Gastrointestinal Transit In Mice Research Articles

New biofunctional effects of oleanane-type triterpene saponins.

In the current review, we describe the novel biofunctional effects of oleanane-type triterpene saponins, including elatosides, momordins, senegasaponins, camelliasaponins, and escins, obtained from Aralia elata (bark, root cortex, young shoot), Kochia scoparia (fruit), Polygala senega var. latifolia (roots), Camellia japonica (seeds), and Aesculus hippocastanum (seeds), considering the following biofunctional activities: (1) inhibitory effects on elevated levels of blood alcohol and glucose in alcohol and glucose-loaded rats, respectively, (2) inhibitory effects on gastric emptying in rats and mice, (3) accelerative effects on gastrointestinal transit in mice, and (4) protective effects against gastric mucosal lesions in rats. In addition, we describe (5) suppressive effects of the extract and chakasaponins from Camellia sinensis (flower buds) on obesity based on inhibition of food intake in mice. The active saponins were classified into the following three types: (1) olean-12-en-28-oic acid 3-O-monodesmoside, (2) olean-12-ene 3,28-O-acylated bisdesmoside, and (3) acylated polyhydroxyolean-12-ene 3-O-monodesmoside. Furthermore, common modes of action, such as involvements of capsaicin-sensitive nerves, endogenous NO and PGs, and possibly sympathetic nerves, as well as common structural requirements, were observed. Based on our findings, a common mechanism of action might mediate the pharmacological effects of active saponins. It should be noted that the gastrointestinal tract is an important action site of saponins, and the role of the saponins in the gastrointestinal tract should be carefully considered.

Oceanapia magna Sponge Presents Dual Effect on the Gastrointestinal Motility of Rodents: In Vitro and In Vivo Assays.

Oceanapia magna Santos-Neto, Nascimento, Cavalcanti and Pinheiro sponges are distributed across tropical worldwide seas. Some studies of marine products have shown interesting activities in smooth muscle models. Hence, we assessed the effect of the ethanolic extract of Oceanapia magna. (OC-EtOH) on acute toxicity and gastrointestinal motility (in vitro and in vivo) in rodent models. On guinea pig ileum, OC-EtOH induced a concentration dependent contraction on basal tonus, which was not inhibited by atropine, but in the presence of pyrilamine or verapamil, the effect was antagonized. Contrastingly, on KCl- or histamine-induced contractions, OC-EtOH presented a transient contraction followed by a concentration-dependent relaxation. Moreover, OC-EtOH presented a relaxant profile on cumulative curves to CaCl2 and tonic contraction induced by S-(-)-BayK8644, through Cav blockade. The acute toxicity assay showed that OC-EtOH (2,000 mg/kg, p.o.) did not present any sign of toxicity in female mice. Additionally, OC-EtOH presented antidiarrheal effect in mice, increased the intestinal normal transit and reduced the castor oil-induced intestinal transit. Thus, OC-EtOH presented a dual effect on guinea pig ileum promoting contraction through activation of H1 and CaV, and relaxation through CaV blockade, besides the effect on upper gastrointestinal transit in mice, showing a potential medicinal use of this sponge in intestinal diseases such as diarrhea.

Central and peripheral modulation of gastrointestinal transit in mice by DN-9, a multifunctional opioid/NPFF receptor agonist.

