Delta-9-tetrahydrocannabinol delays the gastric emptying of solid food in humans: a double-blind, randomized study

Cannabinoid Hyperemesis Syndrome: Diagnosis, Pathophysiology, and Treatment-a Systematic Review

Cannabinoid hyperemesis syndrome (CHS) is a syndrome of cyclic vomiting associated with cannabis use. Our objective is to summarize the available evidence on CHS diagnosis, pathophysiology, and treatment. We performed a systematic review using MEDLINE, Ovid MEDLINE, Embase, Web of Science, and the Cochrane Library from January 2000 through September 24, 2015. Articles eligible for inclusion were evaluated using the Grading and Recommendations Assessment, Development, and Evaluation (GRADE) criteria. Data were abstracted from the articles and case reports and were combined in a cumulative synthesis. The frequency of identified diagnostic characteristics was calculated from the cumulative synthesis and evidence for pathophysiologic hypothesis as well as treatment options were evaluated using the GRADE criteria. The systematic search returned 2178 articles. After duplicates were removed, 1253 abstracts were reviewed and 183 were included. Fourteen diagnostic characteristics were identified, and the frequency of major characteristics was as follows: history of regular cannabis for any duration of time (100%), cyclic nausea and vomiting (100%), resolution of symptoms after stopping cannabis (96.8%), compulsive hot baths with symptom relief (92.3%), male predominance (72.9%), abdominal pain (85.1%), and at least weekly cannabis use (97.4%). The pathophysiology of CHS remains unclear with a dearth of research dedicated to investigating its underlying mechanism. Supportive care with intravenous fluids, dopamine antagonists, topical capsaicin cream, and avoidance of narcotic medications has shown some benefit in the acute setting. Cannabis cessation appears to be the best treatment. CHS is a cyclic vomiting syndrome, preceded by daily to weekly cannabis use, usually accompanied by symptom improvement with hot bathing, and resolution with cessation of cannabis. The pathophysiology underlying CHS is unclear. Cannabis cessation appears to be the best treatment.

Dronabinol increases pain threshold in patients with functional chest pain: a pilot double-blind placebo-controlled trial

Noncardiac chest pain is associated with poor quality of life and high care expenditure. The majority of noncardiac chest pain is either gastresophageal reflux disease related or due to esophageal motility disorders, and the rest are considered functional chest pain (FCP) due to central and peripheral hypersensitivity. Current treatment of FCP improves 40-50% of patients. Cannabinoid receptors 1 (CB1) and 2 (CB2) modulate release of neurotransmitters; CB1 is located in the esophageal epithelium and reduces excitatory enteric transmission and potentially could reduce esophageal hypersensitivity. We performed a prospective study to evaluate its effects on pain threshold, frequency, and intensity in FCP. Subjects with FCP received dronabinol (5 mg, twice daily; n = 7; average age, 44 years; mean body mass index, 26.7) or placebo (n = 6; average age, 42 years; mean body mass index, 25.9) for 28 days (4 weeks). Chest pain, general health, and anxiety/depression questionnaires were assessed at baseline and at 4 weeks. Subjects underwent an esophageal balloon distention test prior to treatment and on last day of the study. Dronabinol increased pain thresholds significantly (3.0 vs. 1.0; P = 0.03) and reduced pain intensity and odynophagia compared to placebo (0.18 vs. 0.01 and 0.12 vs. 0.01, respectively, P = 0.04). Depression and anxiety scores did not differ between the groups at baseline or after treatment. No significant adverse effects were observed. In this novel study, dronabinol increased pain threshold and reduced frequency and intensity of pain in FCP. Further, large scale studies are needed to substantiate these findings.

Role of cannabis in digestive disorders

Cannabis sativa, a subspecies of the Cannabis plant, contains aromatic hydrocarbon compounds called cannabinoids. [INCREMENT]-Tetrahydrocannabinol is the most abundant cannabinoid and is the main psychotropic constituent. Cannabinoids activate two types of G-protein-coupled cannabinoid receptors: cannabinoid type 1 receptor and cannabinoid type 2 receptor. There has been ongoing interest and development in research to explore the therapeutic potential of cannabis. [INCREMENT]-Tetrahydrocannabinol exerts biological functions on the gastrointestinal (GI) tract. Cannabis has been used for the treatment of GI disorders such as abdominal pain and diarrhea. The endocannabinoid system (i.e. endogenous circulating cannabinoids) performs protective activities in the GI tract and presents a promising therapeutic target against various GI conditions such as inflammatory bowel disease (especially Crohn's disease), irritable bowel syndrome, and secretion and motility-related disorders. The present review sheds light on the role of cannabis in the gut, liver, and pancreas and also on other GI symptoms, such as nausea and vomiting, cannabinoid hyperemesis syndrome, anorexia, weight loss, and chronic abdominal pain. Although the current literature supports the use of marijuana for the treatment of digestive disorders, the clinical efficacy of cannabis and its constituents for various GI disorders remains unclear.

Cannabinoid Hyperemesis Syndrome: A Case Report of Cyclic Severe Hyperemesis and Abdominal Pain with Long-Term Cannabis Use

Introduction. Cannabinoid Hyperemesis Syndrome (CHS) is a rare condition that includes cyclic severe vomiting in subjects who have been consuming large doses of cannabis for several years. One of the major diagnostic criteria is the alleviation of symptoms by hot showers. The syndrome was first described in 2004 and is so far neither completely understood nor well known. The latter leads to continued morbidity in concerned subjects and unnecessary expenses for futile investigations. Standard treatments of vomiting as 5-HT3 or D2-receptor antagonists have been shown to be ineffective in alleviating the symptoms. The only long-term satisfying treatment option is the complete abstinence from cannabis consumption. Case Summary. In this case report we describe a 26-year-old male Caucasian long-term cannabis consumer who repeatedly presented in our emergency room with cyclic severe nausea and vomiting ceased by hot showers and resistant to all other treatments. The final diagnosis was not established until his third visit to the ER. Conclusion. CHS is an important differential diagnosis in patients who present with cyclic vomiting and abdominal pain with a history of long-term cannabis use. Recognition of this syndrome is important in order to avoid unnecessary clinical testing and to help the patients break the cycle of drug use.

Cannabinoid hyperemesis syndrome and the onset of a manic episode

Cannabinoid hyperemesis syndrome is a rare, recently described, clinically diagnosed condition that is characterised by a chronic history of cannabis use, cyclic nausea and vomiting, symptomatic relief with hot water bathing, and resolution with cessation of use. We present a case of this syndrome concurrent in a patient with bipolar mania. We suggest that a 3-week period of vomiting in the context of this syndrome contributed to the precipitation of a manic episode by lowering mood stabiliser serum levels, and that this syndrome will have significant consequences for the patient's mental health.

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.

