Pharmacological and pharmacokinetic aspects of functional gastrointestinal disorders

Oral Phyto-thymol ameliorates the stress induced IBS symptoms

Physical stressors play a crucial role in the progression of irritable bowel syndrome (IBS). Here we report a heterogeneous physical stress induced IBS rat model which shows depression and subsequent modulation of IBS by oral treatment of thymol. Oral administration of Thymol reduces the stress induced IBS significantly altering the stress induced gastrointestinal hypermotility, prolonged the whole gut transit time, and increased abdominal withdrawal reflex suggesting gastrointestinal hypermotility and visceral discomfort caused the onset of depression. Immunohistochemical analysis in small intestine and colon of rats shows the decreased 5-HT3AR expression level while thymol treatment normalized the 5-HT3AR expression in the stressed rats. Molecular docking studies showed that thymol competes with endogenous serotonin and an antagonist, Tropisetron and all have similar binding energies to 5-HT3AR. Molecular dynamics simulations revealed that thymol and tropisetron might have similar effects on 5-HT3AR. Our study suggest that thymol improves IBS symptoms through 5-HT3AR, could be useful for the treatment of IBS.

Evaluating the Effect of Oral Gabapentin on the Improvement of Gastrointestinal Symptoms in Patients with Functional Dyspepsia Resistant to Conventional Treatments

Background:

Dyspepsia is one of the most common gastrointestinal (GI) problems and is more prevalent in adults. Environmental hypersensitivity and anxiety and depression are among the factors that can cause this disease. In this regard, gabapentin as a gamma-aminobutyric acid (GABA) analog used in the treatment of neuropathic pain and may be effective in controlling the symptoms of GI disorders. Therefore, the present study aimed to evaluate the effect of oral gabapentin on the improvement of GI symptoms in patients with functional dyspepsia (FD) resistant to conventional treatments.

Materials and Methods:

In a double-blind clinical trial, 126 patients with FD resistant to conventional treatments, referred to gastroenterology clinic of Hajar Hospital of Shahrekord in 2017–2018, were randomly assigned to two groups; patients in the control group received omeprazole alone, and the case group received omeprazole plus gabapentin. The severity of GI symptoms was recorded and evaluated by the Gastrointestinal Symptom Rating Scale (GSRS) questionnaire before and after treatment (4 weeks).

Results:

GSRS total score in the group who received gabapentin (16.89 ± 6.89) was significantly lower than controls (20.00 ± 9.31) (P = 0.036). It also found that gabapentin, as an adjunctive drug, plus omeprazole could play a significant role in GI symptom improvement, such as pain, reflux, and indigestion.

Conclusion:

Gabapentin as an adjunctive drug could be more effective in reducing the severity of GI symptoms in patients with dyspepsia, especially neurological symptoms (such as pain, reflux, and indigestion).

DA-9701 (Motilitone): A Multi-Targeting Botanical Drug for the Treatment of Functional Dyspepsia

Functional dyspepsia (FD) is the most common functional gastrointestinal disorder (FGID). FD is characterized by bothersome symptoms such as postprandial fullness, early satiety, and epigastric pain or burning sensations in the upper abdomen. The complexity and heterogeneity of FD pathophysiology, which involves multiple mechanisms, make both treatment and new drug development for FD difficult. Current medicines for FD targeting a single pathway have failed to show satisfactory efficacy and safety. On the other hand, multicomponent herbal medicines that act on multiple targets may be a promising alternative treatment for FD. DA-9701 (Motilitone), a botanical drug consisting of Corydalis Tuber and Pharbitidis Semen, has been prescribed for FD since it was launched in Korea in 2011. It has multiple mechanisms of action such as prokinetic effects, fundus relaxation, and visceral analgesia, which are mediated by dopamine D₂ and several serotonin receptors involved in gastrointestinal (GI) functions. In clinical studies, DA-9701 has been found to be beneficial for improvement of FD symptoms and GI functions in FD patients, while showing better safety compared to that associated with conventional medicines. In this review, we provide updated information on the pharmacological effects, safety, and clinical results of DA-9701 for the treatment of FGIDs.

