBT, monoclonal FAT, and serology, respectively, corresponding expected total costs were US$424.99, $466.41, and $404.98/patient. Test costs were higher for the UBT, but were fully or partially offset by higher excess lifetime costs for the monoclonal FAT and serology. The QALYs gained/patient with the UBT vs monoclonal FAT and serology were 0.86 and 0.27, respectively. The UBT was dominant vs the monoclonal FAT, leading to lower costs and higher QALYs; the UBT was cost-effective vs serology (incremental cost/QALY gained $74).Conclusion: Based on a comprehensive modeled analysis that included consideration of patient test adherence and long-term consequences resulting from continuing H. pylori infection, the UBT provided the greatest economic value among noninvasive tests for diagnosis of H. pylori infection, because of high patient adherence and excellent test performance. Keywords: Helicobacter pylori, urea breath test, fecal antigen test, serology, cost-effectiveness, noninvasive diagnostic testing

Claire M Ervin,1 Sheri E Fehnel,1 Mollie J Baird,2 Robyn T Carson,3 Jeffrey M Johnston,2 Steven J Shiff,3 Caroline B Kurtz,2 Allen W Mangel11RTI Health Solutions, Research Triangle Park, NC, USA; 2Ironwood Pharmaceuticals, Inc., Cambridge, MA, USA; 3Forest Research Institute, Jersey City, NJ, USABackground: While chronic constipation (CC) clinical trials have focused primarily on bowel symptoms (symptoms directly related to bowel movements), abdominal symptoms are also prevalent among patients. The United States Food and Drug Administration’s (FDA’s) guidance on the use of patient-reported outcome measures to support product approvals or labeling claims recommends that endpoints be developed with direct patient input and include all symptoms important to patients.Aim: To identify a comprehensive set of CC symptoms that are important to patients for measurement in clinical trials.Methods: Following a targeted literature review to identify CC symptoms previously reported by patients, 28 patient interviews were conducted consistent with the FDA’s guidance on patient-reported outcomes. Subsequent to open-ended questions eliciting descriptions of all symptoms, rating and ranking methods were used to identify those of greatest importance to patients.Results: All 67 studies reviewed included bowel symptoms; more than half also addressed at least one abdominal symptom. Interview participants reported 62 potentially distinct concepts: 12 bowel symptoms; 21 abdominal symptoms; and 29 additional symptoms/impacts. Patients’ descriptions revealed that many symptom terms were highly related and/or could be considered secondary to CC. The rating and ranking task results suggest that both bowel (for example, stool frequency and consistency) and abdominal symptoms (for example, bloating, abdominal pain) comprise patients’ most important symptoms. Further, improvements in both bowel and abdominal symptoms would constitute an improvement in patients’ CC overall.Conclusion: Abdominal symptoms in CC patients are equal in relevance to bowel symptoms and should also be addressed in clinical trials to fully evaluate treatment benefit.Keywords: abdominal symptoms, straining, infrequent bowel movements, incomplete bowel movements, patient-reported outcomes

Sarah B Marion, Allen W MangelRTI Health Solutions, Research Triangle Park, NC, USAAbstract: For decades, it was believed that the diameter of gastrointestinal smooth muscle cells is sufficiently narrow, and that the diffusion of calcium across the plasma membrane is sufficient, to support contractile activity. Thus, depolarization-triggered release of intracellular calcium was not believed to be operative in gastrointestinal smooth muscle. However, after the incubation of muscle segments in solutions devoid of calcium and containing the calcium chelator ethylene glycol tetraacetic acid, an alternative electrical event occurred that was distinct from normal slow waves and spikes. Subsequently, it was demonstrated in gastrointestinal smooth muscle segments that membrane depolarization associated with this alternative electrical event triggered rhythmic contractions by release of intracellular calcium. Although this concept of depolarization-triggered calcium release was iconoclastic, it has now been demonstrated in multiple gastrointestinal smooth muscle preparations. On the basis of these observations, we investigated whether a rhythmic electrical and mechanical event would occur in aortic smooth muscle under the same calcium-free conditions. The incubation of aortic segments in a solution with no added calcium plus ethylene glycol tetraacetic acid induced a fast electrical event without corresponding tension changes. On the basis of the frequency of these fast electrical events, we pursued, contrary to what has been established dogma for more than three centuries, the question of whether the smooth muscle wall of the aorta undergoes rhythmic activation during the cardiac cycle. As with depolarization-triggered contractile activity in gastrointestinal smooth muscle, it was “well known” that rhythmic activation of the aorta does not occur in synchrony with the heartbeat. In a series of experiments, however, it was demonstrated that rhythmic contractions occur in the aortic wall in synchrony with the heartbeat and share a common pacemaker with the heart. We conclude that important observations in the vascular system became derivative from those in the gastrointestinal system. The challenging of scientific dogma potentially leads to the expansion of our fundamental knowledge base.Keywords: gastrointestinal smooth muscle, aortic smooth muscle, contractions, intracellular calcium pools, Windkessel hypothesis, pulse-synchronized contractions

Allen W Mangel1, Gareth A Hicks21RTI Health Solutions, Research Triangle Park, NC, 2Tioga Pharmaceuticals Inc, San Diego, CA, USAAbstract: Irritable bowel syndrome (IBS) is a multifactorial condition with principal symptoms of pain and altered bowel function. The kappa-opioid agonist asimadoline is being evaluated in Phase III as a potential treatment for IBS. Asimadoline, to date, has shown a good safety profile and the target Phase III population – diarrhea-predominant IBS patients with at least moderate pain – was iteratively determined in a prospective manner from a Phase II dose-ranging study. The clinical data in support of this population are reviewed in this article. Furthermore, the scientific rationale for the use of asimadoline in the treatment of IBS is reviewed. Considering the high patient and societal burdens of IBS, new treatments for IBS represent therapeutic advances.Keywords: irritable bowel syndrome, kappa-opioid agonist, asimadoline, visceral pain, visceral hypersensitivity