AM841, a covalent cannabinoid ligand, powerfully slows gastrointestinal motility in normal and stressed mice in a peripherally restricted manner

BACKGROUND AND PURPOSE

Cannabinoid (CB) ligands have been demonstrated to have utility as novel therapeutic agents for the treatment of pain, metabolic conditions and gastrointestinal (GI) disorders. However, many of these ligands are centrally active, which limits their usefulness. Here, we examine a unique novel covalent CB receptor ligand, AM841, to assess its potential for use in physiological and pathophysiological in vivo studies.

EXPERIMENTAL APPROACH

The covalent nature of AM841 was determined in vitro using electrophysiological and receptor internalization studies on isolated cultured hippocampal neurons. Mouse models were used for behavioural analysis of analgesia, hypothermia and hypolocomotion. The motility of the small and large intestine was assessed in vivo under normal conditions and after acute stress. The brain penetration of AM841 was also determined.

KEY RESULTS

AM841 behaved as an irreversible CB1 receptor agonist in vitro. AM841 potently reduced GI motility through an action on CB1 receptors in the small and large intestine under physiological conditions. AM841 was even more potent under conditions of acute stress and was shown to normalize accelerated GI motility under these conditions. This compound behaved as a peripherally restricted ligand, showing very little brain penetration and no characteristic centrally mediated CB1 receptor-mediated effects (analgesia, hypothermia or hypolocomotion).

CONCLUSIONS AND IMPLICATIONS

AM841, a novel peripherally restricted covalent CB1 receptor ligand that was shown to be remarkably potent, represents a new class of potential therapeutic agents for the treatment of functional GI disorders.

Cannabis and hyperemesis

The adverse effects of marijuana are well documented, as well as its positive therapeutic uses. Cannabis has traditionally been associated with an antiemetic action following acute ingestion and synthetic cannabinoids have an established use as antiemetics for chemotherapy induced nausea. However, there has been limited recognition of chronic cannabis use as a cause of cyclic vomiting syndrome. Cannabinoid hyperemesis was first identified by Allen er al in 2004. Compulsive bathing was also described as part of the clinical picture. This same syndrome has been confirmed a number of times in the medical literature in the interim. The condition has, to our knowledge, never been reported, in a psychiatric patient.

Compulsive showering and marijuana use - the cannabis hyperemisis syndrome

Patient: Male, 26

Final Diagnosis: Marihuana addiction

Symptoms: Compulsive showering • nausea • vomiting

Medication: —

Clinical Procedure: —

Specialty: Toxicology

A case of cannabinoid hyperemesis syndrome caused by synthetic cannabinoids

BACKGROUND

Cannabinoid hyperemesis syndrome (CHS) was initially described in 2004 and remains an under-recognized clinical entity that occurs in chronic heavy marijuana smokers.

CASE REPORT

We describe the first report of CHS in an abuser of synthetic cannabinoids. CHS is thought to be caused by over-stimulation of the cannabinoid 1 receptor. The synthetic cannabinoids found in K2, Spice, and other commonly abused designer cannabinoids, including those used by our patient (JWH-018, JWH-073, JWH-122, AM-2201, and AM-694), are potent agonists of the cannabinoid 1 receptor.

CONCLUSION

Our report suggests that frequent habitual smoking of synthetic cannabinoids can cause cannabinoid hyperemesis syndrome.

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.

The effects of fasting duration on gastric emptying in man, an exploration of the role of the endocannabinoid system and inter-individual responsiveness

BACKGROUND

In animal studies, gut vagal afferent neurons express cannabinoid (CB1) receptors, whose expression is increased by fasting. We aimed to explore the possibility that similar effects might be relevant in man in controlling gastric emptying.

METHODS

Fourteen healthy volunteers underwent measurements of gastric emptying using the (13) C acetate breath test, after either a nutrient (skimmed milk) or non-nutrient (water) meal following both a 12 and 24 h fast. Further gastric emptying studies were performed with and without the CB1 receptor antagonist Rimonabant (20 mg or 80 mg). Because of the inter-individual variations observed, two subjects underwent additional studies with and without Rimonabant to determine intra-individual consistency. Gastric emptying was evaluated as cumulative C13 : C12 ratio values, measured at 5 min intervals for 30 min.

KEY RESULTS

In the group as a whole, fasting duration slowed gastric emptying for both the nutrient [120 ± 30 (mean ± SD) vs 101 ± 34, P < 0.05] and non-nutrient [226 ± 62 vs 177 ± 47, P < 0.05] meals, but there was no effect of Rimonabant. However, there was consistent inter individual variation; thus while 12 subjects showed a slowing, two (14%) exhibited accelerated gastric emptying for both the nutrient and the non-nutrient meal after 24 h fasting and in one of whom, Rimonabant consistently reversed the fasting effect on the non-nutrient meal.

CONCLUSIONS & INFERENCES

Extended fasting alters the gastric emptying of liquid meals but there are consistent differences between individuals. Where there is an accelerated response to fasting, Rimonabant appears to reverse the effect.

Association of marijuana use and cyclic vomiting syndrome

Cannabis use has become one of the most commonly abused drugs in the world. It is estimated that each year 2.6 million individuals in the USA become new users and most are younger than 19 years of age. Reports describe marijuana use as high as 40–50% in male Cyclic Vomiting Syndrome patients. It is this interest in cannabis in the World, coupled with recognition of a cyclic vomiting illness associated with its chronic use that beckons a review of the most current articles, as well as a contribution from our own experiences in this area. The similarities we have demonstrated for both cannibinoid hyperemesis syndrome and cyclic vomiting make the case that cannibinoid hyperemesis syndrome is a subset of patients who have the diagnoses of cyclic vomiting syndrome and the role of marijuana should always be considered in the diagnosis of CVS, particularly in males.

Influence of gastric acid on gastric emptying and gastric distension-induced pain response in rats--effects of famotidine and mosapride

BACKGROUND

Gastroduodenal acidification has been reported to aggravate upper abdominal discomfort and pain that are symptoms suffered by functional dyspepsia (FD) patients. Delayed gastric emptying and hypersensitivity to gastric distension (GD) contribute importantly to the pathophysiology of FD.

METHODS

In the present study, we determined the influence of pentagastrin-stimulated endogenous gastric acid on gastric emptying and GD-induced pain responses using rat model systems. Moreover, we evaluated the effects of famotidine and mosapride on changes in gastric emptying and the GD-induced pain response to gastric acid hypersecretion. Gastric emptying was measured by excretion of glass beads that had been intragastrically administered with a liquid nutrient, and gastric pain response was evaluated by observing whether a GD-induced increase in mean blood pressure occurred.

KEY RESULTS

Pentagastrin (2 mg kg(-1), s.c.) which markedly and continuously stimulated gastric acid secretion, significantly delayed and enhanced respectively, gastric emptying and pain compared with saline-injected groups. Oral famotidine (0.1-3 mg kg(-1)) and mosapride (0.3-3 mg kg(-1)) administration in a dose-dependent manner accelerated the delay of gastric emptying. Furthermore, famotidine (0.3-3 mg kg(-1)) significantly alleviated the aggravation of the GD-induced pain response, but mosapride (10 mg kg(-1)) did not.

