Contractility Of Ileum Research Articles

Impacts of Perigestational Exposure to Chlorpyrifos And High-Fat Diet on Ileum Contractility in Male Rats at Early Adulthood

Impacts of Perigestational Exposure to Chlorpyrifos And High-Fat Diet on Ileum Contractility in Male Rats at Early Adulthood

Thymus vulgaris L. Essential Oil Solid Formulation: Chemical Profile and Spasmolytic and Antimicrobial Effects.

A new Thymus vulgaris L. solid essential oil (SEO) formulation composed of liquid EO linked to solid excipients has been chemically analysed and evaluated for its intestinal spasmolytic and antispastic effects in ex vivo ileum and colon of guinea pig and compared with liquid EO and excipients. Liquid EO and solid linked EO were analysed by original capillary electrochromatography coupled to diode array detection (CEC-DAD) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) methodologies. The main bioactive constituents are thymol and carvacrol, with minor constituents for a total of 12 selected analysed compounds. Liquid EO was the most effective in decreasing basal contractility in ileum and colon; excipients addiction permitted normal contractility pattern in solid linked EO SEO. In ileum and colon, the Thymus vulgaris L. solid formulation exerted the relaxant activity on K+-depolarized intestinal smooth muscle as well as liquid EO. The solid essential oil exhibits antimicrobial activity against different strains (Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, Escherichia coli, Salmonella Thyphimurium, Candida albicans) similarly to liquid oil, with activity against pathogen, but not commensal strains (Bifidobacterium Breve, Lactobacillus Fermentum) in intestinal homeostasis. Therefore, Thymus vulgaris L. solid essential oil formulation can be proposed as a possible spasmolytic and antispastic tool in medicine.

Mechanical analysis of intestinal contractility in a neonatal maternal deprivation irritable bowel syndrome rat model

The aims of the present study are to investigate biomechanical properties and provide mechanical analysis of contractility in ileum and colon in a neonatal maternal deprivation (NMD) irritable bowel syndrome (IBS) rat model. Mechanical testing was done on segments from ileum and colon in 25 IBS rats and 13 Control rats. Morphometric data were obtained from digitized images of the segments at no-load and zero-stress states. Pressure and diameter changes were measured during flow and ramp distensions under active and passive experimental conditions. Circumferential stresses (force per area) and strains (deformation) were computed with referenced to the zero-stress state. The contraction frequency was analyzed. Contraction thresholds and maximum contraction amplitude were calculated in terms of mechanical stress and strain. Compared with controls, the IBS rats had lower body weight (P < 0.01), smaller colonic opening angle (P < 0.05), higher colonic contraction frequency (P < 0.05 and P < 0.01) and lower contraction thresholds of pressure, stress and strain in both ileum and colon (P < 0.05 and P < 0.01). The maximum contraction pressure, stress and strain did not differ between IBS and Control groups (P > 0.05). In conclusion, the pressure, stress, and strain to evoke contractility in ileum and colon were lower whereas the frequency of induced colon contractions was higher in NMD IBS rats compared to normal rats. Furthermore, zero-stress state remodeling occur in colon in NMD IBS rats. Further studies on the association between intestinal biomechanical properties, hypersensitivity and afferent signaling in the IBS animal models are warranted.

New potent and selective A1 adenosine receptor antagonists as potential tools for the treatment of gastrointestinal diseases

The synthesis of 9-alkyl substituted adenine derivatives presenting aromatic groups and cycloalkyl rings in 8- and N6-position, respectively, is reported. The compounds were tested with radioligand binding studies showing, in some cases, a low nanomolar A1 adenosine receptor affinity and a very good selectivity versus the other adenosine receptor subtypes. Functional assays at human adenosine receptors and at a mouse ileum tissue preparation clearly demonstrate the antagonist profile of these molecules, with inhibitory potency at nanomolar level. A molecular modeling study, consisting in docking analysis at the recently reported A1 adenosine receptor crystal structure, was performed for the interpretation of the obtained pharmacological results. The N6-cyclopentyl-9-methyl-8-phenyladenine (17), resulting the most active derivative of the series (Ki = 2.8 nM and IC50 = 14 nM), was also very efficacious in counteracting the effect of the agonist CCPA on mouse ileum contractility. This new compound represents a tool for the development of new agents for the treatment of intestinal diseases as constipation and postoperative ileus.