The pyloric sphincter receives parasympathetic vagal innervation from the dorsal motor nucleus of the vagus (DMV). However, little is known about its higher-order neurons and the nuclei that engage the DMV neurons controlling the pylorus. The purpose of the present study was twofold. First, to identify neuroanatomical connections between higher-order neurons and the DMV. This was carried out by using the transneuronal pseudorabies virus PRV-152 injected into rat pylorus torus and examining the brains of these animals for PRV labeling. Second, to identify the specific sites within the DMV that functionally control the motility and tone of the pyloric sphincter. For these studies, experiments were performed to assess the effect of DMV stimulation on pylorus activity in urethane-anesthetized male rats. A strain gauge force transducer was sutured onto the pyloric tonus to monitor tone and motility. L-glutamate (500 pmol/30 nL) was microinjected unilaterally into the rostral and caudal areas of the DMV. Data from the first study indicated that neurons labeled with PRV occurred in the DMV, hindbrain raphe nuclei, midbrain Edinger-Westphal nucleus, ventral tegmental area, lateral habenula, and arcuate nucleus. Data from the second study indicated that microinjected L-glutamate into the rostral DMV results in contraction of the pylorus blocked by intravenously administered atropine and ipsilateral vagotomy. L-glutamate injected into the caudal DMV relaxed the pylorus. This response was abolished by ipsilateral vagotomy but not by intravenously administered atropine or L-NG-nitroarginine methyl ester (L-NAME). These findings identify the anatomical and functional brain neurocircuitry involved in controlling the pyloric sphincter. Our results also show that site-specific stimulation of the DMV can differentially influence the activity of the pyloric sphincter by separate vagal nerve pathways., (© 2023 The Authors. The Journal of Comparative Neurology published by Wiley Periodicals LLC.)

For over a century, the behavior of the aorta and other large arteries has been described as passive elastic tubes in which no active contraction occurs in the smooth muscle wall. In response to pulsatile pressure changes, the vessels undergo a 'passive' elastic dilatation-contraction cycle, described as a "Windkessel" effect. However, Mangel and colleagues have presented evidence that is contrary to this view. They reported that in the rabbit, the aorta undergoes rhythmic 'active' (contraction) during the cardiac cycle; but these findings have been largely ignored. In the present study, we observed spontaneous contractions in synchrony with the heartbeat in another species (rat). In addition we demonstrate that aorta contractions are of neurogenic origin. Electrical stimulation of the aorta evoked contractions that occur at a rate that is in the range of the animal's heartbeat and are suppressed by tetrodotoxin and the alpha-adrenergic receptor blocker, phentolamine. Altogether, these findings indicate that aortic contractions are under neural control from the heart.

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders and it is characterized by episodes of abdominal pain and altered bowel functions. The specific bowel disturbances of diarrhea, constipation or an alternation between the two defines the IBS subtypes of diarrhea-predominant, constipation-predominant, and mixed or alternating IBS. Because of the abnormalities in bowel states associated with each IBS subtype, it is not likely that one agent would successfully treat all three subtypes. As a result, clinical trials have focused, for the most part, on one IBS subtype. Over the past 2 decades very few agents have achieved regulatory approval for the treatment of IBS. In the present article we review publications reporting on phase 2 and phase 3 studies evaluating agents to potentially be used in the treatment of patients with IBS.

Background: The choice of endpoints is crucial for proper evaluation of agents in clinical trials of irritable bowel syndrome (IBS). In a recently published draft guidance for IBS from the United States Food and Drug Administration (FDA), urgency was not considered an appropriate primary endpoint. The FDA's position is that it is not clear how patients with diarrhea-predominant IBS (D-IBS) "define or describe urgency". The aims of this study were to evaluate the association of urgency with stool frequency and consistency in patients with D-IBS and to describe results from patient interviews on their understanding of the term urgency., Methods: A retrospective analysis of clinical trial data in patients with D-IBS was conducted. Analyses focused on the relationship of urgency to stool frequency and consistency. Interviews were conducted with patients with D-IBS to test their understanding of the term urgency., Results: On the days that patients reported urgency, as compared to the days that patients did not report urgency, they had more frequent bowel movements (3.9 versus 1.8) and looser stools (Bristol Stool Score: 5.4 versus 4.2). The differences for both parameters, evaluated on the days with or without urgency, were statistically significant. In patient interviews, patients with D-IBS had a clear understanding of the concept and terminology of urgency and considered it one of their two most bothersome symptoms., Conclusions: Urgency should be considered a suitable co-primary endpoint in D-IBS studies.

The membrane of most gastrointestinal smooth muscles shows slow waves, slow rhythmic changes in membrane potential. Slow waves serve to bring the membrane potential of smooth muscle cells to a threshold level that elicits a second electrical event known as the spike or action potential. The inward current of the spike, in most gastrointestinal smooth muscle preparations, is carried, at least in part, by calcium. Indeed, considering the narrow diameter of smooth muscle cells, some have hypothesized that the influx of calcium during the spike is sufficient for activation of the contractile machinery. Findings consistent with this include marked reduction in contractility during exposure of muscle segments to blockers of L-type calcium channels or following reductions in external calcium levels. However, it has also been observed that following exposure of muscle segments to external bathing solutions containing no added calcium plus 5 mM EGTA to remove any remaining extracellular calcium, contractions can be triggered following membrane depolarization. It is noteworthy that in isolated smooth muscle cells or in small muscle segments, during incubation in calcium-free solution, depolarization does not induce contractions. The present paper discusses the evidence in support of depolarization-mediated contractions occurring in gastrointestinal smooth muscle segments during incubation in solutions devoid of calcium.

Background: Velusetrag is an orally active 5-HT(4) receptor agonist of potential benefit in treating chronic idiopathic constipation., Aim: To evaluate the efficacy, safety and tolerability of velusetrag in chronic idiopathic constipation., Methods: After a 2-week baseline period, patients [<3 spontaneous bowel movements (SBM)/week] received placebo or velusetrag (15, 30 or 50 mg) daily for 4 weeks in a randomized, double-blind design, followed by a 1-week follow-up period. The primary endpoint was the change from baseline in weekly SBM frequency averaged over the 4-week treatment period., Results: Patients receiving velusetrag (15, 30 and 50 mg) achieved statistically and clinically significant increases in weekly SBM frequency relative to those receiving placebo. Mean increases were 3.6, 3.3 and 3.5 SBM/week respectively, compared with 1.4 SBM/week for placebo (P < 0.0001). Statistically significant increases in the weekly frequency of complete SBM (CSBM) were also reported (mean increases of 2.3, 1.8 and 2.3 for 15, 30 and 50 mg velusetrag respectively, compared with 0.6 for placebo). Common adverse events associated with velusetrag were diarrhoea, headache, nausea and vomiting, generally occurring during the initial days of dosing., Conclusion: Velusetrag was efficacious and well tolerated in patients with chronic idiopathic constipation (ClinicalTrials.gov identifier NCT00391820)., (© 2010 Theravance, Inc.)