CONCLUSIONS & INFERENCES

We established rat models to evaluate the effect of gastric acid hypersecretion on gastric emptying and the GD-induced pain response. In these models, acid hypersecretion delayed gastric emptying and aggravated the pain response. Furthermore, we showed that famotidine ameliorated both delayed gastric emptying and gastric hypersensitivity, whereas mosapride only improved delayed gastric emptying.

Review article: cyclic vomiting syndrome in adults--rediscovering and redefining an old entity

BACKGROUND

Cyclic vomiting syndrome is a disorder characterised by recurrent episodes of severe nausea and vomiting separated by symptom-free periods.

AIMS

To review the history, epidemiology, clinical aspects, pathophysiology, diagnosis and treatments of adult cyclic vomiting syndrome as well as to identify areas for further clinical research and the unanswered questions in this field.

METHODS

We conducted a PubMed search using such keywords as cyclic vomiting syndrome; nausea; vomiting; pathophysiology; diagnosis; treatment; trigger factors; gastric emptying test; autonomic nerve function test; gastrointestinal hormones; outcome and natural history and combined this information with the knowledge and extensive clinical research and publications from the authors.

RESULTS

Available data show that in adult cyclic vomiting syndrome, severe epigastric and sometimes diffuse abdominal pain accompanies most cycles of nausea and vomiting interspersed with periods of symptomatic remission. Psychological disorders, specifically anxiety and depression are common, and gastric emptying is actually rapid in approximately 60% of patients and normal in the remainder. There is an impressive and sustained response to high-dose tricyclic antidepressants. In up to 15% who are regarded as poor responders to tricyclic antidepressants, a predictable profile can be identified related to co-existing psychological disorders, marijuana use, poorly controlled migraine headache or chronic narcotic use.

CONCLUSIONS

Cyclic vomiting syndrome in adults is an entity that is being increasingly recognised, but the need to educate Internists, Gastroenterologists and Emergency Department staff remains an ongoing challenge.

Pediatric cannabinoid hyperemesis: two cases

Cannabinoid hyperemesis has recently been described in the literature. It is a syndrome characterized by severe nausea and hyperemesis in the setting of chronic marijuana abuse and, to date, has been described only in adults. We describe the syndrome in 2 pediatric patients, for whom extensive gastrointestinal workups failed to identify a clear cause and cessation of marijuana use resulted in the alleviation of their symptoms. As in most published adult cases, compulsive bathing was present in both of these cases.

Spectrum of gastric emptying patterns in adult patients with cyclic vomiting syndrome

BACKGROUND

Cyclic vomiting syndrome (CVS) in adults is a disorder characterized by recurrent and stereotypic episodes of severe nausea, vomiting and abdominal pain separated by symptom-free intervals. Both rapid and delayed gastric emptying (GE) have been observed but the reports involved small numbers of CVS patients.

METHODS

We performed a retrospective study of 92 adult patients who met Rome Ш diagnostic criteria for CVS between 2003 and 2009 at the Kansas University Medical Center. Gastric emptying was measured by a standardized scintigraphic method involving a low fat (2%) isotope labeled egg white meal of 250 Kcal, with anterior and posterior gastric imaging in the standing position obtained at 0, 1, 2, 4 h after meal ingestion. Rapid GE was defined as <50% isotope retention at 1st h and/or <30% at 2nd h and delayed GE as >10% at 4 h.

KEY RESULTS

Ninety two patients were analyzed: 47 males and 45 females mean of age 37 ± 12 years (range: 20-68 years). There were 27 patients with a personal history of migraine headache, 30 with history of marijuana use, 12 had diabetes mellitus (DM) and 10 had irritable bowel syndrome (IBS) as an accompanying diagnosis. Fifty four patients (59%) met criteria for rapid GE, 25 (27%) had normal GE and 13 (14%) had slow GE. Eighty percent of patients with co-existing IBS symptoms were identified as rapid. The subset with delayed emptying was often associated with narcotics use, DM and marijuana use (P < 0.05).

CONCLUSIONS & INFERENCES

(i) In adult CVS patients, GE is generally either rapid or normal. (ii) Cyclic vomiting syndrome is an important new etiology to explain the finding of rapid GE on a radionuclide test. (iii) The small subset of CVS patients (14%) whose GE was slow were explained by the role of narcotics and/or marijuana.

The cannabis hyperemesis syndrome characterized by persistent nausea and vomiting, abdominal pain, and compulsive bathing associated with chronic marijuana use: a report of eight cases in the United States

GOALS/BACKGROUND

The cannabis hyperemesis syndrome, which is associated with chronic cannabis use, was recently reported in seven case reports and one clinical series of ten patients from Australia. We further characterize this syndrome with eight well-documented cases in the United States and report results of cannabis discontinuation and cannabis rechallenge.

STUDY METHODS

Patients were identified by the three investigators in gastroenterology clinic or inpatient wards at William Beaumont Hospital from January to August 2009 based on chronic cannabis use; otherwise unexplained refractory, recurrent vomiting; and compulsive bathing. Charts were retrospectively analyzed with follow-up data obtained from subsequent physician visits and patient interviews.

RESULTS

The eight patients on average were 32.4 ± 4.1 years old. Five were male. The mean interval between the onset of cannabis use and development of recurrent vomiting was 19.0 ± 3.7 years. Patients had a mean of 7.1 ± 4.3 emergency room visits, 5.0 ± 2.7 clinic visits, and 3.1 ± 1.9 admissions for this syndrome. All patients had visited at least one other hospital in addition to Beaumont Hospital. All patients had vomiting (mean vomiting episodes every 3.0 ± 1.7 h), compulsive bathing (mean = 5.0 ± 2.0 baths or showers/day; mean total bathing time = 5.0 ± 5.1 h/day), and abdominal pain. Seven patients took hot baths or showers, and seven patients experienced polydipsia. Four out of five patients who discontinued cannabis use recovered from the syndrome, while the other three patients who continued cannabis use, despite recommendations for cessation, continued to have this syndrome. Among those four who recovered, one patient had recurrence of vomiting and compulsive bathing with cannabis resumption.

CONCLUSIONS

Cannabis hyperemesis is characterized by otherwise unexplained recurrent nausea and vomiting, compulsive bathing, abdominal pain, and polydipsia associated with chronic cannabis use. This syndrome can occur in the United States as well as in Australia. Cannabis cessation may result in complete symptomatic recovery.

