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Emeran A Mayer

Publications and source records attributed to Emeran A Mayer.

At least 37 records · Page 2Linked to original sources
PubMed2004

Clinical determinants of health-related quality of life in patients with irritable bowel syndrome.

BACKGROUND: Current guidelines recommend routine assessment of health-related quality of life (HRQOL) in patients with irritable bowel syndrome (IBS). However, physicians rarely have the time to measure HRQOL with the appropriate methodological rigor, and data suggest that HRQOL in patients with IBS is often estimated using inaccurate clinical gestalt. The identification of predictive factors could allow physicians to better assess HRQOL without using misleading clinical clues. We, therefore, sought to identify determinants of HRQOL in patients with IBS. METHODS: We examined 770 patients, 18 years or older, with IBS at a university-based referral center. Subjects completed a symptom questionnaire, the Symptoms Checklist-90 items psychometric checklist, and the 36-Item Short-Form Health Survey. The main outcome was HRQOL as measured by the mental and physical component scores of the 36-Item Short-Form Health Survey. We first developed a list of hypothesis-driven HRQOL predictors, and then performed multivariate regression analysis to measure the independent association of each predictor with HRQOL. RESULTS: Seven factors (r(2) = 0.39) independently predicted physical HRQOL: (1) more than 5 physician visits per year, (2) tiring easily, (3) low in energy, (4) severe symptoms, (5) predominantly painful symptoms, (6) the feeling that there is "something seriously wrong with body," and (7) symptom flares for longer than 24 hours. Eight factors (r(2) = 0.36) independently predicted mental HRQOL: (1) feeling tense, (2) feeling nervous, (3) feeling hopeless, (4) difficulty sleeping, (5) tiring easily, (6) low sexual interest, (7) IBS symptom interference with sexual function, and (8) low energy. CONCLUSIONS: Health-related quality of life in patients with IBS is primarily related to extraintestinal symptoms rather than traditionally elicited gastrointestinal symptoms. These findings suggest that rather than focusing on physiological epiphenomena (stool characteristics and subtype of IBS) and potentially misleading clinical factors (age and disease duration), physicians might be better served to gauge global symptom severity, address anxiety, and eliminate factors contributing to chronic stress in patients with IBS.

Activities of Daily Living↗
PubMed2004

Protease-activated receptor 2 sensitizes the capsaicin receptor transient receptor potential vanilloid receptor 1 to induce hyperalgesia.

Inflammatory proteases (mast cell tryptase and trypsins) cleave protease-activated receptor 2 (PAR2) on spinal afferent neurons and cause persistent inflammation and hyperalgesia by unknown mechanisms. We determined whether transient receptor potential vanilloid receptor 1 (TRPV1), a cation channel activated by capsaicin, protons, and noxious heat, mediates PAR2-induced hyperalgesia. PAR2 was coexpressed with TRPV1 in small- to medium-diameter neurons of the dorsal root ganglia (DRG), as determined by immunofluorescence. PAR2 agonists increased intracellular [Ca2+] ([Ca2+]i) in these neurons in culture, and PAR2-responsive neurons also responded to the TRPV1 agonist capsaicin, confirming coexpression of PAR2 and TRPV1. PAR2 agonists potentiated capsaicin-induced increases in [Ca2+]i in TRPV1-transfected human embryonic kidney (HEK) cells and DRG neurons and potentiated capsaicin-induced currents in DRG neurons. Inhibitors of phospholipase C and protein kinase C (PKC) suppressed PAR2-induced sensitization of TRPV1-mediated changes in [Ca2+]i and TRPV1 currents. Activation of PAR2 or PKC induced phosphorylation of TRPV1 in HEK cells, suggesting a direct regulation of the channel. Intraplantar injection of a PAR2 agonist caused persistent thermal hyperalgesia that was prevented by antagonism or deletion of TRPV1. Coinjection of nonhyperalgesic doses of PAR2 agonist and capsaicin induced hyperalgesia that was inhibited by deletion of TRPV1 or antagonism of PKC. PAR2 activation also potentiated capsaicin-induced release of substance P and calcitonin gene-related peptide from superfused segments of the dorsal horn of the spinal cord, where they mediate hyperalgesia. We have identified a novel mechanism by which proteases that activate PAR2 sensitize TRPV1 through PKC. Antagonism of PAR2, TRPV1, or PKC may abrogate protease-induced thermal hyperalgesia.

Animals↗
PubMed2004

Sex-based differences in gastrointestinal pain.