Importance of the Field: Irritable bowel syndrome (IBS) represents one of the most common gastrointestinal disorders, with the diarrhea-predominant form (D-IBS) representing an area of high unmet medical need. One difficulty in identifying suitable treatments for IBS is that although there are animal models for the components of IBS, it is not clear whether animals are afflicted by the disease. In a recently completed Phase II study, the kappa-opioid agonist, asimadoline, was shown to be efficacious in a prospectively defined subgroup of D-IBS patients. This study confirmed a good safety profile for asimadoline., Areas Covered in This Review: The chemistry, pharmacology, pharmacokinetics, pharmacodynamics and clinical safety and efficacy of asimadoline in relationship to IBS is reviewed. Papers were searched over the past 20 years using the PubMed database and key words 'asimadoline', 'kappa-opioid agonist' and 'irritable bowel syndrome'. Abstracts were reviewed and appropriate full papers were then evaluated., What the Reader Will Gain: The reader will gain an appreciation of kappa-opioid agonists as IBS treatments., Take Home Message: In a prospectively defined, clinically relevant patient subgroup, asimadoline shows efficacy in the treatment of D-IBS.

Background: Sigmoidoscopy/colonoscopy is usually performed prior to enrollment into clinical trials of irritable bowel syndrome (IBS). Two main reasons are to rule out alternative diagnoses and to ensure that colitis is not present. However, the possible impact of a recent versus remote colon procedure on symptoms in IBS trials has not been evaluated. The aim of this study was to evaluate the effect of timing of colon procedures on symptoms in IBS trials., Methods: Post hoc analyses were conducted using placebo patients with diarrhea-predominant IBS in a phase 2 trial. Pain, frequency, consistency, and urgency were analyzed using repeated measures models during the first 7 days of treatment and over the entire 12-week treatment period., Results: Fifty-two placebo patients were grouped by whether they had a colon exam performed between screening and randomization (Group 1) or had a normal colon procedure during the 3 years prior to screening for this trial (Group 2). Average screening symptom scores were comparable between the two groups. Evaluation of various symptoms showed that there were no consistent significant differences between the two groups in pain, frequency, consistency, or urgency., Conclusions: After the required 3-day post-procedure recovery period, there was no evidence that colonoscopy timing affected subsequent IBS symptoms.

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder characterized by abdominal pain and altered bowel function. Few agents are available for the treatment of IBS. Historically, one impediment to the development of agents to treat IBS was lack of a uniform and robust clinical trial design. Studies occurred with different durations of treatment, endpoints and with different target populations. Great advances have been made over the past decade in trial design including: optimal duration of study, mode of data collection, populations to evaluate and identification of endpoints. Using these refinements, it was possible to demonstrate the efficacy of some new agents. These advances are illustrated by a review of trials with kappa opioid agonists and atypical benzodiazepine antagonists, which appear to be promising new classes of treatments for symptoms in IBS.

Background: In models of irritable bowel syndrome (IBS), asimadoline, a kappa-opioid agonist, improves pain and abnormal bowel function., Aim: To evaluate the effects of three doses of asimadoline and placebo in subjects with IBS through a double-blind, randomized, placebo-controlled trial., Methods: Patients were randomly assigned to receive asimadoline 0.15, 0.5, 1.0 mg or placebo BID for 12 weeks. The primary efficacy measure was number of months of adequate relief of IBS pain or discomfort, with a prospective plan to evaluate adequate relief data by entry baseline pain and subtype. Several other endpoints were also evaluated., Results: Five hundred and ninety-six patients were randomized. In the ITT population, statistically significant improvement on the primary endpoint was not seen. However, in diarrhoea-predominant IBS patients with at least baseline moderate pain, asimadoline (0.5 mg) produced significant improvement on total number of months with adequate relief of IBS pain or discomfort (46.7% vs. 20.0%), adequate relief of IBS symptoms (46.7% vs. 23.0%), pain scores (week 12: -1.6 vs. -0.7), pain free days (42.9% vs. 18.0%), urgency and stool frequency (-2.3 vs. -0.3). In patients with alternating IBS, significant improvement was seen on adequate relief endpoints. Asimadoline was well tolerated., Conclusion: Asimadoline warrants further evaluation as a treatment for IBS.

Background: Gastrointestinal side effects are commonly associated with opioid treatment for pain., Aim: To understand gastrointestinal side effects associated with opioid treatment., Methods: This study was a population-based survey of adults in the US who use opioids to manage pain unrelated to cancer. Participants were recruited from an existing Web-enabled panel and a supplemental panel of individuals who previously indicated an interest in participating in Web-based surveys., Results: Overall, 2055 individuals participated in the main phase of the survey. Fifty-seven per cent of participants reported having had constipation that they associated with opioid treatment, and 49% reported constipation in the previous 4 weeks. Thirty-six per cent of participants reported new or worsening constipation in the previous 4 weeks. Thirty-three per cent of participants reported constipation as their most bothersome symptom associated with opioid treatment, 13% reported nausea, 11% abdominal pain and 10% gas. Seventy-three per cent of the participants who reported any GI symptoms did not change the dosage level or frequency of use of opioids because of adverse events, which may be explained by the fact that 72% of participants used over-the-counter laxatives and 12% a prescription laxative., Conclusion: Constipation is a frequent and significant event occurring with opioid use.

