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

The Enteric Glia and Its Modulation by the Endocannabinoid System, a New Target for Cannabinoid-Based Nutraceuticals?

The enteric nervous system (ENS) is a part of the autonomic nervous system that intrinsically innervates the gastrointestinal (GI) tract. Whereas enteric neurons have been deeply studied, the enteric glial cells (EGCs) have received less attention. However, these are immune-competent cells that contribute to the maintenance of the GI tract homeostasis through supporting epithelial integrity, providing neuroprotection, and influencing the GI motor function and sensation. The endogenous cannabinoid system (ECS) includes endogenous classical cannabinoids (anandamide, 2-arachidonoylglycerol), cannabinoid-like ligands (oleoylethanolamide (OEA) and palmitoylethanolamide (PEA)), enzymes involved in their metabolism (FAAH, MAGL, COX-2) and classical (CB1 and CB2) and non-classical (TRPV1, GPR55, PPAR) receptors. The ECS participates in many processes crucial for the proper functioning of the GI tract, in which the EGCs are involved. Thus, the modulation of the EGCs through the ECS might be beneficial to treat some dysfunctions of the GI tract. This review explores the role of EGCs and ECS on the GI tract functions and dysfunctions, and the current knowledge about how EGCs may be modulated by the ECS components, as possible new targets for cannabinoids and cannabinoid-like molecules, particularly those with potential nutraceutical use.

Cannabinoid drugs against chemotherapy-induced adverse effects: focus on nausea/vomiting, peripheral neuropathy and chemofog in animal models

Although new drugs are being developed for cancer treatment, classical chemotherapeutic agents are still front-line therapies, despite their frequent association with severe side effects that can hamper their use. Cannabinoids may prevent or palliate some of these side effects. The aim of the present study is to review the basic research which has been conducted evaluating the effects of cannabinoid drugs in the treatment of three important side effects induced by classical chemotherapeutic agents: nausea and vomiting, neuropathic pain and cognitive impairment. Several published studies have demonstrated that cannabinoids are useful in preventing and reducing the nausea, vomits and neuropathy induced by different chemotherapy regimens, though other side effects can occur, such as a reduction of gastrointestinal motility, along with psychotropic effects when using centrally-acting cannabinoids. Thus, peripherally-acting cannabinoids and new pharmacological options are being investigated, such as allosteric or biased agonists. Additionally, due to the increase in the survival of cancer patients, there are emerging data that demonstrate an important cognitive deterioration due to chemotherapy, and because the cannabinoid drugs have a neuroprotective effect, they could be useful in preventing chemotherapy-induced cognitive impairment (as demonstrated through studies in other neurological disorders), but this has not yet been tested. Thus, although cannabinoids seem a promising therapeutic approach in the treatment of different side effects induced by chemotherapeutic agents, future research will be necessary to find pharmacological options with a safer profile. Moreover, a new line of research awaits to be opened to elucidate their possible usefulness in preventing cognitive impairment.

Gastroparesis with Cannabis Use: A Retrospective Study from the Nationwide Inpatient Sample

Background: With increasing utilization of cannabis in the United States (US), clinicians may encounter more cases of Gastroparesis (GP) in coming years.Objective: The primary outcome was inpatient mortality for GP with cannabis use. Secondary outcomes included system-based complications and the burden of the disease on the US healthcare system.Methods: From the Nationwide Inpatient Sample (NIS), we identified adult hospitalizations with a primary discharge diagnosis of GP for 2016 and 2017. Individuals ≤18 years of age were excluded. The study population was subdivided based on a secondary diagnosis of cannabis use. The outcomes included biodemographic characteristics, mortality, complications, and burden of disease on the US healthcare system.Results: For 2016 and 2017, we identified 99,695 hospitalizations with GP. Of these hospitalizations, 8,870 had a secondary diagnosis of cannabis use while 90,825 served as controls. The prevalence of GP with cannabis use was 8.9%. For GP with cannabis use, the patients were younger (38.5 vs 48.1 years, p < 0.001) with a Black predominance (Table 1) and lower proportion of females (52.3 vs 68.3%, p < 0.001) compared to the non-cannabis use cohort. Additionally, the cannabis use cohort had higher percentage of patients with co-morbidities like hypertension, diabetes mellitus and a history of smoking. The inpatient mortality for GP with cannabis use was noted to be 0.27%. Furthermore, we noted shorter mean length of stay (LOS) (3.4 vs 4.4 days, aMD: -0.7, 95%CI: -0.9 - [-0.5], p < 0.001), lower mean total hospital charge (THC) ($30,400 vs $38,100, aMD: -5100, 95%CI: -6900 - [-3200], p < 0.001), and lower rates of sepsis (0.11 vs 0.60%, aOR: 0.22, 95% CI: 0.05-0.91, p = 0.036) for GP hospitalizations with cannabis use compared to the non-cannabis use cohort.Conclusion: Inpatient mortality for GP hospitalizations with cannabis use was 0.27%. Additionally, these patients had shorter LOS, lower THC, and lower sepsis rates.

Role of the stress response and the endocannabinoid system in Δ9-tetrahydrocannabinol (THC)-induced nausea

RATIONALE

Dysregulation of the endocannabinoid (eCB) system by high doses of Δ⁹-tetrahydrocannabinol (THC) is hypothesized to generate a dysfunctional hypothalamic-pituitary-adrenal (HPA) axis contributing to cannabinoid hyperemesis syndrome (CHS).

OBJECTIVES AND METHODS

Using the conditioned gaping model of nausea, we aimed to determine if pre-treatments that interfere with stress, or an anti-emetic drug, interfere with THC-induced nausea in male rats. The corticotropin-releasing hormone (CRH) antagonist, antalarmin, was given to inhibit the HPA axis during conditioning. Since eCBs inhibit stress, MJN110 (which elevates 2-arachidonylglycerol (2-AG)) and URB597 (which elevates anandamide (AEA)) were also tested. Propranolol (β-adrenergic antagonist) and WAY-100635 (5-HT_1A antagonist) attenuate HPA activation by cannabinoids and, therefore, were assessed. In humans, CHS symptoms are not alleviated by anti-emetic drugs, such as ondansetron (5-HT₃ antagonist); however, benzodiazepines are effective. Therefore, ondansetron and chlordiazepoxide were tested. To determine if HPA activation by THC is dose-dependent, corticosterone (CORT) was analyzed from serum of rats treated with 0.0, 0.5, or 10 mg/kg THC.