Recent interest has focused on sex-related differences in irritable bowel syndrome (IBS) physiology and treatment responsiveness to novel pharmacologic therapies. Similar to a variety of other chronic pain conditions and certain affective disorders, IBS is more prevalent amongst women, both in population-based studies as well as in clinic-based surveys. Non-painful gastrointestinal symptoms, constipation and somatic discomfort are more commonly reported by female IBS patients. While perceptual differences to rectosigmoid stimulation are only observed following repeated noxious stimulation of the gut, sex-related differences in certain sympathetic nervous system (SNS) responses to rectosigmoid stimulation are consistently seen. Consistent with experimental findings in animals, current evidence is consistent with a pathophysiological model which emphasizes sex-related differences in autonomic and antinociceptive responses to certain visceral stimuli.

Animals↗
PubMed2004

The neural correlates of placebo effects: a disruption account.

The neurocognitive pathways by which placebo effects operate are poorly understood. Positron emission tomography (PET) imaging was used to assess the brain response of patients with chronic abdominal pain (irritable bowel syndrome; IBS) to induced intestinal discomfort both before and after a 3-week placebo regimen. A daily symptom diary was used to measure symptom improvement. Increases in right ventrolateral prefrontal cortex (RVLPFC) activity from pre- to post-placebo predicted self-reported symptom improvement, and this relationship was mediated by changes in dorsal anterior cingulate (dACC), typically associated with pain unpleasantness. These results are consistent with disruption theory [Lieberman, M.D., 2003. Reflective and reflexive judgment processes: a social cognitive neuroscience approach. In: Forgas, J.P., Williams, K.R., von Hippel, W. (Eds.), Social Judgments: Explicit and Implicit Processes. Cambridge Univ. Press, New York, pp. 44-67], which proposes that activation of prefrontal regions associated with thinking about negative affect can diminish dACC and amygdala reactivity to negative affect stimuli. This is the first study to identify a neural pathway from a region of the brain associated with placebos and affective thought to a region closely linked to the placebo-related outcome of diminished pain unpleasantness.

Adult↗
PubMed2004

Electrophysiological characterization of N-methyl-D-aspartate receptors in rat dorsal root ganglia neurons.

In the peripheral nervous system, N-methyl-D-aspartate receptors (NMDAR) expressed on the central and peripheral terminals of primary afferent neurons are involved in nociception. We used single cell imaging of intracellular calcium concentration ([Ca2+]i) and patch clamp techniques to characterize the functional properties of NMDARs on adult rat dorsal root ganglia (DRG) neurons in primary culture and selectively on those innervating the distal colon. In Mg2+-free extracellular solution, rapid perfusion of DRG neurons with 250 microM NMDA and 10 microM glycine caused a significant increase in [Ca2+]i, and elicited inward currents in whole cell patch clamp recordings when the holding potential was -60 mV. Both effects were reversibly inhibited by 200 microM ketamine in a use-dependent manner. The EC50 values for NMDA and glycine were 64 and 1.9 microM with Hill slope coefficients of 1.4 and 1.3, respectively. At negative potentials, extracellular Mg2+ blocked currents in a concentration- and voltage-dependent manner. The IC50 for Mg2+ at a holding potential of -100 mV was 2.0 microM. The NMDAR subtype-selective antagonist, ifenprodil, inhibited 94% of the NMDA and glycine-induced current with an IC50 of 2.6 microM. There was no evidence of multiple binding sites for ifenprodil. There was no significant difference in the NMDAR current density on DRG neurons that had innervated the colon, nor was there a difference in the EC50 for ifenprodil. These results demonstrate that functional NMDARs expressed by DRG neurons innervating both somatic and visceral tissues of adult rats are composed predominantly of NR2B subunits.

Animals↗
PubMed2004

Racial differences in the impact of irritable bowel syndrome on health-related quality of life.