Background: Dextofisopam modulates stimulated activity in animal models of stress, altered bowel motility, and visceral hypersensitivity., Aim: To evaluate the effects of dextofisopam in men and women with diarrhoea-predominant or alternating irritable bowel syndrome (IBS) (d-IBS or a-IBS)., Methods: In this double-blind, placebo-controlled study, patients were randomly assigned to receive dextofisopam 200 mg b.d. or placebo for 12 weeks. The prospectively defined primary endpoint was number of months of adequate overall relief of IBS symptoms. Bowel function was assessed primarily via stool frequency and consistency., Results: Of 140 enrolled patients, 66 received dextofisopam and 74 placebo; 73% of the patients were women, and 78% had d-IBS. Dextofisopam was superior to placebo on the primary endpoint (P = 0.033). In d-IBS patients treated with dextofisopam, both men and women had improved stool consistency, but stool frequency was reduced only in women. Benefit diminished over time on the primary endpoint, but persisted on frequency and consistency. Dextofisopam and placebo had similar rates and types of adverse events, with more events of worsening abdominal pain with dextofisopam (12% vs. 4%) and more headaches with placebo (12% vs. 5%). Constipation was rare., Conclusion: Dextofisopam should be further evaluated as a new treatment for men and women with d-IBS and a-IBS.

Background: Crofelemer improves bowel function in several conditions characterized by states of prominent secretory diarrhea., Aim: This double-blind, randomized, placebo-controlled trial evaluated the effects of 3 dose levels of crofelemer in patients with diarrhea-predominant irritable bowel syndrome (D-IBS)., Methods: Male and female patients were randomly assigned to receive crofelemer 125, 250 or 500 mg or placebo twice daily for 12 weeks. The primary efficacy measure was a responder for improvement in stool consistency. In addition, abdominal pain- and discomfort-free days, pain and discomfort scores as well as other bowel function parameters (such as stool frequency and consistency, urgency, bloating) were evaluated., Results: Two hundred and forty-two D-IBS patients were randomized. Crofelemer did not produce significant improvement in stool consistency (primary endpoint), stool frequency, urgency or adequate relief. However, female D-IBS patients showed improvement in the proportion of pain- and discomfort-free days during treatment with 500 mg crofelemer: month 1 (crofelemer vs. placebo: 17.7 vs. 10.2%, p = 0.098); month 2 (23.5 vs. 13.3%, p = 0.076); month 3 (26.1 vs. 10.6%, p = 0.0076). No benefit was seen in male D-IBS patients. Crofelemer was well tolerated., Conclusions: Crofelelmer did not produce benefit on bowel function; an increase in the number of pain- and discomfort-free days in female D-IBS patients was seen. Further studies with crofelemer are warranted to evaluate it as a potential visceral analgesic.

The choice of primary endpoint for a clinical trial is one of the most important determinants of the ability of a clinical trial to demonstrate efficacy of therapeutic agents. Although there are still no clear, universally accepted guidelines on the definition of clinical benefit for irritable bowel syndrome (IBS), consensus guidelines stress the importance of using validated endpoints. This article reviews the evidence available in the literature on the psychometric validation and performance of the 3 endpoints recommended by the Rome III Committee for use as primary endpoints in treatment trials of IBS. The Rome III Committee recommends 2 types of measures: binary endpoints addressing the construct of relief (that is, adequate relief and satisfactory relief) and an integrative symptom questionnaire that addresses the change in severity of a representative group of symptoms of IBS (that is, the IBS Severity Scale). The current evidence suggests that at present, adequate relief should be recognized by regulatory authorities as an acceptable primary endpoint in clinical trials. This analysis also suggests that data from individual clinical trials should be pooled and undergo meta-analysis, and that prospective studies should be considered to further characterize the performance of available endpoints as outcome measures in pharmacotherapeutic trials in IBS.

Background: Doctor visits for irritable bowel syndrome are associated with high medical costs. Predictors of medical consultation for irritable bowel syndrome remain poorly understood., Aim: To determine factors associated with healthcare seeking for irritable bowel syndrome., Methods: Subjects from previous US population-based survey were contacted 2 years later. Those who continued to have irritable bowel syndrome were included., Results: 49% of subjects sought medical care for abdominal symptoms in the past year. Healthcare seeking did not differ significantly between males and females, but more females received an irritable bowel syndrome diagnosis. Predictors of irritable bowel syndrome healthcare seeking differed by gender. In multivariate analysis, age > or = 55 years (OR = 2.8, 95% CI: 1.5-5.4), fear abdominal symptoms relates to serious illness (OR = 1.7, 95% CI: 0.95-3.1), decreased bowel movements (OR = 1.8, 95% CI: 0.98-3.2), dyspepsia (OR = 1.7, 95% CI: 0.94-3.2) and pelvic pain (OR = 2.3, 95% CI: 1.2-4.4) were associated with seeking care in females. Among males, being disabled (OR = 11.6, 95% CI: 2.4-56.1) and abdominal cramping (OR =4.3, 95% CI: 1.2-15.4) were associated with seeking care. Healthcare seekers had lower irritable bowel syndrome-related quality of life. Neither pain severity nor mental health status was associated with seeking care., Conclusion: Healthcare-seeking behaviour among irritable bowel syndrome patients was determined by presence of comorbidities and extent that irritable bowel syndrome affected quality of life, not physical symptoms or mental health status.

The success of a clinical trial is judged by achieving statistical and clinical significance on the primary endpoint. This is particularly relevant in those trials that are initiated to achieve regulatory approval of a new therapeutic agent. Selection of an endpoint for which statistical significance will be too difficult to achieve can result in clinical trial data that fails to meet regulatory requirements for product approval. Over the past decade, significant progress has been made in development and refinement of the study design for evaluating new therapeutic agents targeted for the treatment of irritable bowel syndrome. One aspect of trial design that has been advanced is recognition of the endpoint of 'Adequate Relief.' Adequate relief has been used as a primary endpoint in treatment trials with alosetron, cilansetron and dextofisopam. With each of these agents, statistically significant benefit was seen when compared to placebo. As an endpoint, adequate relief is responsive, reproducible and moves in the same direction as other meaningful measures, and, therefore, displays properties of a validated endpoint. Adequate relief should be considered an acceptable primary endpoint by regulatory agencies for use in clinical trials of novel therapeutic agents for irritable bowel syndrome.