The effect of the aqueous and methanol fennel stem extracts (Foeniculum vulgare Miller) on isolated rat ileum contractility

Background/Aim. The fennel (Foeniculum vulgare Miller, Apiaceae) has a long history of use as traditional herb medicine due to its carminative properties. The study was aimed to investigate the effects of aqueous and methanol fennel stem extracts on intestinal activity. Methods. Relaxant activity of aqueous and methanol fennel stem extracts was evaluated in vitro in three experimental models: spontaneous contraction, acetylcholine and potassium chloride (KCl)-induced contraction of an isolated rat ileum. The composition of aqueous and methanol fennel stem extracts was qualitatively analyzed using the high performance liquid chromatographic (HPLC) analysis. Results. In the presence of an aqueous fennel stem extract at a concentration of 3 mg/mL, the inhibition of the spontaneous contractions of isolated rat ileum was 35.05% ? 3.57%. In presence of a methanol fennel stem extract at the same concentration, the maximum reduction of the spontaneous contractions was 48.91% ? 6.31%. The extracts in a concentration- dependent manner significantly inhibited the acetylcholine and KCl induced contractions of the isolated rat ileum (p &lt; 0.01). The following components were identified in fennel methanol stem extract: 3-caffeoylquinic acid, chlorogenic acid, 4-caffeoylquinic acid, 1,3-dicaffeoylquinic acid, rutin, miquelianin, quercetin heterosides, 1,5-dicaffeoylquinic acid, 1,4-dicaffeoylquinic acid, apigenin and rosmarinic acid. In an aqueous extract, their presence is found in trace amounts. Conclusion. The results of this study showed that the aqueous and methanol fennel stem extracts have spasmolytic effects on the intestinal smooth muscle and may be used for the control of intestinal motility.

The lipopolysaccharide from Escherichia coli O127:B8 induces inflammation and motility disturbances in rabbit ileum

&lt;p&gt;The aim of this work was to evaluate the effects of lipopolysaccharide (LPS) from &lt;em&gt;Escherichia coli &lt;/em&gt;O127:B8 on the expression of toll-like receptor 4 (TLR4), the histology, and motor function in rabbit ileum. Rabbits were injected intravenously with saline or LPS (100 μg/kg, 2 h). The mRNA expression and localization of TLR4 were determined by reverse transcriptase-PCR and immunofluorescence, respectively. Histological damage induced by LPS was evaluated in sections of ileum stained with haematoxylin and eosin. Contractility studies of ileum were performed in an organ bath. The mRNA expression of TLR4 decreased in the muscular but not in the mucosal layer of rabbits treated with LPS. TLR4 was localised in both the mucosal and muscular layers of rabbit ileum. LPS induced intestinal inflammation and altered the spontaneous contractions and the serotonin-, acetylcholine- and KCl-induced contractions. In conclusion, LPS from &lt;em&gt;E. coli &lt;/em&gt;O127:B8 induced a decrease in the mRNA expression of TLR4, an inflammatory response, and changes in the contractility of rabbit ileum.&lt;/p&gt;

Newer Insights into the Antidiarrheal Effects of Acacia catechu Willd. Extract in Guinea Pig.

Acacia catechu Willd. is a plant diffused in India and other Asian countries, where it is used as a traditional medicine for the treatment of several ailments including diarrhea, one of the most common pathologies worldwide. In this study, we determined the chemical composition of Acacia catechu Willd. extract (AC) and evaluated its effect on spontaneous and induced contractility in isolated guinea pig ileum and proximal colon. Preliminary data about its antimicrobial effect against some pathogen agents versus some microbiota intestinal strain have been also reported. Chemical analysis revealed the presence of catechins, such as (-)-Epicatechin and (+)-Catechin. AC extract reduced frequency and amplitude of colon smooth muscle spontaneous contractility, in a concentration-dependent manner. A weaker effect of the extract was exerted toward ileum smooth muscle spontaneous contractility. The observed calcium antagonistic effect was more potent in proximal colon than in ileum. The extract showed a noncompetitive reversible antagonism to carbachol, both in proximal colon and ileum, with a higher potency in proximal colon. The antimicrobial effects of AC extract were observed toward Campylobacter jejuni, Escherichia coli, and Salmonella spp., while Bifido and Lactobacillus were not affected by treatment. These effects, however, occurred at concentrations fivefold higher than those inhibiting ileum and colon contractility. In conclusion, our results suggest that AC affects intestinal contractility without affecting intestinal bacterial flora and this may result in clinical benefits in patients suffering from nonbacterial diarrhea.