Cannabinoid hyperemesis

A 21-year-old woman presented with a 4-week history of sudden onset vomiting, nausea and anorexia. Questioning revealed that she had a 7-year history of heavy cannabis use (smoking). She did not describe abdominal pain, change in bowel habit, antibiotic use, foreign travel or contact with gastroenteritis. Biochemistry results demonstrated mild metabolic derangement with a low potassium and a low bicarbonate, and urine toxicology was positive for cannabinoids. Other investigations, including a full blood count, renal function tests, liver function tests, a coagulation sample, an ECG, urinary β-hCG and a CT head scan, were all normal. A diagnosis of cannabinoid hyperemesis was made and her symptoms resolved after treatment with intravenous fluids, antiemetics and abstinence from cannabis. Since her discharge and abstinence she has had several relapses, each related to cannabis use and each resolving with abstinence. The patient is now seeking cognitive behavioural therapy to achieve permanent abstinence.

Selective lack of tolerance to delayed gastric emptying after daily administration of WIN 55,212-2 in the rat

The use of cannabinoids to treat gastrointestinal (GI) motor disorders has considerable potential. However, it is not clear if tolerance to their actions develops peripherally, as it does centrally. The aim of this study was to examine the chronic effects of the cannabinoid agonist WIN 55,212-2 (WIN) on GI motility, as well as those in the central nervous and cardiovascular systems. WIN was administered for 14 days, at either non-psychoactive or psychoactive doses. Cardiovascular parameters were measured in anaesthetized rats, whereas central effects and alterations in GI motor function were assessed in conscious animals using the cannabinoid tetrad and non-invasive radiographic methods, respectively. Tests were performed after first (acute effects) and last (chronic effects) administration of WIN, and 1 week after discontinuing treatment (residual effects). Food intake and body weight were also recorded throughout treatment. Blood pressure and heart rate remained unchanged after acute or chronic administration of WIN. Central activity and GI motility were acutely depressed at psychoactive doses, whereas non-psychoactive doses only slightly reduced intestinal transit. Most effects were reduced after the last administration. However, delayed gastric emptying was not and could, at least partially, account for a concomitant reduction in food intake and body weight gain. The remaining effects of WIN administration in GI motility were blocked by the CB1 antagonist AM 251, which slightly accelerated motility when administered alone. No residual effects were found 1 week after discontinuing cannabinoid treatment. The different systems show differential sensitivity to cannabinoids and tolerance developed at different rates, with delayed gastric emptying being particularly resistant to attenuation upon chronic treatment.

Cannabinoid hyperemesis syndrome: Clinical diagnosis of an underrecognised manifestation of chronic cannabis abuse

Cannabis is a common drug of abuse that is associated with various long-term and short-term adverse effects. The nature of its association with vomiting after chronic abuse is obscure and is underrecognised by clinicians. In some patients this vomiting can take on a pattern similar to cyclic vomiting syndrome with a peculiar compulsive hot bathing pattern, which relieves intense feelings of nausea and accompanying symptoms. In this case report, we describe a twenty-two year-old-male with a history of chronic cannabis abuse presenting with recurrent vomiting, intense nausea and abdominal pain. In addition, the patient reported that the hot baths improved his symptoms during these episodes. Abstinence from cannabis led to resolution of the vomiting symptoms and abdominal pain. We conclude that in the setting of chronic cannabis abuse, patients presenting with chronic severe nausea and vomiting that can sometimes be accompanied by abdominal pain and compulsive hot bathing behaviour, in the absence of other obvious causes, a diagnosis of cannabinoid hyperemesis syndrome should be considered.

Pharmacotherapy of gastroparesis

Gastroparesis is a relatively common and often disabling condition that is characterized by a broad range of clinical presentation ranging from dyspeptic symptoms to nausea, vomiting, abdominal pain, malnutrition, frequent hospitalizations and incapacitation. The treatment of gastroparetic symptoms can be challenging to the gastroenterologist and the intensity of therapy varies with the physician's knowledge. Hence the determination that a patient is refractory to 'standard medical therapy' is an assessment that is subspeciality-based and could differ around the world depending on medications available. In this article, we review the use of available prokinetics, antiemetic agents, the approach for analgesia in the context of gastroparesis, and also discuss potential and evolving pharmacotherapies. The progress has been relatively limited as far as availability of new medications for gastroparesis is concerned; however, active research in developing newer prokinetics holds great promise for the future of management of this challenging entity.

Cannabinoid hyperemesis relieved by compulsive bathing

Cannabinoid hyperemesis is a clinical syndrome characterized by repeated vomiting and associated learned compulsive hot water bathing behavior due to long-term marijuana use. Research has identified type 1 cannabinoid receptors in the intestinal nerve plexus that have an inhibitory effect on gastrointestinal motility. This inhibitory effect may lead to hyperemesis in marijuana users. The thermoregulatory role of endocannabinoids may be responsible for the patient's need to take hot showers. We report 2 cases of cannabinoid hyperemesis that demonstrate this unusual adverse effect of marijuana use.

Cannabinoid hyperemesis relieved by compulsive bathing

Cannabinoid hyperemesis is a clinical syndrome characterized by repeated vomiting and associated learned compulsive hot water bathing behavior due to long-term marijuana use. Research has identified type 1 cannabinoid receptors in the intestinal nerve plexus that have an inhibitory effect on gastrointestinal motility. This inhibitory effect may lead to hyperemesis in marijuana users. The thermoregulatory role of endocannabinoids may be responsible for the patient's need to take hot showers. We report 2 cases of cannabinoid hyperemesis that demonstrate this unusual adverse effect of marijuana use.

Gastrointestinal endocannabinoid system: multifaceted roles in the healthy and inflamed intestine

1. The endogenous cannabinoid (endocannabinoid) system is emerging as a key modulator of intestinal physiology, influencing motility, secretion, epithelial integrity and immune function in the gut, in addition to influencing satiety and emesis. 2. Accumulating evidence suggests that the endocannabinoid system may play a pivotal role in the pathophysiology of gastrointestinal disease, particularly in the light of recent studies demonstrating an effect of endocannabinoids on the development of experimental inflammation and linkages with functional clinical disorders characterized by altered motility. 3. The predominant endocannabinoids, anandamide and 2-arachidonoylglycerol, not only mediate their effects via two recognized cannabinoid receptor subtypes, namely CB(1) and CB(2), but emerging evidence now shows they are also substrates for cyclo-oxygenase (COX)-2, generating a distinct and novel class of prostaglandin ethanolamides (prostamides) and prostaglandin glycerol esters. These compounds are bioactive and may mediate an array of biological effects distinct to those of conventional prostanoids. 4. The effects of prostamides on gastrointestinal motility, secretion, sensation and immune function have not been characterized extensively. Prostamides may play an important role in gastrointestinal inflammation, particularly given the enhanced expression of both COX-2 and endocannabinoids that occurs in the inflamed gut. 5. Further preclinical studies are needed to determine the therapeutic potential of drugs targeting the endocannabinoid system in functional and inflammatory gut disorders, to assist with the determination of feasibility for clinical translation.