Improved health-related quality of life after surgical management of severe refractory constipation-dominant irritable bowel syndrome

Irritable bowel syndrome (IBS) is the most common of the functional gastrointestinal disorders (FGIDs). Despite its prevalence and health-care costs, there are few effective therapies for patients with severe symptoms. Our objective was to determine whether surgical management would improve health-related quality of life (HRQOL) in severe refractory constipation-dominant FGIDs. From 2003 to 2005, 6 patients underwent total colectomy with end ileostomy or primary anastomosis. They completed Short Form 36 (SF-36) and IBS-36 questionnaires preoperatively and postoperatively. HRQOL was compared with age- and sex-matched Canadian norms using Welch's unpaired t test. Preoperative SF-36 physical and mental health summary scores were significantly lower than Canadian norms (P < 0.0001), while postoperative scores were not significantly different than Canadian norms (P = 0.50 and P = 0.57, respectively). After surgical management, HRQOL in patients with severe constipation-dominant IBS improved from drastically below that of Canadian norms to a comparable level. This finding questions the convention of avoiding operations in IBS patients and demonstrates that surgical management may be suitable for the appropriately screened patient.

Pharmacological, Pharmacokinetic, and Pharmacogenomic Aspects of Functional Gastrointestinal Disorders

This article reviews medications commonly used for the treatment of patients with functional gastrointestinal disorders. Specifically, we review the animal models that have been validated for the study of drug effects on sensation and motility; the preclinical pharmacology, pharmacokinetics, and toxicology usually required for introduction of new drugs; the biomarkers that are validated for studies of sensation and motility endpoints with experimental medications in humans; the pharmacogenomics applied to these medications and their relevance to the FGIDs; and the pharmacology of agents that are applied or have potential for the treatment of FGIDs, including psychopharmacologic drugs.

Randomized, Controlled, Multi-center Trial: Comparing the Safety and Efficacy of DA-9701 and Itopride Hydrochloride in Patients With Functional Dyspepsia

Background/Aims

Therapies of functional dyspepsia (FD) are limited. DA-9701 is a novel prokinetic agent formulated with Pharbitis semen and Corydalis Tuber. We aimed to assess the efficacy of DA-9701 compared with itopride in FD patients.

Methods

Patients with FD randomly received either itopride 50 mg or DA-9701 30 mg t.i.d after a 2-week baseline period. After 4 weeks of treatment, 2 primary efficacy endpoints were analyzed: the change from baseline in composite score of the 8 dyspeptic symptoms and the overall treatment effect. Impact on patients’ quality of life was assessed using the Nepean Dyspepsia Index (NDI) questionnaire.

Results

We randomly assigned 464 patients with 455 having outcome data. The difference of the composite score change of the 8 symptoms between the 2 groups was 0.62, indicating that DA-9701 was not inferior to itopride. The overall treatment effect response rate was not different between the groups. When responder was defined as ≥ 5 of the 7 Likert scale, responder rates were 37% of DA-9701 and 36% of itopride group. Patients receiving DA-9701 experienced similar mean percentage of days with adequate relief during the 4-week treatment period compared with those receiving itopride (56.8% vs 59.1%). Both drugs increased the NDI score of 5 domains without any difference in change of the NDI score between the groups. The safety profile of both drugs was comparable.

Conclusions

DA-9701 significantly improves symptoms in patients with FD. DA-9701 showed non-inferior efficacy to itopride with comparable safety.