The nonapeptide DN-9 functions as a multifunctional agonist to opioid and neuropeptide FF (NPFF) receptors and exhibits antinociceptive effects at the central and peripheral levels. The effects of DN-9 on small and colonic intestinal transit were evaluated using the upper gastrointestinal (GI) transit test and colonic bead expulsion assay, respectively. Opioid and NPFF receptor antagonists were used to investigate the mechanisms of DN-9-induced GI inhibition. Furthermore, the agonism of the DN-9 analog [Phg9 ]-DN-9 to opioid and NPFF receptors was tested by the cAMP assay. Intracerebroventricular administration of DN-9 dose-dependently slowed upper GI transit and colonic expulsion via mu- and kappa-opioid receptors in the brain, independent of the delta-opioid receptor. Similarly, intraperitoneal injection of DN-9 dose-dependently inhibited GI propulsion via the peripheral opioid receptors. DN-9-induced GI transit inhibitions were significantly aggravated by the NPFF receptor antagonist RF9. Moreover, the DN-9 analog [Phg9 ]-DN-9, an agonist at mu-, delta-, and kappa-opioid receptors but not NPFF receptors, inhibited GI more potently than DN-9. In addition, intracerebroventricular NPFF significantly attenuated the central inhibitory effects induced by [Phg9 ]-DN-9 and morphine. However, central and peripheral injections of NPFF or RF9 almost had no significant effects on GI transit by itself. Intracerebroventricular and intraperitoneal administrations of DN-9 inhibit GI transit via opioid receptors in mice by central and peripheral mechanisms, respectively. In addition, the NPFF agonism of DN-9 possesses antiopioid effects on GI transit, which might explain the reduced constipation at the antinociceptive doses.

Gastrointestinal motility and morphology in mice: Strain-dependent differences.

BALB/c and C57BL/6mice are widely used in biomedical research; however, the differences between strains are still underestimated.Our aims were to develop an experimental protocol to evaluate the duodenal contractility and gastrointestinal transit in miceusing theAlternating Current Biosusceptometry (ACB)techniqueand to compare gastrointestinal motor function and morphology between BALB/c and C57BL/6 strains. Male mice wereused inexperiments (a) duodenal contractility: animalswhich had a magnetic marker surgically fixed in the duodenum to determine the frequency and amplitude of contractions and (b) gastrointestinal transit: animals which ingested a magnetically marked chowto calculate theOro-Anal Transit Time (OATT) and the Fecal Pellet Elimination Rate (FPER). The animals were killedafter the experiments for organ collection andmorphometric analysis. BALB/c and C57BL/6 had two different duodenal frequencies (high and low)with similar amplitudes. After 10hours of monitoring, BALB/c eliminated around 89% of the ingestedmarker and C57BL/6 eliminated33%; OATT and FPER were slower for C57BL/6 compared with BALB/c. The OATT and amplitude of low frequencyhad a strong positive correlation in C57BL/6. For BALB/c, thegastric muscular layer was thickercompared to that measured for C57BL/6. The experimental protocolto evaluate duodenal contractility and fecal magnetic pellets output using the ACB techniquein micewas successfully established.BALB/c strains had higher duodenal frequencies and a shorter timeto eliminate the ingested marker. Our resultsshowed differences in bothmotor function and gastrointestinal morphology betweenBALB/c and C57BL/6 strains.

Development of Oxygen-Bridged Pyrazole-Based Structures as Cannabinoid Receptor 1 Ligands.

In this work, the synthesis of the cannabinoid receptor 1 neutral antagonists 8-chloro-1-(2,4-dichlorophenyl)-N-piperidin-1-yl-4,5-dihydrobenzo-1H-6-oxa-cyclohepta[1,2-c]pyrazole-3-carboxamide 1a and its deaza N-cyclohexyl analogue 1b has led to a deepening of the structure-activity studies of this class of compounds. A series of novel 4,5-dihydrobenzo-oxa-cycloheptapyrazoles analogues of 1a,b, derivatives 1c–j, was synthesized, and their affinity towards cannabinoid receptors was determined. Representative terms were evaluated using in vitro tests and isolated organ assays. Among the derivatives, 1d and 1e resulted in the most potent CB1 receptor ligands (KiCB1 = 35 nM and 21.70 nM, respectively). Interestingly, both in vitro tests and isolated organ assays evidenced CB1 antagonist activity for the majority of the new compounds, excluding compound 1e, which showed a CB1 partial agonist behaviour. CB1 antagonist activity of 1b was further confirmed by a mouse gastrointestinal transit assay. Significant activity of the new CB1 antagonists towards food intake was showed by preliminary acute assays, evidencing the potentiality of these new derivatives in the treatment of obesity.

Assemblages A and B of Giardia duodenalis reduce enteric glial cells in the small intestine in mice.