GOALS: To compare the impact of irritable bowel syndrome (IBS) on health related quality of life (HRQOI) for non-white and white IBS patients. BACKGROUND: There are no reported data evaluating the HRQOL of non-white persons with IBS. STUDY: SF-36 scores are compared between non-white IBS patients (n = 166), white IBS patients (n = 707), the general US population, and patients with selected chronic diseases. RESULTS: Of the n = 166 non-white IBS patients included for analysis, 66 (40%) described themselves as African-American, 56 (34%) as Hispanic, 25 (15%) as Asian-American, 2 (1%) as Native American and the remaining 17 (10%) as "other." Compared with white IBS patients, non-white IBS patients reported similar decrements in their HRQOL after controlling for age, gender, income and education level. On all 8 SF-36 scales, non-white IBS patients had significantly worse HRQOL compared with the general US population, (P < 0.001). Compared with GERD patients, non-white IBS patients scored significantly lower on all SF-36 scales (P < 0.001) except physical functioning. Similarly, non-white IBS patients had significantly worse HRQOL on selected SF-36 scales compared with diabetes mellitus and ESRD patients. Non-white IBS patients had significantly better emotional well-being than depressed patients, (P < 0.001). CONCLUSIONS: Non-white IBS patients experience impairment in vitality, role limitations-physical, and bodily pain. Yet overall, non-white IBS patients report similar HRQOL to white IBS patients. These data provide the first detailed evaluation of the impact of IBS on HRQOL in non-white IBS patients.

Adult↗
PubMed2003

Delayed stress-induced colonic hypersensitivity in male Wistar rats: role of neurokinin-1 and corticotropin-releasing factor-1 receptors.

The mechanism(s) underlying stress-induced colonic hypersensitivity (SICH) are incompletely understood. Our aims were to assess the acute and delayed (24 h) effect of water avoidance (WA) stress on visceral nociception in awake male Wistar rats and to evaluate the role of two stress-related modulation systems: the substance P/neurokinin-1 receptor (SP/NK(1)R) and the corticotropin-releasing factor (CRF)/CRF(1) receptor (CRF/CRF(1)R) systems, as well as the possible involvement of the sympathetic nervous system. Visceral pain responses were measured as the visceromotor response to colorectal distension (CRD) at baseline, immediately after WA and again 24 h later. The NK(1)R antagonists RP-67580 and SR-140333 and the CRF(1)R antagonist CP-154526 were injected 15 min before WA or 1 h before the CRD on day 2. Chemical sympathectomy was performed by repeated injection of 6-hydroxydopamine. WA stress resulted in a significant increase in the visceromotor response on day 2, but no change immediately after WA. Injection of CP-154526 abolished delayed SICH when applied either before WA stress or before the CRD on day 2. Both NK(1)R antagonists only decreased SICH when injected before the CRD on day 2. Chemical sympathectomy did not affect delayed SICH. Our results indicate that in male Wistar rats, both NK(1)R and CRF(1)R activation, but not sympathetic nervous system activation, play a role in the development of SICH.

Animals↗
PubMed2003

A novel water-soluble selective CRF1 receptor antagonist, NBI 35965, blunts stress-induced visceral hyperalgesia and colonic motor function in rats.

The stress response involves the activation of two corticotropin-releasing factor (CRF) receptor subtypes. We investigated the role of CRF1 in stress-related visceral responses. A novel water-soluble tricyclic CRF1 antagonist, NBI 35965 was developed that displayed a high affinity for CRF1 (Ki approximately 4 nM) while having no binding affinity to CRF2. This antagonist also inhibited the stimulation of cAMP induced by sauvagine in CRF1 transfected cells. NBI 35965 administered per orally (p.o.) in rats (1, 3, 10 or 30 mg/kg) inhibited dose-dependently [125I]sauvagine binding selectively at brain sites of CRF1 distribution as shown by ex vivo receptor autoradiography. At the highest doses, NBI 35965 completely prevented [125I]sauvagine labeling in the cortex. NBI 35965 (10 mg/kg) administered p.o. or subcutaneously (s.c.) 1 h before intravenous CRF completely blocked the 81% shortening of distal colonic transit time induced by CRF. NBI 35965 (20 mg/kg s.c.) significantly reduced the defecation in response to water avoidance stress but not that induced by s.c. carbachol. In adult male Long-Evans rats that had undergone maternal separation, acute water avoidance stress significantly increased the visceromotor response to colorectal distention (20-80 mmHg) by 42+/-19% compared with the response before stress. Stress-induced visceral hyperalgesia was abolished by NBI 35965 (20 mg/kg, s.c.). The data show that NBI 35965 is a novel water-soluble selective CRF1 antagonist with bioavailability to the brain upon peripheral administration and that CRF1 receptor signaling pathways are involved in water avoidance stress-induced hyperalgesia to colorectal distention and stimulation of colonic transit.

Amphibian Proteins↗
PubMed2003

Current insights into the pathophysiology of irritable bowel syndrome.

