Role of tachykinins in castor oil diarrhoea in rats

Unraveling the multi-faceted role of Rosmarinus officinalis L. (rosemary) and diosmetin in managing gut motility

ETHNOPHARMACOLOGICAL RELEVANCE

Rosmarinus officinalis L. (Rosemary) is a popular herb with reported effectiveness against diarrhea, anxiety and constipation, albeit with limited pharmacological evidence.

AIM OF THE STUDY

The current study was aimed at evaluating the therapeutic potential, possible pharmacological mechanisms of action and active constituents of hydro-ethanolic extract of rosemary (Rs.Cr), as potential anti-diarrheal, laxative and anxiolytic agent.

METHOD

Rs.Cr was analyzed through reverse-phase high pressure liquid chromatography (RP-HPLC). Laxative, antidiarrheal, and anxiolytic activities were assessed using in vivo models. Spasmogenic and spasmolytic mechanisms were studied on isolated guinea pig ileum and rabbit jejunum tissues, respectively. Possible role of diosmetin, one of the active constituents of Rs.Cr was also evaluated.

RESULTS

RP-HPLC analysis revealed presence of diosmetin, rutin and apigenin in Rs.Cr. Laxative effect was seen at low doses, which was partially reversed in atropinized mice. The spasmogenic mechanism was mediated by cholinergic and histaminergic receptors stimulation. At higher doses, antidiarrheal activity was evident, with reduction in gastrointestinal motility and secretions using charcoal meal and enteropooling assays, respectively. Rs.Cr also showed dose-dependent anxiolytic effect. The antispasmodic mechanisms were mediated by anti-muscarinic and K+ channel opening-like effect (predominant KATP-dependent). Diosmetin exhibited antidiarrheal and antispasmodic activities, but spasmogenic effect was not seen.

CONCLUSION

Rosemary leaves have dual antidiarrheal and laxative effects, and as well as anxiolytic activity. In addition, the possible modulation of muscarinic and histaminergic receptors, and KATP channels show it as potential herb to be explored for irritable bowel syndrome. Diosmetin is possibly one of its constituents that contributes to its antidiarrheal activity.

The Detailed Pharmacodynamics of the Gut Relaxant Effect and GC-MS Analysis of the Grewia tenax Fruit Extract: In Vivo and Ex Vivo Approach

The study was performed to assess and rationalize the traditional utilization of the fruit part of Grewia tenax (G. tenax). The phytoconstituents present in the methanolic extract were analyzed using Gas-Chromatography-Mass Spectroscopy (GC-MS), while the anti-diarrheal activity was investigated in the Swiss albino mice against castor oil-provoked diarrhea in vivo. The antispasmodic effect and the possible pharmacodynamics of the observed antispasmodic effect were determined in an isolated rat ileum using the organ bath setup as an ex vivo model. GC-MS findings indicate that G. tenax is rich in alcohol (6,6-dideutero-nonen-1-ol-3) as the main constituent (20.98%), while 3-Deoxy-d-mannoic lactone (15.36%) was detected as the second major constituents whereas methyl furfural, pyranone, carboxylic acid, vitamin E, fatty acid ester, hydrocarbon, steroids, sesquiterpenes, phytosterols, and ketones were verified as added constituents in the methanolic extract. In mice, the orally administered G. tenax inhibited the diarrheal episodes significantly (p < 0.05) at 200 mg/kg (40% protection), and this protection was escalated to 80% with the next higher dose of 400 mg/kg. Loperamide (10 mg/kg), a positive control drug, imparted 100% protection, whereas no protection was shown by saline. In isolated rat ileum, G. tenax completely inhibited the carbamylcholine (CCh; 1 µM) and KCl (high K+; 80 mM)-evoked spasms in a concentrations-mediated manner (0.03 to 3 mg/mL) by expressing equal potencies (p > 0.05) against both types of evoked spasms, similar to papaverine, having dual inhibitory actions at phosphodiesterase enzyme (PDE) and Ca2+ channels (CCB). Similar to papaverine, the inhibitory effect of G. tenax on PDE was further confirmed indirectly when G. tenax (0.1 and 0.3 mg/mL) preincubated ileal tissues shifted the isoprenaline-relaxation curve towards the left. Whereas, pre-incubating the tissue with 0.3 and 1 mg/mL of G. tenax established the CCB-like effect by non-specific inhibition of CaCl2−mediated concentration-response curves towards the right with suppression of the maximum peaks, similar to verapamil, a standard CCB. Thus, the present investigation revealed the phytochemical constituents and explored the detailed pharmacodynamic basis for the curative use of G. tenax in diarrhea and hyperactive gut motility disorders.

Dual Inhibition of Phosphodiesterase and Ca++ Channels Explains the Medicinal Use of Balanites aegyptiaca (L.) in Hyperactive Gut Disorders

The present study attempted to evaluate and rationalize the medicinal use of the methanolic extract of the fruits of Balanites aegyptiaca (B. aegyptiaca) in the treatment of hyperactive gut disorders. The in vivo, castor oil-induced diarrhea model in mice was followed to test its antidiarrheal effect. To test the antispasmodic effect and to explore its pharmacodynamic details, isolated small intestines (ileum) obtained from rats were selected to provide physiological conditions for the ex vivo assays. In the in vivo assays, the orally administered extract of B. aegyptiaca protected mice from diarrheal drops with resultant percent inhibitions of 40% and 80% at the respective doses of 200 mg/kg and 400 mg/kg, while the highest protection (100%) was observed with a positive control drug, loperamide, at 10 mg/kg. In the ileum, B. aegyptiaca produced an antispasmodic effect in a concentration-dependent manner by inhibiting the carbachol (CCh; 1 µM) and high K⁺ (80 mM)-evoked spasms with resultant EC₅₀ values of 1.44 mg/mL (1.08–1.78) and 1.27 mg/mL (0.98–1.66), respectively. Papaverine, a known phosphodiesterase enzyme (PDE) inhibitor and blocker of Ca⁺⁺ channels (CCB), also inhibited both CCh and high K⁺ induced contractions at comparable EC₅₀ values of 8.72 µM (7.92–9.24) and 8.14 µM (7.62–8.84), respectively. Contrary to the extract and papaverine, verapamil showed distinctly higher potency in regard to inhibiting high K⁺, compared to CCh-evoked spasms that had EC₅₀ values of 0.16 µM (0.13–0.261) and 2.54 µM (2.28–2.92), respectively. The inhibitory effects of B. aegyptiaca on PDE were further confirmed when the pre-incubated extract shifted the isoprenaline-mediated relaxation curves (CRCs) towards the left, similar to papaverine, whereas the CCB-like effect was confirmed when the pre-incubated tissues with B. aegyptiaca caused deflection in the Ca⁺⁺ CRCs towards the right, constructed in Ca⁺⁺ free medium with suppression of the maximum response. Thus, this study provides detailed, mechanistic support for the medicinal use of B. aegyptiaca in the treatment of hyperactive gut disorders.

Dose-dependent Spasmolytic, Bronchodilator, and Hypotensive Activities of Panicum miliaceum L

Panicum miliaceum L. is a medicinally effective plant used in indigenous system of medicine for a variety of ailments. However, there is no comprehensive study explaining its effectiveness in gastrointestinal tract, respiratory, and cardiovascular system ailments. This study was designed to validate the pharmacological basis for the folkloric use of Panicum miliaceum L. in diarrhea, asthma, and hypertension. Panicum miliaceum extract was analyzed to detect the presence of bioactive compounds by HPLC. The isolated rabbit jejunum, trachea, and aorta were used for in vitro experiments using tissue bath assembly coupled with Power Lab data acquisition system to explore their relative effects. In-vivo experiments were performed for anti-diarrheal activity. HPLC analysis revealed the presence of gallic acid, butylated hydroxytoluene, catechin, and quercetin. Concentration dependent activities were observed by relaxing K+ (low) induced contractions having spasmolytic effect with EC50 = .358 ± .052, bronchodilator (EC50 = 2.483 ± .05793), and vasorelaxant (EC50 = .383 ± .063), probably due to the ATP dependent potassium channel activation. It was confirmed through pre-exposure of glibenclamide (specific ATP-dependent K+ channel blocker) having similarities with cromakalim. Pm.Cr revealed its antidiarrheal via in vivo experiments on rats. This study indicates that Panicum miliaceum has antidiarrheal, spasmolytic, bronchodilator, and vasorelaxant activities probably due to the ATP dependent K+ channel activation.

GC-MS Analysis and In Vivo and Ex Vivo Antidiarrheal and Antispasmodic Effects of the Methanolic Extract of Acacia nilotica

This present study evaluated and rationalized the medicinal use of the fruit part of Acacia nilotica methanolic extract. The phytochemicals were detected using gas chromatography−mass spectrometry (GC−MS) while the in vivo antidiarrheal test was done using Swiss albino mice. To determine the details of the mechanism(s) involved in the antispasmodic effect, isolated rat ileum was chosen using different ex vivo assays by maintaining a physiological environment. GC−MS results showed that A. nilotica contained pyrogallol as the major polyphenol present (64.04%) in addition to polysaccharides, polyphenol, amino acid, steroids, fatty acid esters, and triterpenoids. In the antidiarrheal experiment, A. nilotica inhibited diarrheal episodes in mice significantly (p < 0.05) by 40% protection of mice at 200 mg/kg, while 80% protection was observed at 400 mg/kg by the orally administered extract. The highest antidiarrheal effect was observed with loperamide (p < 0.01), used as a control drug. In the ex vivo experiments, A. nilotica inhibited completely in increasing concentrations (0.3 to 10 mg/mL) the carbachol (CCh; 1 µM) and high K+ (80 mM)-evoked spasms in ileum tissues at equal potencies (p > 0.05), similar to papaverine, a dual inhibitor of the phosphodiesterase enzyme (PDE) and Ca++ channels. The dual inhibitory-like effects of A. nilotica on PDE and Ca++ were further validated when A. nilotica extract (1 and 3 mg/mL)-pre-incubated ileum tissues potentiated and shifted isoprenaline relaxation curves towards lower doses (leftward), similar to papaverine, thus confirming the PDE inhibitory-like mechanism whereas its CCB-like effect of the extract was confirmed at 3 and 5 mg/mL by non-specific inhibition of CaCl2-mediated concentration response curves towards the right with suppression of the maximum peaks, similar to verapamil, used as standard CCB. Thus, this study characterized the chemical composition and provides mechanistic support for medicinal use of A. nilotica in diarrheal and hyperactive gut motility disorders.

