Rat Gastric Fundus Research Articles

Relaxant Effects of Curcuma aeruginosa Rhizome Extracts on Isolated Rat Gastric Fundus and Ileum Contraction

Curcuma aeruginosa (CA) rhizomes are used in traditional medicine as gastrointestinal remedies, postpartum care and uterine issues. However, its effects on gastrointestinal motility have not yet been explored. Extracts of CA rhizomes prepared using chloroform, methanol and water were evaluated for their effects on gastrointestinal contractions using isolated rat gastric fundus and ileum. Varied solvents aim for extraction of different compounds of CA rhizome. In the ileum, the 3 extracts did not significantly affect spontaneous contractions, but significantly reduced contractions induced by acetylcholine (ACh, 0.3 µM) and KCl (40 mM) in a concentration-dependent manner. The order of potency, based on ACh-induced contraction, was chloroform > methanol > water extracts, with respective IC50 values of 0.025 ± 0.001, 0.46 ± 0.02 and 2.57 ± 0.47 mg/mL. Similar potency order against KCl-induced contraction was observed, with IC50 values of 0.011 ± 0.002, 0.47 ± 0.06 and 1.18 ± 0.18 mg/mL, respectively. In the isolated gastric fundus model, both methanol and water extracts resulted in an increase in the force of contraction in the absence of stimulation. However, when ACh (0.3 µM) was introduced, the methanol and water extracts exhibited a concentration-dependent reduction in contractions, with IC50 values of 0.62 ± 0.06 and 2.30 ± 0.32 mg/mL, respectively. As for KCl (40 mM)-induced contraction, only the highest concentration of the water extract (3.75 mg/mL) significantly decreased the contraction by 41.29 ± 2.94 %. CA extract demonstrated relaxant effects on both isolated rat gastric fundus and ileal contractions induced by ACh and KCl. These findings support the use of CA in traditional medicine as a gastrointestinal remedy. These extracts have the potential to be used as antispasmodics and to treat infectious and non-infectious diarrhea, the latter of which occurs in functional gastrointestinal diseases. It might also be useful as a gastroprokinetic. HIGHLIGHTS C. aeruginosa extracts had no impact on rat ileum’s spontaneous contraction Extracts caused dose-dependent relaxation of precontracted ileum Extracts enhanced spontaneous contraction of isolated gastric fundus Extracts induced relaxation in the precontracted isolated gastric fundus GRAPHICAL ABSTRACT

Electrophysiology, molecular modelling, and functional analysis of the effects of dietary quercetin and flavonoid analogues on Kir6.1 channels in rat stomach fundus smooth muscle

Flavonoids, ubiquitously distributed in the plant world, are regularly ingested with diets rich in fruit, vegetables, wine, and tea. During digestion, they are partially absorbed in the stomach. The present work aimed to assess the in vitro effects of quercetin and ten structurally related flavonoids on the rat gastric fundus smooth muscle, focussing on ATP-dependent K+ (Kir6.1) channels, which play a central role in the regulation of resting membrane potential, membrane excitability and, consequently, of gastric motility. Whole-cell currents through Kir6.1 channels (IKir6.1) were recorded with the patch-clamp technique and the mechanical activity of gastric fundus smooth muscle strips was studied under isometric conditions. Galangin ≈ tamarixetin > quercetin > kaempferol > isorhamnetin ≈ luteolin ≈ fisetin > (±)-taxifolin inhibited pinacidil-evoked, glibenclamide-sensitive IKir6.1 in a concentration-dependent manner. Morin, rutin, and myricetin were ineffective. The steric hindrance of the molecule and the number and position of hydroxyl groups on the B ring played an important role in the activity of the molecule. Molecular docking simulations revealed a possible binding site for flavonoids in the C-terminal domain of the Kir6.1 channel subunit SUR2B, in a flexible loop formed by residues 251 to 254 of chains C and D. Galangin and tamarixetin, but not rutin relaxed both high K+- and carbachol-induced contraction of fundus strips in a concentration-dependent manner. Furthermore, both flavonoids shifted to the right the concentration-relaxation curves to either pinacidil or L-cysteine constructed in strips pre-contracted by high K+, rutin being ineffective. In conclusion, IKir6.1 inhibition exerted by dietary flavonoids might counterbalance their myorelaxant activity, affect gastric accommodation or, at least, some stages of digestion.