RESULTS

Antalarmin (10 and 20 mg/kg), MJN110 (10 mg/kg), URB597 (0.3 mg/kg), propranolol (2.5 and 5 mg/kg), WAY-100635 (0.5 mg/kg), and chlordiazepoxide (5 mg/kg) interfered with THC-induced conditioned gaping, but the anti-emetic ondansetron (0.1 and 0.01 mg/kg) did not. THC produced significantly higher CORT levels at 10 mg/kg than at 0.0 and 0.5 mg/kg THC.

CONCLUSIONS

Treatments that interfere with the stress response also inhibit THC-induced conditioned gaping, but a typical anti-emetic drug does not, supporting the hypothesis that THC-induced nausea, and CHS, is a result of a dysregulated stress response.

Targeting the Endocannabinoid CB1 Receptor to Treat Body Weight Disorders: A Preclinical and Clinical Review of the Therapeutic Potential of Past and Present CB1 Drugs

Obesity rates are increasing worldwide and there is a need for novel therapeutic treatment options. The endocannabinoid system has been linked to homeostatic processes, including metabolism, food intake, and the regulation of body weight. Rimonabant, an inverse agonist for the cannabinoid CB1 receptor, was effective at producing weight loss in obese subjects. However, due to adverse psychiatric side effects, rimonabant was removed from the market. More recently, we reported an inverse relationship between cannabis use and BMI, which has now been duplicated by several groups. As those results may appear contradictory, we review here preclinical and clinical studies that have studied the impact on body weight of various cannabinoid CB1 drugs. Notably, we will review the impact of CB1 inverse agonists, agonists, partial agonists, and neutral antagonists. Those findings clearly point out the cannabinoid CB1 as a potential effective target for the treatment of obesity. Recent preclinical studies suggest that ligands targeting the CB1 may retain the therapeutic potential of rimonabant without the negative side effect profile. Such approaches should be tested in clinical trials for validation.

Cannabinoid Hyperemesis Syndrome: A Review of Potential Mechanisms

Introduction: Cannabinoids have long been known for their ability to treat nausea and vomiting. Recent reports, however, have highlighted the paradoxical proemetic effects of cannabinoids. Cannabinoid hyperemesis syndrome (CHS) is characterized by cyclical episodes of nausea and vomiting, accompanied by abdominal pain following prolonged, high-dose cannabis use, which is alleviated by hot baths and showers. Little is known about the cause of this syndrome. Discussion: Cannabinoids produce a biphasic effect on nausea and vomiting, with low doses having an antiemetic effect and high doses producing emesis. Presentation and treatment of CHS are similar to cyclical vomiting syndrome as well as chemotherapy-related anticipatory nausea and vomiting, suggesting that these phenomena may share mechanisms. The prevalence of CHS is not known because of the symptomatic overlap with other disorders and the lack of knowledge of the syndrome by the public and physicians. Treatment with typical antiemetic drugs is ineffective for CHS, but anxiolytic and sedative drugs, along with hot showers, seem to be consistently effective at reducing symptoms. The only known way to permanently end CHS, however, is abstinence from cannabinoids. Case studies and limited pre-clinical data on CHS indicate that prolonged high doses of the main psychotropic compound in cannabis, Δ9-tetrahydrocannabinol (THC), result in changes to the endocannabinoid system by acting on the cannabinoid 1 (CB1) receptor. These endocannabinoid system changes can dysregulate stress and anxiety responses, thermoregulation, the transient receptor potential vanilloid system, and several neurotransmitters systems, and are thus potential candidates for mediating the pathophysiology of CHS. Conclusions: Excessive cannabinoid administration disrupts the normal functioning of the endocannabinoid system, which may cause CHS. More clinical and pre-clinical research is needed to fully understand the underlying pathophysiology of this disorder and the negative consequences of prolonged high-dose cannabis use.

Cannabidiol and Other Non-Psychoactive Cannabinoids for Prevention and Treatment of Gastrointestinal Disorders: Useful Nutraceuticals?

Cannabis sativa is an aromatic annual flowering plant with several botanical varieties, used for different purposes, like the production of fibers, the production of oil from the seeds, and especially for recreational or medical purposes. Phytocannabinoids (terpenophenolic compounds derived from the plant), include the well-known psychoactive cannabinoid Δ9-tetrahydrocannabinol, and many non-psychoactive cannabinoids, like cannabidiol. The endocannabinoid system (ECS) comprises of endocannabinoid ligands, enzymes for synthesis and degradation of such ligands, and receptors. This system is widely distributed in the gastrointestinal tract, where phytocannabinoids exert potent effects, particularly under pathological (i.e., inflammatory) conditions. Herein, we will first look at the hemp plant as a possible source of new functional food ingredients and nutraceuticals that might be eventually useful to treat or even prevent gastrointestinal conditions. Subsequently, we will briefly describe the ECS and the general pharmacology of phytocannabinoids. Finally, we will revise the available data showing that non-psychoactive phytocannabinoids, particularly cannabidiol, may be useful to treat different disorders and diseases of the gastrointestinal tract. With the increasing interest in the development of functional foods for a healthy life, the non-psychoactive phytocannabinoids are hoped to find a place as nutraceuticals and food ingredients also for a healthy gastrointestinal tract function.