Effects of Essential Oils of Elettaria cardamomum Grown in India and Guatemala on Gram-Negative Bacteria and Gastrointestinal Disorders

The present study examined the chemical composition and antimicrobial and gastrointestinal activity of the essential oils of Elettaria cardamomum (L.) Maton harvested in India (EC-I) and Guatemala (EC-G). Monoterpenes were present in higher concentration in EC-I (83.24%) than in EC-G (73.03%), whereas sesquiterpenes were present in a higher concentration in EC-G (18.35%) than in EC-I (9.27%). Minimum inhibitory concentrations (MICs) of 0.5 and 0.25 mg/mL were demonstrated against Pseudomonas aeruginosa in EC-G and EC-I, respectively, whereas MICs of 1 and 0.5 mg/mL were demonstrated against Escherichia coli in EC-G and EC-I, respectively. The treatment with control had the highest kill-time potential, whereas the treatment with oils had shorter kill-time. EC-I was observed to be more potent in the castor oil-induced diarrhea model than EC-G. At 100 and 200 mg/kg, P.O., EC-I exhibited 40% and 80% protection, respectively, and EC-G exhibited 20% and 60% protection, respectively, in mice, whereas loperamide (10 mg/kg, i.p., positive control) exhibited 100% protection. In the in vitro experiments, EC-I inhibited both carbachol (CCh, 1 µM) and high K⁺ (80 mM)-induced contractions at significantly lower concentrations than EC-G. Thus, EC-I significantly inhibited P. aeruginosa and E. coli and exhibited more potent antidiarrheal and antispasmodic effects than EC-G.

Ethnopharmacological basis for folkloric claims of Anagallis arvensis Linn. (Scarlet Pimpernel) as prokinetic, spasmolytic and hypotensive in province of Punjab, Pakistan

ETHNOPHARMACOLOGICAL RELEVANCE

The conventional naturopaths of Punjab Province (Pakistan) have trivial usage of Anagallis arvensis Linn.(Primulaceae) for cure of diarrhea, constipation, asthma as well as hypertension.

AIM

Present research was focused to discover comprehensive mechanism of spasmogenic, spasmolytic, bronchorelaxant and hypotensive folkloric usage of Anagallis arvensis Linn..

METHODOLOGY

The crude extract of Anagallis arvensis Linn. (Aa.Cr) & its (aqueous & organic) portions tested in-vitro on isolated jejunum, ileum, trachea, aorta, paired atria preparations as well as in-vivo in mice & normotensive anaesthetized rats. The responses have been noted by transducers (isotonic & isometric) coupled to Power Lab.

RESULT

Anagallis arvensis Linn. (Aa.Cr; crude aqueous-alcoholic extract) produced contractile action at low concentrations but relaxant action was observed by increasing concentrations on spontaneous contractions of isolated jejunum of rabbit. But, pre-treatment of tissue with atropine prior extract caused suppression of contractile effect indicating presence of cholinergic muscarinic response of Aa.Cr. It also triggered relaxation of high Potassium -stimulated contractions of jejunum with subsequent non-parallel right move in Ca++ CRCs. Moreover, Aa.Cr relaxed carbachol - & high Potassium - stimulated contractions in trachea of rabbit but observed relaxant effect was powerful against CCh (1 μM)- stimulated contractions with rightside parallel move of CCh-curves succeeded by non-parallel move, like Dicyclomine, having dual activities. The Aa.Cr also showed relaxant result on Phenylephrine and High Potassium -prompted contractions in endothelium intact aorta. The fractionation revealed segregations of contractile & relaxant effects in relevant aqueous & organic portions. The Intravenous administration of Aa.Cr to ketamine-diazepam anaesthetized normo-tensive albino rats resulted in decreased MABP, SBP & DBP. The Aa.Cr applied negative (-) inotropic & chronotropic action on paired atria. The Aa.Cr also exhibited anti-diarrheal action in mice against castor oil prompted diarrhea and also mitigated distance covered by charcoal meal in gastrointestinal tract in a manner comparable with loperamide.

CONCLUSION

These results revealed presence of CCB and selective muscarinic agonist activity in Aa.Cr, hence validating folkloric practice of Anagallis arvensis Linn. in diarrhea, constipation, asthma & hypertension.

Multiple Pathway-Mediated Gut-Modulatory Effects of Maerua subcordata (Gilg) DeWolf

BACKGROUND

Gastrointestinal disorders are often poorly managed, especially in developing countries, where there are limited resources and therapeutic options. Despite the rich diversity of medicinal plants that offer effective treatment options with fewer side effects, studies that provide scientific verification are lacking. Maerua subcordata (Gilg) DeWolf is among the plants claimed to have wide traditional medicine, use, including as a remedy against gastrointestinal problems. Therefore, this work aimed to evaluate the gut-modulatory effects of a crude leaf extract of M. subcordata (MSL.Cr), as well as its possible mechanism of action.

METHODS

A castor oil (10 mL/kg)-induced diarrheal mouse model was used to evaluate the antidiarrheal effect of MSL.Cr, and the spasmodic/antispasmodic effect of the extract was assessed using isolated rabbit jejunum with and without addition of standard cholinergic agonists/antagonists to predict the possible mechanism of action.

RESULTS

MSL.Cr exhibited 40% and 80% protection against castor oil-induced diarrhea in mice at doses of 500 and 1,000 mg/kg, respectively. In isolated rabbit jejunum, the extract increased spontaneous contractions at low doses (0.01-0.1 mg/mL), and was sensitive to atropine, whereas it showed complete inhibition at higher doses (0.3-1 mg/mL). It was shown that the relaxant effect was possibly mediated by the involvement of phosphodiesterase-enzyme inhibition and K+-channel activation. The extract potentiated the control concentration-response curve of carbachol, shifting it to the left, similarly to the control drug papaverine. The potassium-channel opening-like activity of MSL.Cr was possibly mediated by the involvement of aspecific K+-channels inhibition, since tetraethylammonium, anunselective antagonist of K+ channels, significantly reversed its inhibitory effect.

CONCLUSION

This study showed that the M. subcordata leaf extract demonstrated gut-modulatory effects, possibly mediated by a combination of muscarinic-receptor stimulation, phosphodiesterase inhibition, and aspecific K+-channel activation.

In Silico, Ex Vivo and In Vivo Studies of Roflumilast as a Potential Antidiarrheal and Antispasmodic agent: Inhibition of the PDE-4 Enzyme and Voltage-gated Ca++ ion Channels

The aim of the present study was to evaluate the possible gut inhibitory role of the phosphodiesterase (PDE) inhibitor roflumilast. Increasing doses of roflumilast were tested against castor oil-induced diarrhea in mice, whereas the pharmacodynamics of the same effect was determined in isolated rabbit jejunum tissues. For in silico analysis, the identified PDE protein was docked with roflumilast and papaverine using the Autodock vina program from the PyRx virtual screening tool. Roflumilast protected against diarrhea significantly at 0.5 and 1.5 mg/kg doses, with 40% and 80% protection. Ex vivo findings from jejunum tissues show that roflumilast possesses an antispasmodic effect by inhibiting spontaneous contractions in a concentration-dependent manner. Roflumilast reversed carbachol (CCh, 1 µM)-mediated and potassium (K+, 80 mM)-mediated contractile responses with comparable efficacies but different potencies. The observed potency against K+ was significantly higher in comparison to CCh, similar to verapamil. Experiments were extended to further confirm the inhibitory effect on Ca++ channels. Interestingly, roflumilast deflected Ca++ concentration–response curves (CRCs) to the right with suppression of the maximum peak at both tested doses (0.001-0.003 mg/mL), similar to verapamil. The PDE-inhibitory effect was authenticated when pre-incubation of jejunum tissues with roflumilast (0.03-0.1 mg/mL) produced a leftward deflection of isoprenaline-mediated inhibitory CRCs and increased the tissue level of cAMP, similar to papaverine. This idea was further strengthened by molecular docking studies, where roflumilast exhibited a better binding affinity (-9.4 kcal/mol) with the PDE protein than the standard papaverine (-8.3 kcal/mol). In conclusion, inhibition of Ca++ channels and the PDE-4 enzyme explains the pharmacodynamics of the gut inhibitory effect of roflumilast.