Recent reports have emphasized the possible role of mucosal immune activation and inflammation in neuropathic changes in the pathophysiology of irritable bowel syndrome (IBS). However, novel findings using functional brain imaging techniques have underlined the importance of altered perception of visceral stimuli to symptom generation in IBS. These new developments have rekindled an old debate on peripheral versus central mechanisms in the pathophysiology of IBS. In this review we discuss the latest findings in light of these two concepts. In addition, we provide evidence for the hypothesis that, in the absence of alterations in endogenous pain modulation systems and changes in visceral perception, chronic inflammatory mucosal changes in the gut are not a plausible mechanism to explain the presence of chronic abdominal pain, a cardinal IBS symptom.

Colonic Diseases, Functional↗
PubMed2003

Sex-related differences in IBS patients: central processing of visceral stimuli.

BACKGROUND & AIMS: Women have a higher prevalence of irritable bowel syndrome (IBS) and possible differences in response to treatment, suggesting sex-related differences in underlying pathophysiology. The aim of this study was to determine possible sex-related differences in brain responses to a visceral and a psychological stressor in IBS. METHODS: Regional cerebral blood flow measurements using H(2)(15)O positron emission tomography were compared across 23 female and 19 male nonconstipated patients with IBS during a visceral stimulus (moderate rectal inflation) and a psychological stimulus (anticipation of a visceral stimulus). RESULTS: In response to the visceral stimulus, women showed greater activation in the ventromedial prefrontal cortex, right anterior cingulate cortex, and left amygdala, whereas men showed greater activation of the right dorsolateral prefrontal cortex, insula, and dorsal pons/periaqueductal gray. Similar differences were observed during the anticipation condition. Men also reported higher arousal and lower fatigue. CONCLUSIONS: Male and female patients with IBS differ in activation of brain networks concerned with cognitive, autonomic, and antinociceptive responses to delivered and anticipated aversive visceral stimuli.

Adult↗
PubMed2003

Prevalence of irritable bowel syndrome among university students: the roles of worry, neuroticism, anxiety sensitivity and visceral anxiety.

OBJECTIVE: Relationships between presence of irritable bowel syndrome (IBS) and generalized anxiety disorder (GAD), chronic worry, neuroticism, anxiety sensitivity and anxiety about visceral sensations were examined among university students. METHODS: College student participants were administered self-report diagnostic measures of IBS and GAD, the Penn State Worry Questionnaire (PSWQ), the Neuroticism subscale of the Eysenck Personality Questionnaire, the Anxiety Sensitivity Index (ASI) and five additional items designed to measure visceral anxiety. RESULTS: The prevalence of IBS and its associated characteristics among students were similar to previous community survey studies, with the exception of lower symptom severity in the university sample. IBS was associated with a higher frequency of GAD and greater worry, neuroticism, anxiety sensitivity and visceral anxiety. Logistic regression analyses further showed that the measure of anxiety specific to visceral sensations was the strongest predictor of IBS diagnostic status. CONCLUSIONS: While various aspects of anxiety appear related to IBS, specific anxiety about visceral sensations appears to be the most significant factor. Implications of the associations between anxiety-related variables, particularly anxiety about visceral sensations, are discussed.

Abdominal Pain↗
PubMed2003

Inflammatory bowel disease and irritable bowel syndrome: separate or unified?

Both irritable bowel syndrome and inflammatory bowel diseases share symptoms of altered bowel habits associated with abdominal pain or discomfort. Irritable bowel syndrome has been referred to as a functional bowel disorder, which is diagnosed by a characteristic cluster of symptoms in the absence of detectable structural abnormalities. Inflammatory bowel disease is a heterogeneous group of disorders characterized by various forms of chronic mucosal and/or transmural inflammation of the intestine. In this review, the authors discuss recent evidence suggesting several potential mechanisms that might play a pathophysiologic role in both syndromes. Possible shared pathophysiologic mechanisms include altered mucosal permeability, an altered interaction of luminal flora with the mucosal immune system, persistent mucosal immune activation, alterations in gut motility, and a role of severe, sustained life stressors in symptom modulation. It is proposed that similarities and differences between the two syndromes can best be addressed within the framework of interactions between the central nervous system and the gut immune system. Based on recent reports of low-grade mucosal inflammation in subpopulations of patients meeting current diagnostic criteria for irritable bowel syndrome, therapeutic approaches shown to be effective in inflammatory bowel disease, such as probiotics, antibiotics, and antiinflammatory agents, have been suggested as possible therapies for certain patients with irritable bowel syndrome.

Journal Article↗
PubMed2003

Irritable bowel syndrome patients show enhanced modulation of visceral perception by auditory stress.