Infection of Giardia duodenalis is one of the most common human parasitic disease worldwide. This infection may be related to important changes in the enteric nervous system. The objective of this study was to evaluate the myenteric and submucosal plexuses, the intestinal muscle layer, and gastrointestinal transit in mice infected with assemblages A and B of G. duodenalis. Swiss albino mice (Mus musculus) were infected with assemblages A and B of G. duodenalis for 15days. Gastrointestinal transit time was evaluated before euthanasia. Duodenum and jejunum were removed for histological and immunohistochemical analyses. It was observed a reduction in the enteric glial cell count and a decrease in the ratio of enteric glial cells to neurons. The number of neurons did not change, but morphological changes were observed in the duodenum and jejunum in both plexuses, including an increase in the nuclear area and a reduction of cell bodies in the myenteric plexus and a decrease in the nuclear area in the submucosal plexus. A reduction of the thickness of the muscle layer was observed in the duodenum, with no significant differences in the gastrointestinal transit times. Assemblages A and B of G. duodenalis decrease the number of enteric glial cells in the myenteric and submucosal plexuses, decrease the thickness of the muscle layer, and change the morphology of neurons. Graphical abstract ᅟ.

Brazilian green propolis hydroalcoholic extract reduces colon damages caused by dextran sulfate sodium-induced colitis in mice.

This study investigated the effects of Brazilian green propolis hydroalcoholic extract (BPE) in 3% w/v dextran sodium sulfate (DSS)-inducedcolitisin mice. The effects of BPE (3, 30 and 300mg/kg, p.o, by 7days) on the morphological (colon length and colon weight), clinical (disease activity index and weight loss), microscopic (histological score and mucin levels) and biochemical parameters were determined. The effects of BPE (300mg/kg, p.o) in the gastrointestinal transit of mice were also evaluated. As expected, the DSS ingestion damaged the colonic tissue, lowered the body weight, decreased the mucin levels, increased MPO activity,reduced SOD activity and GSH amount. In contrast, the treatment with BPE (300mg/kg) significantly reduced macroscopic colonic injury and the mucosal damage in colon on histopathological examination and reversed the decrease in mucin levels induced byDSS. It also significantly normalized the SOD activity and the levels of GSH, but did not elicit any effect on MPO activity in the colon. In addition, BPE did not change the gastric emptying or the intestinal transit rate of mice. Together, these results suggested that BPE reduced the signs of DSS-induced colitis in mice through maintenance of intestinal mucin barrier and favoring intestinal antioxidant defenses.

Fecal imaging demonstrates that low-methoxyl pectin supplementation normalizes gastro-intestinal transit in mice given a liquid diet.

This study has the following aims: (1) to confirm a methodology for a fecal indocyanine green (ICG) imaging test for measuring gastro‐intestinal transit time (GITT); and (2) to compare GITT in mice given a liquid diet in which viscosity increases under acidic conditions to that in mice given stable liquid diets with comparable viscosity or regular chow. To address Aim 1, mice received ICG orally along with intraperitoneal injection of atropine in Study 1, and mice were given ICG orally with concurrent carmine red for Study 2. Fluorescence imaging of feces collected for 8 h thereafter was used to detect the first feces with fluorescence and thereby determine GITT. To address Aim 2, mice were fed ad libitum for 1 week with either liquid diet or regular chow for Study 3, or with liquid diet containing low‐methoxyl (LM) pectin or high‐methoxyl (HM) pectin, or regular chow for Study 4. GITT was then determined by fecal ICG imaging. Atropine delayed GITT in a dose‐dependent manner. The GITT of ICG completely corresponded to that of carmine red (correlation coefficient, 1.00). The first ICG excretion in the loose/some diarrheal feces of mice given a liquid diet was seen at 170 min. Feces of mice given liquid diet were loose with LM pectin and loose/some diarrhea with HM pectin. GITT of mice given liquid diet with HM pectin was significantly delayed (280 min) compared to that of mice given liquid diet with LM pectin (111 min) or regular chow (130 min). Fecal imaging of ICG enables measurements of GITT. LM pectin supplementation in a liquid diet may normalize GITT in mice to that of a normal meal and may be associated with changes in fecal properties.