The Potential Involvement of an ATP-Dependent Potassium Channel-Opening Mechanism in the Smooth Muscle Relaxant Properties of Tamarix dioica Roxb

Background: Tamarix dioica is traditionally used to manage various disorders related to smooth muscle in the gastrointestinal, respiratory, and cardiovascular systems. This study was planned to establish a pharmacological basis for the uses of Tamarix dioica in certain medical conditions related to the digestive, respiratory, and cardiovascular systems, and to explore the underlying mechanisms. Methods: A phytochemical study was performed by preliminary methods, followed by HPLC-DAD and spectrometric methods. In vivo evaluation of a crude hydromethanolic extract of T. dioica (TdCr) was done with a castor-oil-provoked diarrheal model in rats to determine its antidiarrheal effect. Ex vivo experiments were done by using isolated tissues to determine the effects on smooth and cardiac muscles and explore the possible mechanisms. Results: TdCr tested positive for flavonoids, saponins, phenols, and tannins as methanolic solvable constituents in a preliminary study. The maximum quantity of gallic acid equivalent (GAE), phenolic, and quercetin equivalent (QE) flavonoid content found was 146 ± 0.001 μg GAE/mg extract and 36.17 ± 2.35 μg QE/mg extract. Quantification based on HPLC-DAD (reverse phase) exposed the presence of rutin at the highest concentration, followed by catechin, gallic acid, myricetin, kaempferol, and apigenin in TdCr. In vivo experiments showed the significant antidiarrheal effect of TdCr (100, 200, and 400 mg/kg) in the diarrheal (castor-oil-provoked) model. Ex vivo experiments revealed spasmolytic, bronchodilatory, and vasorelaxant activities as well as partial cardiac depressant activity, which may be potentiated by a potassium channel opener mechanism, similar to that of cromakalim. The potassium channel (K_ATP channel)-opening activity was further confirmed by repeating the experiments in glibenclamide-pretreated tissues. Conclusions: In vivo and ex vivo studies of T. dioica provided evidence of the antidiarrheal, spasmolytic, bronchodilator, vasorelaxant, and partial cardiodepressant properties facilitated through the opening of the K_ATP channel.

Ultrasonic extraction, structural characterization, and bioactivities of nonstarch polysaccharides from red yeast rice

Red yeast rice (RYRP) has been utilized for coloring food, brewing wine, and preserving meat, which is also used as a folk medicine for centuries. In this study, a water-soluble nonstarch polysaccharide from RYRP was extracted by using ultrasonic-assisted extraction method. By using the Box-Behnken design to optimize the parameters for extracting the RYRP, the maximum extraction yield (3.37 ± 0.78%) was obtained under the optimal extraction conditions as follows: ratio of water to raw material (40 mL/g), extraction temperature (62 °C), extraction time (75 Min), and ultrasonic power (200 W). Moreover, monosaccharide composition analysis showed that RYRP was consisted of mannose, glucosamine, glucose, and galactose with a molar ratio of 0.152:0.015:1:0.149. The molecular weight distribution analysis showed that the average molecular weight of the RYRP fraction was about 3.49 × 10³ Da. Furthermore, RYRP exhibited significant antioxidant activities in vitro and the gastrointestinal-protective effect in vivo using gastrointestinal disorders model mice. RYRP could be explored as a potential source in the pharmaceutical and functional food industries.

Butyrlycholine esterase inhibitory activity and effects of extracts (fruit, bark and leaf) from Zanthoxylum armatum DC in gut, airways and vascular smooth muscles

BACKGROUND

Fruit, bark and leaves of Zanthoxylum armatum DC are popular remedies for gastrointestinal, cardiovascular and respiratory disorders in the subcontinent traditional practices. The aim of the study was to individually probe the profile of methanol extracts from three different parts of Zanthoxylum armatum.

METHODS

The ex-vivo muscle relaxant effects of extracts were assessed in the isolated intestine, trachea and thoracic aortic rings and were compared with the positive controls and CRC were constructed. The anti-diarrheal effect of extracts was evaluated in mice by inducing diarrhea with castor oil. The extracts were also studied for acute toxicity and butyrylcholine esterase inhibition.

RESULTS

The extracts from fruit, bark and leaves of Z. armatum showed inhibitory effect against the butyrylcholine esterase enzyme with percent inhibition of 50.75 ± 1.23, 82.57 ± 1.33, and 37.52 ± 1.11respectively, compared to standard serine (IC₅₀: 0.04 ± 0.001 μmol/L). The fruit and bark extracts provided 75, and 52% diarrheal protection, compared to verapamil (96%). In isolated rabbit jejunum strips, increasing addition of the extracts inhibited the spontaneous and high K⁺ precontractions with EC₅₀ values of 0.71 and 3 mg/mL for fruit, EC₅₀ values of 0.61 and 0.5 mg/mL for bark, EC₅₀ 0.81 and 3.1 mg/mL for leaves, like verapamil. The extracts induced a concentration-dependent relaxation of the carbachol (1 μM) and high K⁺ (80 mM) precontractions with EC₅₀ values of 2.4 and 0.9 mg/mL for fruit, EC₅₀ values of 1.2 and 3 for leaves. The bark extract was equipotent against both contractions with EC₅₀ 3.1 and 0.7 mg/mL, respectively. In the aortic rings, the fruit extract completely relaxed the phenylephrine (1 μM)-induced contractions with (EC₅₀ value = 0.8 mg/ml) and a partial inhibition of high K⁺ induced contractions. The leaves extract completely relaxed the aortic contractions with (EC₅₀ values = 1.0 and 8.5 mg/ml). The extracts caused no acute toxicity up to 3 g/kg dose.

CONCLUSIONS

The experiments revealed that the extracts of aerial parts of Z. armatum have antidiarrheal properties in vivo and showed spasmolytic effect in intestinal and tracheal preparations with possible mechanism involving the blockage of Ca⁺⁺ channels. These experiments provide enough justification for use of this plant in ethnomedicine in diarrhea, gut and bronchial spasms.

Dual mechanisms of anti-muscarinic and Ca++ antagonistic activities to validate the folkloric uses of Cyperus niveus Retz. as antispasmodic and antidiarrheal

ETHNOPHARMACOLOGICAL RELEVANCE

Cyperus species are famous for their traditional uses and very commonly used for their anti-spasmodic and anti-diarrheal activities. Cyperus niveus Retz. is used in local traditional system of medicine in Pakistan to treat diarrhea and emesis.

AIM OF THE STUDY

The aim of the study was to validate the traditional uses and to provide the possible mechanisms for the medicinal use of Cyperus niveus Retz. as anti-spasmodic, anti-diarrheal and anti emetic.

MATERIALS AND METHODS

The in-vivo studies of anti-diarrheal, charcoal meal GI transit test and anti-emetic activities were conducted in rats, mice and chicks respectively, while isolated tissues of rabbit's jejunum and rat's ileum were used for in-vitro experiments. Phytochemical analysis was also undertaken.

RESULTS

The phytochemical study of hydro-ethanolic extract of Cyperus niveus Retz. showed the presence of flavonoids, phenols, alkaloids, tannins, saponins and glycosides. Cn. Cr caused significant inhibition of castor oil-induced diarrhea in rats (300,500 & 700mg/kg) using loperamide (10mg/kg, p.o) as standard. Cn. Cr also significantly decreased the motility in charcoal meal GI transit test at 100-200mg/kg in mice, using atropine (3.0mg/kg) as positive control. In jejunum tissue, Cn. Cr relaxed carbachol(1µM) and K⁺(80mM)-induced contractions, similar to the effect of dicyclomine. Pre-incubation of isolated rat ileum tissues with Cn. Cr (0.1mg/mL) caused the corresponding shift of CCh concentration response curve (CRC) to right without decrease in max. response whereas at the concentration of 0.3mg/mL caused the rightward nonparallel shift with max. response suppression, similar to dicyclomine. Antimuscarinic effect was further confirmed when prior administration of Cn. Cr (0.1, 0.3 and 1mg/mL) caused concentration dependent inhibition of induced contractions of carbachol, comparable to atropine (1µM). To confirm the Ca²⁺ channel blocking (CCB), the rabbit jejunum was pre-incubated with Cn. Cr (0.3 & 1.0mg/mL), produced a shift in CRCs of calcium toward right with decrease in the maximum response at next concentration, similar to that of dicyclomine. The organic fraction of Cyperus niveus Retz. (Cn. Dcm) showed Ca²⁺ antagonist and anticholinergic activities with higher potency against K⁺(80mM) induced contractions, like verapamil, while aqueous fraction (Cn. Aq) relaxed only carbachol(1µM) induced contractions with no prominent effect on K⁺ (80mM)-contractions even at the higher concentration of 10mg/mL, similar to atropine. Cn. Cr also showed significant anti-emetic effect in Chick emesis model using chlorpromazine as standard.

CONCLUSION

This study shows the presence of antidiarrheal and spasmolytic activities in Cyperus niveus Retz. extract, mediated by dual blocking mechanisms of muscarinic receptors and Ca²⁺ channels. The results further indicate the presence of anti-emetic activity in Cn. Cr, which may be because of its anti-muscarinic potential. This study provides the scientific bases to the traditional use of Cn. Cr in diarrhea and emesis.

Evaluation of cytotoxic, analgesic, antidiarrheal and phytochemical properties of Hygrophila spinosa (T. Anders) whole plant

BACKGROUND

Synthetic drugs are going to be replaced by plant-derived traditional drugs due to their cost effectiveness, relatively less harmfulness, and efficacy against multidrug resistance organisms. Hygrophila spinosa (Acanthaceae) has been used in a wide range of ailments including flatulence, diarrhea, dysentery, gonorrhea, and menorrhagia. Therefore, we investigated the cytotoxic, antinociceptive, and antidiarrheal effects of H. spinosa ethanol extract (EExHs).

METHODS

Preliminary phytochemical screening was accomplished by established methods modified in experimental protocol. EExHs was undertaken for cytotoxic assay by Brine shrimp lethality bioassay, antinociceptive action by acetic acid induced writhing test, and antidiarrheal activity by castor oil induced antidiarrheal test. Data were analyzed by GraphPad Prism 6.0 software using Dunnett's test for multiple comparisons.