DA-9701: A New Multi-Acting Drug for the Treatment of Functional Dyspepsia

Motilitone^® (DA-9701) is a new herbal drug that was launched for the treatment of functional dyspepsia in December 2011 in Korea. The heterogeneous symptom pattern and multiple causes of functional dyspepsia have resulted in multiple drug target strategies for its treatment. DA-9701, a compound consisting of a combination of Corydalis Tuber and Pharbitidis Semen, has being developed for treatment of functional dyspepsia. It has multiple mechanisms of action such as fundus relaxation, visceral analgesia, and prokinetic effects. Furthermore, it was found to significantly enhance meal-induced gastric accommodation and increase gastric compliance in dogs. DA-9701 also showed an analgesic effect in rats with colorectal distension induced visceral hypersensitivity and an antinociceptive effect in beagle dogs with gastric distension-induced nociception. The pharmacological effects of DA-9701 also include conventional effects, such as enhanced gastric emptying and gastrointestinal transit. The safety profi le of DA-9701 is also preferable to that of other treatments.

Drug development for the irritable bowel syndrome: current challenges and future perspectives

Medications are frequently used for the treatment of patients with the irritable bowel syndrome (IBS), although their actual benefit is often debated. In fact, the recent progress in our understanding of the pathophysiology of IBS, accompanied by a large number of preclinical and clinical studies of new drugs, has not been matched by a significant improvement of the armamentarium of medications available to treat IBS. The aim of this review is to outline the current challenges in drug development for IBS, taking advantage of what we have learnt through the Rome process (Rome I, Rome II, and Rome III). The key questions that will be addressed are: (a) do we still believe in the "magic bullet," i.e., a very selective drug displaying a single receptor mechanism capable of controlling IBS symptoms? (b) IBS is a "functional disorder" where complex neuroimmune and brain-gut interactions occur and minimal inflammation is often documented: do we need to target gut motility, visceral sensitivity, or minimal inflammation? (c) are there validated biomarkers (accepted by regulatory agencies) for studies of sensation and motility with experimental medications in humans? (d) do animal models have predictive and translational value? (e) in the era of personalized medicine, does pharmacogenomics applied to these medications already play a role? Finally, this review will briefly outline medications currently used or in development for IBS. It is anticipated that a more focused interaction between basic science investigators, pharmacologists, and clinicians will lead to better treatment of IBS.

Ehlers-danlos syndrome, hypermobility type: an underdiagnosed hereditary connective tissue disorder with mucocutaneous, articular, and systemic manifestations

Ehlers-Danlos syndrome, hypermobility type, constituting a phenotypic continuum with or, perhaps, corresponding to the joint hypermobility syndrome (JHS/EDS-HT), is likely the most common, though the least recognized, heritable connective tissue disorder. Known for decades as a hereditary condition with predominant rheumatologic manifestations, it is now emerging as a multisystemic disorder with widespread manifestations. Nevertheless, the practitioners' awareness of this condition is generally poor and most patients await years or, perhaps, decades before reaching the correct diagnosis. Among the various sites of disease manifestations, skin and mucosae represent a neglected organ where the dermatologist can easily spot diagnostic clues, which consistently integrate joint hypermobility and other orthopedic/neurologic manifestations at physical examination. In this paper, actual knowledge on JHS/EDS-HT is summarized in various sections. Particular attention has been posed on overlooked manifestations, including cutaneous, mucosal, and oropharyngeal features, and early diagnosis techniques, as a major point of interest for the practicing dermatologist. Actual research progresses on JH/EDS-HT envisage an unexpected link between heritable dysfunctions of the connective tissue and a wide range of functional somatic syndromes, most of them commonly diagnosed in the office of various specialists, comprising dermatologists.