Involvement of peripheral alpha2A adrenoceptor in the acceleration of gastrointestinal transit and abdominal visceral pain induced by intermittent deprivation of REM sleep

Many studies have associated sleep alterations with the severity of irritable bowel syndrome (IBS) symptoms, but the direct pathophysiological relationship has not been clarified. In addition, alterations in noradrenergic signaling have been implicated in the pathophysiology of IBS, and alpha2-adrenoceptors are potential treatment targets. We have previously shown that acceleration of gastrointestinal transit (GIT) elicited by intermittent rapid eye movement (REM) sleep deprivation stress may fulfill the profile of a model of IBS. Moreover, we showed hypernoradrenergic function in the brain of sleep-deprived mice. On the other hand, acetic acid-induced writhes indicate visceral pain features of IBS model animals. In this study, using mice, we investigated whether intermittent REM sleep deprivation stress causes changes in acetic acid-induced writhing and whether the number of writhes and GIT are improved by administration of the hydrophilic clonidine analogue, ST-91. Mice were deprived of REM sleep intermittently using the small-platform method (20h/day) for 3days. The intermittent REM sleep deprivation stress elicited acceleration of GIT and the increased number of writhes was significantly improved by ST-91 treatment. The ID50 values of ST-91 on the GIT in cage-control mice and intermittent REM sleep-deprived mice were 0.24 and 0.70mg/kg, respectively. In addition, the ID50 values of ST-91 on the writhes in cage-control mice and intermittent REM sleep-deprived mice were 0.52 and 0.73mg/kg, respectively. Further, the expression of alpha2A-adrenoceptor was decreased in the distal ileum of intermittent REM sleep-deprived mice compared to that in cage-control mice. Moreover, the effects of ST-91 on GIT and writhes in cage-control and intermittent REM sleep-deprived mice were decreased by the administration of BRL44408 (6mg/kg, i.p.), a selective alpha2A–adrenoceptor antagonist, and not by the administration of imiloxan (3mg/kg, i.p.), or JP-1302 (3mg/kg, i.p.), selective alpha2B-and alpha2C–adrenoceptor antagonists, respectively. These results suggest that the increase in GIT and writhes induced by intermittent REM sleep deprivation stress may serve as a model of diarrhea and visceral pain symptoms in IBS. Further, the onset of these symptoms may be related to the hypofunction of peripheral alpha2A–adrenoceptor.

Chemical constituents, antioxidant and gastrointestinal transit accelerating activities of dried fruit of Crataegus dahurica

Crataegus dahurica Koehne is an edible wild fruit mainly distributed in Northeast China. The purpose of this study was to elucidate the chemical constituents and investigate the bioactivities of dried fruit of C. dahurica methanol extract (CdME). Through various chromatographic methods, thirty-five compounds were isolated from CdME for the first time and their structures were identified on the basis of physicochemical properties and spectroscopic data. The main structural types of these compounds were triterpenoids and polyphenolics. Pharmacological experiments results showed that CdME had potently antioxidant capacity and ethyl acetate fraction was the active part with the greatest antioxidant activities. Moreover, CdME especially n-butanol fraction significantly accelerated the gastrointestinal transit in mice (acceleration rate: 78.5 ± 1.5% vs. 69.9 ± 3.2% at a dose of 250 mg/kg, compared to the control group, P < .01). On the basis of these results, C. dahurica may be considered as a good resource of antioxidants and digestion-improving agents.

Effects of Trang Phuc Linh Plus-Food Supplement on Irritable Bowel Syndrome Induced by Mustard Oil.

Trang phuc linh plus (TPLP) is a food supplement product derived from dried extracts of herbal agents Atractylodes macrocephala, Poria cocos, Paeonia lactiflora, Phellodendron amurense, and added lactobacillus fermentum lysate (ImmuneGamma®) and 5-hydroxytryptophan. TPLP is a functional food used as adjunctive treatment for treating irritable bowel syndrome (IBS). However the biological effect and its mechanism of action in IBS have not been elucidated. In this study, we aimed to determine the pharmacological activities and mode of action of TPLP on IBS animal models. Mice were given a single administration of 5% mustard oil (MO) intracollonically. Acute colitis induction by MO resulted in later development of an IBS-like accelerated upper gastrointestinal transit in mice. Mice were treated with different does of TPLP and controls. Results showed that TPLP at the dose of 654 mg/kg/day given orally significantly decreased intestinal motility (IM) compared with the control animals. The effect was similar to Duspatalin (80 mg/kg/day) (Mebeverine Hydrochloride, an antispasmodic that helps to relieve the pain and discomfort associated with gastrointestinal spasms). Increased TPLP dose (1962 mg/kg/day) had a better effect on relief of IM than Duspatalin (80 mg/kg/day). TPLP also reduced peristalsis frequency and decreased fluid volume and electrolytes excretion in intestine tested in ex vivo models. Overall, TPLP may be an effective nutraceutical supplement for IBS.