RESULTS

Reducing sugar, steroid, glycoside, tannin, alkaloid, saponins, and flavonoids were found to be present in EExHs. Lethal concentration (LC50) of EExHs for brine shrimps was 50.59 µg/mL which was relatively lower than that of the standard drug vincristine sulfate. In acetic acid induced writhing test, oral administration of EExHs at three different doses (125, 250, and 500 mg/kg) decreased writhing in dose-dependent manner while the highest dose (500 mg/kg) achieved the maximum percentages of pain inhibition (58.8%). Diclofenac sodium (25 mg/kg) was used as a reference antinociceptive drug. The antidiarrheal action of EExHs was not found to be very promising for further use; however, the pure compounds from EExHs could be analyzed to justify the effects.

CONCLUSIONS

This research demonstrates that the secondary metabolites guided cytotoxic and analgesic effects could be extensively studied in multiple models to confirm the effects.

Freeze dried extracts of Bidens biternata (Lour.) Merr. and Sheriff. show significant antidiarrheal activity in in-vivo models of diarrhea

ETHNOPHARMACOLOGICAL RELEVANCE OF THE STUDY

Diarrhea remains one of the main killers of children aged below five years. Traditional antidiarrheal remedies form a potentially viable source of novel low cost efficacious treatments in low resource settings. There is therefore a pressing need to scientifically evaluate these remedies.

AIM OF THE STUDY

This study aimed to investigate the in vivo and in vitro antidiarrheal activity of freeze dried Bidens biternata, a herb used in traditional Ayurvedic medicine in the management of diarrhea.

MATERIALS AND METHODS

In the castor oil test, twenty (20) adult Sprague-Dawley rats were randomized to a negative control (normal saline, n=5), a positive control (5mg/kg loperamide, n=5), and two test groups. The low dose test group received 200mg/kg Bidens biternata extract (n=5) while the high dose test group received 400mg/kg B. biternata extract (n=5). Castor oil (4ml/kg) was then administered to the animals one hour after administration of the respective treatments after which the total mass of fecal output excreted after four (4) hours was determined. In the charcoal meal test fifteen (15) Sprague Dawley rats were randomized to a control group (normal saline 5ml/kg orally, n=5), a positive control group (atropine sulfate 0.1mg/kg i.p., n=5) and a test group (400mg/kg B. biternata extract, n=5). Charcoal meal was then administered via oral gavage to each rat thirty (30) minutes after the administration of the various treatments. The distance covered by the charcoal meal from the pylorus was then determined after sacrifice of the animals thirty minutes after the meal. In the enteropooling test twenty (20) Sprague-Dawley rats were randomized to a control group (5% v/v ethanol in normal saline, n=5), a positive control group (5mg/kg loperamide, n=5) and a test group (400mg/kg B. biternata extract, n=5). For each group prostaglandin E2 (PGE2) (100μg/kg) was administered immediately after the treatments. The animals were then sacrificed half an hour later and the volume of the small intestine contents determined. The effects of different concentrations of B. biternata extract (0.5. 1.0, 2.0, 3.0 and 5.0mg/ml) on jejunal contraction were investigated and a dose-response curve constructed using the experimental data after which The ED50 dose was determined. The effect of tamsulosin (α1 adrenergic blocker), yohimbine (α2 adrenergic blocker), propranolol (β adrenergic blocker) and naloxone (μ opioid blocker) on the contractile activity of the extract were also investigated. The experimental data were expressed as mean±standard error of mean (SEM) and then analyzed using one-way ANOVA followed by Tukey's post hoc test in cases of significance (set at p<0.05).

RESULTS

The freeze dried extracts of B. biternata had significant antidiarrheal effects in the castor oil induced diarrhea model (p<0.01) with the highest activity being observed at the 400mg/kg dosage level (1.66±0.81g vs. 4.54±0.51g control, p=0.01). B. biternata extract had significant effects on intestinal motility in the charcoal meal test compared to the control group (43.61±4.42% vs. 60.54±3.33%: p<0.05). B. biternata extract had a significant effect on PGE2 induced enteropooling (3.06±0.07ml vs. 4.74±0.10ml; p<0.001). The freeze dried extracts of B. biternata had a significant negative effect on the contractility of the isolated rabbit jejunum (p<0.001). The effects of the extract were significantly attenuated by tamsulosin (53.94±4.20% vs. 80.57±4.09%; p<0.01) and naloxone (53.94±4.20% vs. 73.89±7.26%; p<0.05). Yohimbine (p>0.05) and propranolol (p>0.05) however did not have any significant effect on the contractile activity of the extract.

CONCLUSIONS

The freeze dried extract of B. biternata possess significant antidiarrheal activity in both in vitro and in vivo models which appears to be mediated by modulating both the intestinal motility as well as the secretory activity. The results of this study also validate its traditional use as an antidiarrheal remedy.

Gut modulatory and butyrylcholinesterase inhibitory activities of Gaultheria trichophylla

CONTEXT

Gaultheria trichophylla Royle (Ericaceae) and related species have been used in the traditional system of medicine for the treatment of diarrhoea, pain and inflammation.

OBJECTIVE

The present investigation explores G. trichophylla for its potential activity in hyperactive gut disorders.

MATERIALS AND METHODS

Antidiarrheal activity was evaluated on castor oil induced diarrhoea in mice with reference to standard drug verapamil. Gut modulatory activity was performed on isolated jejunum tissue preparations on spontaneous and high potassium induced contractions. Butyrylcholinesterase (BChE) inhibitory activity was performed with an in vitro study. Extract was tested for toxicity in mice.

RESULTS

In the in vivo studies, the methanol extract of G. trichophylla and verapamil significantly (p < 0.05, 0.01, 0.001) inhibited the frequency of defecation as well as wetting of faeces when compared with the negative control. The methanol (Gt. MeOH) extract of G. trichophylla caused a dose-dependent inhibitory effect on spontaneous contractions in isolated rabbit jejunum preparations and exhibited a partial inhibitory effect against high K⁺(80 mM) induced precontractions. Gt. MeOH shifted the Ca²⁺concentration-response curves (CRCs) to the right, suggesting calcium channel blocking like constituents. In an in vitro assay Gt. MeOH inhibited BChE enzyme with an IC₅₀ values of 35.52 ± 1.17 μg/mL. The extract showed no toxicity in mice at the dose of 3 g/kg.

DISCUSSION AND CONCLUSION

This study provides evidence that G. trichophylla possesses combinations of inhibitory and stimulatory effects mediated through possible cholinergic and less potent calcium blocking constituents, respectively. The latter may be responsible for the antidiarrheal effect.

Curcumin Ameliorates Reserpine-Induced Gastrointestinal Mucosal Lesions Through Inhibiting IκB-α/NF-κB Pathway and Regulating Expression of Vasoactive Intestinal Peptide and Gastrin in Rats

The objective of our study was to investigate whether curcumin protects against reserpine-induced gastrointestinal mucosal lesions (GMLs) in rats and to explore the mechanism of curcumin's action. Sprague-Dawley rats were randomly divided into four groups: control group, reserpine-treated group, reserpine treatment group with curcumin at high dose (200 mg/kg), and reserpine treatment group with curcumin at low dose (100 mg/kg). Rats in reserpine-treated group were induced by intraperitoneally administered reserpine (0.5 mg/kg) for 28 days. TUNEL staining and hematoxylin and eosin staining were used to evaluate the apoptotic cells and morphologic changes. In addition, to explore the mechanism of curcumin in protecting GMLs, we used serum of experimental rats to assess the level of vasoactive intestinal peptide (VIP), gastrin, interleukin-6, interleukin-10, tumor necrosis factor-α and interferon-γ by ELISA and radioimmunoassay. The protein levels of NF-κB, p-IκB-α, IκB-α, Bcl-2, Bax, and cleaved-caspase-3 were examined by western blot analysis. Data were analyzed with SPSS 19.0 software package. Curcumin treatment prevented tissue damage and cell death in the reserpine-treated rats and effectively decreased inflammatory response and balanced the expression of VIP and gastrin in the reserpine-treated rats. NF-κB, p-IκB-α, Bax, and cleaved-caspase-3 were increased in the reserpine group, but the curcumin high-dose group inhibited them. Curcumin can target the IκB-α/NF-κB pathway to inhibit inflammatory response and regulate the level of VIP and gastrin in reserpine-induced GML rats.

Antidiarrhoeal, antisecretory and antispasmodic activities of Matricaria chamomilla are mediated predominantly through K(+)-channels activation

Background

Matricaria chamomilla commonly known as “Chamomile” (Asteraceae) is a popular medicinal herb widely used in indigenous system of medicine for a variety of ailments. However, there is no detailed study available showing its effectiveness in hyperactive gut disorders like, abdominal colic and diarrhoea. This study was designed to determine the pharmacological basis for the folkloric use of Matricaria chamomilla in diarrhoea.

Methods

The crude aqueous-methanolic extract of Matricaria chamomilla (Mc.Cr) was studied for its protective effect in mice against castor oil-induced diarrhoea and intestinal fluid accumulation. The isolated rabbit jejunum was selected for the in-vitro experiments using tissue bath assembly coupled with PowerLab data acquisition system.

Results

Oral administration of Mc.Cr to mice at 150 and 300 mg/kg showed marked antidiarrhoeal and antisecretory effects against castor oil-induced diarrhoea and intestinal fluid accumulation, simultaneously, similar to the effects of cromakalim and loperamide. These effects of plant extract were attenuated in animals pretreated with K⁺ channel antagonist, glibenclamide (GB) or 4-aminopyridine (4-AP). When tested in isolated rabbit jejunum, Mc.Cr caused a dose-dependent (0.3-3 mg/ml) relaxation of spontaneous and low K⁺ (25 mM)-induced contractions, while it exhibited weak inhibitory effect on high K⁺ (80 mM). The inhibitory effect of Mc.Cr on low K⁺-induced contractions was partially inhibited in the presence of GB, while completely blocked by 4-AP. Cromakalim, an ATP-sensitive K⁺ channel opener, caused complete relaxation of low K⁺-induced contractions with little effect on high K⁺. Pretreatment of tissues with GB blocked the inhibitory effects of cromakalim on low K⁺, while the presence of 4-AP did not alter the original effect. Verapamil, a Ca⁺⁺ channel antagonist, caused complete relaxation of both low and high K⁺-induced contractions with similar potency. The inhibitory effect of verapamil was insensitive to GB or 4-AP. When assessed for Ca⁺⁺ antagonist like activity, Mc.Cr at high concentrations caused rightward shift in the Ca⁺⁺ concentration-response curves with suppression of the maximum response, similar to the effect of verapamil, while cromakalim did not show similar effect.