Antispasmodic Effects and Action Mechanism of Essential Oil of Chrysactinia mexicana A. Gray on Rabbit Ileum.

The Chrysactinia mexicana A. Gray (C. mexicana) plant is used in folk medicine to treat fever and rheumatism; it is used as a diuretic, antispasmodic; and it is used for its aphrodisiac properties. This study investigates the effects of the essential oil of C. mexicana (EOCM) on the contractility of rabbit ileum and the mechanisms of action involved. Muscle contractility studies in vitro in an organ bath to evaluate the response to EOCM were performed in the rabbit ileum. EOCM (1–100 µg·mL−1) reduced the amplitude and area under the curve of spontaneous contractions of the ileum. The contractions induced by carbachol 1 µM, potassium chloride (KCl) 60 mM or Bay K8644 1 µM were reduced by EOCM (30 µg·mL−1). Apamin 1 µM and charybdotoxin 0.01 µM decreased the inhibition induced by EOCM. The d-cAMP 1 µM decreased the inhibition induced by EOCM. l-NNA 10 µM, Rp-8-Br-PET-cGMPS 1 µM, d,l-propargylglycine 2 mM, or aminooxyacetic acid hemihydrochloride 2 mM did not modify the EOCM effect. In conclusion, EOCM induces an antispasmodic effect and could be used in the treatment of intestinal spasms or diarrhea processes. This effect would be mediated by Ca2+, Ca2+-activated K+ channels and cAMP.

English

Vanillin consumption is common within the global population, often as a flavoring agent. Many vanillin-containing drinks claim a soothing effect on the body as a whole with some reports on their benefit in reducing gastrointestinal (GI) upset. In this study, vanillin was investigated for its ability to reduce rat ileal smooth muscle contractility induced by acetylcholine (Ach) and potassium chloride (KCl). A section of rat ileum was suspended in an organ bath containing Tyrode’s solution. The tissue was stimulated using Ach or KCl and kept under 1 g tension at 37°C while continuously gassing with oxygen. Ileal smooth muscle contractility was studied in the absence and presence of vanillin. The results illustrated that vanillin (1.4e-6 and 2.2e-6 M) hindered ileal smooth muscle contractility induced by both Ach and KCl. Vanillin (1.4e-6 and 2.2e-6 M) also caused a rightward shift of the Ach concentration response curve and brought about a decrease (21.6 and 38.3%, respectively) in the maximum response. It also produced a rightward shift in the KCl dose response curve but without affecting the maximum response. These results indicate that vanillin counteracts Ach and KCl induced smooth muscle contractility in rat ileum. The results also suggest that vanillin prevented Ach induced contractility via non competitive inhibition kinetics. The reduction in KCl induced contractility also indicates that vanillin, at least partially, conveyed its effect through acting on ileal smooth muscle calcium channels. Key words: Vanillin, acetylcholine, KCl, rat Ileum, smooth muscle contraction.

Single-walled carbon nanotubes (SWCNTs) enhance KCl-, acetylcholine-, and serotonin-induced contractions and evoke oxidative stress on rabbit ileum.