New Morphine Analogs Produce Peripheral Antinociception within a Certain Dose Range of Their Systemic Administration.

Growing data support peripheral opioid antinociceptive effects, particularly in inflammatory pain models. Here, we examined the antinociceptive effects of subcutaneously administered, recently synthesized 14-O-methylmorphine-6-O-sulfate (14-O-MeM6SU) compared with morphine-6-O-sulfate (M6SU) in a rat model of inflammatory pain induced by an injection of complete Freund's adjuvant and in a mouse model of visceral pain evoked by acetic acid. Subcutaneous doses of 14-O-MeM6SU and M6SU up to 126 and 547 nmol/kg, respectively, produced significant and subcutaneous or intraplantar naloxone methiodide (NAL-M)-reversible antinociception in inflamed paws compared with noninflamed paws. Neither of these doses significantly affected thiobutabarbital-induced sleeping time or rat pulmonary parameters. However, the antinociceptive effects of higher doses were only partially reversed by NAL-M, indicating contribution of the central nervous system. In the mouse writhing test, 14-O-MeM6SU was more potent than M6SU after subcutaneous or intracerebroventricular injections. Both displayed high subcutaneous/intracerebroventricular ED50 ratios. The antinociceptive effects of subcutaneous 14-O-MeM6SU and M6SU up to 136 and 3043 nmol/kg, respectively, were fully antagonized by subcutaneous NAL-M. In addition, the test compounds inhibited mouse gastrointestinal transit in antinociceptive doses. Taken together, these findings suggest that systemic administration of the novel compound 14-O-MeM6SU similar to M6SU in specific dose ranges shows peripheral antinociception in rat and mouse inflammatory pain models without central adverse effects. These findings apply to male animals and must be confirmed in female animals. Therefore, titration of systemic doses of opioid compounds with limited access to the brain might offer peripheral antinociception of clinical importance.

Bead study: a novel method to measure gastrointestinal transit in mice.

Intestinal transit assessment in mice using existing methods requires long recording periods or euthanization of animals to localize a tracer. We have developed a novel in vivo method to assess gastrointestinal (GI) transit in mice based on a clinically used 'shapes study'. Mice (n = 70) were gavaged with 5 steel beads and barium 3 h before, with another dose of barium gavaged 10 min before imaging. Mice were fluoroscoped for 20-60 s, and then most of them were euthanized and the GI tract removed to confirm the localization of the beads fluoroscopically. The in vivo and postmortem recordings were analyzed and each bead was scored depending on its location; a total score was calculated by adding individual bead scores. Total scores obtained from the two methods were compared. A group of mice (n = 10) were examined on three occasions, before and after treatment with loperamide or prucalopride. The stomach and cecum were consistently outlined by barium, serving as reference landmarks. There was an excellent overall correlation between in vivo and postmortem transit scores (r = 0.93). Analysis of scores for individual gut segments revealed high agreement for stomach, cecum, and expelled beads, and moderate agreement for the small bowel and colon. Gastrointestinal transit scores were decreased by loperamide and increased by prucalopride compared with baseline. Metallic beads are reliably localized by videofluoroscopy in vivo within the GI tract. This novel imaging method enables repetitive measurements of GI transit in vivo and detects changes induced by motility-modifying agents.