Conclusions

This study indicates that Matricaria chamomilla possesses antidiarrhoeal, antisecretory and antispasmodic activities mediated predominantly through K⁺-channels activation along with weak Ca⁺⁺ antagonist effect.

Antispasmodic and antidiarrhoeal activity of the fruit of Rosa moschata (J)

Background

The fruit of Rosa moschata has traditionally been used for the treatment of abdominal spasm and diarrhoea. Therefore, the aim of this study was to investigate mechanism(s) responsible for its medicinal use in gut spasm and diarrhea.

Methods

Hydro-methanolic extract of Rosa moschata (Rm.Cr) was studied in isolated rabbit’s jejunal preparations for possible antispasmodic activity. Based upon in vitro relaxant activity in isolated gut preparations, in vivo antidiarrheal activity was carried out in mice to confirm its antidiarrheal effect. Acute toxicity study was performed to determine safe dose range before in vivo experiments.

Results

In isolated rabbits’ jejunal preparations, Rm.Cr inhibited the spontaneous and high K⁺-induced contractions with respective EC₅₀ values of 0.66 (0.44-0.97; n = 5) and 2.28 mg/mL (1.43-3.62; n = 5), like that of verapamil. This suggests the presence of calcium channel blocking (CCB) activity as a possible mode of action. The Ca⁺⁺ channel blocking activity was further confirmed when pre-treatment of isolated jejunums with Rm.Cr (1-5 mg/mL) caused a rightward shift in the Ca⁺⁺ concentration-response curves (CRCs), similar to verapamil. Rm.Cr was safe up to 2000 mg/kg for in vivo acute toxicity. Rm.Cr provided 55% and 80% protection from diarrhoea in respective doses of 100 mg/kg and 1000 mg/kg. These data indicates that the crude extract of Rosa moschata possesses Ca⁺⁺ antagonist-like constituent(s), which explains its inhibitory effect on gut motility; a mechanism that underlies its antidiarrheal and antispasmodic activities.

Conclusion

The study shows that the crude extract of fruits of Rosa moschata possesses antispasmodic effects mediated possibly through voltage gated Ca++ channel blockade, which provides sound pharmacological base to its medicinal use in gut spasms and diarrhoea, though additional mechanism(s) cannot be ruled out.

Studies on antidiarrhoeal, antispasmodic and bronchodilator activities of Operculina turpethum Linn

Background

Traditionally, Operculina turpethum has been used in a wide range of ailments such as, gastrointestinal disturbances and asthma. It is found in China, South Asia, Pacific Islands, and Australia. This study was aimed to provide a possible pharmacological basis for the medicinal use of O. turpethum in gut and airways disorders.

Methods

Castor oil-induced diarrhoeal mice model and isolated tissue preparations such as, rabbit jejunum and guinea-pig tracheal preparations were used to test the antidiarrhoeal, antispasmodic and bronchodilator effects and the possible mode of action(s) of the 70% aqueous-ethanolic extract of O. turpethum black variety (OTB).

Results

In the castor oil-induced diarrhoea in mice, the crude extract of OTB caused a dose-dependent (300–1000 mg/kg) protection from diarrhoea, similar to that of loperamide. In isolated rabbit jejunum preparations, OTB produced a dose-dependent inhibition of spontaneous and high K⁺(80 mM)-induced contractions with resultant median effective concentrations (EC₅₀ with 95% confidence interval) of 1.04 mg/ml (0.59-1.54) and 0.12 mg/ml (0.10-0.15; n = 4) respectively, thus showing more potency against K⁺. Pretreatment of the tissue with OTB (0.01 and 0.03 mg/ml) caused a rightward shift in the concentration response curves of Ca⁺⁺, similar to that of verapamil. In isolated guinea-pig tracheal preparations, OTB caused inhibition of carbachol and high K⁺-induced constriction at similar concentrations with respective EC₅₀ value of 0.66 mg/ml (0.53-0.82) and 0.59 mg/ml (0.45-0.62). Activity-directed fractionation revealed that the ethyl acetate fraction was more potent than the parent crude extract and hexane fraction.

Conclusion

These results suggest that the crude extract of O. turpethum possesses antidiarrhoeal, antispasmodic and bronchodilator activities, mediated possibly through the presence of Ca⁺⁺ antagonist like constituent(s), though additional mechanism(s) cannot be ruled out. Thus, this study provides the evidence for the medicinal use of plant in diarrhoea and asthma.

Molecular characterization of eluxadoline as a potential ligand targeting mu-delta opioid receptor heteromers

Eluxadoline, an orally active mixed μ opioid receptor (μOR) agonist δ opioid receptor (δOR) antagonist developed for the treatment of diarrhea-predominant irritable bowel syndrome, normalizes gastrointestinal (GI) transit and defecation under conditions of novel environment stress or post-inflammatory altered GI function. Furthermore, compared to loperamide, which is used to treat non-specific diarrhea, the effects of eluxadoline on GI transit occur over a wider dosage range. However, the mechanisms of action of eluxadoline are unclear. In this study, we compared the ability of eluxadoline and loperamide to activate G-protein- and β-arrestin-mediated signaling at μOR homomers or μOR-δOR heteromers in heterologous cells. We also examined the ability of both compounds to reduce castor oil induced diarrhea in wild type (WT) and mice lacking δOR. We find that eluxadoline is more potent than loperamide in eliciting G-protein activity and β-arrestin recruitment in μOR expressing cells. However, in cells expressing μOR-δOR heteromers, the potency of eluxadoline is higher, but its maximal effect is lower than that of loperamide. Moreover, in these cells the signaling mediated by eluxadoline but not loperamide is reduced by μOR-δOR heteromer-selective antibodies. We find that in castor oil-induced diarrhea eluxadoline is more efficacious compared to loperamide in WT mice, and δOR appears to play a role in this process. Taken together these results indicate that eluxadoline behaves as a potent μOR agonist in the absence of δOR, while in the presence of δOR eluxadoline's effects are mediated through the μOR-δOR heteromer.

Pharmacological basis for medicinal use of Lens culinaris in gastrointestinal and respiratory disorders

Crude extract of Lens culinaris (Lc.Cr), which tested positive for presence of anthraquinones, flavonoids, saponins, sterol, tannins, and terpenes exhibited protective effect against castor oil-induced diarrhea in mice at 100-1000 mg/kg. In rabbit jejunum preparations, Lc.Cr caused relaxation of spontaneous contractions at 0.03-5.0 mg/mL. Lc.Cr inhibited carbachol (CCh, 1 μM) and K(+) (80 mM)-induced contractions in a pattern similar to dicyclomine, but different from verapamil and atropine. Lc.Cr shifted the Ca(++) concentration-response curves to the right, like dicyclomine and verapamil. Pretreatment of tissues with Lc.Cr (0.03-0.1 mg/mL) caused leftward shift of isoprenaline-induced inhibitory CRCs, similar to papaverine. In guinea-pig ileum, Lc.Cr produced rightward parallel shift of CCh curves, followed by non-parallel shift at higher concentration with suppression of maximum response, similar to dicyclomine, but different from verapamil and atropine. Lc.Cr (3.0-30 mg/kg) caused suppression of carbachol (CCh, 100 µg/kg)-induced increase in inspiratory pressure of anesthetized rats. In guinea-pig trachea, Lc.Cr relaxed CCh and high K(+) -induced contractions, shifted CCh curves to right and potentiated isoprenaline response. These results suggest that L. culinaris possesses antidiarrheal, antispasmodic, and bronchodilator activities mediated possibly through a combination of Ca(++) antagonist, anticholinergic, and phosphodiesterase inhibitory effects, and this study provides sound mechanistic background to its medicinal use in disorders of gut and airways hyperactivity, like diarrhea and asthma.

Composition and Antidiarrheal Activity of Bidens odorata Cav

The antidiarrheal effects of chloroform, methanol, and aqueous extracts of Bidens odorata Cav. were investigated at doses of 200 mg/kg on castor-oil-induced diarrhea. The chloroform extract of B. odorata (CBO) reduced diarrhea by 72.72%. The effect of CBO was evaluated on mice with diarrhea induced by castor oil, MgSO4, arachidonic acid, or prostaglandin E2. CBO inhibited the contraction induced by carbachol chloride on ileum (100 µg/mL) and intestinal transit (200 mg/kg) in Wistar rats. The active fraction of CBO (F4) at doses of 100 mg/kg inhibited the diarrhea induced by castor oil (90.1%) or arachidonic acid (72.9%) but did not inhibit the diarrhea induced by PGE2. The active fraction of F4 (FR5) only was tested on diarrhea induced with castor oil and inhibited this diarrhea by 92.1%. The compositions of F4 and FR5 were determined by GC-MS, and oleic, palmitic, linoleic, and stearic acids were found. F4 and a mixture of the four fatty acids inhibited diarrhea at doses of 100 mg/kg (90.1% and 70.6%, resp.). The results of this study show that B. odorata has antidiarrheal effects, as is claimed by folk medicine, and could possibly be used for the production of a phytomedicine.