Hidrolat matičnjaka (Melissa officinalis L.) slabo utiče na motilitet fundusa želuca pacova

Introduction. Lemon balm has been used for centuries due to its strong sedative, antimicrobial and spasmolytic effects. Besides different types of extracts and essential oils, hydrolates (by-products obtained during essential oil extraction) are preparations of aromatic medicinal plants with potential pharmacological activity. Aim. To estimate Melissa officinalis leaves hydrolate effects on gastric motility. Methods. The influence of the hydrolate was tested in vitro in a tissue bath in the rat fundus spontaneous contraction experimental model. Increasing volumes of sample (making the final concentration span 0.5 - 500 µl/ml) were successively added to the tissue bath. Results. Lower doses of the hydrolate did not produce any significant changes in the contraction patterns, while the higher ones led to a statistically significant increase in basal tone of the stomach fundus. Yet, these changes in basal tonus were still modest. Phytochemical qualitative characterization, done by liquid chromatography with ultra-high performances, showed that rosmarinic acid was dominant compound of M. officinalis hydrolate. Conclusion. Although the tested hydrolate poorly influences isolated rat gastric fundus motility, further studies could clarify its pharmacological activity and potential future application of this by-product of M. officinalis hydrodestilation.

Differential effects of β-methylphenylethylamine and octopamine on contractile parameters of the rat gastrointestinal tract

This study tested the effects of β-methylphenylethylamine (β-MPEA) and octopamine on contractile parameters of the gastrointestinal tract in rats. We hypothesized that some of their effects result from interactions with trace amine (TA)-associated receptors or serotoninergic 5-hydroxytryptamine (5-HT) receptors. β-MPEA-induced contractions in rat gastric fundus strips under resting tonus conditions, but induced relaxation in preparations that were previously contracted with carbachol. Octopamine relaxed gastric fundus strips maintained at resting tonus or contracted with carbachol. The contractile effect of β-MPEA was reduced by cyproheptadine and methiothepin, antagonists of excitatory 5-HT receptors. The relaxing effect of β-MPEA on gastric fundus was insensitive to pretreatment with N-(3-ethoxyphenyl)-4-(1-pyrrolidinyl)-3-(trifluoromethyl)benzamide (EPPTB) and tropisetron, antagonists of TA1 and 5-HT4 receptors, respectively. Both EPPTB and tropisetron inhibited the relaxant effects of octopamine on carbachol-contracted preparations. Contrarily, EPPTB did not reduce the relaxant effects of RO5263397 (TA1 agonist) or zacopride (5-HT4 agonist). Octopamine, but not β-MPEA, delayed the gastrointestinal transit of a liquid test meal in awaken rats. In isolated preparations of the small intestine under resting conditions, β-MPEA did not alter the basal tonus, but octopamine relaxed it. Intestinal preparations previously contracted with carbachol relaxed after the addition of octopamine and decreased the magnitude of their spontaneous rhythmic contractions in a tropisetron-dependent manner. Thus, β-MPEA and octopamine exerted pharmacological actions on the rat gastrointestinal tract. The excitatory effects of β-MPEA involved 5-HT receptors. Octopamine inhibited the rat gut contractility through the likely involvement of 5-HT4 and TA receptors. Overall, octopamine effectively inhibited rat gastrointestinal transit.

The Selective Rat Toxicant Norbormide Blocks KATP Channels in Smooth Muscle Cells But Not in Insulin-Secreting Cells.

Norbormide is a toxicant selective for rats to which it induces a widespread vasoconstriction. In a recent paper, we hypothesized a role of ATP-sensitive potassium (KATP) channels in norbormide-induced vasoconstriction. The current study was undertaken to verify this hypothesis by comparing the effects of norbormide with those of glibenclamide, a known KATP channel blocker. The whole-cell patch-clamp method was used to record KATP currents in myocytes freshly isolated from the rat and mouse caudal artery and from the rat gastric fundus, as well as in insulin-secreting pancreatic beta cells (INS-1 cells). Smooth muscle contractile function was assessed on either rat caudal artery rings or gastric fundus strips. Molecular modeling and docking simulation to KATP channel proteins were investigated in silico. Both norbormide (a racemic mixture of endo and exo isomers) and glibenclamide inhibited KATP currents in rat and mouse caudal artery myocytes, as well as in gastric fundus smooth muscle cells. In rat INS-1 cells, only glibenclamide blocked KATP channels, whereas norbormide was ineffective. The inhibitory effect of norbormide in rat caudal artery myocytes was not stereo-specific as both the endo isomers (active as vasoconstrictor) and the exo isomers (inactive as vasoconstrictor) had similar inhibitory activity. In rat caudal artery rings, norbormide-induced contraction was partially reverted by the KATP channel opener pinacidil. Computational approaches indicated the SUR subunit of KATP channels as the binding site for norbormide. KATP channel inhibition may play a role in norbormide-induced vasoconstriction, but does not explain the species selectivity, tissue selectivity, and stereoselectivity of its constricting activity. The lack of effect in INS-1 cells suggests a potential selectivity of norbormide for smooth muscle KATP channels.