We examined the effects of intravenous administration of purified arc-discharge single-walled carbon nanotubes (SWCNTs) on rabbit ileum to establish the possibility of using these SWCNTs as cell markers or drug carriers for the treatment of intestinal diseases. The SWCNT purification process eliminated carbonaceous impurities and decreased the amount of metals. SWCNTs increased the contractile responses induced by KCl, acetylcholine (ACh), and serotonin (5-HT) in rabbit ileum. Verapamil, apamin, glibenclamide, quinine and charybdotoxin reduced the contractile responses induced by ACh and 5-HT in ileum from rabbits treated with SWCNTs, indicating that voltage-dependent Ca2+ channels and small, intermediate, and large-conductance Ca(2+)-activated, ATP-sensitive, and voltage-dependent K+ channels are involved in these effects. Atropine and hexamethonium reduced the ACh response, indicating that muscarinic and nicotinic receptors are involved in this effect. Ondansetron and GR 113808 reduced the 5-HT response, indicating that serotonin 5-HT3 and 5-HT4 receptors are involved in this effect. SWCNTs increased the malondialdehyde plus 4-hydroxyalkenals and carbonyl levels in rabbit plasma and ileum, indicating that SWCNTs produce oxidative stress. SWCNTs did not produce relevant histological changes or modify the levels of the inflammatory mediators iNOS and COX-2 in the ileum. In conclusion, this study demonstrates that the intravenous administration of SWCNTs can evoke oxidative stress and affect contractility in rabbit ileum. These effects could reduce the possibility of using the arc-discharge SWCNTs as cell markers or drug carriers to treat intestinal diseases.

Peppermint Aqueous Extract Counteracts Smooth Muscle Contraction in Rat Ileum = مستخلص النعناع المائي يثبط تقلص العضلات الملساء في لفائف الأمعاء الدقيقة للفئران

Peppermint is widely used for gastrointestinal disorders; however, its pharmacological action on isolated rat ileum has not yet been evaluated. In this study, the effect of peppermint aqueous extract was investigated for its ability to reduce rat illial smooth muscle contractility induced by acetylcholine (Ach) and potassium chloride (KCl). The experiments were conducted using an organ bath apparatus. A section of rat ileum was suspended in an organ bath containing Tyrode’s solution. The tissue was stimulated with either Ach or KCl. The tissue was kept under 1 g tension at 37°C and continuously gassed with O2. Illial smooth muscle contractility was studied in the absence and presence of peppermint. Peppermint aqueous extract prevented illial smooth muscle contractility induced by both Ach and KCl. The aqueous extract of peppermint (1g/ml) caused a rightward shift of the Ach dose response curve and brought about a decrease in the maximum response. This extract also produced a rightward shift in the KCl dose response curve but without affecting the maximum response. These results indicate that peppermint aqueous extract counteracts Ach and KCl induced smooth muscle contractility in rat ileum. The results also suggest that the peppermint effect on Ach induced contractility was non competitive in nature. The reduction in KCl induced contractility also indicates that peppermint aqueous extract was at least partially mediated by its effect on illial smooth muscle calcium channels.

The Effect of Whole Gut Irrigation on Contractile Responses of Guinea Pig Gallbladder, Ileum, and Tissue Cholecystokinin Levels

An experimental study was performed to evaluate the effect of whole gut irrigation (WGI) solutions on contractile responses of the gallbladder and ileum and also on tissue cholecystokinin (CCK) levels. Thirty guinea pigs were enrolled into five groups including control group (CG) and WGI group (saline physiologic [SP], Ringer lactated [RL], polyethylene glycol [PEG], and dibasic sodium phosphate [DNP]). After median laparotomy, the distal esophagus was ligated and SP, PEG, RL, and DNP infusions (2 mL/kg/min) were performed via gastric catheter until rectal discharge became clear in WGI groups. Ileum and gallbladder samples were obtained for in vitro and biochemical studies without irrigation in CG and after irrigation with different WGI solutions. Isolated ileum and gallbladder preparations were suspended in organ baths for contractile responses of carbachol and CCK. Also, biochemical analysis of tissue CCK levels was performed in ileum and gallbladder samples. In PEG group, gallbladder and ileum CCK levels were significantly higher than CG (p < 0.05). Also, DNP irrigation caused increased CCK levels in gallbladder samples (p < 0.05). In lower carbachol concentrations, PEG group showed increased contraction responses in gallbladder samples when compared with controls (p < 0.05). However, ileal responses to carbachol did not show any significant difference between groups, contraction responses to CCK was decreased in PEG group when compared with CG (p < 0.05). Among WGI solutions, PEG caused the highest CCK levels in gallbladder and ileum samples. Different WGI solutions affected the contractile responses of gallbladder and ileum smooth muscles divergently. Increased levels of CCK in PEG group support the decreased contractile responses in ileum. Therefore, our results confirm that the effect of WGI on gallbladder and ileum contractility may be CCK related.