Calcium channel blocking activity in Desmostachya bipinnata (L.) explains its use in gut and airways disorders

Desmostachya bipinnata, despite of its popular medicinal uses, has not been widely studied for its effect in diarrhea, indigestion, and asthma. The aim of the present investigation was to provide scientific rationale for these applications. The crude aqueous-methanolic extract of D. bipinnata (Db.Cr) was evaluated through in vivo and in vitro experiments. Db.Cr (100-500 mg/kg) protected mice against castor oil-induced diarrhea, similar to loperamide. When tested on gut preparations, Db.Cr produced an atropine-sensitive spasmogenic effect in rabbit jejunum up to 5 mg/mL, followed by a partial relaxation at 10 mg/mL. With atropine preincubation, a verapamil-like inhibitory effect was evident against spontaneous and high K(+) (80 mM)-induced contractions. The maximum stimulant effect was comparable with the acetylcholine-induced maximum contraction and was similarly reproducible in guinea pig ileum. Db.Cr inhibited carbachol (1 μM)-induced contraction in rabbit trachea but caused an atropine-sensitive accentuation of high K(+) -induced contraction at 0.003-0.3 mg/mL followed by inhibition at 1-5 mg/mL. On activity-directed fractionation, inhibitory effect was concentrated on organic and stimulant effect in aqueous fraction. This study, suggesting the presence of calcium antagonist activity, possibly underlying its medicinal effect in hyperactive gut and respiratory disorders, and cholinergic activity, possibly underlying its digestive effect, provides rationale for these therapeutic uses of D. bipinnata.

Gut and airways relaxant effects of Carum roxburghianum

ETHNOPHARMACOLOGICAL RELEVANCE

Carum roxburghianum is traditionally used in hyperactive gastrointestinal and respiratory disorders. The present study was carried out to investigate the possible gut and airways relaxant potential of Carum roxburghianum to rationalize its folk uses.

MATERIALS AND METHODS

Crude extract of Carum roxburghianum (Cr.Cr) was studied in in vivo and in vitro techniques.

RESULTS

Cr.Cr exhibited protective effect against castor oil-induced diarrhea in mice at 100-1000 mg/kg. In rabbit jejunum preparations, Cr.Cr (0.03-3.0 mg/mL) caused relaxation of spontaneous and K(+) (80 mM)-induced contractions at similar concentrations, like papaverine. Pretreatment of tissues with Cr.Cr (0.1-1.0 mg/mL) shifted Ca(++) concentration-response curves (CRCs) to right, like verapamil. Cr.Cr (0.03 and 0.1 mg/mL) caused leftward shift of isoprenaline-induced inhibitory CRCs, similar to papaverine. In isolated guinea-pig ileum, Cr.Cr (0.01 and 0.03 mg/mL) produced rightward parallel shift of acetylcholine-curves, like atropine. Cr.Cr (1.0-30 mg/kg) caused suppression of carbachol (CCh, 100 μg/kg)-induced increase in inspiratory pressure of anaesthetized rats. In guinea-pig trachea, Cr.Cr (0.03-1.0 mg/mL) relaxed CCh and high K(+)-induced contractions, shifted isoprenaline-induced inhibitory CRCs to left at 0.1 and 0.3 mg/mL and CCh-curves parallel to right (0.01 and 0.03 mg/mL). Cr.Cr did not cause any mortality of mice up to 10 g/kg dose.

CONCLUSION

These results indicate that Carum roxburghianum possess combination of antidiarrheal, antispasmodic and bronchodilatory effects, which provides pharmacological basis to its traditional use in the disorders of gut and airways hyperactivity, like diarrhea, colic and asthma.

Establishment and validation of a rabbit model for in vivo pharmacodynamic screening of tachykinin NK2 antagonists

We attempted to establish and validate an in vivo pharmacodynamic (PD) rabbit model to screen tachykinin NK(2) receptor (NK(2)-R) antagonists using pharmacological and pharmacokinetic (PK)/PD analyses. Under urethane anesthesia, changes in intracolonic pressure associated with intravenous (i.v.) administration of a selective NK(2)-R agonist, βAla(8)-neurokinin A(4-10) (βA-NKA), was monitored as a PD marker. The analgesic effects of NK(2)-R antagonists were evaluated by monitoring visceromotor response (VMR) to colorectal distension in a rabbit model of visceral hypersensitivity induced by intracolonic treatment of acetic acid. Intravenous administration of βA-NKA induced transient colonic contractions dose-dependently, which were inhibited by the selective NK(2)-R antagonists in dose- and/or plasma concentration-dependent manners. The correlation between PD inhibition and plasma concentration normalized with the corresponding in vitro binding affinity was relatively high (r(2) = 0.61). Furthermore, the minimum effective doses on the VMR and ID(50) values calculated in the PD model were highly correlated (r(2) = 0.74). In conclusion, we newly established and validated a rabbit model of agonist-induced colonic contractions as a screening tool for NK(2)-R antagonists. In a drug discovery process, this PD model could enhance the therapeutic candidate selection for irritable bowel syndrome, pharmacologically connecting in vitro affinity for NK(2)-R with in vivo therapeutic efficacy.

Pharmacological explanation for the medicinal use of Juniperus excelsa in hyperactive gastrointestinal and respiratory disorders

Crude extract of Juniperus excelsa (JeExt), which tested positive for the presence of anthraquinone, flavonoids, saponins, sterols, terpenes and tannin, exhibited a protective effect against castor oil-induced diarrhoea in mice at 100-1000 mg/kg. In rabbit jejunum preparations, JeExt (0.01-1.0 mg/mL) caused relaxation of spontaneous and K(+) (80 mM)-induced contractions at similar concentrations to papaverine, whereas verapamil was relatively more potent against K(+). JeExt (0.03-0.3 mg/mL) shifted Ca(2+) concentration-response curves to the right, like papaverine or verapamil. JeExt (0.003-0.01 mg/mL) caused a leftward shift of isoprenaline-induced inhibitory concentration-response curves, similar to papaverine. JeExt (1.0-30 mg/kg) caused suppression of carbachol (CCh, 100 μg/kg)-induced increase in inspiratory pressure of anaesthetized rats. In guinea-pig trachea, JeExt (0.001-3.0 mg/mL) relaxed CCh (1 μM)- and high K(+)-induced contractions and shifted isoprenaline-induced inhibitory curves to the left. This study suggests that Juniperus excelsa possibly exhibits a combination of Ca(2+) antagonist and phosphodiesterase inhibitory effects, which provides a pharmacological basis for its traditional use in disorders of gut and airways hyperactivity, such as diarrhoea, colic and asthma.

Antidiarrhoeal and bronchodilatory potential of Valeriana wallichii

This study describes the antidiarrhoeal and bronchodilatory activities of Valeriana wallichii D.C. (Valerianaceae). The crude extract of V. wallichii (Vw.Cr) caused inhibition of castor oil-induced diarrhoea in mice at 300-600 mg kg⁻¹. In guinea-pig trachea, Vw.Cr concentration dependently (0.03-3.0 mg mL⁻¹) relaxed the low K+ (25 mM)-induced contractions, with a mild effect on the contractions induced by high K+ (80 mM). In the presence of glibenclamide, the relaxation of low K+-induced contractions was prevented. Similarly, cromakalim caused glibenclamide-sensitive inhibition of low K+, without any effect on high K+. These results indicate that V. wallichii exhibits antidiarrhoeal and bronchodilatory activities, possibly through K+ channel activation, and thus reveal its medicinal usefulness in hyperactive gut and airway disorders such as diarrhoea and asthma.

Antispasmodic and Antidiarrheal Activities of Valeriana hardwickii Wall. Rhizome Are Putatively Mediated through Calcium Channel Blockade

Valeriana hardwickii is indigenous to Pakistan, Burma and Ceylon, where it is traditionally being used as an antispasmodic and antidiarrheal, besides its culinary use as spice. The aim of this paper was to provide pharmacological validation to these medicinal uses. The crude aqueous-methanolic extract of Valeriana hardwickii rhizome (Vh.Cr) was studied on isolated rabbit jejunum and castor oil-induced diarrhea in mice for spasmolytic and antidiarrheal properties, respectively. Vh.Cr caused concentration-dependent (0.01–1 mg/mL) relaxation of spontaneous contractions in isolated rabbit jejunum and inhibited K⁺-induced contractions (0.01–0.3 mg/mL), similar to verapamil, suggestive of calcium channel blockade (CCB). The CCB effect was confirmed when pretreatment of the jejunum preparations with Vh.Cr produced a concentration-dependent (0.03–0.1 mg/mL) rightward shift in the Ca⁺⁺ concentration-response curves, as caused by verapamil. Vh.Cr exhibited dose-dependent (100–300 mg/kg) protection against castor oil-induced diarrhea in mice. Loperamide, a standard antidiarrheal drug, similarly prevented the diarrhea. These data indicate the presence of CCB effect in the extract of Valeriana hardwickii rhizome, possibly mediating its antispasmodic and antidiarrheal activities and provide a scientific base for its traditional use in hyperactive gut disorders.

Antidiarrhoeal and spasmolytic activities of the methanolic crude extract of Alstonia scholaris L. are mediated through calcium channel blockade

This study was aimed to provide a pharmacological basis to the medicinal use of Alstonia scholaris as an antidiarrhoeal and antispasmodic by using in vivo and in vitro techniques. In the in vivo study the crude extract of Alstonia scholaris (As.Cr), which tested positive for the presence of alkaloids, provided 31-84% protection against castor oil-induced diarrhoea in mice at 100-1000 mg/kg doses, similar to loperamide. In isolated rabbit jejunum preparation, the As.Cr caused inhibition of spontaneous and high K(+) (80 mm)-induced contractions, with respective EC(50) values of 1.04 (0.73-1.48) and 1.02 mg/mL (0.56-1.84; 95% CI), thus showing spasmolytic activity mediated possibly through calcium channel blockade (CCB). The CCB activity was further confirmed when pretreatment of the tissue with the As.Cr (0.3-1 mg/mL) caused a rightward shift in the Ca(++) concentration-response curves similar to verapamil, a standard calcium channel blocker. Loperamide also inhibited spontaneous and high K(+) precontractions as well as shifted the Ca(++) CRCs to the right. These results indicate that the crude extract of Alstonia scholaris possesses antidiarrhoeal and spasmolytic effects, mediated possibly through the presence of CCB-like constituent(s) and this study provides a mechanistic base for its medicinal use in diarrhoea and colic.