Role of cannabinoid receptors in the control of gastrointestinal motility and perception

The identification of endocannabinoids and cannabinoid CB1 receptors in key areas of the intestinal wall, such as cholinergic neurons, supports a role for cannabinoids in the control of gastrointestinal motility. Activation of CB1 receptors inhibits the peristaltic reflex and slows down gastrointestinal and colonic transit. Endocannabinoids play an important inhibitory role in the control of the occurrence of transient lower esophageal sphincter relaxations. Cannabinoid receptor agonists inhibit gastric emptying and intestinal motility in humans. There is strong anatomical support for a role of CB1 receptors in the control of gastrointestinal perception, since these receptors have been identified in key sites of the neuronal circuitry involved in the transmission of visceral pain. Experimental data indicate a visceral antinociceptive action of cannabinoid receptor agonists, which remains to be confirmed in humans.

Cyclic vomiting and compulsive bathing with chronic cannabis abuse

Cannabis is commonly recognized for its antiemetic properties. However, chronic cannabis use can lead to paroxysmal vomiting. In some patients this vomiting can take on a pattern identical to cyclic vomiting syndrome. Interestingly cyclic vomiting syndrome has been associated with compulsive bathing which patients report can relieve their intense feelings of nausea and lessen their vomiting intensity. We report a case of a patient with chronic cannabis use who developed symptoms similar to cyclic vomiting syndrome who also engaged in compulsive bathing behavior as observed by members of the medical and nursing staff. The patient reported that frequent hot showers would prevent him from vomiting and also relieve his concomitant abdominal pain. Previous hospitalizations at our hospital for the same complaint also noted similar showering behavior. During the hospital stay, the patient agreed to engage in a outpatient drug rehabilitation program which he subsequently completed. Abstinence from cannabis use caused the patients vomiting symptoms and abdominal pain to disappear completely. Likewise, his compulsive showering behavior also ceased. Other investigators have reported similar findings in patients with cyclic vomiting syndrome who initially used cannabis to treat their vomiting episodes but subsequently found that it contributed to their vomiting. Our patient has lead us to conclude that in patients seen for chronic severe vomiting and abdominal pain which has no obvious structural or chemical etiology and which is accompanied by compulsive showering and/or bathing behavior a diagnosis of cyclic vomiting syndrome with concomitant cannabis abuse needs to be considered.

The role of endocannabinoids in the regulation of gastric emptying: alterations in mice fed a high-fat diet

BACKGROUND AND PURPOSE

Endocannabinoids (via cannabinoid CB(1) receptor activation) are physiological regulators of intestinal motility and food intake. However, their role in the regulation of gastric emptying is largely unexplored. The purpose of the present study was to investigate the involvement of the endocannabinoid system in the regulation of gastric emptying in mice fed either a standard diet (STD) or a high-fat diet (HFD) for 14 weeks.

EXPERIMENTAL APPROACH

Gastric emptying was evaluated by measuring the amount of phenol red recovered in the stomach after oral challenge; CB(1) expression was analysed by quantitative reverse transcription-PCR; endocannabinoid (anandamide and 2-arachidonoyl glycerol) levels were measured by liquid chromatography-mass spectrometry.

KEY RESULTS

Gastric emptying was reduced by anandamide, an effect counteracted by the CB(1) receptor antagonist rimonabant, but not by the CB(2) receptor antagonist SR144528 or by the transient receptor potential vanilloid type 1 (TRPV1) antagonist 5'-iodoresiniferatoxin. The fatty acid amide hydrolase (FAAH) inhibitor N-arachidonoyl-5-hydroxytryptamine (but not the anandamide uptake inhibitor OMDM-2) reduced gastric emptying in a way partly reduced by rimonabant. Compared to STD mice, HFD mice exhibited significantly higher body weight and fasting glucose levels, delayed gastric emptying and lower anandamide and CB(1) mRNA levels. N-arachidonoylserotonin (but not rimonabant) affected gastric emptying more efficaciously in HFD than STD mice.

CONCLUSIONS AND IMPLICATIONS

Gastric emptying is physiologically regulated by the endocannabinoid system, which is downregulated following a HFD leading to overweight.

Cannabinoid CB(1) receptor activation modulates spontaneous contractile activity in mouse ileal longitudinal muscle

The purpose of the present study was to examine whether cannabinoid receptor agonists influence spontaneous contractile activity of longitudinal muscle in mouse ileum in vitro. Isolated segments of mouse ileum displayed spontaneous contractions with an amplitude and frequency of about 300 mg and 30 cpm, respectively. The endocannabinoid anandamide (1-100 microM), the selective cannabinoid CB(1) receptor agonist, ACEA (0.1 microM-10 microM), but not the selective cannabinoid CB(2) receptor agonist, JWH 133 (0.1 microM-10 microM), reduced in a concentration-dependent manner the spontaneous mechanical activity. The inhibitory effect consisted in a decrease of the mean amplitude of longitudinal spontaneous contractions, without changes in the resting tone. The inhibitory effect induced by cannabinoids was significantly antagonized by the selective cannabinoid CB(1) receptor antagonist, SR141716A (0.1 microM), but not by the selective cannabinoid CB(2) receptor antagonist, AM630 (0.1 microM). None of the cannabinoid antagonists, at the concentration used, did affect the spontaneous mechanical activity. The ACEA-induced reduction of spontaneous contractions was almost abolished by tetrodotoxin, atropine or apamin and it was unaffected by hexamethonium or N(omega)-nitro-l-arginine methyl ester (l-NAME), inhibitor of nitric oxide synthase. The myogenic contractions evoked by carbachol were not affected by ACEA. In conclusion, the present results suggest that activation of neural cannabinoid CB(1) receptors may play a role in the control of spontaneous mechanical activity through inhibition of acetylcholine release from cholinergic nerve. Activation of small conductance Ca(2+)-dependent K(+) channels is involved in this action.