Relaxant effect of atorvastatin on isolated rat gastric fundus strips: implications for Ca2+-signalling mechanisms.

Statins are determined to have various pleiotropic effects apart from their lipid-lowering properties. Herein, we investigated the direct effects of atorvastatin on gastric smooth muscle tone. Atorvastatin effectively relaxed isolated rat gastric fundus strips precontracted with acetylcholine, potassium chloride, and serotonin. Incubation of the strips with nitric oxide synthase inhibitor, l-NOARG (10-4 M, 20 min), l-type voltage-operated Ca2+ channel (VOCC) blocker, nifedipine (10-6 M, 30 min), KATP channel blocker, glibenclamide (10-5 M, 30 min), or precursor of cholesterol, mevalonate (10-2 M, 45 min) did not change the relaxations to atorvastatin. However, pretreatment of fundus strips with atorvastatin (3×10-5-3×10-4 M, 30 min) inhibited the contractions to calcium chloride (10-4-10-1 M), acetylcholine (10-4 M), and caffeine (20 mM) in the calcium-free medium. Moreover, atorvastatin reduced the contractions induced by sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) inhibitor, cyclopiazonic acid (10-7-3×10-5 M). The current study demonstrated that atorvastatin produces an acute relaxant effect on gastric fundus strips, which appears to be mediated by several Ca2+-signalling mechanisms such as the blockade of l-type VOCC-independent Ca2+ entry, decrease in smooth muscle Ca2+ sensitivity, inhibition of IP3- and ryanodine-sensitive intracellular stores to mediate Ca2+ release, as well as the activation of SERCA. This acute relaxing effect seems unlikely to be related with nitric oxide, KATP channels, and the mevalonate pathway.

Dual excitatory and smooth muscle-relaxant effect of β-phenylethylamine on gastric fundus strips in rats.

β-Phenylethylamine (β-PEA) is a trace amine with chemical proximity to biogenic amines and amphetamines. It is an endogenous agonist of trace amine-associated receptors (TAARs) that acts as a neuromodulator of classic neurotransmitters in the central nervous system. At high concentrations, β-PEA contracts smooth muscle, and a role for TAARs in these responses has been postulated. The high dietary intake of trace amines has been associated with such symptoms as hypertension and migraine, especially after the intake of foods containing such compounds. In gastrointestinal tissues, TAAR expression was reported, although the effect of β-PEA on gastric contractile behaviour is unknown. Here, isolated strips that were obtained from the rat gastric fundus were stimulated with high micromolar concentrations of β-PEA. Under resting tonus, β-PEA induced contractions. In contrast, when the strips were previously contracted with KCl, a relaxant response to β-PEA was observed. The contractile effect of β-PEA was inhibited by 5-hydroxytryptamine (5-HT) receptor antagonists (i.e., cyproheptadine and ketanserin) but not by the TAAR1 antagonist EPPTB. In gastric fundus strips that were previously contracted with 80mmol/L KCl, the relaxant effect of β-PEA intensified in the presence of 5-HT receptor antagonists, which was inhibited by EPPTB and the adenylyl cyclase inhibitor MDL-12,330A. The guanylyl cyclase inhibitor ODQ did not alter the relaxant effects of β-PEA. In conclusion, β-PEA exerted dual contractile and relaxant effects on rat gastric fundus. The contractile effect appeared to involve the recruitment of 5-HT receptors, and the relaxant effect of β-PEA on KCl-elicited contractions likely involved TAAR1 .

The sphingosine analog fingolimod (FTY720) enhances tone and contractility of rat gastric fundus smooth muscle.