Psychopharmacological treatment and psychological interventions in irritable bowel syndrome

Irritable bowel syndrome (IBS) accounts for 25% of gastroenterology output practice, making it one of the most common disorders in this practice. Psychological and social factors may affect the development of this chronic disorder. Furthermore, psychiatric symptoms and psychiatric diseases are highly prevalent in this condition, but the approach to treating these is not always straightforward. As emphasized in the biopsychosocial model of IBS, with regard to the modulatory role of stress-related brain-gut interactions and association of the disease with psychological factors and emotional state, it proves useful to encourage psychopharmacological treatments and psychosocial therapies, both aiming at reducing stress perception. The aim of this paper is to analyze the effectiveness of psychopharmacological treatment and psychological interventions on irritable bowel syndrome.

The enteric nervous system and neurogastroenterology

Neurogastroenterology is defined as neurology of the gastrointestinal tract, liver, gallbladder and pancreas and encompasses control of digestion through the enteric nervous system (ENS), the central nervous system (CNS) and integrative centers in sympathetic ganglia. This Review provides a broad overview of the field of neurogastroenterology, with a focus on the roles of the ENS in the control of the musculature of the gastrointestinal tract and transmucosal fluid movement. Digestion is controlled through the integration of multiple signals from the ENS and CNS; neural signals also pass between distinct gut regions to coordinate digestive activity. Moreover, neural and endocrine control of digestion is closely coordinated. Interestingly, the extent to which the ENS or CNS controls digestion differs considerably along the digestive tract. The importance of the ENS is emphasized by the life-threatening effects of certain ENS neuropathies, including Hirschsprung disease and Chagas disease. Other ENS disorders, such as esophageal achalasia and gastroparesis, cause varying degrees of dysfunction. The neurons in enteric reflex pathways use a wide range of chemical messengers that signal through an even wider range of receptors. These receptors provide many actual and potential targets for modifying digestive function.

Intestinal serotonin release, sensory neuron activation, and abdominal pain in irritable bowel syndrome

OBJECTIVES

Serotonin (5-hydroxytryptamine, 5-HT) metabolism may be altered in gut disorders, including in the irritable bowel syndrome (IBS). We assessed in patients with IBS vs. healthy controls (HCs) the number of colonic 5-HT-positive cells; the amount of mucosal 5-HT release; their correlation with mast cell counts and mediator release, as well as IBS symptoms; and the effects of mucosal 5-HT on electrophysiological responses in vitro.

METHODS

We enrolled 25 Rome II IBS patients and 12 HCs. IBS symptom severity and frequency were graded 0-4. 5-HT-positive enterochromaffin cells and tryptase-positive mast cells were assessed with quantitative immunohistochemistry on colonic biopsies. Mucosal 5-HT and mast cell mediators were assessed by high-performance liquid chromatography or immunoenzymatic assay, respectively. The impact of mucosal 5-HT on electrophysiological activity of rat mesenteric afferent nerves was evaluated in vitro.

RESULTS

Compared with HCs, patients with IBS showed a significant increase in 5-HT-positive cell counts (0.37 ± 0.16% vs. 0.56 ± 0.26%; P=0.039), which was significantly greater in patients with diarrhea-predominant IBS vs. constipation-predominant IBS (P=0.035). Compared with HCs, 5-HT release in patients with IBS was 10-fold significantly increased (P < 0.001), irrespective of bowel habit, and was correlated with mast cell counts. A significant correlation was found between the mucosal 5-HT release and the severity of abdominal pain (r(s)=0.582, P=0.047). The area under the curve, but not peak sensory afferent discharge evoked by IBS samples in rat jejunum, was significantly inhibited by the 5-HT₃ receptor antagonist granisetron (P<0.005).

CONCLUSIONS

In patients with IBS, 5-HT spontaneous release was significantly increased irrespective of bowel habit and correlated with mast cell counts and the severity of abdominal pain. Our results suggest that increased 5-HT release contributes to development of abdominal pain in IBS, probably through mucosal immune activation.