Involvement of CB1 and CB2 receptors in the modulation of cholinergic neurotransmission in mouse gastric preparations

While most of the studies concerning the role of cannabinoids on gastric motility have focused the attention on the gastric emptying in in vivo animal models, there is little information about the cannabinoid peripheral influence in the stomach. In addition, the functional features of CB2 receptors in the gastrointestinal tract have been poorly characterized. The purpose of the present study was to investigate the effects of cannabinoid drugs on the excitatory cholinergic and inhibitory non-adrenergic non-cholinergic (NANC) neurotransmission in mouse isolated gastric preparations. Intraluminal pressure from isolated whole stomach was recorded and mechanical responses induced by electrical field stimulation (EFS) were analyzed in different experimental conditions. EFS (0.5ms duration, supramaximal voltage, in trains of 5s, 2-16Hz) caused a cholinergic contraction, which was abolished by atropine or tetrodotoxin (TTX). The cannabinoid receptor agonist, WIN 55,212-2, the endogenous ligand, anandamide, the selective CB1 receptor agonist ACEA, and the selective CB2 receptor agonists, JWH015 and JWH133, produced a concentration-dependent reduction of the EFS-evoked cholinergic contractions. SR141716A, CB1 receptor antagonist, significantly attenuated the inhibitory effects induced by WIN 55,212-2, anandamide or ACEA, without affecting those caused by JWH133. AM630, CB2 receptor antagonist, reduced the inhibitory effects induced by WIN 55,212-2, anandamide, JWH015 or JWH133, without affecting those caused by ACEA. The joint application of SR141716A and AM630 was able of fully preventing the WIN 55,212-2 and anandamide actions. The cannabinoid antagonists failed per se to affect the neurally evoked responses. Cannabinoids did not modify the contractions produced by exogenous carbachol. In the presence of atropine and guanethidine (NANC conditions) EFS-induced TTX-sensitive relaxation consisting in an early and rapid component followed by a second slow phase, which were unaffected by cannabinoid drugs. In conclusion, the present results suggest that cannabinoids play a prejunctional modulatory role on the cholinergic excitatory transmission without affecting the NANC inhibitory transmission. In addition, this study provides experimental evidence that also the activation of CB2 receptors is able to reduce cholinergic neurotransmission in the mouse stomach.

Clinical, psychiatric and manometric profile of cyclic vomiting syndrome in adults and response to tricyclic therapy

Our goal was to investigate 31 adult patients (mean age 29 years, range 18-62 years) meeting Rome II criteria for cyclic vomiting syndrome (CVS). All subjects completed a clinical questionnaire, a Hamilton Rating Scale for Anxiety (HAM-A) and Zung Depression Inventory. Gastric emptying time was assessed in 30 subjects and electrogastrogram (EGG) in 11 between acute attacks. Twenty-seven patients treated with amitriptyline completed a follow-up questionnaire. The mean age of onset of the patients was 30 years (range 14-53 years) and cycles of nausea and vomiting were accompanied by often-severe epigastric and diffuse abdominal pain. A typical attack ranged from 1 to 14 days, with the majority being 4-6 days. The HAM-A revealed that 84% had an anxiety disorder, and based on Zung Depression Inventory 78% suffered from mild-to-severe depression. Only 4 (13%) patients reported migraine, but 14 had a family history of migraine. Gastric emptying time was rapid in 23 (77%), normal in 4 and delayed in 3. The EGG was abnormal in 7 of 11 patients, with 4 having tachygastria. Of 13 patients using marijuana, 7 had symptom relief, while 2 had resolution of CVS after stopping use. The overall treatment experience in the 24 patients receiving amitriptyline up to 1 mg kg(-1) day(-1) for at least 3 months indicated that 93% had decreased symptoms and 26% achieved full remission. Cyclic vomiting syndrome in adults has the following hallmarks: prominence of accompanying abdominal pain and increased prevalence of anxiety and depression, rapid gastric emptying and tachygastric EGG, and successful suppression of attacks by chronic amitriptyline therapy.

Effect of a cannabinoid agonist on gastrointestinal transit and postprandial satiation in healthy human subjects: a randomized, placebo-controlled study

Cannabinoid receptor (CBR) stimulation inhibits motility and increases food intake in rodents. Effects of CBR stimulation in human gastrointestinal (GI) tract are unclear. We compared effects of dronabinol (DRO) and placebo (PLA) on GI transit, gastric volume and satiation in humans. In a double-blind, randomized study, 30 healthy volunteers were randomly assigned to DRO 5 mg b.i.d. or PLA for three doses. We measured GI functions noninvasively: day 0, Ensure satiation test to measure maximum tolerated volume (MTV) and 30-min post-Ensure symptoms; day 1, scintigraphic transit ((111)In-egg meal) and fasting and postprandial gastric volume ((99Tcm)-SPECT); day 2, 24-h colonic transit and repeat satiation test. ancova was used to compare treatment groups with gender, age, and, for the satiation test, the baseline MTV, as covariates. A log-rank test was used to assess treatment effects on gastric emptying. Planned sample size had 80% power to detect 25-30% differences in primary end points. There was an overall retardation of gastric emptying with DRO (P = 0.018); this was more pronounced in females (P = 0.011), than in males (P = 0.184). No significant treatment differences were detected for gastric volumes, MTV, post-Ensure(R) symptoms, small bowel and colonic transit. Fasting gastric volume was greater in males receiving DRO compared with PLA (238 +/- 17 vs 185 +/- 16, P = 0.04). DRO retards gastric emptying in humans; effects are gender-related. Dronabinol also increases fasting gastric volumes in males.

Advances in anti-obesity therapeutics

Obesity is rapidly becoming an epidemic in developed countries. Currently available anti-obesity therapeutics are only modestly effective and are accompanied by significant adverse effects. In recent years, substantial advances have been made in the basic understanding of brain control of feeding behaviour and metabolism. As a result, several compounds have progressed to Phase III development, with additional compounds at various stages of Phase II development. Most of the late-stage development candidates are CNS agents, which reflects the consensus that the brain exerts a dominant control on feeding behaviour and peripheral metabolism through the autonomic nervous system. Homeostatic mechanisms encompassing hypothalamic/brainstem pathways have long been recognised in obesity research. In addition, non-homeostatic mechanisms encompassing the reward circuit and volitional control need to be targeted to control feeding behaviour and physical activity, especially in humans. While recognising the importance of CNS control, certain peripherally acting agents can affect mitochondrial metabolism, lipolysis, nutrient absorption or the vagal feedback pathway, such that these peripherally acting agents can potentially be combined with CNS agents to achieve maximal efficacy. It is expected that newer generations of anti-obesity therapeutics will be superior to existing agents and will facilitate lifestyle modification.

Treatment of gastroparesis: a multidisciplinary clinical review

This clinical review on the treatment of patients with gastroparesis is a consensus document developed by the American Motility Society Task Force on Gastroparesis. It is a multidisciplinary effort with input from gastroenterologists and other specialists who are involved in the care of patients with gastroparesis. To provide practical guidelines for treatment, this document covers results of published research studies in the literature and areas developed by consensus agreement where clinical research trials remain lacking in the field of gastroparesis.

Pharmacological and pharmacokinetic aspects of functional gastrointestinal disorders

Medications are commonly used for the treatment of patients with functional gastrointestinal disorders. The general goal of this report is to review the pharmacokinetics and pharmacology of medications used in functional gastrointestinal disorders. Methods included literature review, consensus evaluation of the evidence for each topic assigned originally to 1 or 2 authors, and broader review at a harmonization session as part of the Rome III process. This report reviews the animal models that have been validated for the study of effects of pharmacologic agents on sensation and motility; the preclinical pharmacology, pharmacokinetics, and toxicology usually required for introduction of novel therapeutic agents; the biomarkers validated for studies of sensation and motility end points with experimental medications in humans; the pharmacogenomics applied to these medications and disorders; and the pharmacology of agents that are applied or have potential for treatment of functional gastrointestinal disorders, including psychopharmacologic agents. Clinician and basic investigators involved in the treatment or investigation of functional gastrointestinal disorders or disease models need to have a comprehensive understanding of a vast range of medications. It is anticipated that the interaction between investigators of basic science, basic and applied pharmacology, and clinical trials will lead to better treatment of these disorders.