Radiographic dose-dependency study of loperamide effects on gastrointestinal motor function in the rat. Temporal relationship with nausea-like behavior

BACKGROUND

Loperamide is a potent mu opioid receptor agonist available over the counter to treat diarrhea. Although at therapeutic doses loperamide is devoid of central effects, it may exert them if used at high doses or combined with drugs that increase its systemic and/or central bioavailability. Recently, public health and scientific interest on loperamide has increased due to a growing trend of misuse and abuse, and consequent reports on its toxicity. Our aim was to evaluate in the rat the effects of increasing loperamide doses, with increasing likelihood to induce central effects, on gastrointestinal motor function (including gastric dysmotility and nausea-like behavior).

METHODS

Male Wistar rats received an intraperitoneal injection of vehicle or loperamide (0.1, 1, or 10 mg kg^-1 ). Three sets of experiments were performed to evaluate: (a) central effects (somatic nociceptive thresholds, immobility time, core temperature, spontaneous locomotor activity); (b) general gastrointestinal motility (serial X-rays were taken 0-8 hours after intragastric barium administration and analyzed semiquantitatively, morphometrically, and densitometrically); and (c) bedding intake (a rodent indirect marker of nausea). Animals from sets 1 and 3 were used to evaluate gastric dysmotility ex vivo at 2 and 4 hours after administration, respectively.

KEY RESULTS

Loperamide significantly induced antinociception, hypothermia, and hypolocomotion (but not catalepsy) at high doses and dose-dependently reduced gastrointestinal motor function, with the intestine exhibiting higher sensitivity than the stomach. Whereas bedding intake occurred early and transiently, gastric dysmotility was much more persistent.

CONCLUSIONS AND INFERENCES

Our results suggest that loperamide-induced nausea and gastric dysmotility might be temporally dissociated.

Bioaccesibility, Metabolism, and Excretion of Lipids Composing Spent Coffee Grounds

The bioaccessibility, metabolism, and excretion of lipids composing spent coffee grounds (SCGs) were investigated. An analysis of mycotoxins and an acute toxicity study in rats were performed for safety evaluation. Total fat, fatty acids, and diterpenes (cafestol and kahweol) were determined in SCGs and their digests obtained in vitro. A pilot repeated intake study was carried out in Wistar rats using a dose of 1 g SCGs/kg b.w. for 28 days. Fat metabolism was evaluated by analysis of total fat, cholesterol, and histology in liver. The dietary fiber effect of SCGs was measured radiographically. The absence of mycotoxins and toxicity was reported in SCGs. A total of 77% of unsaturated fatty acids and low amounts of kahweol (7.09 µg/g) and cafestol (414.39 µg/g) were bioaccessible after in vitro digestion. A significantly lower (p < 0.1) accumulation of lipids in the liver and a higher excretion of these in feces was found in rats treated with SCGs for 28 days. No lipid droplets or liver damage were observed by histology. SCGs acutely accelerated intestinal motility in rats. SCGs might be considered a sustainable, safe, and healthy food ingredient with potential for preventing hepatic steatosis due to their effect as dietary fiber with a high fat-holding capacity.

Fluoroscopic Characterization of Colonic Dysmotility Associated to Opioid and Cannabinoid Agonists in Conscious Rats

Background/Aims

Gastrointestinal adverse effects have a major impact on health and quality of life in analgesics users. Non-invasive methods to study gastrointestinal motility are of high interest. Fluoroscopy has been previously used to study gastrointestinal motility in small experimental animals, but they were generally anesthetized and anesthesia itself may alter motility. In this study, our aim is to determine, in conscious rats, the effect of increasing doses of 2 opioid (morphine and loperamide) and 1 cannabinoid (WIN 55,212-2) agonists on colonic motility using fluoroscopic recordings and spatio-temporal maps.

Methods

Male Wistar rats received barium sulfate intragastrically, 20–22 hours before fluoroscopy, so that stained fecal pellets could be seen at the time of recording. Animals received an intraperitoneal administration of morphine, loperamide, or WIN 55,212-2 (at 0.1, 1, 5, or 10 mg/kg) or their corresponding vehicles (saline, Cremophor, and Tocrisolve, respectively), 30 minutes before fluoroscopy. Rats were conscious and placed within movement-restrainers for the length of fluoroscopic recordings (120 seconds). Spatio-temporal maps were built, and different parameters were analyzed from the fluoroscopic recordings in a blinded fashion to evaluate colonic propulsion of endogenous fecal pellets.

Results

The analgesic drugs inhibited propulsion of endogenous fecal pellets in a dose-dependent manner.

Conclusions

Fluoroscopy allows studying colonic propulsion of endogenous fecal pellets in conscious rats. Our method may be applied to the noninvasive study of the effect of different drug treatments and pathologies.

An Assessment of the Bioactivity of Coffee Silverskin Melanoidins

Melanoidins present in coffee silverskin, the only by-product of the roasting process, are formed via the Maillard reaction. The exact structure, biological properties, and mechanism of action of coffee silverskin melanoidins, remain unknown. This research work aimed to contribute to this novel knowledge. To achieve this goal, melanoidins were obtained from an aqueous extract of Arabica coffee silverskin (WO2013004873A1) and was isolated through ultrafiltration (>10 kDa). The isolation protocol was optimized and the chemical composition of the high molecular weight fraction (>10 kDa) was evaluated, by analyzing the content of protein, caffeine, chlorogenic acid, and the total dietary fiber. In addition, the structural analysis was performed by infrared spectroscopy. Antioxidant properties were studied in vitro and the fiber effect was studied in vivo, in healthy male Wistar rats. Melanoidins were administered to animals in the drinking water at a dose of 1 g/kg. At the fourth week of treatment, gastrointestinal motility was evaluated through non-invasive radiographic means. In conclusion, the isolation process was effective in obtaining a high molecular weight fraction, composed mainly of dietary fiber, including melanoidins, with in vitro antioxidant capacity and in vivo dietary fiber effects.