Diabetes attenuates the inhibitory effects of endomorphin-2, but not endomorphin-1 on gastrointestinal transit in mice

Diabetes affects the entire gastrointestinal tract from the esophagus to the anus. In the present study, the charcoal meal test was undertaken to evaluate and compare the effects of intracerebroventricular (i.c.v.) administration of endomorphins (EMs) on gastrointestinal transit in non-diabetic and diabetic mice. Significantly delayed gastrointestinal transit was found in both 4 and 8 weeks alloxan-induced diabetes compared to non-diabetes. Moreover, i.c.v. EM-1 and EM-2 dose-dependently delayed gastrointestinal transit in non-diabetes and diabetes. The EM-1-induced inhibitory effects of gastrointestinal transit in 4 weeks diabetes were qualitatively similar to those of non-diabetes. However, at higher doses, the EM-1-induced effects in 8 weeks diabetes were largely enhanced. Different to EM-1, the EM-2-induced inhibition of gastrointestinal transit in diabetic mice was significantly attenuated compared to non-diabetic mice. Moreover, these effects were further decreased in 8 weeks diabetes. The delayed gastrointestinal transit effects caused by EM-1 may be primarily mediated by μ2-opioid receptor in both non-diabetes and 4 weeks diabetes. Interestingly, in 8 weeks diabetes, these effects were mediated by μ2- and δ-receptors. However, the inhibitory effects of EM-2 were mediated by μ1-opioid receptor, which exerted a reduced function in diabetes. Also, poor blood glucose control might result in the attenuated effects of EM-2. Our present results demonstrated that diabetes attenuates the inhibitory effects of EM-2, but not EM-1 on gastrointestinal transit in mice. The different effects of EM-1 and EM-2 on gastrointestinal transit in diabetes may be due to changes of opioid receptor subtypes and their functional responses.

In vitro binding affinities of a series of flavonoids for μ-opioid receptors. Antinociceptive effect of the synthetic flavonoid 3,3-dibromoflavanone in mice

The pharmacotherapy for the treatment of pain is an active area of investigation. There are effective drugs to treat this problem, but there is also a need to find alternative treatments free of undesirable side effects. In the present work the capacity of a series of flavonoids to bind to the μ opioid receptor was evaluated. The most active compound, 3,3-dibromoflavanone (31), a synthetic flavonoid, presented a significant inhibition of the binding of the selective μ opioid ligand [3H]DAMGO, with a Ki of 0.846 ± 0.263 μM. Flavanone 31 was further synthesized using a simple and cheap procedure with good yield. Its in vivo effects in mice, after acute treatments, were studied using antinociceptive and behavioral assays. It showed no sedative, anxiolytic, motor incoordination effects or inhibition of the gastrointestinal transit in mice at the doses tested. It evidenced antinociceptive activity on the acetic acid-induced nociception, hot plate and formalin tests (at 10 mg/kg and 30 mg/kg). The results showed that the 5-HT2 receptor and the adrenoceptors seem unlikely to be involved in its antinociceptive effects. Naltrexone, a nonselective opioid receptors antagonist, totally blocked compound 31 antinociceptive effects on the hot plate test, but naltrindole (δ opioid antagonist) and nor-binaltorphimine (κ opioid antagonist) did not. These findings demonstrated that 3,3-dibromoflavanone (31), at doses that did not interfere with the motor performance, exerted clear dose dependent antinociception when assessed in the chemical and thermal models of nociception in mice and it seems that its action is related to the activation of the μ opioid receptor.

Mangiferin, a natural xanthone, accelerates gastrointestinal transit in mice involving cholinergic mechanism.