The endocannabinoid system in the physiology and pathophysiology of the gastrointestinal tract

Numerous investigations have recently demonstrated the important roles of the endocannabinoid system in the gastrointestinal (GI) tract under physiological and pathophysiological conditions. In the GI tract, cannabinoid type 1 (CB1) receptors are present in neurons of the enteric nervous system and in sensory terminals of vagal and spinal neurons, while cannabinoid type 2 receptors are located in immune cells. Activation of CB1 receptors was shown to modulate several functions in the GI tract, including gastric secretion, gastric emptying and intestinal motility. Under pathophysiological conditions induced experimentally in rodents, the endocannabinoid system conveys protection to the GI tract (e.g. from inflammation and abnormally high gastric and enteric secretions). Such protective activities are largely in agreement with anecdotal reports from folk medicine on the use of Cannabis sativa extracts by subjects suffering from various GI disorders. Thus, the endocannabinoid system may serve as a potentially promising therapeutic target against different GI disorders, including frankly inflammatory bowel diseases (e.g. Crohn's disease), functional bowel diseases (e.g. irritable bowel syndrome) and secretion- and motility-related disorders. As stimulation of this modulatory system by CB1 receptor agonists can lead to unwanted psychotropic side effects, an alternative and promising avenue for therapeutic applications resides in the treatment with CB1 receptor agonists that are unable to cross the blood-brain barrier, or with compounds that inhibit the degradation of endogenous ligands (endocannabinoids) of CB1 receptors, hence prolonging the activity of the endocannabinoid system.

Cannabinoids and the digestive tract

In the digestive tract there is evidence for the presence of high levels of endocannabinoids (anandamide and 2-arachidonoylglycerol) and enzymes involved in the synthesis and metabolism of endocannabinoids. Immunohistochemical studies have shown the presence of CB1 receptors on myenteric and submucosal nerve plexuses along the alimentary tract. Pharmacological studies have shown that activation of CB1 receptors produces relaxation of the lower oesophageal sphincter, inhibition of gastric motility and acid secretion, as well as intestinal motility and secretion. In general, CB1-induced inhibition of intestinal motility and secretion is due to reduced acetylcholine release from enteric nerves. Conversely, endocannabinoids stimulate intestinal primary sensory neurons via the vanilloid VR1 receptor, resulting in enteritis and enhanced motility. The endogenous cannabinoid system has been found to be involved in the physiological control of colonic motility and in some pathophysiological states, including paralytic ileus, intestinal inflammation and cholera toxin-induced diarrhoea. Cannabinoids also possess antiemetic effects mediated by activation of central and peripheral CB1 receptors. Pharmacological modulation of the endogenous cannabinoid system could provide a new therapeutic target for the treatment of a number of gastrointestinal diseases, including nausea and vomiting, gastric ulcers, secretory diarrhoea, paralytic ileus, inflammatory bowel disease, colon cancer and gastro-oesophageal reflux conditions.

Involvement of cannabinoid receptors in gut motility and visceral perception

From a historical perspective to the present day, all the evidence suggests that activation of cannabinoid receptors (CBRs) is beneficial for gut discomfort and pain, which are symptoms related to dysmotility and visceral perception. CBRs comprise G-protein coupled receptors that are predominantly in enteric and central neurones (CB1R) and immune cells (CB2R). In the last decade, evidence obtained from the use of selective agonists and inverse agonists/antagonists indicates that manipulation of CB1R can alter (1) sensory processing from the gut, (2) brain integration of brain-gut axis, (3) extrinsic control of the gut and (4) intrinsic control by the enteric nervous system. The extent to which activation of CB1R is most critical at these different levels is related to the region of the GI tract. The upper GI tract is strongly influenced by CB1R activation on central vagal pathways, whereas intestinal peristalsis can be modified by CB1R activation in the absence of extrinsic input. Actions at multiple levels make the CB1R a target for the treatment of functional bowel disorders, such as IBS. Since low-grade inflammation may act as a trigger for occurrence of IBS, CB2R modulation could be beneficial, but there is little supporting evidence for this yet. The challenge is to accomplish CBR activation while minimizing adverse effects and abuse liabilities. Potential therapeutic strategies involve increasing signaling by endocannabinoids (EC). The pathways involved in the biosynthesis, uptake and degradation of EC provide opportunities for modulation of CB1R and some recent evidence with inhibitors of EC uptake and metabolism suggest that these could be exploited for therapeutic gain.

Pharmacokinetics and pharmacodynamics of cannabinoids

Delta(9)-Tetrahydrocannabinol (THC) is the main source of the pharmacological effects caused by the consumption of cannabis, both the marijuana-like action and the medicinal benefits of the plant. However, its acid metabolite THC-COOH, the non-psychotropic cannabidiol (CBD), several cannabinoid analogues and newly discovered modulators of the endogenous cannabinoid system are also promising candidates for clinical research and therapeutic uses. Cannabinoids exert many effects through activation of G-protein-coupled cannabinoid receptors in the brain and peripheral tissues. Additionally, there is evidence for non-receptor-dependent mechanisms. Natural cannabis products and single cannabinoids are usually inhaled or taken orally; the rectal route, sublingual administration, transdermal delivery, eye drops and aerosols have only been used in a few studies and are of little relevance in practice today. The pharmacokinetics of THC vary as a function of its route of administration. Pulmonary assimilation of inhaled THC causes a maximum plasma concentration within minutes, psychotropic effects start within seconds to a few minutes, reach a maximum after 15-30 minutes, and taper off within 2-3 hours. Following oral ingestion, psychotropic effects set in with a delay of 30-90 minutes, reach their maximum after 2-3 hours and last for about 4-12 hours, depending on dose and specific effect. At doses exceeding the psychotropic threshold, ingestion of cannabis usually causes enhanced well-being and relaxation with an intensification of ordinary sensory experiences. The most important acute adverse effects caused by overdosing are anxiety and panic attacks, and with regard to somatic effects increased heart rate and changes in blood pressure. Regular use of cannabis may lead to dependency and to a mild withdrawal syndrome. The existence and the intensity of possible long-term adverse effects on psyche and cognition, immune system, fertility and pregnancy remain controversial. They are reported to be low in humans and do not preclude legitimate therapeutic use of cannabis-based drugs. Properties of cannabis that might be of therapeutic use include analgesia, muscle relaxation, immunosuppression, sedation, improvement of mood, stimulation of appetite, antiemesis, lowering of intraocular pressure, bronchodilation, neuroprotection and induction of apoptosis in cancer cells.