Cannabinoid pharmacology and therapy in gut disorders

Cannabis sp. and their products (marijuana, hashish…), in addition to their recreational, industrial and other uses, have a long history for their use as a remedy for symptoms related with gastrointestinal diseases. After many reports suggesting these beneficial effects, it was not surprising to discover that the gastrointestinal tract expresses endogenous cannabinoids, their receptors, and enzymes for their synthesis and degradation, comprising the so-called endocannabinoid system. This system participates in the control of tissue homeostasis and important intestinal functions like motor and sensory activity, nausea, emesis, the maintenance of the epithelial barrier integrity, and the correct cellular microenvironment. Thus, different cannabinoid-related pharmacological agents may be useful to treat the main digestive pathologies. To name a few examples, in irritable bowel syndrome they may normalize dysmotility and reduce pain, in inflammatory bowel disease they may decrease inflammation, and in colorectal cancer, apart from alleviating some symptoms, they may play a role in the regulation of the cell niche. This review summarizes the main recent findings on the role of cannabinoid receptors, their synthetic or natural ligands and their metabolizing enzymes in normal gastrointestinal function and in disorders including irritable bowel syndrome, inflammatory bowel disease, colon cancer and gastrointestinal chemotherapy-induced adverse effects (nausea/vomiting, constipation, diarrhea).

Pathophysiological Mechanisms of Gastrointestinal Toxicity

Humans swallow a great variety and often large amounts of chemicals as nutrients, incidental food additives and contaminants, drugs, and inhaled particles and chemicals, thus exposing the gastrointestinal tract to many potentially toxic substances. It serves as a barrier in many cases to protect other components of the body from such substances and infections. Fortunately, the gastrointestinal tract is remarkably robust and generally is able to withstand multiple daily assaults by the chemicals to which it is exposed. Some chemicals, however, can affect one or more aspects of the gastrointestinal tract to produce abnormal events that reflect toxicity. It is the purpose of this chapter to evaluate the mechanisms by which toxic chemicals produce their deleterious effects and to determine the consequences of the toxicity on integrity of gastrointestinal structure and function. Probably because of the intrinsic ability of the gastrointestinal tract to resist toxic chemicals, there is a paucity of data regarding gastrointestinal toxicology. It is therefore necessary in many cases to extrapolate toxic mechanisms from infectious processes, inflammatory conditions, ischemia, and other insults in addition to more conventional chemical sources of toxicity.

Computer vision-based diameter maps to study fluoroscopic recordings of small intestinal motility from conscious experimental animals

BACKGROUND

When available, fluoroscopic recordings are a relatively cheap, non-invasive and technically straightforward way to study gastrointestinal motility. Spatiotemporal maps have been used to characterize motility of intestinal preparations in vitro, or in anesthetized animals in vivo. Here, a new automated computer-based method was used to construct spatiotemporal motility maps from fluoroscopic recordings obtained in conscious rats.

METHODS

Conscious, non-fasted, adult, male Wistar rats (n=8) received intragastric administration of barium contrast, and 1-2 hours later, when several loops of the small intestine were well-defined, a 2 minutes-fluoroscopic recording was obtained. Spatiotemporal diameter maps (Dmaps) were automatically calculated from the recordings. Three recordings were also manually analyzed for comparison. Frequency analysis was performed in order to calculate relevant motility parameters.

KEY RESULTS

In each conscious rat, a stable recording (17-20 seconds) was analyzed. The Dmaps manually and automatically obtained from the same recording were comparable, but the automated process was faster and provided higher resolution. Two frequencies of motor activity dominated; lower frequency contractions (15.2±0.9 cpm) had an amplitude approximately five times greater than higher frequency events (32.8±0.7 cpm).

CONCLUSIONS & INFERENCES

The automated method developed here needed little investigator input, provided high-resolution results with short computing times, and automatically compensated for breathing and other small movements, allowing recordings to be made without anesthesia. Although slow and/or infrequent events could not be detected in the short recording periods analyzed to date (17-20 seconds), this novel system enhances the analysis of in vivo motility in conscious animals.

May cannabinoids prevent the development of chemotherapy-induced diarrhea and intestinal mucositis? Experimental study in the rat

BACKGROUND

The antineoplastic drug 5-fluoruracil (5-FU) is a pirimidine analog, which frequently induces potentially fatal diarrhea and mucositis. Cannabinoids reduce gastrointestinal motility and secretion and might prevent 5-FU-induced gut adverse effects. Here, we asked whether cannabinoids may prevent diarrhea and mucositis induced by 5-FU in the rat.

METHODS

Male Wistar rats received vehicle or the non-selective cannabinoid agonist WIN 55,212-2 (WIN; 0.5 mg kg^-1 injection^-1 , 1 injection day^-1 , 4 consecutive days) by intraperitoneal (ip) route; on the first 2 days, animals received also saline or 5-FU (150 mg kg^-1 injection^-1 , cumulative dose of 300 mg kg^-1 ). Gastrointestinal motor function was radiographically studied after barium contrast intragastric administration on experimental days 1 and 4. Structural alterations of the stomach, small intestine and colon were histologically studied on day 4. PAS staining and immunohistochemistry for Ki67, chromogranin A and CD163 were used to detect secretory, proliferating, and endocrine cells, and activated macrophages respectively.

KEY RESULTS

As shown radiographically, 5-FU induced significant gastric emptying delay (on days 1 and 4) and diarrhea (on day 4). WIN did not significantly alter the motility curves obtained for either control or 5-FU-treated animals but tended to reduce the severity of 5-FU-induced diarrhea and increased permanence of barium from day 1 to the beginning of day 4 in 5-FU-treated animals. 5-FU-induced mucositis was severe and not counteracted by WIN.

CONCLUSIONS AND INFERENCES

5-FU-induced diarrhea, but not mucositis, was partly prevented by WIN at a low dose. Cannabinoids might be useful to prevent chemotherapy-induced diarrhea.

Involvement of Cannabinoid Signaling in Vincristine-Induced Gastrointestinal Dysmotility in the Rat

Background: In different models of paralytic ileus, cannabinoid receptors are overexpressed and endogenous cannabinoids are massively released, contributing to gastrointestinal dysmotility. The antitumoral drug vincristine depresses gastrointestinal motility and a similar mechanism could participate in this effect. Therefore, our aim was to determine, using CB₁ and CB₂ antagonists, whether an increased endocannabinoid tone is involved in vincristine-induced gastrointestinal ileus.