Sphingosine and its metabolite sphingosine phosphate (S1P) regulate a multitude of biological functions, including the contractile state of smooth. Gastrointestinal side effects have been reported in patients treated with FTY720, a sphingosine analog that is approved for the treatment of multiple sclerosis. The aim of this study was to characterize the effects of FTY720 on rat gastric fundus smooth muscle under basal conditions and during activation induced by high-K+ solution. Isometric contractions of isolated circular strips of gastric fundus smooth muscle were recorded using the organ bath method. The effects of FTY720 or vehicle were recorded under control conditions and in the presence of indomethacin, L-NAME, HA-1100, nifedipine, JTE-013, and suramin. Tone and contractions recorded in the presence of FTY720 or vehicle are reported as % of the amplitude of an initial high-K+ contraction obtained under control conditions. From a concentration of 10μmol L-1 onwards, FTY720 increased the tone, reaching 8.9%±7.5% at 100μmol L-1 (P<.05). With indomethacin in the solution, the effects of FTY720 were enhanced (32.1%±7.7%; P<.001). The FTY720-induced increase in tone was abolished in the absence of extracellular Ca2+ and reduced by nifedipine, HA-1100, JTE-013, and suramin. Furthermore, FTY720 increased high-K+ contractions in the presence of indomethacin. FTY720 increases tone and contractile responses to depolarization in gastric fundus smooth muscle by triggering calcium entry and calcium sensitization in a S1P receptor-dependent manner. Taken together, the experimental results presented in this work suggest that FTY720 may increase gastric tone and contractility in patients.

Potential rat model of anxiety-like gastric hypersensitivity induced by sequential stress.

AIMTo establish a rat model of anxiety-like gastric hypersensitivity (GHS) of functional dyspepsia (FD) induced by novel sequential stress.METHODSAnimal pups were divided into two groups from postnatal day 2: controls and the sequential-stress-treated. The sequential-stress-treated group received maternal separation and acute gastric irritation early in life and restraint stress in adulthood; controls were reared undisturbed with their mothers. Rats in both groups were followed to adulthood (8 wk) at which point the anxiety-like behaviors and visceromotor responses to gastric distention (20-100 mmHg) and gastric emptying were tested. Meanwhile, alterations in several anxiety-related brain-stomach modulators including 5-hydroxytryptamine (5-HT), γ-aminobutyric acid (GABA), brain-derived neurotrophic factor (BDNF) and nesfatin-1 in the rat hippocampus, plasma and gastric fundus and the 5-HT1A receptor (5-HT1AR) in the hippocampal CA1 subfield and the mucosa of the gastric fundus were examined.RESULTSSequential-stress-treated rats simultaneously demonstrated anxiety-like behaviors and GHS in dose-dependent manner compared with the control group. Although rats in both groups consumed similar amount of solid food, the rate of gastric emptying was lower in the sequential-stress-treated rats than in the control group. Sequential stress significantly decreased the levels of 5-HT (51.91 ± 1.88 vs 104.21 ± 2.88, P < 0.01), GABA (2.38 ± 0.16 vs 5.01 ± 0.13, P < 0.01) and BDNF (304.40 ± 10.16 vs 698.17 ± 27.91, P < 0.01) in the hippocampus but increased the content of nesfatin-1 (1961.38 ± 56.89 vs 1007.50 ± 33.05, P < 0.01) in the same site; significantly decreased the levels of 5-HT (47.82 ± 2.29 vs 89.45 ± 2.61, P < 0.01) and BDNF (257.05 ± 12.89 vs 536.71 ± 20.73, P < 0.01) in the plasma but increased the content of nesfatin-1 in it (1391.75 ± 42.77 vs 737.88 ± 33.15, P < 0.01); significantly decreased the levels of 5-HT (41.15 ± 1.81 vs 89.17 ± 2.31, P < 0.01) and BDNF (226.49 ± 12.10 vs 551.36 ± 16.47, P < 0.01) in the gastric fundus but increased the content of nesfatin-1 in the same site (1534.75 ± 38.52 vs 819.63 ± 38.04, P < 0.01). The expressions of 5-HT1AR in the hippocampal CA1 subfield and the mucosa of the gastric fundus were down-regulated measured by IHC (Optical Density value: Hippocampus 15253.50 ± 760.35 vs 21149.75 ± 834.13; gastric fundus 15865.25 ± 521.24 vs 23865.75 ± 1868.60; P < 0.05, respectively) and WB (0.38 ± 0.01 vs 0.57 ± 0.03, P < 0.01) (n = 8 in each group).CONCLUSIONSequential stress could induce a potential rat model of anxiety-like GHS of FD, which could be used to research the mechanisms of this intractable disease.

Extracellular acidosis selectively inhibits pharmacomechanical coupling induced by carbachol in strips of rat gastric fundus.