OBJECTIVES: Symptoms in irritable bowel syndrome (IBS) patients are sensitive to psychological stressors. These effects may operate through an enhanced responsiveness of the emotional motor system, a network of brain circuits that modulate arousal, viscerosomatic perception, and autonomic responses associated with emotional responses, including anxiety and anger. The aim of this study was to test the primary hypothesis that IBS patients show altered perceptual responses to rectal balloon distention during experimentally induced psychological stress compared with healthy control subjects. METHODS: A total of 15 IBS patients (nine women and six men) and 14 healthy controls (seven women and seven men) were studied during two laboratory sessions: 1) a mild stress condition (dichotomous listening to two conflicting types of music), and 2) a control condition (relaxing nature sounds). The stress and relaxation auditory stimuli were delivered over a 10-min listening period preceding rectal distentions and during the rectal distentions but not during the distention rating process. Ratings of intensity and unpleasantness of the visceral sensations, subjective emotional responses, heart rate, and neuroendocrine measures (norepinephrine, cortisol, adrenocorticotropic hormone [ACTH], and prolactin) were obtained during the study. RESULTS: IBS patients, but not healthy controls, rated the 45-mm Hg visceral stimulus significantly higher in terms of intensity and unpleasantness during the stress condition compared with the relaxation condition. IBS patients also reported higher ratings of stress, anger, and anxiety during the stress compared with the relaxing condition, whereas controls had smaller and nonsignificant subjective responses. Heart rate measurements, but not other neuroendocrine stress measures, were increased under the stress condition in both groups. CONCLUSION: These findings confirm the hypothesis of altered stress-induced modulation of visceral perception in IBS patients.

Acoustic Stimulation↗
PubMed2003

Brain responses to visceral and somatic stimuli in patients with irritable bowel syndrome with and without fibromyalgia.

OBJECTIVE: Symptoms of irritable bowel syndrome (IBS) and fibromyalgia (FM) commonly coexist. We hypothesized that one of the mechanisms underlying this comorbidity is increased activation of brain regions concerned with the processing and modulation of visceral and somatic afferent information, in particular subregions of the anterior cingulate cortex (ACC). METHODS: Regional cerebral blood flow (rCBF) was assessed in age-matched female IBS (n = 10) and IBS + FM (n = 10) subjects using H(2)(15)O positron emission tomography during noxious visceral (rectal) and somatic pressure stimuli. RESULTS: GI symptom severity was significantly higher in the IBS patients compared with the IBS + FM patients (p < 0.05). In addition, IBS + FM patients rated somatic pain as more intense than their abdominal pain (p < 0.05). Whereas the somatic stimulus was less unpleasant than the visceral stimulus for IBS patients without FM, the somatic and visceral stimuli were equally unpleasant in the IBS + FM group. Group differences in regional brain activation were entirely within the middle subregion of the ACC. There was a greater rCBF increase in response to noxious visceral stimuli in IBS patients and to somatic stimuli in IBS + FM patients. CONCLUSION: Chronic stimulus-specific enhancement of ACC responses to sensory stimuli in both syndromes may be associated with cognitive enhancement of either visceral (IBS) or somatic (IBS + FM) sensory input and may play a key pathophysiologic role in these chronic pain syndromes.

Adult↗
PubMed2003

Alosetron and irritable bowel syndrome.

Alosetron (Lotronex, GlaxoSmithKline) is a potent and selective 5-HT(3)-receptor antagonist approved by the FDA for the treatment of women with diarrhoea-predominant irritable bowel syndrome (IBS) in whom conventional therapy has failed. Studies involving healthy volunteers and IBS patients have demonstrated a beneficial effect of treatment with alosetron on global IBS symptoms, abdominal pain and discomfort, altered bowel function as well as improvement of quality of life (QOL). Data from animals studies suggest the involvement of 5-HT(3) receptors on intrinsic primary afferent neurons in the mediation of the effect of alosetron on gastrointestinal motility and secretion. While definitive proof of a visceroanalgesic action is not available, an additional central mechanism of action is suggested by findings obtained in animal models, as well as from human brain imaging studies. Alosetron shows a greater effectiveness in women, and the role of genetic factors underlying inter-individual differences in the response to alosetron is currently under investigation. The most frequent adverse event associated with the use of alosetron is constipation and in some rare cases, the development of colonic mucosal ischaemia. In the following review, the most recent reported effects of alosetron on gastrointestinal motility, visceral sensitivity and anxiety, both in terms of preclinical and clinical data will be discussed. The impact of alosetron on QOL in IBS patients and the safety of treatment with alosetron, will also be covered.

Carbolines↗