Biopsychosocial model of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common chronic disorder seen in gastroenterology and primary care practice. It is characterized by recurrent abdominal pain or discomfort associated with disturbed bowel function. It is a heterogeneous disorder with varying treatments, and in this regard physicians sometimes struggle with finding the optimal approach to management of patients with IBS. This disorder induces high health care costs and variably reduces health-related quality of life. IBS is in the class of functional gastrointestinal disorders, and results from dysregulation of central and enteric nervous system interactions. Psychosocial factors are closely related to their gut physiology, associated cognitions, symptom manifestations and illness behavior. Therefore, it is important for the physician to recognize the psychosocial issues of patients with IBS and in addition to build a good patient-physician relationship in order to optimize treatment. This review focuses on the interaction between psychological and physiological factors associated with IBS by using a biopsychosocial model. In this article, we describe (1) the predisposing psychological features seen in early life; (2) the psychological factors associated with life stress, the symptom presentation, and their associated coping patterns; (3) gut pathophysiology with emphasis on disturbances in motility, visceral hypersensitivity and brain-gut interactions; and finally (4) the clinical outcomes and effective treatments including psychotherapeutic methods.

Biopsychosocial model of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common chronic disorder seen in gastroenterology and primary care practice. It is characterized by recurrent abdominal pain or discomfort associated with disturbed bowel function. It is a heterogeneous disorder with varying treatments, and in this regard physicians sometimes struggle with finding the optimal approach to management of patients with IBS. This disorder induces high health care costs and variably reduces health-related quality of life. IBS is in the class of functional gastrointestinal disorders, and results from dysregulation of central and enteric nervous system interactions. Psychosocial factors are closely related to their gut physiology, associated cognitions, symptom manifestations and illness behavior. Therefore, it is important for the physician to recognize the psychosocial issues of patients with IBS and in addition to build a good patient-physician relationship in order to optimize treatment. This review focuses on the interaction between psychological and physiological factors associated with IBS by using a biopsychosocial model. In this article, we describe (1) the predisposing psychological features seen in early life; (2) the psychological factors associated with life stress, the symptom presentation, and their associated coping patterns; (3) gut pathophysiology with emphasis on disturbances in motility, visceral hypersensitivity and brain-gut interactions; and finally (4) the clinical outcomes and effective treatments including psychotherapeutic methods.

Visualization and quantification of intestinal transit and motor function by real-time tracking of 19F labeled capsules in humans

A combined (19)F and (1)H MRI framework for the assessment of human intestinal transit and motor function is presented. This framework consists of silicone coated polychlorotrifluoroethylene capsules filled with perfluoro-[15]-crown-5-ether as (19)F marker, a flexible (19)F surface coil and a (19)F projection imaging sequence, allowing for real-time tracking of a single or multiple capsules. The capsules (length 11.5 mm, Ø 7.2 mm) contain 140 μL perfluoro-[15]-crown-5-ether and were tested for cytotoxicity and leakage prior to oral administration. A balanced SSFP projection sequence was implemented, yielding a temporal resolution of 133 ms. Optional multi-frequency excitation, allowing for interleaved tracking of differently labeled (19)F capsules, was incorporated. The passage of the (19)F capsules through intestinal sections was monitored in two healthy volunteers. Capsule coordinates were successfully coregistered with anatomical reference scans. Intestinal motility, residence times, lengths and forward velocities were determined. Simultaneous tracking of two capsules allowed for the assessment of peristaltic patterns with correction for respiratory motion. By providing the means for real-time multiple capsule tracking and high resolution anatomical imaging, the presented multinuclear imaging framework has the potential to provide important supplemental information for physiological and pharmaceutical research.