What is the central question of this study? Acute acidosis that results from short-term exercise is involved in delayed gastric emptying in rats and the lower responsiveness of gastric fundus strips to carbachol. Does extracellular acidosis decrease responsiveness to carbachol in tissues of sedentary rats? How? What is the main finding and its importance? Extracellular acidosis inhibits cholinergic signalling in the rat gastric fundus by selectively influencing the Gq/11 protein signalling pathway. Acute acidosis that results from short-term exercise delays gastric emptying in rats and decreases the responsiveness to carbachol in gastric fundus strips. The regulation of cytosolic Ca2+ concentrations appears to be a mechanism of action of acidosis. The present study investigated the way in which acidosis interferes with gastric smooth muscle contractions. Rat gastric fundus isolated strips at pH6.0 presented a lower magnitude of carbachol-induced contractions compared with preparations at pH7.4. This lower magnitude was absent in carbachol-stimulated duodenum and KCl-stimulated gastric fundus strips. In Ca2+ -free conditions, repeated contractions that were induced by carbachol progressively decreased, with no influence of extracellular pH. In fundus strips, CaCl2 -induced contractions were lower at pH6.0 than at pH7.4 but only when stimulated in the combined presence of carbachol and verapamil. In contrast, verapamil-sensitive contractions that were induced by CaCl2 in the presence of KCl did not change with pH acidification. In Ca2+ store-depleted preparations that were treated with thapsigargin, the contractions that were induced by extracellular Ca2+ restoration were smaller at pH6.0 than at pH7.4, but relaxation that was induced by SKF-96365 (an inhibitor of store-operated Ca2+ entry) was unaltered by extracellular acidification. At pH6.0, the phospholipase C inhibitor U-73122 relaxed carbachol-induced contractions less than at pH7.4, and this phenomenon was absent in tissue that was treated with the RhoA kinase blocker Y-27632. Thus, extracellular acidosis inhibited pharmacomechanical coupling in gastric fundus by selectively inhibiting the Gq/11 protein signalling pathway, whereas electromechanical coupling remained functionally preserved.

Gastric and pyloric sphincter muscle function and the developmental-dependent regulation of gastric content emptying in the rat.

Feeding intolerance is a common issue in the care of preterm neonates. The condition manifests as delayed emptying of gastric contents and represents a therapeutic challenge, since the factors accounting for its manifestations are unknown. The main goal of this study was to comparatively investigate the age-related function of rat gastric and pyloric smooth muscle and their putative regulators. We hypothesized that a reduced gastric muscle contraction potential early in life contributes to the delayed gastric emptying of the newborn. Newborn and adult rat gastric (fundus) and pyloric sphincter tissues were comparatively studied in vitro. Shortening of the tissue-specific dissociated smooth muscle cell was evaluated, and expression of the key regulatory proteins Rho-associated kinase 2 and myosin light chain kinase was determined. Gastric and pyloric smooth muscle cell shortening was significantly greater in the adult than the respective newborn counterpart. Expression of myosin light chain kinase and Rho-associated kinase 2 was developmentally regulated and increased with age. Pyloric sphincter muscle expresses a higher neuronal nitric oxide synthase and phosphorylated vasodilator-stimulated phosphoprotein content in newborn than adult tissue. Compared with later in life, the newborn rat gastropyloric muscle has a Ca(2+)-related reduced potential for contraction and the pyloric sphincter relaxation-dependent modulators are overexpressed. To the extent that these rodent data can be extrapolated to humans, the delayed gastric emptying in the newborn reflects reduced stomach muscle contraction potential, as opposed to increased pyloric sphincter tone.

Effects of Ca2+-activated K+ channel modulators on the contractility of the rat gastric fundus

Effects of Ca2+-activated K+ channel modulators on the contractility of the rat gastric fundus

Pharmacodynamic Study of Interaction of Aqueous Leaf Extract of Psidium Guajava Linn. (Myrtaceae) with Receptor Systems Using Isolated Tissue Preparations.

The present study investigates the interaction of aqueous leaf extract of Psidium guajava with muscarinic, serotonergic and adrenergic receptor system using isolated rat ileum, gastric fundus and trachea, respectively. The concentration-dependent contractile response of aqueous leaf extract of Psidium guajava was parallel and rightward of standard agonists, ACh and 5-HT indicating agonistic activity on muscarinic and serotonergic receptor systems. The inhibition of aqueous leaf extract of Psidium guajava mediated contractions in presence of atropine (10(-7) M) and ketanserin (10(-6) M) confirmed the activity. Relaxant effect of PG (0.2 mg/ml) on carbachol induced pre-contracted rat tracheal chain indicated its agonistic action on adrenergic receptor system. Inhibition (P<0.05) of the action in the presence of propranolol (1 ng/ml) confirmed the activity. It may be concluded that PG possesses agonistic action on muscarinic, serotonergic and adrenergic receptor systems.