To investigate the effects of mangiferin on gastrointestinal transit (GIT) in normal and constipated mice, together with the possible mechanism. Intragastrically-administered charcoal meal was used to measure GIT in overnight starved Swiss mice. In the first experiments, mangiferin (3 mg/kg, 10 mg/kg, 30 mg/kg, and 100 mg/kg, po) or tegaserod (1 mg/kg, ip) were administered 30 min before the charcoal meal to study their effects on normal transit. In the second series, mangiferin (30 mg/kg) was tested on delayed GIT induced by several different pharmacological agonists (morphine, clonidine, capsaicin) or antagonists (ondansetron, verapamil, and atropine) whereas in the third series, mangiferin (30 mg/kg, 100 mg/kg and 300 mg/kg) or tegaserod (1 mg/kg) were tested on 6 h fecal pellets outputted by freely fed mice. The ratio of wet to dry weight was calculated and used as a marker of fecal water content. Mangiferin administered orally significantly (P < 0.05) accelerated GIT at 30 mg/kg and 100 mg/kg (89% and 93%, respectively), similarly to 5-hydroxytryptamine(4) (5-HT(4)) agonist tegaserod (81%) when compared to vehicle-treated control (63%). Co-administered mangiferin (30 mg/kg) totally reversed the inhibitory effect of opioid agonist morphine, 5-HT(3)-receptor antagonist ondansetron and transient receptor potential vanilloid-1 receptor agonist capsaicin on GIT, but only to a partial extent with the GIT-delay induced by α(2)-adrenoceptor agonist clonidine, and calcium antagonist verapamil. However, co-administered atropine completely blocked the stimulant effect of mangiferin on GIT, suggesting the involvement of muscarinic acetylcholine receptor activation. Although mangiferin significantly enhanced the 6 h fecal output at higher doses (245.5 ± 10.43 mg vs 161.9 ± 10.82 mg and 227.1 ± 20.11 mg vs 161.9 ± 10.82 mg of vehicle-treated control, at 30 and 100 mg/kg, P < 0.05, respectively), the effect of tegaserod was more potent (297.4 ± 7.42 mg vs 161.9 ± 10.82 mg of vehicle-treated control, P < 0.05). Unlike tegaserod, which showed an enhanced water content in fecal pellets (59.20% ± 1.09% vs 51.44% ± 1.19% of control, P < 0.05), mangiferin evidenced no such effect, indicating that it has only a motor and not a secretomotor effect. Our data indicate the prokinetic action of mangiferin. It can stimulate the normal GIT and also overcome the drug-induced transit delay, via a cholinergic physiological mechanism.

Induction of Glucose Intolerance by Acute Administration of Rimonabant

Background/Aims: Rimonabant is a cannabinoid CB1 receptor antagonist. Other CB1 antagonists have biphasic effects on blood glucose levels following acute administration. We therefore tested the effects of rimonabant on glucose tolerance following acute administration. Methods: We tested the effects of oral and intracerebroventricular administration of rimonabant on blood glucose and gastrointestinal transit in mice following oral and intravenous glucose challenge. Results: We found a dose-dependent increase in blood glucose from oral doses of rimonabant of 3 mg/kg and above. WIN55,212-2 (3 mg/kg), a cannabinoid receptor agonist, did not influence blood glucose in the presence or absence of rimonabant. Rimonabant did not induce release of glucose from isolated rat hepatocytes or modify serum insulin concentration in mice. Intracerebroventricular administration of rimonabant caused increases in blood glucose and gastrointestinal transit, suggesting a central nervous system site of action. Increases in blood glucose by rimonabant were partially blocked by the dopamine receptor antagonist haloperidol and significantly blocked by the 5-hydroxytryptophan (5-HT) depleting agent p-CPA and the 5-HT₃ receptor antagonist ondansetron. Conclusions: Rimonabant causes a dose-dependent increase in glucose profile upon glucose challenge partially mediated by the central nervous system control of gastrointestinal carbohydrate absorption through pathways that are modulated by both 5-HT and dopamine.