Species differences in the gut stimulatory effects of radish seeds

This study describes the gastrointestinal (GI) prokinetic effects of the aqueous extract of radish seeds (Rs.Cr). Rs.Cr, which tested positive for terpenes, flavonoids, phenols, alkaloids and saponins, showed a spasmogenic effect in isolated rabbit jejunum and ileum, rat stomach fundus and ileum, and guinea-pig ileum and jejunum. Rs.Cr was around 10 times more potent in the guinea-pig tissues and this effect was resistant to atropine, pyrilamine or SB203186 while the spasmogenic effect in the rat and rabbit tissues was atropine sensitive. The extract exhibited atropine-sensitive GI prokinetic and laxative effects in vivo in mice. In the atropinized rabbit jejunum, Rs.Cr produced a spasmolytic effect independent of Ca++ or K+ channels, adrenergic or opioid receptor involvement. Activity-directed fractionation of Rs.Cr yielded four fractions, all showing effects similar to that of the parent extract. Rs.Cr and its fractions were found to be non-lethal up to 10 g kg−1 in mice for 24 h, except for the petroleum fraction, which showed 50% mortality at high doses. Some known radish compounds (spermine, spermidine, putrescine and sinigrin) were also tested and found to be devoid of any activity. The study shows species-specific spasmogenic effects of radish in rabbit, rat and mouse via muscarinic receptors but through an uncharacterized pathway in guinea-pig tissues. Additionally, a dormant relaxant effect was also seen, while the three polyamines and one glucosinolate from radish were found to be inactive, indicating that the compound(s) responsible for the activities reported remains to be isolated.

Antispasmodic and bronchodilator activities of Artemisia vulgaris are mediated through dual blockade of muscarinic receptors and calcium influx

AIM OF THE STUDY

The present study describes antispasmodic, antidiarrheal, bronchodilatory and tracheo-relaxant activities of Artemisia vulgaris to rationalize some of its traditional uses.

MATERIALS AND METHODS

Crude extract of Artemisia vulgaris (Av.Cr) was studied in the isolated tissue preparations of rabbit jejunum and guinea-pig trachea, as well as in the in vivo castor oil-induced diarrhea and bronchodilatory techniques.

RESULTS

Av.Cr which tested positive for alkaloids, coumarins, flavonoids, saponins, sterols, tannins and terpenes caused concentration-dependent (0.03-10mg/mL) relaxation of jejunum spontaneous contractions. Av.Cr inhibited the carbachol (CCh, 1 microM) and K(+) (80 mM)-induced contractions in a pattern, similar to that of dicyclomine. Av.Cr shifted the Ca(2+) concentration-response curves to right, like that caused by verapamil and dicyclomine. Av.Cr produced rightward parallel shift in CCh-curves, followed by non-parallel shift at higher concentration with the suppression of the maximum response, similar to that caused by dicyclomine. It exhibited protective effect against castor oil-induced diarrhea and CCh-mediated bronchoconstriction in rodents. In trachea, Av.Cr relaxed the CCh (1 microM) and K(+) (80 mM)-induced contractions and shifted the CCh-curves to right.

CONCLUSION

These results indicate that Artemisia vulgaris exhibits combination of anticholinergic and Ca(2+) antagonist mechanisms, which provides pharmacological basis for its folkloric use in the hyperactive gut and airways disorders, such as abdominal colic, diarrhea and asthma.

Isoliquiritigenin, a flavonoid from licorice, plays a dual role in regulating gastrointestinal motility in vitro and in vivo

Licorice root has been used for years to regulate gastrointestinal function in traditional Chinese medicine. This study reveals the gastrointestinal effects of isoliquiritigenin, a flavonoid isolated from the roots of Glycyrrhiza glabra (a kind of Licorice). In vivo, isoliquiritigenin produced a dual dose-related effect on the charcoal meal travel, inhibitory at the low doses, while prokinetic at the high doses. In vitro, isoliquiritigenin showed an atropine-sensitive concentration-dependent spasmogenic effect in isolated rat stomach fundus. However, a spasmolytic effect was observed in isolated rabbit jejunums, guinea pig ileums and atropinized rat stomach fundus, either as noncompetitive inhibition of agonist concentration-response curves, inhibition of high K(+) (80 mM)-induced contractions, or displacement of Ca(2+) concentration-response curves to the right, indicating a calcium antagonist effect. Pretreatment with N(omega)-nitro-L-arginine methyl ester (L-NAME; 30 microM), indomethacin (10 microM), methylene blue (10 microM), tetraethylammonium chloride (0.5 mM), glibenclamide (1 microM), 4-aminopyridine (0.1 mM), or clotrimazole (1 microM) did not inhibit the spasmolytic effect. These results indicate that isoliquiritigenin plays a dual role in regulating gastrointestinal motility, both spasmogenic and spasmolytic. The spasmogenic effect may involve the activating of muscarinic receptors, while the spasmolytic effect is predominantly due to blockade of the calcium channels.

Mechanisms underlying the antispasmodic and bronchodilatory properties of Terminalia bellerica fruit

AIM OF THE STUDY

The present investigation was carried out to provide the pharmacological basis for the medicinal use of Terminalia bellerica in hyperactive gastrointestinal and respiratory disorders.

MATERIALS AND METHODS

Crude extract of Terminalia bellerica fruit (Tb.Cr) was studied in in vitro and in vivo.

RESULTS

Tb.Cr caused relaxation of spontaneous contractions in isolated rabbit jejunum at 0.1-3.0mg/mL. Tb.Cr inhibited the carbachol (CCh, 1microM) and K(+) (80mM)-induced contractions in a pattern similar to that of dicyclomine, but different from nifedipine and atropine. Tb.Cr shifted the Ca(++) concentration-response curves to right, like nifedipine and dicyclomine. In guinea-pig ileum, Tb.Cr produced rightward parallel shift of acetylcholine-curves, followed by non-parallel shift at higher concentration with the suppression of maximum response, similar to dicyclomine, but different from nifedipine and atropine. Tb.Cr exhibited protective effect against castor oil-induced diarrhea and carbachol-mediated bronchoconstriction in rodents. In guinea-pig trachea, Tb.Cr relaxed the CCh-induced contractions, shifted CCh-curves to right and inhibited the contractions of K(+). Anticholinergic effect was distributed both in organic and aqueous fractions, while CCB was present in the aqueous fraction.

CONCLUSIONS

These results indicate that Terminalia bellerica fruit possess a combination of anticholinergic and Ca(++) antagonist effects, which explain its folkloric use in the colic, diarrhea and asthma.

Gastrointestinal, selective airways and urinary bladder relaxant effects of Hyoscyamus niger are mediated through dual blockade of muscarinic receptors and Ca2+ channels

This study describes the spasmolytic, antidiarrhoeal, antisecretory, bronchodilatory and urinary bladder relaxant properties of Hyoscyamus niger to rationalize some of its medicinal uses. The crude extract of H. niger seeds (Hn.Cr) caused a complete concentration-dependent relaxation of spontaneous contractions of rabbit jejunum, similar to that caused by verapamil, whereas atropine produced partial inhibition. Hn.Cr inhibited contractions induced by carbachol (1 microM) and K(+) (80 mM) in a pattern similar to that of dicyclomine, but different from verapamil and atropine. Hn.Cr shifted the Ca(2+) concentration-response curves to the right, similar to that caused by verapamil and dicyclomine, suggesting a Ca(2+) channel-blocking mechanism in addition to an anticholinergic effect. In the guinea-pig ileum, Hn.Cr produced a rightward parallel shift of the acetylcholine curves, followed by a non-parallel shift with suppression of the maximum response at a higher concentration, similar to that caused by dicyclomine, but different from that of verapamil and atropine. Hn.Cr exhibited antidiarrhoeal and antisecretory effects against castor oil-induced diarrhoea and intestinal fluid accumulation in mice. In guinea-pig trachea and rabbit urinary bladder tissues, Hn.Cr caused relaxation of carbachol (1 microM) and K(+) (80 mM) induced contractions at around 10 and 25 times lower concentrations than in gut, respectively, and shifted carbachol curves to the right. Only the organic fractions of the extract had a Ca(2+) antagonist effect, whereas both organic and aqueous fractions had anticholinergic effect. A constituent, beta-sitosterol exhibited Ca(2+) channel-blocking action. These results suggest that the antispasmodic effect of H. niger is mediated through a combination of anticholinergic and Ca(2+) antagonist mechanisms. The relaxant effects of Hn.Cr occur at much lower concentrations in the trachea and bladder. This study offers explanations for the medicinal use of H. niger in treating gastrointestinal and respiratory disorders and bladder hyperactivity.