Nitrergic Pathway Is the Major Mechanism for the Effect of DA-9701 on the Rat Gastric Fundus Relaxation.

Background/AimsDA-9701 significantly improved gastric accommodation by increasing the postprandial gastric volume. In this study, we investigated how DA-9701 affects the rat gastric fundus relaxation.MethodsGastric fundus muscle strips (9 longitudinal and 7 circular muscles) were obtained from rats. Electrical field stimulation (EFS) was performed at various frequencies (1, 5, 10 and 20 Hz) and train durations (1, 5, 10 and 20 seconds) to select optimal condition for experiments. Isometric force measurements were performed in response to EFS. Peak and nadir were observed during the first 1 minute after initiation of EFS in control state and after sequential addition of atropine (1 μM), DA-9701 (0.5, 5, 25 and 50 μg), N-nitro-L-arginine (L-NNA, 100 μM), MRS2500 (1 μM) and tetrodotoxin (TTX, 1 μM) to the organ bath.ResultsThe optimal frequency and duration of EFS to evoke nerve-mediated relaxation was determined as 5 Hz for 10 seconds. Addition of L-NNA in the presence of atropine and DA-9701 (50 μg) decreased nadir by inhibiting relaxation from −0.054 ± 0.021 g to −0.022 ± 0.015 g (P = 0.026) in longitudinal muscles. However, subsequent application of MRS2500 in the presence of atropine, DA-9701 (50 μg) and L-NNA did not affect nadir. In circular muscles, subsequent addition of L-NNA and MRS2500 in the presence of atropine and DA-9701 (50 μg) did not show significant change of nadir.ConclusionsOur data suggest that the effect of DA-9701 on the rat gastric fundus relaxation is mainly mediated by nitrergic rather than purinergic pathway.

Effect of biliary cirrhosis on neurogenic relaxation of rat gastric fundus and anococcygeus muscle: role of nitric oxide pathway.

Cirrhosis, associated with a host of hemodynamic abnormalities, could affect the gastrointestinal (GI) tract motility. On the other hand, the nonadrenergic noncholinergic (NANC) neurotransmission has been shown to play a pivotal role in GI tract motility and has been linked with release of nitric oxide (NO) on electrical stimulation. In this study, we investigated the effect of biliary cirrhosis on the neurogenic relaxation of rat gastric fundus and anococcygeus muscle and also the possible role of nitric oxide system in this manner. Isolated gastric fundus and anococcygeus strips of sham-operated and biliary cirrhotic (4weeks after bile duct ligation) rats were mounted under tension in a standard organ bath. Electrical stimulation was applied to obtain NANC-mediated relaxations in precontracted gastric fundus and anococcygeus muscle. The neurogenic relaxations were examined in the presence of different doses of NO synthase inhibitor, N (w)-Nitro-L-Arginine Methyl Ester (L-NAME). The concentration-dependent relaxant responses to the NO donor sodium nitroprusside were also evaluated. The neurogenic relaxation of both gastric fundus and anococcygeus muscle was significantly (P<0.001) increased in cirrhotic animals. L-NAME (0.03-1,000µM) inhibited relaxations in both groups in a dose-dependent manner (P<0.001), but cirrhotic groups were more resistant to the inhibitory effects of L-NAME (P<0.01). Sodium nitroprusside-mediated relaxations were similar in two groups. This study for the first time demonstrated that cirrhosis increases the NO-mediated neurogenic relaxation of both rat gastric fundus and anococcygeus muscle, suggesting a crucial role for the neurogenic NO in the pathophysiology of disturbed GI motility in cirrhosis.

Uridine adenosine tetraphosphate induces contraction of circular and longitudinal gastric smooth muscle by distinct signaling pathways