Methods: First, we confirmed the effects of vincristine on the gut mucosa, by conventional histological techniques, and characterized its effects on motility, by radiographic means. Conscious male Wistar rats received an intraperitoneal injection of vincristine (0.1–0.5 mg/kg), and barium sulfate (2.5 ml; 2 g/ml) was intragastrically administered 0, 24, or 48 h later. Serial X-rays were obtained at different time-points (0–8 h) after contrast. X-rays were used to build motility curves for each gastrointestinal region and determine the size of stomach and caecum. Tissue samples were taken for histology 48 h after saline or vincristine (0.5 mg/kg). Second, AM251 (a CB₁ receptor antagonist) and AM630 (a CB₂ receptor antagonist) were used to determine if CB₁ and/or CB₂ receptors are involved in vincristine-induced gastrointestinal dysmotility.

Key results: Vincristine induced damage to the mucosa of ileum and colon and reduced gastrointestinal motor function at 0.5 mg/kg. The effect on motor function was particularly evident when the study started 24 h after administration. AM251, but not AM630, significantly prevented vincristine effect, particularly in the small intestine, when administered thrice. AM251 alone did not significantly alter gastrointestinal motility.

Conclusions: The fact that AM251, but not AM630, is capable of reducing the effect of vincristine suggests that, like in other experimental models of paralytic ileus, an increased cannabinoid tone develops and is at least partially responsible for the alterations induced by the antitumoral drug on gastrointestinal motor function. Thus, CB₁ antagonists might be useful to prevent/treat ileus induced by vincristine.

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.

X-ray analysis of gastrointestinal motility in conscious mice. Effects of morphine and comparison with rats

BACKGROUND

Non-invasive methods to study gastrointestinal (GI) motility are of high interest, particularly in chronic studies. Amongst these, radiographic techniques after contrast intragastric administration may offer many advantages. In previous studies, we have successfully and reproducibly applied these techniques together with a semiquantitative analysis method to characterize the effect of different drugs, acutely or repeatedly administered in rat models, but we have never before used these techniques in mice. These are very convenient in basic research. Our aim was to determine if our method is also valid in mice. Additionally, we determined the effect of morphine on GI motor function in both species.

METHODS

Animals received an intraperitoneal administration of morphine (at 10 and 5 mg/kg for rats and mice, respectively). Twenty min later, barium contrast (at 2 g/mL) was gavaged (2.5 and 0.4 mL for rats and mice respectively) and serial X-rays were obtained 0-8 h after contrast. X-rays were analyzed as previously described, using a semiquantitative score to build motility curves for each GI region.

KEY RESULTS

Motility was much faster in mice than in rats for all GI regions. Morphine at the doses used significantly depressed motility in both species to a similar extent if the whole gut or the upper GI regions (stomach, small intestine) were considered, although its effect seemed to be more intense in the lower GI regions (caecum, colorectum) in rats than in mice.

CONCLUSIONS & INFERENCES

We have validated our X-rays method for its use in mice.

Cannabinoid Receptors in Regulating the GI Tract: Experimental Evidence and Therapeutic Relevance

Cannabinoid receptors are fundamentally involved in all aspects of intestinal physiology, such as motility, secretion, and epithelial barrier function. They are part of a broader entity, the so-called endocannabinoid system which also includes their endocannabinoid ligands and the ligands' synthesizing/degrading enzymes. The system has a strong impact on the pathophysiology of the gastrointestinal tract and is believed to maintain homeostasis in the gut by controlling hypercontractility and by promoting regeneration after injury. For instance, genetic knockout of cannabinoid receptor 1 leads to inflammation and cancer of the intestines. Derivatives of Δ⁹-tetrahydrocannabinol, such as nabilone and dronabinol, activate cannabinoid receptors and have been introduced into the clinic to treat chemotherapy-induced emesis and loss of appetite; however, they may cause many psychotropic side effects. New drugs that interfere with endocannabinoid degradation to raise endocannabinoid levels circumvent this obstacle and could be used in the future to treat emesis, intestinal inflammation, and functional disorders associated with visceral hyperalgesia.

In vitro and non-invasive in vivo effects of the cannabinoid-1 receptor agonist AM841 on gastrointestinal motor function in the rat

BACKGROUND

Cannabinoids have been traditionally used for the treatment of gastrointestinal (GI) symptoms, but the associated central effects, through cannabinoid-1 receptors (CB1R), constitute an important drawback. Our aims were to characterize the effects of the recently developed highly potent long-acting megagonist AM841 on GI motor function and to determine its central effects in rats.

METHODS

Male Wistar rats were used for in vitro and in vivo studies. The effect of AM841 was tested on electrically induced twitch contractions of GI preparations (in vitro) and on GI motility measured radiographically after contrast administration (in vivo). Central effects of AM841 were evaluated using the cannabinoid tetrad. The non-selective cannabinoid agonist WIN 55,212-2 (WIN) was used for comparison. The CB1R (AM251) and CB2R (AM630) antagonists were used to characterize cannabinoid receptor-mediated effects of AM841.

KEY RESULTS

AM841 dose-dependently reduced in vitro contractile activity of rat GI preparations via CB1R, but not CB2R or opioid receptors. In vivo, AM841 acutely and potently reduced gastric emptying and intestinal transit in a dose-dependent and AM251-sensitive manner. The in vivo GI effects of AM841 at 0.1 mg/kg were comparable to those induced by WIN at 5 mg/kg. However, at this dose, AM841 did not induce any sign of the cannabinoid tetrad, whereas WIN induced significant central effects.

CONCLUSIONS & INFERENCES

The CB1R megagonist AM841 may potently depress GI motor function in the absence of central effects. This effect may be mediated peripherally and may be useful in the treatment of GI motility disorders.