Effects of Forsythiae Fructus on guinea pig ileum contractility in vitro

To study contractility of guinea pig ileum in vitro,and analyze the mechanism of anti-emetic effects of Lianqiao. Using emesis-relating agonists as drugs, the inhibitory effects of Lianqiao on guinea pig ileum contractility in vitro were observed in organ bath. Lianqiao could inhibit guinea pig ileum spontaneous contractions, reducing the tone of contractions dose-dependently. Acetylcholine (Ach), histamine (His), 5-hydroxytryptamine (5-HT) stimulated contractions of the guinea pig ileum, enhanced the tone and amplitude. All the three doses (10, 5, 2 g x L(-1)) of Lianqiao could suppress the contractility, significantly reduced the tone and amplitude of ileum contractions stimulated by drugs but not the frequency. Dopamine could inhibit the spontaneous contraction tone and amplitude of ileum; Both the large doses (10, 5 g x L(-1)) of Lianqiao could antagonise the inhibitory effect of DA, enhance the tone and amplitude. Small dose(2 g x L(-1)) had additive effects on tone of ileum contractions with DA,but enhanced the amplitude not the frequency. Lianqiao have an inhibitory effect on guinea pig ileum contractions,the mechanism might be blocking M receptor, H1 receptor, 5-HT receptor and D2 receptor or directly suppressed ileum smooth muscle. The mechanisms of anti-emetic effect of Lianqiao needs further study.

The role of nitric oxide and l-type calcium channel blocker in the contractility of rabbit ileum in vitro

Nitric oxide (NO) and calcium channel blockers are two agents that can affect gastrointestinal motility. The goal of this work was to study the rabbit intestinal smooth muscle contraction response to (1) sodium nitroprusside (SNP), the NO donor, and its potential mechanism of action, and (2) nifedipine, the L-type Ca(2+) channel blocker; to clarify the degree of participation by extra- and intracellular Ca(2+) in smooth muscle contraction. We used standard isometric tension and intracellular micro-electrode recordings. To record the activity of the longitudinal smooth muscle of the ileum, segments of 1.5 cm length of the ileum were suspended vertically in organ baths of Krebs solution. The mechanical activity of the isolated ileal longitudinal muscle was recorded. Different substances were added, and the changes produced on spontaneous contraction were recorded. We found that SNP produced significant decrease, while nitric oxide synthase inhibitor produced significant increase in the amplitude of spontaneous contractions. Both apamin, the Ca(2+)-dependent K(+) channel blocker, and methylene blue, the inhibitor of soluble guanylate cyclase, alone, partially decreased relaxation induced by SNP. Addition of both methylene blue and apamine together abolished the inhibitory effect produced by SNP on spontaneous contractions. Nifedipine produced significant decrease in the amplitude of spontaneous contractions. In conclusion, in longitudinal muscle of rabbit ileum, calcium channels blocker are potent inhibitors of spontaneous activity. However, both extracellular and intracellular Ca(2+) participates in the spontaneous contractions. NO also has inhibitory effect on spontaneous activity, and this effect is mediated by cGMP generation system and Ca(2+)-dependent K(+) channels.

The Involvement of the Serotonergic Transmission System in Neonatal and Adult Rat Ileum Contractility Varies with Age

The relevance of age on serotonergic involvement in the control of alimentary contractility has not been pharmacologically described. Experiments were performed to investigate the effects of acetylcholine, atropine, 5-hydroxytryptamine (5-HT) and its related drugs on intestinal segments taken from the neonatal and adult ileum. 5-HT induced concentration-dependent contractions of ileum irrespective of age; however, these contractions were diminished by pretreatment with atropine only in neonatal tissues. In tissues taken from both the neonatal and adult ileum, methysergide (5-HT_1/2/5–7 receptor antagonist), ritanserin (5-HT₂ receptor antagonist), and RS23597-190/SB204070 (5-HT₄ receptor antagonists) all differentially reduced 5-HT-induced contractions at a concentration <100 µmol/l. At higher concentrations, the contractions were comparable to those in control tissues. Granisetron and ondansetron (5-HT₃ receptor antagonists) significantly reduced contractions induced by 5-HT at concentrations >30 µmol/l in both neonatal and adult ileum. Combined treatments with ritanserin, granisetron, plus RS23597-190 reduced or abolished contraction responses induced in neonatal ileum by 5-HT. SB269970A (5-HT₇ receptor antagonist) and WAY100635 (5-HT_1A receptor antagonist) failed to influence contractile responses induced by 5-HT or 5-HT receptor agonists. Pretreatments with WAY100635 and SB267790A also had no influence on the contractile responses induced by 5-HT_1A/7 receptor agonist, 5-CT, and 5-HT_1A receptor agonist, 8-OH-DPAT, which itself failed to induce a measurable response. It is concluded that the 5-HT-induced contractions in segments taken from both the neonatal and adult rat ileum were mediated via 5-HT₂ receptors, 5-HT₃ receptors and 5-HT₄ receptors. However, the effect of atropine on the neonatal rat intestine indicates that the mechanism of serotonergic involvement in ileal contractility is influenced by age.

