Emptying In Conscious Rats Research Articles

Intracerebroventricular urocortin 3 counteracts central acyl ghrelin-induced hyperphagic and gastroprokinetic effects via CRF receptor 2 in rats.

PurposeUrocortin 3 is a key neuromodulator in the regulation of stress, anxiety, food intake, gut motility, and energy homeostasis, while ghrelin elicits feeding behavior and enhances gastric emptying, adiposity, and positive energy balance. However, the interplays between urocortin 3 and ghrelin on food intake and gastric emptying remain uninvestigated.MethodsWe examined the differential effects of central O-n-octanoylated ghrelin, des-Gln14-ghrelin, and urocortin 3 on food intake, as well as on charcoal nonnutrient semiliquid gastric emptying in conscious rats that were chronically implanted with intracerebroventricular (ICV) catheters. The functional importance of corticotropin-releasing factor (CRF) receptor 2 in urocortin 3-induced responses was examined by ICV injection of the selective CRF receptor 2 antagonist, astressin2-B.ResultsICV infusion of urocortin 3 opposed central acyl ghrelin-elicited hyperphagia via CRF receptor 2 in satiated rats. ICV injection of O-n-octanoylated ghrelin and des-Gln14-ghrelin were equally potent in accelerating gastric emptying in fasted rats, whereas ICV administration of urocortin 3 delayed gastric emptying. In addition, ICV infusion of urocortin 3 counteracted central acyl ghrelin-induced gastroprokinetic effects via CRF receptor 2 pathway.ConclusionICV-infused urocortin 3 counteracts central acyl ghrelin-induced hyperphagic and gastroprokinetic effects via CRF receptor 2 in rats. Our results clearly showed that enhancing ghrelin and blocking CRF receptor 2 signaling in the brain accelerated gastric emptying, which provided important clues for a new therapeutic avenue in ameliorating anorexia and gastric ileus found in various chronic wasting disorders.

Effect of pancreatic polypeptide on gastric accommodation and gastric emptying in conscious rats.

Pancreatic polypeptide (PP) is an anorexigenic hormone released from pancreatic F cells upon food intake. We aimed to determine the effect of PP on gastric accommodation and gastric emptying in conscious Wistar HAN rats to investigate whether effects on motor function could contribute to its anorexigenic effects. Intragastric pressure (IGP) was measured through a chronically implanted gastric fistula during the infusion of a nutrient meal (Nutridrink; 0.5 ml/min). Rats were treated with PP (0, 33 and 100 pmol·kg(-1)·min(-1)) in combination with N(G)-nitro-L-arginine methyl ester (L-NAME; 180 mg·kg(-1)·h(-1)), atropine (3 mg·kg(-1)·h(-1)), or vehicle. Furthermore, the effect of PP was tested after subdiaphragmal vagotomy of the stomach. Gastric emptying of a noncaloric and a caloric meal after treatment with 100 pmol·kg(-1)·min(-1) PP or vehicle was compared using X-rays. PP significantly increased IGP during nutrient infusion compared with vehicle (P < 0.01). L-NAME and atropine significantly increased IGP during nutrient infusion compared with vehicle treatment (P < 0.005 and 0.01, respectively). The effect of PP on IGP during nutrient infusion was abolished in the presence of L-NAME and in the presence of atropine. In vagotomized rats, PP increased IGP compared with intact controls (P < 0.05). PP significantly delayed gastric emptying of both a noncaloric (P < 0.05) and a caloric (P < 0.005) meal. PP inhibits gastric accommodation and delays gastric emptying, probably through inhibition of nitric oxide release. These results indicate that, besides the well-known centrally mediated effects, PP might decrease food intake through peripheral mechanisms.

Tu1976 A Method to Directly and Continuously Assess Gastric Emptying in Conscious Rats: Effect of Pancreatic Polypeptide and Atropine

Introduction: Gastric emptying (GE) in rats is mostly determined after gavaging a radioactive or colored meal, with determination of the percentage of food remaining in the stomach after sacrificing the animal as a measure for gastric emptying. We hereby present a novel method to directly and continuously assess gastric emptying of a liquid meal in conscious rats without the need to sacrifice animals. Methods: After an overnight fast, 6 Wistar HAN rats were placed in a custom-made Bolmann cage to minimize movement artefacts. Rats were treated with atropine (1 mg kg-1; subcutaneous), pancreatic polypeptide (PP; 100 pmol kg-1 min-1; intravenous infusion) or vehicle (administered on 2 occasions). 15 minutes after the start of the treatment, rats were gavaged with 3 ml of a liquid test meal containing 1% hydroxypropyl methylcellulose solution and 0.5 g ml-1 BaSO4 (0 cal). The abdomen was visualized as a dorsal projection using X-ray imaging (29 kV, 40mAs; Embracemammography device; Selenia software (Hologic)). X-ray imaging was possible throughout the whole experiment. In order to estimate the test meal fraction in the stomach, X-rays were taken every 5-10 minutes and analyzed using Image J software. After manually outlining the stomach, the software was used to calculate the area of the image of the stomach. The area directly after gavage of the meal was set at 100% and GE was expressed as the fraction of the original stomach area over time. The average percentage emptied over 60 minutes was compared. Data were represented as mean±S.E.M. and compared using a paired ttest (p 0.1). Atropine caused a significant delay in GE compared to vehicle (55.6±3.1 vs. 40.3±2.7% emptied over 60 minutes, p<0.01). Similarly, PP-treatment significantly inhibited GE (60.5±3.2 vs. 48.5±1.9% emptied over 60 minutes, p<0.05; Fig.1). Conclusion: Using X-rays to visualize a radio-opaque meal allows to determine gastric emptying in a continuous non-invasive manner. Both atropine and PP significantly delayed gastric emptying rate.