Effects of chronic dietary exposure to monosodium glutamate on feeding behavior, adiposity, gastrointestinal motility, and cardiovascular function in healthy adult rats

BACKGROUND

Monosodium glutamate (MSG) is a flavor-enhancer widely used as a food additive. However, its safe dietary concentration and its toxicity, including its possible implication in the recent metabolic syndrome pandemia, is still a controversial issue. Therefore, a deep knowledge of its effects upon regular dietary use is needed. Our aim was to evaluate the effects of chronic exposure to MSG on feeding behavior, abdominal fat, gastrointestinal motility, and cardiovascular function in rats.

METHODS

Two groups of adult male Wistar rats were used: control and treated with MSG (4 g/L in drinking water) for 6 weeks. Different functional parameters were determined and the histological structure was analyzed in tissues of interest.

KEY RESULTS

Compared to control animals, chronic MSG increased water intake but did not modify food ingestion or body weight gain. Neither the abdominal fat volume nor the fat fraction, measured by magnetic resonance imaging, was modified by MSG. Monosodium glutamate did not alter general gastrointestinal motility, but significantly increased the colonic response to mechanical stimulation. It slightly reduced endothelium-dependent relaxation in aorta, without significantly modifying any other cardiovascular parameters. No significant histological alterations were detected in salivary glands, intestinal wall, aorta, heart, and kidney.

CONCLUSIONS & INFERENCES

Chronic treatment with MSG in the adult rat increased water intake. This supports its potential to improve acceptance of low-fat regimens and to increase hydration in the elderly and sportspeople, often at risk of dehydration. Changes in colonic contractility and cardiovascular function could have some long-term repercussions warranting further research.

Cannabinoids may worsen gastric dysmotility induced by chronic cisplatin in the rat

BACKGROUND

Although cannabinoids have traditionally been used for the treatment and/or prevention of nausea and/or emesis, anorexia and weight loss induced by clinical use of antineoplastic drugs, their efficacy and safety in long-term treatments are still controversial. Our aim was to analyze the effects of the non-selective cannabinoid agonist WIN 55 212-2 (WIN) on gastrointestinal (GI) dysmotility and other adverse effects induced by repeated cisplatin administration in the rat.

METHODS

Male Wistar rats received two intraperitoneal injections once a week for 4 weeks: the first one was WIN, at non-psychoactive doses (0.5 or 1 mg kg(-1)), its vehicle or saline; the second one was cisplatin (2 mg kg(-1)) or saline. Radiographic techniques were used to determine the acute (after first dose), chronic (after last dose), and residual (1 week after treatment finalization) effects of cisplatin and/or WIN on GI motility. Bodyweight gain, food ingestion, and mechanical sensitivity were also tested.

KEY RESULTS

Weekly cisplatin induced mechanical allodynia, which WIN prevented, as well as weight gain reduction and anorexia, which WIN did not. Gastric emptying was dose-dependently delayed by cisplatin and this effect was enhanced upon chronic treatment. WIN aggravated cisplatin-induced gastric dysmotility. One week after treatment finalization, only minor alterations of GI motor function were found in rats treated with cisplatin, WIN or both.

CONCLUSIONS & INFERENCES

WIN weekly administered at low doses prevents neuropathy, but does not prevent anorexia or weight loss and aggravates gastric dysmotility induced by cisplatin. Cannabinoids should be handled with caution if chronically administered during chemotherapy.

Characterization of cannabinoid-induced relief of neuropathic pain in a rat model of cisplatin-induced neuropathy

Clinical use of antineoplastic drugs is associated with the development of numerous adverse effects that many patients find intolerable, including peripheral neuropathy. Cannabinoids have relieved neuropathic pain in different animal models. But their therapeutic activities could be affected by their psychoactive properties. The aim of this work was to determine the effect of cannabinoids in cisplatin-evoked neuropathy. For this purpose, the non-selective agonist WIN 55,212-2 (WIN), the CB1-selective agonist ACEA or the CB2-selective agonist JWH133 (or their vehicle) was either systemically administered at a non-psychoactive dose or locally injected in cisplatin-treated rats. Selective CB1 and CB2 cannabinoid antagonists (AM251 and SR144528, respectively) were used to characterize cannabinoid effects. Cisplatin-treated rats showed mechanical allodynia but not thermal hyperalgesia. Cannabinoid agonists alleviated mechanical allodynia. This effect was mediated by both CB1 and CB2 cannabinoid receptors when the cannabinoid was systemically applied. At the dose used, cannabinoid agonists had no psychoactive effect. The local effect of the drug involved the activation of peripheral CB1 receptors whereas involvement of CB2 receptors was less clear. In a rat model of cisplatin-induced neuropathy, cannabinoids have an antinociceptive effect, but the cannabinoid receptors involved could be different depending on the route of administration. Non-psychoactive doses of cannabinoid agonists are capable of alleviating the signs of peripheral neuropathy when systemically applied. Interestingly, local administration of selective CB1 agonists or systemic administration of CB2 agonists, which are non-psychoactive, may serve as new therapeutic alternatives for symptom management in painful neuropathy associated with cisplatin treatment.

Effects of glucagon-like peptide-1 receptor stimulation and blockade on food consumption and body weight in rats treated with a cannabinoid CB1 receptor agonist WIN 55,212-2

Background

Glucagon-like peptide-1 (GLP-1) and endocannabinoids are involved in appetite control. Recently we have demonstrated that cannabinoid (CB)1 receptor antagonist and GLP-1 receptor agonist synergistically suppress food intake in the rat. The aim of the present study was to determine the effects of GLP-1 receptor stimulation or blockade on feeding behavior in rats treated with WIN 55,212-2, a CB1 receptor agonist.

Material/Methods

Experiments were performed on adult male Wistar rats. In the first experiment the effects of increasing doses (0.5–4.0 mg/kg) of WIN 55,212-2 injected intraperitoneally on 24-hour food consumption were tested. In further experiments a GLP-1 receptor antagonist, exendin (9-39), and WIN 55,212-2 or a GLP-1 receptor agonist, exendin-4, and WIN 55,212-2 were injected intraperitoneally at subthreshold doses (that alone did not change food intake and body weight) to investigate whether these agents may interact to affect food intake in rats.