Background: As there is no biological marker for irritable bowel syndrome, a diagnosis is made using symptom-based criteria., Aim: To evaluate the stability of self-reported symptoms consistent with Rome II-based irritable bowel syndrome classification., Methods: Irritable bowel syndrome subjects identified in a 2001 population-based study by modified Rome II criteria were re-contacted 2 years later. Data were collected via a web-based questionnaire., Results: Of the 697 subjects, 30% remained in the same irritable bowel syndrome subtype in both surveys, 18.4% changed irritable bowel syndrome subtype and 52% no longer met the irritable bowel syndrome criteria at follow-up. Subjects continuing to meet the irritable bowel syndrome criteria were more likely to have been initially classified in the alternating irritable bowel syndrome subtype and had more psychological impairment and lower irritable bowel syndrome-related quality of life than subjects not fulfilling the irritable bowel syndrome criteria at follow-up. Lack of pain caused more subjects to fall out of the irritable bowel syndrome criteria than the absence of non-painful bowel symptoms. However, the majority of subjects that did not fulfill the pain component of the irritable bowel syndrome criteria continued to report abdominal pain of at least moderate severity., Conclusion: In a US population-based follow-up study using modified Rome II criteria, we found irritable bowel syndrome is episodic in nature and current classification is limited in capturing fluctuation of disease over time.

Background: Irritable bowel syndrome is a common gastrointestinal disorder, and its prevalence and demographics have been evaluated by different methodologies with varying results., Aim: To evaluate irritable bowel syndrome demographic and prevalence characteristics utilizing a web-enabled panel., Methods: From an existing 150 000-member panel, 31 829 individuals were randomly selected and sent screening questionnaires to evaluate irritable bowel syndrome symptoms. Individuals who agreed to participate and completed the screening questionnaire received a second questionnaire related to a diagnosis of irritable bowel syndrome, a more detailed symptom description, and additional burden of illness data., Results: Irritable bowel syndrome prevalence was 7%. Prevalence was higher in women vs. men, unmarried individuals vs. married individuals and unemployed individuals vs. employed individuals. Of those completing the second questionnaire, 51% had seen their physicians for irritable bowel syndrome symptoms in the past year and most had an episode within the past 3 months. During the past year, approximately half of the participants had used a prescription medication, and over 90% had used an over-the-counter medication for irritable bowel syndrome. Participants with irritable bowel syndrome demonstrated quality-of-life reductions relative to norms of the United States population., Conclusions: Web-enabled data collection represents a novel tool for rapidly surveying a large population of individuals with irritable bowel syndrome symptoms.

In most mammalian cells, regulatory volume decrease (RVD) is mediated by swelling-activated Cl(-) and K(+) channels. Previous studies in the human neuroblastoma cell line CHP-100 have demonstrated that exposure to hypoosmotic solutions activates Cl(-) channels which are sensitive to Ca(2+). Whether a Ca(2+)-dependent K(+) conductance is activated after cell swelling was investigated in the present studies. Reducing the extracellular osmolarity from 290 to 190 mOsm/kg H(2)O rapidly activated 86Rb effluxes. Hypoosmotic stress also increased cytosolic Ca(2+) in fura-2 loaded cells. Pretreatment with 2.5 mM EGTA and nominally Ca(2+) free extracellular solution significantly decreased the hypoosmotically induced rise in cytosolic Ca(2+) and the swelling-activated 86Rb efflux. In cell-attached patch-clamp studies, decreasing the extracellular osmolarity activated a K(+) conductance that was blocked by Ba(2+). In addition, the swelling-activated K(+) channels were significantly inhibited in the presence of nominally free extracellular Ca(2+) and 2.5mM EGTA. These results suggest that in response to hypoosmotic stress, a Ca(2+)-dependent K(+) conductance is activated in the human neuroblastoma cell line CHP-100.

Background: Functional dyspepsia is characterized by upper abdominal pain or discomfort., Aim: To assess the benefit of the 5-HT3-receptor antagonist alosetron in a pilot, dose-ranging, placebo-controlled, multicentre, randomized clinical trial., Methods: A total of 320 functional dyspepsia patients received placebo (n=81), or alosetron 0.5 mg b.d. (n=77), 1.0 mg b.d. (n=79) or 2.0 mg b.d. (n=83) for 12 weeks, followed by 1 week of follow-up. Primary efficacy was the 12-week average rate of adequate relief of upper abdominal pain or discomfort. Secondary endpoints assessed pain and upper gastrointestinal symptoms., Results: Twelve-week average rates of adequate relief of pain or discomfort were 46% (95% CI: 37-54%), 55% (95% CI: 46-63%), 55% (95% CI: 47-64%) and 47% (95% CI: 38-55%) in the placebo, 0.5 mg, 1.0 mg and 2.0 mg alosetron groups, respectively. Alosetron 0.5 mg or 1.0 mg showed potential benefit over placebo for early satiety and postprandial fullness. Females showed greater responses compared to males. Patients with adequate relief had significantly (P < 0.001) greater reductions in severity and frequency of functional dyspepsia symptoms than those without adequate relief. Constipation was the most commonly reported adverse event., Conclusions: Alosetron showed potential benefit in relieving functional dyspepsia symptoms compared to placebo. Patients with adequate relief of upper abdominal pain or discomfort showed improvements in multiple functional dyspepsia symptoms.

Objectives: The aim of this study was to assess the impact of alosetron, a treatment recently approved in the United States for irritable bowel syndrome in diarrhea-predominant female patients, on health-related quality of life., Methods: Quality of life was assessed as part of two 12-wk randomized, double-blind, placebo-controlled irritable bowel syndrome studies comparing alosetron 1 mg b.i.d. with placebo (S3BA3001 and S3BA3002). Patients completed a validated disease-specific quality of life questionnaire, the Irritable Bowel Syndrome Quality of Life Questionnaire (IBSQOL), at baseline and at the 12-wk or final visit. The clinical relevance of data were also evaluated by a minimal meaningful difference instrument., Results: A total of 626 and 647 patients were enrolled in studies S3BA3001 and S3BA3002, respectively. Approximately 70% of patients in each study had diarrhea-predominant IBS. In diarrhea-predominant patients enrolled in S3BA3001, statistically significant (p < 0.05) improvements with alosetron versus placebo were observed on all nine IBSQOL scales (emotional health, mental health, sleep, energy, physical functioning, food/diet, social functioning, role-physical, and sexual relations) and for all but one scale (mental health) in S3BA3002. In both studies, a significantly greater percentage of patients treated with alosetron (p < 0.05) experienced clinically meaningful improvement on three of the nine IBSQOL scales (food/diet, social functioning, and role-physical) compared with patients treated with placebo. Patients treated with alosetron did not show worsening in any quality of life domain compared with patients treated with placebo., Conclusions: These results in women with diarrhea-predominant IBS demonstrate that alosetron significantly improves health-related quality of life.