Cannabinoids for gastrointestinal diseases: potential therapeutic applications

Delta(9)-Tetrahydrocannabinol (the active ingredient of marijuana), as well as endogenous and synthetic cannabinoids, exert many biological functions by activating two types of cannabinoid receptors, CB(1) and CB(2) receptors. CB(1) receptors have been detected on enteric nerves, and pharmacological effects of their activation include gastroprotection, reduction of gastric and intestinal motility and reduction of intestinal secretion. The digestive tract also contains endogenous cannabinoids (i.e., the endocannabinoids anandamide and 2-aracidonylglycerol) and mechanisms for endocannabinoid inactivation (i.e., endocannabinoids uptake and enzymatic degradation). Cannabinoid receptors, endocannabinoids and the proteins involved in endocannabinoids inactivation are collectively referred as the 'endogenous cannabinoid system'. A pharmacological modulation of the endogenous cannabinoid system could provide new therapeutics for the treatment of a number of gastrointestinal diseases, including nausea and vomiting, gastric ulcers, irritable bowel syndrome, Crohn's disease, secretory diarrhoea, paralytic ileus and gastroesophageal reflux disease. Some cannabinoids are already in use clinically, for example, nabilone and delta(9)-tetrahydrocannabinol are used as antiemetics.

Central neurocircuitry associated with emesis

Ingestion of toxin, traumatic events, adverse drug reactions, and motion can all result in nausea and emesis. In addition, cyclic vomiting syndrome is quite prevalent in the pediatric population. Coordination of the various autonomic changes associated with emesis occurs at the level of the medulla oblongata of the hindbrain. Chemosensitive receptors detect emetic agents in the blood and relay this information by means of neurons in the area postrema to the adjacent nucleus tractus solitarius (NTS). Abdominal vagal afferents that detect intestinal luminal contents and gastric tone also terminate in the NTS (gelatinosus, commissural, and medial subnuclei). The NTS is viscerotopically organized into subnuclei that subserve diverse functions related to swallowing (subnucleus centralis), gastric sensation (subnucleus gelatinosus), laryngeal and pharyngeal sensation (intermediate and interstitial NTS), baroreceptor function (medial NTS), and respiration (ventrolateral NTS). Neurons from the NTS project to a central pattern generator (CPG), which coordinates the sequence of behaviors during emesis, as well as directly to diverse populations of neurons in the ventral medulla and hypothalamus. Thus, it is critical to realize that there is not an isolated "vomiting center," but rather groups of loosely organized neurons throughout the medulla that may be activated in sequence by a CPG. The newer antiemetic agents appear to block receptors in the peripheral endings of vagal afferents to reduce "perception" of emetic stimuli and/or act in the dorsal vagal complex. A primary site of action of 5-HT(3)-receptor antagonists is by means of the vagal afferents. Neurokinin-1 receptor (NK(1)R) antagonists are antiemetics, because they act at a site in the dorsal vagal complex. Part of their effectiveness may be the result of inhibition of the NK(1)R on vagal motor neurons to prevent fundic relaxation, which is a prodromal event essential for emesis. Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the major psychoactive component of marijuana, can be therapeutically useful as an antiemetic. The site of action of Delta(9)-THC is on cannabinoid CB1 receptors in the dorsal vagal complex. However, it decreases fundic tone and antral motility. It is not easy to predict the potential antiemetic effects of drugs that alter motility. Although antiemetic drugs are available for management of acute chemotherapeutic-induced emesis, few treatments are effective for delayed emesis or cyclic vomiting syndrome.

Cannabinoids and the gastrointestinal tract

The enteric nervous system of several species, including the mouse, rat, guinea pig and humans, contains cannabinoid CB1 receptors that depress gastrointestinal motility, mainly by inhibiting ongoing contractile transmitter release. Signs of this depressant effect are, in the whole organism, delayed gastric emptying and inhibition of the transit of non-absorbable markers through the small intestine and, in isolated strips of ileal tissue, inhibition of evoked acetylcholine release, peristalsis, and cholinergic and non-adrenergic non-cholinergic (NANC) contractions of longitudinal or circular smooth muscle. These are contractions evoked electrically or by agents that are thought to stimulate contractile transmitter release either in tissue taken from morphine pretreated animals (naloxone) or in unpretreated tissue (gamma-aminobutyric acid and 5-hydroxytryptamine). The inhibitory effects of cannabinoid receptor agonists on gastric emptying and intestinal transit are mediated to some extent by CB1 receptors in the brain as well as by enteric CB1 receptors. Gastric acid secretion is also inhibited in response to CB1 receptor activation, although the detailed underlying mechanism has yet to be elucidated. Cannabinoid receptor agonists delay gastric emptying in humans as well as in rodents and probably also inhibit human gastric acid secretion. Cannabinoid pretreatment induces tolerance to the inhibitory effects of cannabinoid receptor agonists on gastrointestinal motility. Findings that the CB1 selective antagonist/inverse agonist SR141716A produces in vivo and in vitro signs of increased motility of rodent small intestine probably reflect the presence in the enteric nervous system of a population of CB1 receptors that are precoupled to their effector mechanisms. SR141716A has been reported not to behave in this manner in the myenteric plexus-longitudinal muscle preparation (MPLM) of human ileum unless this has first been rendered cannabinoid tolerant. Nor has it been found to induce "withdrawal" contractions in cannabinoid tolerant guinea pig ileal MPLM. Further research is required to investigate the role both of endogenous cannabinoid receptor agonists and of non-CB1 cannabinoid receptors in the gastrointestinal tract. The extent to which the effects on gastrointestinal function of cannabinoid receptor agonists or antagonists/inverse agonists can be exploited therapeutically has yet to be investigated as has the extent to which these drugs can provoke unwanted effects in the gastrointestinal tract when used for other therapeutic purposes.

Gastroduodenal motility

Several major themes emerged over the past year in the area of gastroduodenal motility. Mostly, these themes represented extensions of research areas discussed in prior reviews in this series rather than the emergence of completely new concepts. Thus, for example, considerable emphasis has again been placed on regional gastric motor function in dyspepsia and on the role of fundic relaxation and accommodation, in particular. Not surprisingly, basic physiologic research has also shown a keen interest in the regulation of fundic relaxation. One new and exciting development is the recognition of the stomach's role in satiety. The spectrum of gastric motor dysfunction in diabetes mellitus continues to be explored, and the important role of hyperglycemia in regulating gastric function has been further emphasized. More data have been provided on noninvasive alternatives to gastric motor function testing, and several studies have looked at factors that may influence variability in these various tests. There have been few innovations over the past year in the therapeutic arena; rather, the indications and limitations of current therapies have been further developed.