Spasmolytic effect of stachys lavandulifolia vahl. Crude methanolic extract and fractions on rat ileum.

The aim of this study was to investigate the effect of aerial parts of Stachys lavandulifolia Vahl. Extract on the rat ileum contractions. The crude extract was prepared by maceration method (90% methanol) followed by fractionating into chloroform, ethyl acetate, petroleum ether and water. In adult male Wistar rats, ileum was sectioned and mounted in tissue bath and their contractility was recorded is otonically. KCl (60 mM)- induced ileum contractions were attenuated by crude extract and its fractions. The most potent fraction was chloroformic fraction (CF) with IC50 0.018 ± 0.126 = mg/mL. In calcium-free Tyrode solution with high K(+,) the CF (0.01 - 0.04 mg/ml) attenuated CaCl2-induced contractions (p< 0.001). The CF (0.05-0.8 mg/mL) attenuated the carbachol-induced contraction (p<0.001). The CF antispasmodic effect was reduced by naloxone (as a non-selective opioid antagonist), not by propranolol and L-NAME as β-adrenoceptors antagonist and nitric oxide synthase inhibitor respectively. It was concluded that S . . lavandulifolia can inhibit ileum contractility mainly via disturbing the calcium mobilization and partly by opioid receptors' activation. Our results may support the traditional usage of this herb for treating diarrhea.

The Novel Endomorphin Degradation Blockers Tyr‐Pro‐DClPhe‐Phe‐NH2 (EMDB‐1) and Tyr‐Pro‐Ala‐NH2 (EMDB‐2) Prolong Endomorphin‐2 Action in Rat Ileum In Vitro

The endogenous opioid system is involved in the control of gastrointestinal (GI) motility. The potential use of endogenous MOR ligands, endomorphins (EMs), as therapeutics is limited because of their rapid enzymatic degradation and short duration of action. Targeting enzymatic degradation is an approach to prolong EM activity. In the present study, we characterized the effects of novel blockers of EM degradation in GI tissue preparation in vitro. The effects of actinonin, diprotin A (DIP) and the novel peptide EM degradation blockers Tyr-Pro-DClPhe-Phe-NH(2) (EMDB-1), Tyr-Pro-Ala-NH(2) (EMDB-2) and Tyr-Pro-Ala-OH (EMDB-3) on EM-2-mediated inhibition of electrically induced cholinergic twitch contractions were compared in rat ileum in vitro using an organ bath. EMDB-1 and EMDB-2 significantly prolonged the inhibitory effect of EM-2 on smooth muscle contractility in rat ileum. EMDB-2 extended the EM-2 action for up to 60 min compared to 10 min in controls and was more potent than the conventional peptidase inhibitor DIP. EMDB-1 and EMDB-2 are potent EM degradation blockers, which prolong the inhibitory effects of EM-2 on smooth muscle contractility in rat ileum. These novel compounds may be of future use when targeting the endogenous opioid system in the treatment of GI motility disorders such as diarrhea.