Extracellular nucleotides uridine-5'-triphosphate (UTP) and adenosine-5'-triphosphate (ATP) induce contraction of gastric smooth muscle (SM). The dinucleotide uridine adenosine tetraphosphate (Up4 A), an endothelium-derived contraction factor, induces vascular SM contraction. Its effect on gastric SM contractions, however, is unknown. We addressed the hypothesis that Up4 A induces gastric SM contraction via a mechanism that may differ between circular and longitudinal muscle (CM and LM, respectively). CM and LM were isolated from rat gastric fundus for the measurement of isometric tension. Up4 A induced transient contractile responses in both CM and LM, which were similar to those induced by ATP and UTP. Up4 A failed to induce contraction of either LM or CM in the absence of extracellular Ca(2+) or in the presence of nimodipine, an inhibitor of voltage-gated Ca(2+) channels. P2X1, 2, 4, 5 and 7 and P2Y1, 2, 4 and 6 receptor expression was detected in gastric SM by reverse transcription-polymerase chain reaction. IP5 I (a P2X receptor antagonist) and α,β-methylene-ATP (a P2X receptor agonist) had no effect on Up4 A-induced contractions of either LM or CM, and α,β-methylene-ATP alone failed to induce a contractile response in either tissue. Suramin (a P2Y receptor antagonist), on the other hand, significantly inhibited Up4 A-induced contraction of CM, but not LM. Up4 A-induced contraction of CM, but not LM, was also inhibited by pretreatment with Y-27632, an inhibitor of Rho-associated kinase. We conclude that Up4 A induces extracellular Ca(2+) -dependent contractions of rat gastric LM and CM, and Up4 A-induced contraction of CM is mediated by suramin-sensitive P2Y receptors and subsequent activation of the Rho-associated kinase pathway.

Sa2065 Purinergic Pathway Is the Major Mechanism of Inhibitory Effect of Motilitone on the Rat Gastric Fundus Relaxation

Previous studies found that mechanical stretch in bowel obstruction markedly induced gene expression of COX-2, but not COX-1, in colonic smooth muscle cells (SMCs). The aims of the present study were to determine whether genes encoding individual prostaglandin synthases are mechanically responsive, and whether the composition of prostaglandins resulting from obstruction differs from that in inflammation. Methods: Partial colon obstruction was induced with a silicon band implanted surgically in the distal colon of male SpragueDawley rats. Static mechanical stretch (18% elongation) was mimicked in vitro in the culture of rat colonic circular SMCs with a Flexercell FX-4000 System. Rat colon inflammation was induced by manipulation of the colonic surface with wet cotton applicators. Results: 1. Quantitative RT-PCR found that the expression of PGDS and PGIS genes was not significantly changed on day 3 of obstruction. However, the membrane bound PGES-1 (mPGES-1) mRNA was significantly up-regulated in the obstructed segment, whereas mRNAs for other two types of PGES, cytosolic PGES and mPGES-2, were not changed. On the contrary, the PGFS mRNA was down-regulated in the obstructed colon. 2. PGE2, but not PGF2 α, was significantly increased in the colonic muscularis externae in obstruction. The PGE2 level increased to 4577±1249 pg/mg at day 3 of obstruction, compared to 1264±259 in sham (n=6, p,0.05). The PGF2α level was 5718±910 pg /mg in obstruction compared to 6550±2178 pg/mg in the sham (n=5, p.0.05). 3. Direct stretch of rat colonic circular SMCs in vitro significantly up-regulated the mPGES-1 mRNA, but down-regulated that of PGFS. After stretch for 3 hrs, the mRNA levels of PGES and PGFS changed by 2.61±0.42 fold and 0.82±0.03 fold, respectively (n = 4 or 5, p,0.05). 4. In colonic inflammation, both PGE2 and PGF2α were significantly increased in the colonic smooth muscle (5.2(±1.5)-fold and 4.7(±1.3)-fold of control, respectively, p,0.05, n = 3). 5. Rat colonic circular muscle contractility was inhibited by exogenous PGE2 (10-9 ~10-6 M), but enhanced by PGF2 α (10-9 ~10-6 M) in a concentration-dependent manner (n = 4). Conclusions: Genes involved in the COX pathway of arachidonic acid metabolism are highly mechanosensitive in colonic SMCs, and play a critical role in motility function. Mechano-regulation of prostaglandin synthases accounts for increased PGE2 and unchanged PGF2 α in bowel obstruction, a pathological feature different from inflammation in which both PGE2 and PGF2 α are increased.

The effect of Nigella sativa on the diabetic liver in male albino rats with a special focus on the role of hepatic oval cells