13C-Acetic Acid Is More Sensitive Than 13C-Octanoic Acid for Evaluating Gastric Emptying of Liquid Enteral Nutrient Formula by Breath Test in Conscious Rats

Breath test using 13C-labeled compound has been used as a convenient method to evaluate gastric emptying. 13C-Labeled acetic acid or octanoic acid has been used in clinic. However, there is few report comparing two compounds. This study aimed to compare 13C-acetic acid and 13C-octanoic acid in newly-constituted breath test for monitoring gastric emptying in conscious rats. After fasting, rats were orally administered Racol (liquid enteral nutrient formula) containing 13C-labeled compound (same molar of 13C-acetic acid or 13C-octanoic acid) and housed in a chamber. The expired air in the chamber was collected in a breath-sampling bag using a tube and aspiration pump. The level of 13CO2 in the expired air was measured using an infrared spectrometer at appropriate intervals for 120 min. Expired 13CO2 air from 13C-acetic acid changed at significantly higher levels than that from 13C-octanoic acid. Cmax and AUC120 min values of expired 13CO2 from 13C-acetic acid were significantly higher than those from 13C-octanoic acid, but Tmax was not different between them. These results show that 13C-acetic acid is more sensitive for monitoring gastric emptying than 13C-octanoic acid in liquid test meal although both acids clearly monitored gastric emptying.

Restraint stress augments postprandial gastric contractions but impairs antropyloric coordination in conscious rats

Central corticotropin-releasing factor (CRF) plays an important role in mediating restraint stress-induced delayed gastric emptying. However, it is unclear how restraint stress modulates gastric motility to delay gastric emptying. Inasmuch as solid gastric emptying is regulated via antropyloric coordination, we hypothesized that restraint stress impairs antropyloric coordination, resulting in delayed solid gastric emptying in conscious rats. Two strain gauge transducers were sutured onto the serosal surface of the antrum and pylorus, and postprandial gastric motility was monitored before, during, and after restraint stress. Antropyloric coordination, defined as a propagated single contraction from the antrum to the pylorus within 10 s, was followed by > or = 20 s of quiescence. Restraint stress enhanced postprandial gastric motility in the antrum and pylorus to 140 +/- 9% and 134 +/- 9% of basal, respectively (n = 6). The number of episodes of antropyloric coordination before restraint stress, 2.4 +/- 0.4/10 min, was significantly reduced to 0.6 +/- 0.3/10 min by restraint stress. Intracisternal injection of the CRF type 2 receptor antagonist astressin 2B (60 microg) or guanethidine partially restored restraint stress-induced impairment of antropyloric coordination (1.6 +/- 0.3/10 min, n = 6). The restraint stress-induced augmentation of antral and pyloric contractions was increased by astressin 2B and guanethidine but abolished by atropine, hexamethonium, and vagotomy. Restraint stress enhanced postprandial gastric motility via a vagal cholinergic pathway. Restraint stress-induced delay of solid gastric emptying is due to impairment of antropyloric coordination. Restraint stress-induced impairment of antropyloric coordination might be mediated via a central CRF pathway.

Simple and Noninvasive Breath Test Using 13C-Acetic Acid to Evaluate Gastric Emptying in Conscious Rats and Its Validation by Metoclopramide

The 13C-breath test has been used to clinically evaluate gastric emptying. However, this method has not been sufficiently validated in experimental animals. The present study aimed to establish a simple and noninvasive 13C-breath-test system in Sprague-Dawley male rats. After fasting, rats were orally administered Racol containing 13C-acetic acid and housed in a desiccator. The expired air in the chamber was collected in a breath-sampling bag using a tube and aspiration pump. The level of 13CO2 in the expired air was measured using an infrared spectrometer at appropriate intervals for 120 min. During this period, the rate of 13CO2 excretion increased, peaked, and decreased thereafter. The maximum concentration (Cmax) and area under the curve (AUC120 min) of 13CO2 excretion increased in volume- and dose-dependent manners. The time taken to reach the maximum concentration (Tmax) of 13CO2 excretion increased as the volume increased, but was not affected by the dose of 13C-labeled acetic acid. Metoclopramide dose-dependently increased the Cmax and shortened Tmax of 13CO2 excretion compared with those of the control rats, whereas the AUC120 min was not affected. These results confirm that this simple method can successfully evaluate gastric emptying. Moreover, this system is suitable for investigating additional physiological functions using other labeled compounds.