The role of experimental models in developing new treatments for irritable bowel syndrome

Irritable bowel syndrome (IBS) is characterized by chronic, recurrent abdominal pain and altered bowel habits and is currently defined by symptom criteria and the absence of detectable organic disease. The underlying pathophysiology remains incompletely understood. Despite considerable efforts by the scientific community and the pharmaceutical industry to develop novel pharmacological treatments aimed at chronic visceral pain, the traditional approach to identifying and evaluating novel drugs for this target have largely failed to translate into effective IBS treatments. However, several novel drugs aimed at normalizing bowel movements have produced clinical effects, not only on the primary target, but also on pain and discomfort. While some of the commonly used experimental animal models for the pain dimension of IBS have some face and construct validity, the predictive validity of most of the models is either unknown, or has been disappointing. A reverse translational approach is proposed, which is based on identification and characterization of brain endophenotypes in patients, followed by translation of these endophenotypes for pharmacological studies in rodent models.

[Therapeutic targets]

Based on better recent knowledge of the factors involved in triggering visceral hyperalgesia, the therapeutic approach to irritable bowel syndrome (IBS) treatment is changing. The classical approach targeting first bowel movement alterations or motility disorders using spasmolytic agents has to be replaced by visceral antinociceptive drugs. Several mediators and receptors involved in gut hyperalgesia have already been identified. Serotonin (5-HT), tachykinins, CCK, NGF, and other mediators are involved in experimental models of gut hyperalgesia, and related receptor antagonists have already been introduced in clinical trials. However, IBS is associated with mucosal immune stimulation, considered a microinflammatory state associated with increased density of immunocytes and mast cells, offering new targets. Altered mucosal barrier permeability with increased entry of toxins and bacteria is considered to be responsible for the mucosal microinflammation. Endogenous but predominantly luminal factors have been identified as factors responsible for such altered permeability. These clinical data have opened the door to promising future drugs able to prevent or blunt such permeability alteration, which therefore may constitute a pathophysiological treatment for IBS.

Post-inflammatory modification of colonic afferent mechanosensitivity

1. The present review discusses interactions between the immune and nervous systems in post-infectious irritable bowel syndrome (PI-IBS). 2. Visceral pain is the single symptom that most affects the quality of life of patients with irritable bowel syndrome (IBS), yet it is the least successfully managed. An underlying hypersensitivity of colonic afferents to mechanical stimuli has long been implicated in visceral pain in IBS, but little more is known of the physiological aetiology. 3. The PI-IBS patients are a cohort of IBS patients who attribute their symptoms to a preceding gastrointestinal infection by pathogens such as Campylobacter or Salmonella. Current evidence suggests that the immune system remains activated in these patients and contributes to their visceral hypersensitivity. This is characterized by a shift in the phenotype of circulating immune cells towards a Type 1 (Th1 predominating) state. Products from these immune cells sensitize colonic afferents to mechanical stimuli. 4. Rectal instillation of trinitrobenzene sulphonic acid induces a Th1-mediated inflammatory response, consistent with clinical observations in PI-IBS. The visceral hypersensitivity observed in this model is biphasic, with an initial onset characterized by visceral hypersensitivity correlating with histological damage followed by a delayed phase that occurs after histological recovery. Interestingly, this chronic visceral hypersensitivity is mediated by afferents in closest apposition to blood vessels, but furthest from the initial site of damage. 5. Both clinical and experimental evidence indicates that chronic dysregulation of the immune system induces visceral afferent hypersensitivity and, therefore, may be the central mechanism underlying PI-IBS.

Impact of gastrointestinal symptoms on response to pregabalin in generalized anxiety disorder: results of a six-study combined analysis