The mechanisms by which dopamine (DA) influences gastrointestinal (GI) tract motility are incompletely understood and complicated by tissue- and species-specific differences in dopaminergic function. To improve the understanding of DA action on GI motility, we used an organ tissue bath system to characterize motor function of distal colonic smooth muscle segments from wild-type and DA transporter knockout (DAT -/-) mice. In wild-type mice, combined blockade of D(1) and D(2) receptors resulted in significant increases in tone (62 +/- 9%), amplitude of spontaneous phasic contractions (167 +/- 24%), and electric field stimulation (EFS)-induced (40 +/- 8%) contractions, suggesting that endogenous DA is inhibitory to mouse distal colonic motility. The amplitudes of spontaneous phasic and EFS-induced contractions were lower in DAT -/- mice relative to wild-type mice. These differences were eliminated by combined D(1) and D(2) receptor blockade, indicating that the inhibitory effects of DA on distal colonic motility are potentiated in DAT -/- mice. Motility index was decreased but spontaneous phasic contraction frequency was enhanced in DAT -/- mice relative to wild-type mice. The fact that spontaneous phasic and EFS-induced contractile activity were altered by the lack of the DA transporter suggests an important role for endogenous DA in modulating motility of mouse distal colon.

Background: No currently available treatment provides consistent relief of irritable bowel syndrome. Colonic sensory and motor function are modulated partly through 5HT3-receptors., Aim: To evaluate effects of the 5HT3-receptor antagonist, alosetron, in irritable bowel syndrome., Methods: Randomized, double-blind, placebo-controlled, dose-ranging (1, 2, 4, 8 mg b.d. alosetron), 12-week trial in 370 patients with diarrhoea-predominant or alternating constipation and diarrhoea irritable bowel syndrome. Weekly measurement of adequate relief was the key end-point; other irritable bowel syndrome symptoms were collected daily using an electronic phone system., Results: Alosetron (1 mg or 2 mg b.d.) significantly (P < 0.05 vs. placebo) increased the proportion of females, but not males, reporting adequate relief. Stool consistency, frequency and percentage days with urgency improved over placebo (P < 0.05) within the first month with all doses of alosetron, and persisted throughout the trial with all doses in female patients. With 1 mg b.d. alosetron, females had improved stool consistency and urgency within the first week, and adequate relief and improved stool frequency within the first 2 weeks. There was no consistent improvement in bowel function among male patients., Conclusion: In female irritable bowel syndrome patients with predominant diarrhoea or alternating constipation and diarrhoea, alosetron is effective in treatment of abdominal pain and discomfort and bowel-related symptoms.

Objective: Irritable bowel syndrome (IBS) is diagnosed by the presence of a constellation of symptoms fulfilling the Manning or Rome Criteria, after exclusion of organic disease. To exclude other diagnoses that might contribute to the abdominal pain or bowel symptoms experienced by subjects with IBS, numerous screening algorithms have been advocated, incorporating lactose hydrogen breath tests, thyroid function tests, fecal ova and parasite determination, and colonic endoscopy/radiography. The utility of these tests in uncovering alternative diagnoses, other than IBS, was examined in 1452 patients., Methods: Data were combined from two large multinational studies of IBS patients. All patients exhibited symptoms meeting the Rome criteria for IBS for at least 6 months before study entry. If prior evaluation had been > 2 yr previously, patients underwent colonic endoscopy/radiography at study entry. In addition, thyroid function tests, fecal ova and parasite determination, and a lactose hydrogen breath test were performed., Results: Lactose malabsorption was diagnosed in 23% (256/1122) of patients. Colonic abnormalities were detected in 2% (7/306) of patients; in four patients, colonic inflammation (n = 3) or obstruction (n = 1) may have contributed to symptoms of abdominal pain or altered bowel habits. Abnormal thyroid-stimulating hormone levels were detected in 6% (67/1209) of patients, of whom half were hypothyroid and half were hyperthyroid. Positive fecal ova and parasite tests were noted in 2% (19/1154) of patients., Conclusions: Examination of screening tests in 1452 patients with an established history of IBS revealed an incidence of lactose malabsorption comparable to that in the general U.S. population and a low incidence of thyroid dysfunction, ova and parasite infestation, or colonic pathology. The limited detection rates, added costs, and inconvenience of these tests suggest that their routine use in the diagnostic evaluation of established IBS patients should be scrutinized.

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal-related conditions. In this review, the safety and efficacy of alosetron, a potent and selective 5-HT3 receptor antagonist, in the treatment of IBS are discussed. Alosetron has been shown to produce statistically significant improvements in abdominal pain, stool consistency, stool frequency and urgency in female IBS patients. By contrast, no consistent improvement has been seen in male IBS patients treated with alosetron. The only adverse event of note with alosetron was constipation, and this represents a class effect of 5-HT3 receptor antagonists. In conclusion, alosetron is a safe and effective treatment for female IBS patients.

Distension of the gastrointestinal tract elicits abdominal pain, as well as sensations such as discomfort or fullness. Many patients with irritable bowel syndrome have been reported to show a reduced threshold to the pain or discomfort due to experimental rectal distension. This hypersensitivity of the gut may be characteristics of the irritable bowel, as well as other functional gastrointestinal disorders. Intestinal distension in animals induces a range of responses which have been used as indexes of visceral nociception. This paper reviews a recently introduced canine model used to assess the antinociceptive properties of a novel 5-HT3 receptor antagonist, alosetron.