Results

WIN 55,212-2 administered at low doses (0.5–2 mg/kg) did not markedly change 24-hour food consumption; however, at the highest dose, daily food intake was inhibited. Combined administration of WIN 55,212-2 and exendin (9-39) did not change the amount of food consumed compared to either the control group or to each agent injected alone. Combined injection of WIN 55,212-2 and exendin-4 at subthreshold doses resulted in a significant decrease in food intake and body weight in rats.

Conclusions

Stimulation of the peripheral CB1 receptor by its agonist WIN 55,212-2 can induce anorexigenic effects or potentiate, even at a subthreshold dose, the effects of exendin-4, a known anorectic agent. Hence, this dual action of the cannabinoid system should be considered in the medical use of CB1 agonists.

Characterization of cannabinoid-induced relief of neuropathic pain in rat models of type 1 and type 2 diabetes

Diabetic neuropathy is a frequent complication of diabetes mellitus with a tremendous impact on patients' quality of life, and it remains poorly treated. Cannabinoids relieve the signs of diabetic neuropathy in different experimental models, including streptozotocin- (STZ-) induced type 1 diabetic rodents, and they may also relieve neuropathic signs in type 2 diabetic animals. This study compares the effect of the non-selective cannabinoid agonist WIN 55,212-2 (WIN) in Zucker Diabetic Fatty (ZDF) rats (type 2 diabetes) and in STZ-injected Wistar rats (type 1 diabetes). WIN (or its vehicle) was either systemically administered at a non-psychoactive dose or locally injected. Selective CB1 and CB2 cannabinoid antagonists were used to characterize WIN antineuropathic effects. Both type 1 and type 2 diabetic rats showed mechanical allodynia but not thermal hyperalgesia. WIN alleviated mechanical allodynia in both models of diabetes. In STZ-treated rats, both cannabinoid receptors were involved, whereas in ZDF rats, WIN effects seemed to mainly involve the activation of CB1 receptors. Higher doses of WIN were needed to significantly relieve mechanical allodynia upon intraplantar administration in ZDF vs. STZ-injected rats. Cannabinoids, acting on systemic and/or peripheral receptors, may serve as a new therapeutic alternative for symptom management in painful neuropathy associated with both type 1 and type 2 diabetes. Additionally, our results highlight the need for appropriate selection of diabetic experimental models because the results from studies in STZ-induced diabetic rodents might not be applicable in all diabetic situations.

Cannabinoid-induced delayed gastric emptying is selectively increased upon intermittent administration in the rat: role of CB1 receptors

BACKGROUND

Cannabinoids acutely administered depress central, cardiovascular and gastrointestinal functions. These effects might be modified upon repeated administration. Compared to the effects induced by daily administration, those induced by intermittent administration are less known. The effect of intermittent treatment with the CB1/CB2 cannabinoid agonist WIN55,212-2 (WIN) was studied in the rat.

METHODS

Male rats received saline, vehicle or WIN at 0.5 (low-WIN) or 5 (high-WIN) mg kg(-1) week(-1) for 4 weeks. WIN effects on the central nervous system (cannabinoid tetrad tests), cardiovascular function and gastrointestinal motor function were evaluated after the first and last doses, and, where appropriate, 1 week after the last dose. To determine the involvement of CB1 receptors in the chronic effect of WIN, the CB1 receptor antagonist/inverse agonist AM251 (1 mg kg(-1)) was used.

KEY RESULTS

High- (but not low-) WIN induced the four signs of the cannabinoid tetrad, and reduced gastrointestinal motility, but did not alter cardiovascular parameters. Upon chronic intermittent administration, tolerance did not clearly develop to WIN effects. Quite the opposite, depression of gastric emptying was intensified. No effect was long-lasting. Repeated administration of AM251 was more efficacious than single administration to block WIN chronic central effects, but the opposite occurred regarding lower intestinal motility.

CONCLUSIONS & INFERENCES

Upon intermittent administration, hypersensitization may develop to some effects (particularly delayed gastric emptying) induced by cannabinoid agonists. CB1 antagonists/inverse agonists may show different efficacy upon repeated or single administration to block cannabinoid-induced central and gastrointestinal effects. Thus, cannabinoid effects are dependent on the pattern of drug administration.

Gut feelings about the endocannabinoid system

Stemming from the centuries-old and well known effects of Cannabis on intestinal motility and secretion, research on the role of the endocannabinoid system in gut function and dysfunction has received ever increasing attention since the discovery of the cannabinoid receptors and their endogenous ligands, the endocannabinoids. In this article, some of the most recent developments in this field are discussed, with particular emphasis on new data, most of which are published in Neurogastroenterology & Motility, on the potential tonic endocannabinoid control of intestinal motility, the function of cannabinoid type-1 (CB1) receptors in gastric function, visceral pain, inflammation and sepsis, the emerging role of cannabinoid type-2 (CB2) receptors in the gut, and the pharmacology of endocannabinoid-related molecules and plant cannabinoids not necessarily acting via cannabinoid CB1 and CB2 receptors. These novel data highlight the multi-faceted aspects of endocannabinoid function in the GI tract, support the feasibility of the future therapeutic exploitation of this signaling system for the treatment of GI disorders, and leave space for some intriguing new hypotheses on the role of endocannabinoids in the gut.

Cisplatin-induced gastrointestinal dysmotility is aggravated after chronic administration in the rat. Comparison with pica

BACKGROUND

Chemotherapy induces nausea/emesis and gastrointestinal dysmotility. Pica, the ingestion of non-nutritive substances, is considered as an indirect marker of nausea/emesis in non-vomiting species, like the rat. Cisplatin is the most emetogenic antitumoral drug. In the rat, acute cisplatin induces pica and gastric dysmotility in a temporally related manner, but the effects of chronic cisplatin are not well known. This study analyzed the effects of chronic cisplatin on pica and on gastrointestinal motor function in the rat, using radiographic, non-invasive methods.