D1 receptors play a major role in the dopamine modulation of mouse ileum contractility

Since the role of dopamine in the bowel motility is far from being clear, our aim was to analyse pharmacologically the effects of dopamine on mouse ileum contractility. Contractile activity of mouse ileum was examined in vitro as changes in isometric tension. Dopamine caused a concentration-dependent reduction of the spontaneous contraction amplitude of ileal muscle up to their complete disappearance. SCH-23390, D1 receptor antagonist, which per se increased basal tone and amplitude of spontaneous contractions, antagonized the responses to dopamine, whilst sulpiride or domperidone, D2 receptor antagonists, were without effects. The application of both D1 and D2 antagonists had additive effects. SKF-38393, D1 receptor agonist, mimicked dopamine-induced effects. Dopamine responses were insensitive to tetrodotoxin, atropine, nitric oxide synthase inhibitor or adenosine receptor antagonists, but they were reduced by adenylyl cyclase inhibition or apamin. Dopamine at a concentration which did not cause a significant reduction of phasic contractions inhibited the cholinergic contractions in response to field stimulation. SCH-23390 per se induced an increase of the neural cholinergic contraction and antagonized the dopamine effects, whilst sulpiride or domperidone did not. The application of D1 and D2 antagonists had additive effects. In conclusion, mouse ileum is under basal inhibitory control by dopamine, through D1 receptor activation, linked to adenylyl cyclase and activation of apamin-sensitive potassium channels. An agonistic interaction of the dopamine receptor subtypes in the regulation intestinal contractility has being also highlighted. This study would provide new insight on the pharmacology of the modulation of the gastrointestinal contractility by dopamine.

The Role of NO and cGMP in Antispasmodic Activity of Ruta chalepensis Leaf Extract on Rat Ileum

The aim of present study was to investigate the effect of hydroalcoholic extract of Ruta chalepensis (Rutaceae) leaves on rat ileum contractility and possible mechanism(s) involved. Ruta chalepensis extract was prepared by maceration method (ethanol 70%). Terminal portion of ileum (2 cm) was dissected out from male Wistar rats and mounted in an organ bath containing air bubbled Tyrode solution with 1 g initial tension and ileal contraction induced by KCl (60 mM) was recorded. The spasmolytic effect of the cumulative concentrations of extracts (0.01-0.07 mg mL(-1)) was reduced after tissue incubation with L-NAME (100 microM, 20 min). Methylene blue (30 microM) reduced the extracts (0.01-0.07 mg mL(-1)) spasmolytic effect (p < 0.001). Furthermore, it seems that the portion relaxatory effect of Rue extract on the rat ileum may be due to nitric oxide and the antispasmodic activity of the extract was mainly through a cGMP-dependent mechanism.

Guanylate cyclase regulates ileal longitudinal muscle contractions induced by neurogenic nitrergic activity in the rat

1. Nitrergic neurons regulate gastrointestinal (GI) activity and their dysfunction has been associated with various GI diseases. Nitric oxide (NO) typically relaxes GI smooth muscle, but nitrergic contractions also occur. Although guanylate cyclase is well established as mediating nitrergic GI relaxation, its role in contraction remains uncertain. 2. We used electrical field stimulation (EFS; 0.3 msec pulses, three trains of 1.2 s width, 2 Hz, at 30 s intervals) to evoke biphasic contraction-relaxation responses in rat ileum strips (longitudinal muscle-myenteric plexus preparations), mediated by the endogenous nitrergic transmitter, under non-adrenergic, non-cholinergic (NANC) conditions (1 micromol/L atropine and 4 micromol/L guanethidine). 3. All EFS responses were abolished by tetrodotoxin (1 micromol/L). Inhibition of NO synthase with N(omega)-nitro-L-arginine-methyl-ester (l-NAME; 100 and 300 micromol/L) prevented both EFS-evoked contractions and relaxations. L-Arginine (3 mmol/L) reversed l-NAME inhibition, primarily restoring contractions and suggesting that these require lower nitrergic transmitter levels than relaxations. 4. Pretreatment of preparations with subrelaxant concentrations of sodium nitroprusside (1 micromol/L) selectively desensitized EFS-evoked contractions without affecting relaxations, suggesting different downstream mechanisms. Nevertheless, the selective guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (3 and 10 micromol/L) inhibited both nitrergic contractions and relaxations, indicating that guanylate cyclase activation is required for both responses. 5. The results of the present study support the hypothesis that the endogenous nitrergic transmitter differentially regulates guanylate cyclase, leading to either contractions or relaxations depending on its concentrations, thus providing additional insight into the regulation of ileum contractility by nitrergic activity.