Activation of L-type calcium channels in the neuroendocrine, cholecytstokinin-secreting cell line, STC-1, is vital for secretion of CCK. In the present study, the regulation of L-type Ca2+ channels by cAMP and Ca2+ calmodulin dependent protein kinase II (CaM-KII) in STC-1 cells was investigated. Exposure to 3-isobutyl-1-methylxanthine (IBMX) increased intracellular cAMP levels, whole cell Ca2+ currents and activated Ca2+ channels in cell-attached membrane patches. Furthermore, in Fura-2AM loaded cells, cytosolic Ca2+ levels increased upon exposure to IBMX. By contrast, pretreatment of cells with the CaM-KII inhibitor KN-62, prevented IBMX activation of Ca2+ channels in cell-attached patches or increases in cytosolic Ca2+ levels. Inclusion of the synthetic peptide fragment 290-309 of CaM-KII, a CaM-KII antagonist, in the pipette solution, blocked the activation of whole cell Ca2+ currents upon addition of IBMX. These results indicate a unique mechanism of L-type Ca2+ channel activation involving two phosphorylation events., (Copyright 1999 Academic Press.)

Irritable bowel syndrome (IBS) represents one of the most common gastrointestinal-related diagnoses. Although the precise etiologic basis of IBS is not known, a common presenting symptom is abdominal pain or discomfort that is thought to develop, at least in part, from a heightened awareness of visceral nociceptive input. Agents capable of reducing this heightened visceral nociception would, therefore, have utility in the treatment of IBS. In this study we evaluated the effects of intravenous and intracerebroventricular administration of a 5-HT3 receptor antagonist, alosetron, on blood pressure changes associated with rectal distension in anesthetized and awake dogs. This vasoactive reflex serves as a model for visceral nociception. For intracerebroventricular studies, the cerebroventricular guides were placed over the lateral ventricle. In anesthetized studies, blood pressure was measured by femoral artery cannulation. In awake studies, blood pressure was monitored by noninvasive measurement. A rectal balloon was placed in the rectum of each dog and maintained throughout the experiments. Each dose of alosetron was given to the dogs as an intravenous or intracerebroventricular bolus, and every 30 min the rectal balloon was inflated and blood pressure responses observed. In both anesthetized and awake dogs alosetron produced a significant inhibition of the vasoactive reflex. In particular, alosetron showed high potency when administered intracerebroventricularly. Alosetron, administered either centrally or peripherally, appears to modulate the visceral nociceptive effect of rectal distension in dogs.

Irritable bowel syndrome is characterized by recurrent abdominal pain and altered bowel function. In designing studies to evaluate new treatments for this disease, however, it is difficult to select appropriate endpoints to reflect improvement in the range of symptoms of the syndrome. In the present study we evaluated the parameter of adequate relief of abdominal pain and discomfort, as perceived by the patients, as a key endpoint for efficacy in the treatment of patients with irritable bowel syndrome. Abdominal pain and bowel function data were collected daily from 370 patients with the disease during treatment with placebo or a novel potent 5HT3 receptor antagonist. Once every 7 days adequate relief of pain and discomfort was assessed. Quality-of-life data were collected using self-administered questionnaires. The endpoint of adequate relief was significantly (P < 0.05) correlated with improvement in pain severity scores, percentage of pain-free days, percentage of days with urgency, improvement in stool frequency and consistency, and quality-of-life parameters. Adequate relief of pain and discomfort is significantly correlated with changes in multiple parameters associated with irritable bowel syndrome and can be used as an endpoint for assessing response to therapy in these patients.

Background: The reliability of symptom data collected during efficacy studies in irritable bowel syndrome (IBS) is paramount to the proper assessment of potential therapeutic agents. Historically, data have been collected on paper diary cards, which patients were requested to fill out at a specified interval. However, with paper diary cards it is not possible to determine whether the cards are filled out as required, or at random times. To circumvent this problem, a novel electronic data collection system that ensures the reliability and security of data entry was used., Methods: Data were collected from 640 patients during the 2-week screening and 12-week treatment phases of two multicentre trials of IBS. The electronic data collection system used was based upon a touchtone telephone system., Results: The electronic data collection system had a potential 8135 up-time hours during the study. An up-time of 8040 h and down-time of 95 h was observed. This corresponds to an up-time of approximately 99%. Patient compliance for data entry in the two studies was 81% and 83%, respectively. On a single random day during their daily telephone call, patients were asked questions to assess satisfaction with the system. On aggregate, 79% of patients were satisfied or very satisfied with the system, only 10% were dissatisfied or very dissatisfied., Conclusion: A unique electronic data collection system was tested for use in clinical studies in IBS. This system provided 100% reliability as to the date of data entry, and data were not subject to modification once entered. This methodology represents a marked advancement in clinical studies of IBS.

Polyps of the gallbladder are often incidentally identified during radiographic evaluation of abdominal pain. Once identified, they pose a dilemma with respect to their proper long-term management. Herein, polyps of the gallbladder are reviewed with specific attention to their management in light of their malignant potential. The available data suggest that polyps larger than 10 mm or that show rapid growth should be considered suggestive of malignancy, prompting cholecystectomy.

In the present study we evaluated the effects of agents anticipated to change NO levels on the secretion of cholecystokinin (CCK) from STC-1 cells. After a 15-min treatment with the nitric oxide (NO) generating agent sodium nitroprusside (SNP; 10 microM), a 24% inhibition in basal CCK release and an increase in cellular guanosine 3',5'-cyclic monophosphate (cGMP) levels were noted. By contrast, SNP (10 microM) had no effect on CCK release stimulated by L-phenylalanine (20 mM). Inhibition of NO synthase (NOS) with NG-nitro-L-arginine methyl ester (L-NAME) produced dose-dependent stimulation in CCK release. L-NAME (100-400 microM) also inhibited ATP-sensitive potassium (KATP) channels in cell-attached patches. Pretreatment of cells with disopyramide (200 microM), a KATP channel blocker, blocked L-NAME stimulation of CCK release. After inhibition of potassium channel activity by L-NAME, addition of the nonhydrolyzable cGMP analogue 8-bromo-cGMP (1-2 mM) reactivated potassium channels. NO-generating agents had no effect on channel activity in inside-out membrane patches. It is concluded that NO may serve as an important regulator of basal CCK release.