Tu1997 A Novel In Vivo Method to Measure Gastrointestinal Transit in Mice

INTRODUCTION The intestine is a significant site of gluconeogenesis, with high expression of glucose 6 phosphatase. Abnormal forms of glycogen, including polyglucosan bodies, occur in the muscularis propria in a subset of patients with gastrointestinal motility disorders. Little is known, however, of the distribution of glycogen metabolic enzymes and related proteins in normal gastrointestinal tract, or effects of deficiencies of these proteins on the bowel. METHODS Key enzymes in glycogen metabolism, including glycogen synthase (GS), glycogen branching enzyme (GBE), malin and laforin were examined in stomach, ileum and colon of two mouse strains and in normal human bowel using immunohistochemistry with semiquantitiative analysis of epithelium, muscle, submucosal and myenteric plexus, validated by western blotting and positive and negative controls. The pathological effects of GBE, laforin and malin gene knockout on mouse gastrointestinal tract were also studied. RESULTS GS was present at high levels in the smooth muscle of muscularis propria, GBE in the majority of large ganglion cells of the submucosal and myenteric plexuses, and laforin and malin in submucosal ganglia. Analysis of human bowel showed no significant regional differences in the distribution of GBE, laforin and malin, GS was more prominent in the muscularis propria of the small intestine, compared with stomach and colon. GBE knockout produced a progressive severe myopathy with numerous polyglucosan bodies and vacuolation. Polyglucosan bodies were also present in both laforin and malin knockout models, but with a less severe phenotype than that seen in the GBE knockout, and were not seen in controls. CONCLUSION The distribution of glycogen metabolic proteins in the bowel wall of mouse and man shows a specific neuromuscular distribution for each pathway component. Defects in glycogen metabolism in mouse knockout models reproduce histological features of polyglucosan body myopathy in human digestive motility disorders.

Modulation of mouse gastrointestinal motility by allyl isothiocyanate, a constituent of cruciferous vegetables (Brassicaceae): evidence for TRPA1‐independent effects

Allyl isothiocyanate (AITC, mustard oil), a constituent of many common cruciferous vegetables (Brassicaceae), activates transient receptor potential of ankyrin type-1 (TRPA1) channels, claimed to regulate gastrointestinal contractility. In this study, we have investigated the effect of AITC on intestinal motility. Effects of AITC were investigated in vivo on upper gastrointestinal transit in mice and in mouse isolated ileum [contractions induced by electrical field stimulation (EFS), acetylcholine and spontaneous contractility]. The contractor activity of AITC was studied in mouse isolated colon. The ability of TRPA1 channel antagonists to block AITC-induced elevation of intracellular Ca(2+) [Ca(2+)](i) was assessed in HEK293 cells transfected with rat TRPA1 channels. AITC increased [Ca(2+)](i) in HEK293 cells, reduced ileal contractility (acetylcholine-, EFS-induced contractions and spontaneous contractility), but contracted the isolated colon. Gentamicin and camphor (non-selective TRPA1 channel antagonists), HC-030031 and AP18 (selective TRPA1 channel agonists) inhibited AITC-induced effects in HEK293 cells but not in the ileum or colon. AITC-induced contractions were reduced by tetrodotoxin and strongly reduced by nifedipine, cyclopiazonic acid and ryanodine. In vivo, AITC reduced (following i.p. administration) or increased (following intragastric administration) upper gastrointestinal transit in mice These effects were not affected by HC-030031. AITC, depending, in vitro, on the regions of gut examined and, in vivo, on the route of administration, exerted both stimulatory and inhibitory effects on intestinal motility, which were not sensitive to TRPA1 channel antagonists. The proposition that TRPA1 channels are the primary targets for AITC to induce contraction should be revised.

A New Method Using Flow Cytometry to Measure the Effects of Drugs on Gastric Emptying and Gastrointestinal Transit in Mice

The use of radiolabelled markers is considered to be a gold standard for assessing gastric emptying and gastrointestinal transit in mice and rats, but their use has increasingly been restricted due to health concern. Therefore, a new method using fluorescent polystyrene microbeads and flow cytometry was devised. Saline containing fluorescent markers (together with non-fluorescent microbeads) was infused into the stomach of each mouse and gastric emptying and gastrointestinal transit were calculated by measuring the quantity of the fluorescent microbeads in the gastrointestinal tract using flow cytometer. The effects of saline (as a control), morphine (CAS 52-26-6) and dexmedetomidine (CAS 113775-47-6) were tested. Both gastric emptying and gastrointestinal transit measured with this method (after i.p. injection of saline) were similar to those reported previously using the conventional radiolabelled methods. Morphine significantly inhibited both gastric emptying and gastrointestinal transit in a dose-dependent manner. Dexmedetomidine did not significantly inhibit gastric emptying but inhibited gastrointestinal transit. These results were also similar to those obtained using the conventional radiolabelled method. The method using fluorescent microbeads and flow cytometry may be a reliable alternative to the methods using radioisotope for studying the effects of drugs on gastric emptying and gastrointestinal transit.