Role of tachykinin NK(1) and NK(2) receptors in colonic sensitivity and stress-induced defecation in gerbils

The pharmacology of tachykinin NK receptors varies greatly among species. The aim of the present study was to assess the role of NK(1) and NK(2) receptors in mediating colorectal distension-evoked nociception and psychological stress-induced defecation in gerbils, a species with human-like NK receptor pharmacology. The effects of the selective NK(1) and NK(2) receptor antagonists, aprepitant and saredutant, on acute (1 h) restraint stress-evoked defecation and plasma adenocorticotropin (ACTH) levels in gerbils were assessed. The effects of antagonists alone or in combination on colorectal distension-evoked visceral pain in conscious gerbils were evaluated using the visceromotor response as a surrogate marker of pain. Restraint stress increased fecal pellet output 2-3-fold and plasma ACTH levels 9-fold. Aprepitant inhibited the defecatory and endocrine responses to stress by 50%, while saredutant completely normalized the same parameters. Visceral pain responses during colorectal distension were attenuated by both compounds, but aprepitant (19+/-6% inhibition, P<0.01) was slightly more effective than saredutant (10+/-9% inhibition, P<0.05). A combination of both compounds resulted in an additive effect (30+/-10% inhibition, P<0.01). The results demonstrate that NK(1) and NK(2) receptors are involved in stress-related colonic motor alterations and visceral pain responses in gerbils and that combined antagonism provides enhanced inhibition of visceral pain responses. This suggests that for therapeutic use in for instance functional gastrointestinal disorders, dual NK(1)/NK(2) receptor antagonists may provide better clinical outcome than selective compounds.

Demonstration of functional neuronal beta3-adrenoceptors within the enteric nervous system

BACKGROUND & AIMS

Although the beta(3)-adrenoceptor (AR) has been suggested to be involved in regulation of gut motility and visceral algesia, the precise mechanisms have been unknown. beta(3)-AR has been postulated to have a nonneuronal expression, being initially characterized in adipocytes and subsequently in the smooth muscle. We aimed to investigate the expression of beta(3)-AR in human enteric nervous system and its role in motility and visceral algesia.

METHODS

The expression of beta(3)-AR in human colon myenteric and submucosal plexus was investigated using immunohistochemistry. The effects of a beta(3)-AR agonist on nerve-evoked and carbachol-induced contractions as well as somatostatin release were investigated in strips of human colon. The effect of an agonist on diarrhea and visceral pain was investigated in vivo in rat models.

RESULTS

beta(3)-AR is expressed in cholinergic neurons in the myenteric plexus and submucosal plexus of human colon. Activation of beta(3)-AR causes the release of somatostatin from human isolated colon. In a rat model of visceral pain, beta(3)-AR agonist elicits somatostatin-dependent visceral analgesia. beta(3)-AR agonists inhibit cholinergically mediated muscle contraction of the human colon, as well as chemically induced diarrhea in vivo in a rat model.

CONCLUSIONS

This is the first demonstration of expression of beta(3)-AR in the enteric nervous system. Activation of these receptors results in inhibition of cholinergic contractions and enhanced release of somatostatin, which may lead to visceral analgesia and inhibition of diarrhea. Therefore, beta(3)-AR could be a novel therapeutic target for functional gastrointestinal disorders.

Antispasmodic Effects of Rooibos Tea (Aspalathus linearis) is Mediated Predominantly through K+-Channel Activation

Rooibos tea has been widely used for abdominal spasm and diarrhoea. The aim of the present study was to explore the possible mechanism for its use in such ailments. Its aqueous extract (RT) at 0.3-10 mg/ml produced relaxation of spontaneous and low K(+) (25 mM)-induced contractions of rabbit jejunum, with weak effect on high K(+) (80 mM)-induced contractions. In the presence of glibenclamide, relaxation of low K(+)-induced contractions was prevented. Cromakalim inhibited contractions induced by low K(+), but not high K(+), while verapamil did not differentiate in its inhibitory effect on contractions produced by the two concentrations of K(+). RT also exhibited antidiarrhoeal and antisecretory activities in mice. The spasmolytic effect was concentrated in organic fractions. Its constituents, chrysoeriol, orientin and vitexin showed a similar pattern of spasmolytic effects to the extract, while rutin was more like verapamil. So Rooibos tea possesses a combination of dominant K(ATP) channel activation and weak Ca(++) antagonist mechanisms and hence justifies its use in hyperactive gastrointestinal disorders.

Species differences in the prokinetic effects of ginger

This study describes the prokinetic actions of the aqueous extract of ginger (Zingiber officinale). Ginger extract (Zo.Cr), which tested positive for saponins, terpenes, phenols, flavonoids and alkaloids, showed a spasmogenic effect in isolated guinea-pig ileum with 8-50 times more potency than in rabbit jejunum and ileum and rat stomach fundus and ileum. Spasmogenicity in all the gut preparations except in guinea-pig ileum was atropine-sensitive. Zo.Cr exhibited a stimulant effect in vivo in mice and enhanced the intestinal transit of charcoal meal. A spasmolytic effect, mediated via Ca2 + antagonist activity, was also exhibited by Zo.Cr, reflected in terms of inhibition of spontaneous contractions, K+ (80 mM)-induced contractions and displacement of Ca2 + dose-response curves. The ginger pure compounds (6-shogaol, 6-gingerol, 8-gingerol and 10-gingerol) also exhibited a spasmolytic activity, which reduced with the increasing size of the side chain in their chemical structures. The study showed that the aqueous extract of ginger exhibits species-specific spasmogenicity in gut tissues of rabbit and rat (muscarinic-type) while through an uncharacterized pathway in guinea-pig ileum, along with a dormant relaxant effect, mediated via the blockade of voltage-dependent Ca2 + channels.

Pharmacological basis for the medicinal use of ginger in gastrointestinal disorders

Ginger (rhizome of Zingiber officinale) has been widely used for centuries in gastrointestinal disorders, particularly dyspepsia, but its precise mode of action has yet to be elucidated. This study was undertaken to study the prokinetic action of ginger and its possible mechanism of action. Prokinetic activity of ginger extract (Zo.Cr) was confirmed in an in vivo test when it enhanced the intestinal travel of charcoal meal in mice. This propulsive effect of the extract, similar to that of carbachol, was blocked in atropine-pretreated mice, a standard cholinergic antagonist. Likewise, Zo.Cr showed an atropine-sensitive dose-dependent spasmogenic effect in vitro as well as in isolated rat and mouse stomach fundus tissues. In atropinized tissue, it showed spasmolytic activity as shown by the inhibition of 5-HT- and K+-induced contractions. A spasmolytic effect was also observed in other gut preparations either as noncompetitive inhibition of agonist dose-response curves, inhibition of high K+(80 mM)-induced contractions, or displacement of Ca2+ dose-response curves to the right, indicating a calcium antagonist effect. Phytochemical analysis revealed the presence of saponins, flavonoids, and alkaloids in the crude extract. These data indicate that Zo.Cr contains a cholinergic, spasmogenic component evident in stomach fundus preparations which provides a sound mechanistic insight for the prokinetic action of ginger. In addition, the presence of a spasmolytic constituent(s) of the calcium antagonist type may explain its use in hyperactive states of gut like colic and diarrhea.

Loperamide inhibits tachykinin NK3-receptor-triggered serotonin release without affecting NK2-receptor-triggered serotonin release from guinea pig colonic mucosa

The effect of loperamide on tachykinin NK(2)- and NK(3)-receptor-mediated 5-HT outflow from guinea pig colonic mucosa was investigated in vitro. The selective tachykinin NK(2)-receptor agonist [beta-Ala(8)]-neurokinin A(4-10) (betaAla-NKA) or the selective NK(3)-receptor agonist senktide elicited an increase in 5-HT outflow from whole colonic strips, but not from mucosa-free muscle layer preparations. The enhancing effect of betaAla-NKA and senktide was prevented by the selective NK(2)-receptor antagonist GR94800 or the selective NK(3)-receptor antagonist SB222200. Loperamide concentration-dependently suppressed the senktide-evoked 5-HT outflow, but failed to affect the betaAla-NKA-evoked 5-HT outflow. The kappa-opioid receptor antagonist nor-binaltorphimine or the delta-opioid receptor antagonist naltrindole displaced the concentration-response curve for the suppressant action of loperamide to the right without significant depression of the maximum. However, the mu-opioid receptor antagonist CTOP did not affect the suppressant effect of loperamide. We concluded that the NK(3) receptor-triggered 5-HT release from colonic mucosa is suppressed by loperamide-sensitive mechanisms, whereas the NK(2)-receptor-triggered 5-HT release is loperamide-insensitive. Our data also suggest that the suppressant effect of loperamide is probably mediated by the activation of kappa- and delta-opioid receptors located on intrinsic neurons.

Acute colitis induction by oil of mustard results in later development of an IBS-like accelerated upper GI transit in mice

Oil of mustard (OM) is a potent neuronal activator that promotes allodynia and hyperalgesia within minutes of application. In this study, OM was used to induce an acute colitis. We also investigated whether intracolonic OM-induced inflammation alters gastrointestinal (GI) function over a longer time frame as a model of postinflammatory irritable bowel syndrome (PI-IBS). Mice given a single administration of 0.5% OM developed a severe colitis that peaked at day 3, was reduced at day 7, and was absent by day 14. At the peak response, there was body weight loss, colon shrinkage, thickening and weight increases, distension of the proximal colon, and diarrhea. Macroscopic inspection of the distal colon revealed a discontinuous pattern of inflammatory damage and occasional transmural ulceration. Histological examination showed loss of epithelium, an inflammatory infiltrate, destruction of mucosal architecture, edema, and loss of circular smooth muscle architecture. OM administration increased transit of a carmine dye bolus from 58% of the total length of the upper GI tract in untreated age-matched controls to as high as 74% when tested at day 28 post-OM. Mice in the latter group demonstrated a significantly more sensitive response to inhibition of upper GI transit by the mu-opioid receptor agonist loperamide compared with normal mice. OM induces a rapid, acute, and transient colitis and, in the longer term, functional changes in motility that are observed when there is no gross inflammation and thereby is a model of functional bowel disorders that mimic aspects of PI-IBS in humans.