1. The effects of hypoosmotic stress on cell volume and amino acid efflux were evaluated in the human neuroblastoma cell line CHP-100 with the Coulter Counter Multisizer and radiolabeled amino acid efflux, respectively. 2. CHP-100 cells swelled by approximately 35 +/- 5% (means +/- SE) when the osmolarity of the solution was decreased from 290 to 190 mOsm/kg H2O. The rapid swelling was followed by a biphasic regulatory volume decrease (RVD). 3. In cells loaded with 14C-taurine, hypoosmotic stress induced a 300 +/- 22% (n = 23, P < 0.05) increase in taurine efflux compared with controls. This efflux was inhibited by the chloride channel blockers 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), 4,4'-diisothio-cyanostilbene-2,2'-disulfonic acid (DIDS), niflumic acid and by the volume-activated anion channel blocker tamoxifen. In addition, the swelling-activated taurine efflux was dependent upon extracellular calcium. 4. Similarly, in cells loaded with 14C-glycine, hypoosmotic stress significantly increased glycine efflux, which was also sensitive to NPPB. In contrast, efflux of 3H-glutamate was not significantly altered after hypoosmotic stress. 5. With the use of patch clamp recording techniques, Cl- channels were activated in cell attached patches after exposure to hypoosmotic solutions. 6. In nystatin perforated patches, permeability of the hypoosmotically activated anion channel was observed to be SCN- > I- > Br- > Cl- >> Glutamate. 7. It is concluded that in CHP-100 cells, anion channels are activated during hypoosmotic stress and these channels represent a pathway for efflux of amino acids.

To examine the role of calcium channels in depolarization-activated cholecystokinin (CCK) release, studies were performed in an intestinal CCK-secreting cell line, STC-1. Blockade of potassium channels with barium chloride (5 mM) increased the release of CCK by 374.6 +/- 46.6% of control levels. Barium-induced secretion was inhibited by the L-type calcium-channel blocker, nicardipine. Nicardipine (10(-9)-10(-5) M) produced a dose-dependent inhibition in barium-stimulated secretion with a half-maximal inhibition (IC50) value of 0.1 microM. A second L-type calcium-channel blocker, diltiazem (10(-9)-10(-4) M), also inhibited barium-induced CCK secretion with an IC50 value of 5.1 microM. By contrast, the T-type calcium-channel blocker, nickel chloride (10(-7)-10(-8) M), failed to significantly inhibit barium-induced CCK secretion. To further evaluate a role for L-type calcium channels in the secretion of CCK, the effects of the L-type calcium channel opener, BAY K 8644, were examined. BAY K 8644 (10(-8)-10(-4) M) produced a dose-dependent stimulation in CCK release with a mean effective concentration value of 0.2 microM. Recordings of single-channel currents from inside-out membrane patches showed activation of calcium channels by BAY K 8644 (1 microM), with a primary channel conductance of 26.0 +/- 1.2 pS. It is concluded that inhibition of potassium channel activity depolarizes the plasma membrane, thereby activating L-type, but not T-type, calcium channels. The corresponding influx of calcium serves to trigger secretion of CCK.

Previously, it has been shown that an increase in adenosine 3',5'-cyclic monophosphate (cAMP) levels stimulates intestinal secretion of cholecystokinin (CCK); however, the mechanisms for increasing intracellular cAMP levels are not known. Using the CCK-secreting intestinal cell line, STC-1, we evaluated whether beta-adrenergic receptors (beta-ARs) might be present on STC-1 cells and whether they stimulated CCK release through increases in cAMP. Photoaffinity labeling of beta-ARs from solubilized STC-1 cell membranes revealed photoincorporation of the agonist [125I]iodocyanopindolol into an approximately 75-kDa band. Addition of the beta-AR agonist, isoproterenol, in the presence of 3-isobutyl-1-methylxanthine, produced a concentration-dependent increase in both cAMP levels and CCK release. Blockade of beta 1- and/or beta 2-ARs significantly inhibited isoproterenol-stimulated increases in cAMP production and CCK release. With the use of fura 2-loaded cells to measure changes in intracellular Ca2+ concentration ([Ca2+]i), isoproterenol stimulation was found to increase cytosolic Ca2+ levels. To evaluate whether this increase in [Ca2+]i was due to release of Ca2+ or influx of Ca2+, cells were treated with the L-type calcium channel blocker, diltiazem, which inhibited isoproterenol-stimulated CCK secretion. Furthermore, in patch-clamp studies with inside-out membrane patches, addition of the catalytic subunit of protein kinase A activated diltiazem-sensitive Ca2+ channels. It is concluded that beta-ARs are present on STC-1 cells and are coupled to the production of cAMP, which may increase CCK release through a calcium-dependent process.

The effects of osmotic stress on chloride (CI-) currents in the human neuroblastoma cell line CHP-100 were evaluated. Following exposure to hypoosmotic solution, an increase in whole-cell CI- current was observed. This current was blocked by the CI- channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB). In cells loaded with the CI- permeability marker 125I, exposure to hypoosmotic solution increased 125I efflux by 197 +/- 14% (n = 41, p < 0.05) over controls. This increase was sensitive to NPPB. Hypoosmotic stress also increased cytosolic calcium levels (Ca2+) in fura-2-loaded cells. Pretreatment with EGTA inhibited the increase in cytosolic Ca2+, 125I efflux, and whole-cell CI- current produced by hypoosmotic solution. Antagonists of N-, L-, and T-type Ca2+ channels did not alter stimulation in 125I efflux or cytosolic Ca2+ levels during osmotic stress. However, omega-conotoxin MVIIC, a P-type Ca2+ channel blocker, inhibited hypoosmotically activated whole-cell CI- currents and increases in cytosolic Ca2+. It is concluded that a Ca(2+)-dependent change in CI- permeability is activated in CHP-100 cells in response to osmotic stress.

The control of gastrointestinal CCK secretion may occur at several points. A decrease in potassium conductance may depolarize the plasma membrane, activating calcium channels with a resultant stimulation in CCK release. The opposite may occur with increases in potassium conductance. The model presented in Fig. 8 suggests that the key control point in the understanding of CCK secretion is the regulation of L-type calcium channels. Whether a single second messenger pathway may regulate calcium channels stimulated by agents such as glucose, phenylalanine, bombesin and cAMP is an important area to pursue.