Introduction Aging is believed to affect the structure and function of the enteric nervous system in the gastrointestinal tract. Aim of the work This work was designed to study the histological changes that might occur in the myenteric plexus of rat gastric fundus during aging. Materials and methods: Thirty male albino rats were used in this study and divided equally into three groups: group A (which included 4-month-old rats), group B (which included 18-monthold rats), and group C (which included 24-month-old rats). All the animals were anesthetized, and their stomachs were dissected out and processed for light and electron microscope examination. Also, immunohistochemical staining was carried out for the detection of protein gene product (PGP 9.5) and Bcl-2 proteins. The area% of myenteric ganglia was also determined. The results were analyzed statistically. Results: With age, in group B (early senile), there was obvious neuronal loss and few gaps in the myenteric plexus, with a significant decrease in the number of PGP-positive neurons and moderate immunoreactions for the Bcl-2 protein. Glial cells had cytoplasmic vacuoles and nerve cells had peripheral condensation of heterochromatin in their nuclei. The myenteric plexus of the rats of group C (late senile) showed nerve cell bodies with apoptotic nuclei and cytoplasmic vacuolations. Many large cavities and eosinophillic cellular infiltration were observed within the neuropil. There was a marked apparent decrease in PGP 9.5-positive neurons and minimal immunoreactions for the Bcl-2 protein. Also, the area of myenteric ganglia increased with advancing age. Conclusion: In the current study, it was found that the myenteric plexus of the gastric fundus showed histological and immunohistochemical changes during aging, which may potentially be an explanation for the gastrointestinal tract disturbance in elderly individuals.

Gastrokinetic activity of Morinda citrifolia aqueous fruit extract and its possible mechanism of action in human and rat models

Aims of the studyThis study was to investigate the gastrokinetic activity of Morinda citrifolia aqueous fruit extract (AFE) in human subjects by examining the GI absorption of ranitidine, a putative indicator of GI motility and to elucidate its possible gastrokinetic mechanism of action in rats. Materials and methodsThe single-dose, randomized, open-label and 2-period crossover study was performed on 20 Thai healthy volunteers with a washout period of 14 day between the doses. AFE or drinking water was administered orally 30min prior to a single oral administration of ranitidine (300mg). Blood samples were collected over a 12h period after drug administration and the pharmacokinetic parameters of ranitidine were calculated. The gastrokinetic mechanism of action of AFE was elucidated by measurement of its contractile response on the isolated rat gastric fundus strip. ResultsThe area under the plasma ranitidine concentration–time curve and the maximal plasma ranitidine concentration were significantly increased after pretreatment with AFE (p=0.001). The plasma ranitidine concentrations were significantly greater at 30–120min after its administration. AFE produced a definite contractile response of a rat gastric fundus strip with a dose dependency. Scopoletin at the same equivalent dose present in AFE elicited a concentration-dependent contraction that amounted to 45% of the maximal response to AFE. The contractile response of both AFE and scopoletin was mediated through the 5-HT4 receptor. ConclusionAFE has a unique gastrokinetic activity in enhancement of the rate and the extent of ranitidine absorption. The underlying mechanism can be attributed, at least in part, to the ability of its active component: scopoletin to stimulate the 5-HT4 receptor.

K V7 channels regulate muscle tone and nonadrenergic noncholinergic relaxation of the rat gastric fundus

Voltage-dependent type 7 K + (K V7) channels play important physiological roles in neurons and muscle cells. The aims of the present study were to investigate the motor effects of K V7 channel modulators in the rat gastric fundus and the expression of K V7 channels in this tissue. Muscle tone and electrical field stimulation (EFS)-evoked relaxations of precontracted longitudinal muscle strips of the rat gastric fundus were investigated under nonadrenergic noncholinergic conditions by organ bath studies. Gene expression was studied by real-time PCR and tissue localization of channels was investigated by immunohistochemistry. The K V7 channel blocker XE-991 induced concentration-dependent contractions, with mean pD 2 and E max of 5.4 and 48% of the maximal U46619-induced contraction, respectively. The K V7 channel activators retigabine and flupirtine concentration-dependently relaxed U46619-precontracted strips, with pD 2s of 4.7 and 4.4 and E max of 93% and 91% of the maximal relaxation induced by papaverine, respectively. XE-991 concentration-dependently inhibited retigabine-induced relaxation with a pIC 50 of 6.2. XE-991 and DMP-543, another K V7 channel blocker, increased by 13–25% or reduced by 11–21% the relaxations evoked by low- or high-frequency EFS, respectively. XE-991 also reduced the relaxation induced by vasoactive intestinal polypeptide (VIP) by 33% of controls. Transcripts encoded by all K V7 genes were detected in the fundus, with 7.4 and 7.5 showing the highest expression levels. K V7.4 and 7.5 channels were visualized by confocal immunofluorescence in both circular and longitudinal muscle layers. In conclusion, in the rat proximal stomach, K V7 channels appear to contribute to the resting muscle tone and to VIP- and high-frequency EFS-induced relaxation. K V7 channel activators could be useful relaxant agents of the gastric smooth muscle.