The objective of the study was to evaluate the response of generalized anxiety disorder (GAD) patients with prominent gastrointestinal (GI) symptoms to pregabalin (PGB) treatment. Data were pooled from six double-blind, placebo (PBO)-controlled, 4-6 week trials in outpatients who met Diagnostic and Statistical Manual of Mental Disorders, 4th edition criteria for GAD with a minimum Hamilton Anxiety Rating Scale (HAM-A) total score of 20. Treatment response was evaluated for three PGB fixed-dosage groups: 150, 300-450, and 600 mg/day, and for fixed doses of a benzodiazepine (alprazolam, 1.5 mg/day; lorazepam, 6 mg/day). A GI-high subgroup (high GI symptomatology) was defined by a baseline HAM-A item-11 (GI) score of 3 or greater (severe/very severe). At baseline, 301 patients (16.2%) met criteria for the GI-high subgroup. Baseline characteristics were approximately similar for the four study treatments in the GI-high subgroup. For the GI-high subgroup, last observation carried forward (LOCF) endpoint reduction in HAM-A was significantly higher on PGB-300/450 -13.8+/-1.2 and PGB-600 -14.7+/-1.0 compared with PBO -10.1+/-0.9 (P<0.01 for both comparisons); but the difference on PGB-150 did not achieve significance (-13.5+/-1.6; P=0.083). Also in the GI-high subgroup, endpoint reduction in HAM-A item-11 was significantly higher on PGB-300/450 compared with PBO (-1.93+/-0.16 vs. -1.52+/-0.13; P=0.04), but did not achieve significance on PGB-600 mg (-1.89+/-0.14; P=0.06), or PGB-150 mg (-1.90+/-0.23; P=0.16). In the GI-high subgroup, treatment with a benzodiazepine was not associated with significant endpoint reduction in either the HAM-A total score or the HAM-A item-11 score. Patients in the GI-high subgroup had higher discontinuation rates when treated with benzodiazepines, whereas treatment with PGB 300-600 mg/day was not associated with treatment-emergent worsening in GI symptoms compared with placebo. Treatment with PGB improved overall levels of anxiety, as well as specifically improving GI symptoms.

Vagotomy upregulates expression of the N-methyl-D-aspartate receptor NR2D subunit in the stomach

BACKGROUND

N-methyl-D-aspartate (NMDA) receptor is the major excitatory neurotransmitter receptor in the central nervous system. Recent evidence has pointed to expression of NMDA receptor in peripheral non-neuronal tissues and organs; however, little is known about the expression of the receptor in the stomach. The present study identified what types of NMDA receptor subunits are expressed in the rat stomach and examined whether vagotomy affects their expression.

METHODS

To see the expression and distribution of the mRNAs and proteins for the NMDA receptor subunits, real-time reverse transcription-polymerase chain reaction, Western blotting, in situ hybridization, and immunohistochemistry were carried out on rat stomach with and without vagotomy.

RESULTS

Of the NMDA receptor subunits, NR1, NR2 (2A, 2B, 2C, 2D), and NR3 (3A, 3B), all NR subunit mRNAs except for the NR2B subunit mRNA were expressed in the intact rat stomach, with huge expression of NR2D mRNA. Expression of NR2D subunit mRNA and protein significantly increased after vagotomy. Increased expression was found in mucosal cells, the myenteric plexus, and the outer membrane of the stomach with vagotomy.

CONCLUSIONS

Vagotomy upregulates expression of the NR2D subunit in the stomach and therefore, the NR2D subunit may be implicated in gastric motility.

The enteric nervous system: normal functions and enteric neuropathies

Most aspects of the normal organisation and functioning of the enteric nervous system have been resolved in recent years, especially for the small and large intestines, where the ENS has essential roles in controlling bowel movement and transmucosal fluid exchange. The roles of the ENS in the esophagus are not understood, and the relative roles of intrinsic reflexes in relation to extrinsic control of the stomach require clarification. In the small intestine and colon, it needs to be understood how neural activity is orchestrated to subserve different functional outcomes, for example propulsion, mixing and retrograde movement. However, the most important future challenges are to properly understand the molecular and cellular changes that underlie enteric neuropathies, to utilise knowledge of the normal neurochemistry, pharmacology and physiology of the ENS to devise strategies to treat disorders of motility and secretion, and to develop effective therapeutic compounds. It is suggested that ion channels of enteric neurons have been under-investigated as therapeutic targets. Other future challenges lie in the identification of biomarkers for functional bowel disorders and in the use of neural stem cells for restitution of ENS function.