METHODS

Rats received saline or cisplatin (1-3 mg kg(-1), i.p.) once a week for four consecutive weeks. Serial X-rays were taken 0-8 h after administration of barium sulfate, which was given intragastrically immediately after the first and last cisplatin administrations and 1 week after treatment finalization. Pica (i.e., kaolin intake) was measured in isolated rats.

KEY RESULTS

Cisplatin delayed gastric emptying and induced acute (during the 24 h following each administration) pica. Upon chronic administration, these effects were exacerbated. In addition, basal kaolin intake was enhanced (facilitated) and gastric distension induced. Delayed gastric emptying and gastric distension were not apparent 1 week after treatment, but basal kaolin intake was still elevated.

CONCLUSIONS & INFERENCES

Whereas gastric dysmotility induced by cisplatin is parallel to the development of acute pica and might underlie facilitation of pica throughout chronic treatment, it does not explain its long-term maintenance. These findings should be taken into account in the search for new antiemetic strategies.

The cannabinoid antagonist SR144528 enhances the acute effect of WIN 55,212-2 on gastrointestinal motility in the rat

BACKGROUND

In the absence of pathology, cannabinoid-induced depression of gastrointestinal (GI) motility is thought to be mediated primarily by CB1 receptors, whereas the role of CB2 receptors is still unclear. The aim of this work was to radiographically analyze the acute effect of the mixed cannabinoid agonist WIN 55,212-2 (WIN) on GI motor function in the rat, focusing on the involvement of CB1 and CB2 receptors.

METHODS

Male Wistar rats received different doses of WIN and both psychoactivity (cannabinoid tetrad) and GI motility (radiographic analysis) were tested. The duration of WIN effect on GI motility was also radiographically analyzed. Finally, the involvement of the different cannabinoid receptors on WIN-induced alterations of GI motility was analyzed by the previous administration of selective CB1 (AM251) and CB2 (SR144528 or AM630) antagonists. After administration of contrast medium, alterations in GI motility were quantitatively evaluated in serial radiographs by assigning a compounded value to each region of the GI tract.

KEY RESULTS

Low, analgesic doses of WIN delayed intestinal transit, but high, psychoactive doses were required to delay gastric emptying. Acute WIN effects on GI motility were confined to the first few hours after administration. AM251 partially counteracted the effect of WIN on GI motility. Surprisingly, SR144528 (but not AM630) enhanced WIN-induced delayed gastric emptying.

CONCLUSIONS & INFERENCES

X-ray analyses confirm that cannabinoids inhibit GI motility via CB1 receptors; in addition, cannabinoids could influence motility through interaction with a SR144528-sensitive site. Further studies are needed to verify if such site of action is the CB2 receptor.

Involvement of cannabinoid-1 and cannabinoid-2 receptors in septic ileus

BACKGROUND Cannabinoid (CB) receptors are involved in the regulation of gastrointestinal (GI) motility under physiological and pathophysiological conditions. We aimed to characterize the possible influence of CB(1) and CB(2) receptors on motility impairment in a model of septic ileus. METHODS Lipopolysaccharide (LPS) injections were used to mimic pathophysiological features of septic ileus. Spontaneous jejunal myoelectrical activity was measured in rats in vivo, and upper GI transit was measured in vivo by gavaging of a charcoal marker into the stomach of mice, in absence or presence of LPS, and CB(1) and CB(2) receptor agonists and antagonists. Tumour necrosis factor (TNF)-alpha and interleukin (IL)-6 levels were measured using enzyme-linked immunosorbent assay. Histology was performed with haematoxylin-eosin staining. KEY RESULTS Lipopolysaccharide treatment significantly reduced amplitude and frequency of myoelectric spiking activity and GI transit in vivo in a dose-dependent manner. TNF-alpha and IL-6 were increased in LPS-treated animals and histology showed oedema and cell infiltration. Both, the CB(1) agonist HU210 and the CB(2) agonist JWH133 reduced myoelectrical activity whereas the CB(1) antagonist AM251 caused an increase of myoelectrical activity. Pretreatment with AM251 or AM630 prevented against LPS-induced reduction of myoelectrical activity, and also against the delay of GI transit during septic ileus in vivo. CONCLUSIONS & INFERENCES The LPS model of septic ileus impairs jejunal myoelectrical activity and delays GI transit in vivo. Antagonists at the CB(1) receptor or the CB(2) receptor prevent the delay of GI transit and thus may be powerful tools in the future treatment of septic ileus.

Cannabinoids and the gut: new developments and emerging concepts

Cannabis has been used to treat gastrointestinal (GI) conditions that range from enteric infections and inflammatory conditions to disorders of motility, emesis and abdominal pain. The mechanistic basis of these treatments emerged after the discovery of Delta(9)-tetrahydrocannabinol as the major constituent of Cannabis. Further progress was made when the receptors for Delta(9)-tetrahydrocannabinol were identified as part of an endocannabinoid system, that consists of specific cannabinoid receptors, endogenous ligands and their biosynthetic and degradative enzymes. Anatomical, physiological and pharmacological studies have shown that the endocannabinoid system is widely distributed throughout the gut, with regional variation and organ-specific actions. It is involved in the regulation of food intake, nausea and emesis, gastric secretion and gastroprotection, GI motility, ion transport, visceral sensation, intestinal inflammation and cell proliferation in the gut. Cellular targets have been defined that include the enteric nervous system, epithelial and immune cells. Molecular targets of the endocannabinoid system include, in addition to the cannabinoid receptors, transient receptor potential vanilloid 1 receptors, peroxisome proliferator-activated receptor alpha receptors and the orphan G-protein coupled receptors, GPR55 and GPR119. Pharmacological agents that act on these targets have been shown in preclinical models to have therapeutic potential. Here, we discuss cannabinoid receptors and their localization in the gut, the proteins involved in endocannabinoid synthesis and degradation and the presence of endocannabinoids in the gut in health and disease. We focus on the pharmacological actions of cannabinoids in relation to GI disorders, highlighting recent data on genetic mutations in the endocannabinoid system in GI disease.