Possible involvement of nitric oxide in the inhibition of gastric emptying induced by intracerebroventricular administration of clonidine in conscious rat

Introduction: Our previous findings showed that both clonidine and oxymetazoline inhibited gastric emptying given subcutaneously. The question was raised whether activation of central α2-adrenoceptors are involved also in gastric emptying in conscious rats.

Acute hyperglycemia impairs vagus activity and inhibits antro-pyloric coordination resulting in delayed gastric emptying in conscious rats

Acute hyperglycemia impairs vagus activity and inhibits antro-pyloric coordination resulting in delayed gastric emptying in conscious rats

Acute hyperglycemia impairs vagus activity and inhibits antro-pyloric coordination resulting in delayed gastric emptying in conscious rats

Acute hyperglycemia impairs vagus activity and inhibits antro-pyloric coordination resulting in delayed gastric emptying in conscious rats

Central TRH receptor 1 antisense blocks cold-induced gastric emptying but not brain c-Fos induction

We studied whether TRH receptor 1 (TRH-R1) antisense oligodeoxynucleotides injected intracisternally, impaired acute cold-induced c-Fos expression in the brain and vagally mediated stimulation of gastric emptying in conscious rats. Cold exposure (4–6°C, 90 min) increased gastric emptying and the number of c-Fos positive cells in the paraventricular nucleus of the hypothalamus, supraoptic nucleus, raphe pallidus, dorsal motor nucleus of the vagus, nucleus of the solitary tract and area postrema compared with rats at room temperature. TRH-R1 antisense abolished cold-induced stimulation of gastric transit but not c-Fos expression in the brain. TRH-R1 mismatch did not alter the gastric response to cold. These data indicate that central activation of TRH-R1 mediates cold-induced stimulation of gastric emptying but does not influence the induction of c-Fos expression in the brain.

Astressin analogues (corticotropin-releasing factor antagonists) with extended duration of action in the rat.

In earlier reports we identified specific point substitutions (DPhe12,Nle21,38), cyclization strategies [in particular, introduction of lactam rings such as that of cyclo(Glu30,Lys33)], and deletions (residues 1-7) in the CRF molecule that led to agonists. We also noted that further deletions (residues 8-14) produced antagonists such as astressin ¿cyclo(30-33)[DPhe12,Nle21,38, Glu30, Lys33]hCRF(12-41)¿ (1). We hypothesized that the lactam ring promoted conformational stability to yield analogues with increased potency both in vitro and in vivo as compared to that of their linear counterparts. Additionally, we reported that cyclo(30-33)[DPhe12,Nle21,38, Glu30,DHis32,Lys33]hCRF(12-41) (3) and dicyclo(26-36,30-33)[Ac-Asp9,DPhe12,Nle21,38, Cys26, Glu30,Lys33, Cys36]hCRF(9-41) were ca. twice and 1/100 as potent as astressin, respectively, suggesting a putative turn that encompasses residues 30-33 (previous paper: Koerber et al. J. Med. Chem. 1998, 41). To increase the potency of 1 and/or 3 in vivo, we extended their chain length by one (5-8), two (9, 10), and three (11, 12) residues at the N-terminus and acetylated (6, 8, 10, 12). Of the compounds tested for duration of action (1, 3-6, 8), we found 6 and 8 to be slightly longer-acting than astressin or [DHis32]astressin, while their potencies in vitro were not significantly different from that of 3. Additionally, we introduced CalphaMe-leucine residues in lieu of leucine at positions 14, 15, 19, 27, and 37 in [DHis32]astressin. The analogue [CalphaMe-Leu27,DHis32]astressin (16) was more potent (although not statistically in all cases) than the other four analogues in vitro. While acetylation of the N-terminus of 16 (i.e., 18) or of [CalphaMe-Leu27]astressin (i.e., 19) did not have a significant effect on in vitro potency, elongation of the N-terminus by one or three residues in addition to acetylation resulted in cyclo(30-33)[DPhe12,Nle21,CalphaMe-Leu27,Glu3 0,DHis32,Lys33, Nle38]Ac-hCRF(11-41) (21), cyclo(30-33)[DPhe12,Nle21,CalphaMe-Leu27, Glu30,Lys33,Nle38]Ac-hCRF(9-41) (22), and cyclo(30-33)[DPhe12, Nle21, CalphaMe-Leu27,Glu30,DHis32,Lys33,Nle38 ]Ac-hCRF(9-41) (23) that were longer-acting than 6 and 8 (ca. 2 h inhibition of ACTH secretion at 25 micrograms/adrenalectomized rat). Analogues 22 and 23 were also more potent than astressin at reversing intracisternal CRF- and abdominal surgery-induced delay of gastric emptying in conscious rats.

Delayed gastric emptying by Helicobacter pylori lipopolysaccharide in conscious rats.

The present study was carried out to investigate the possibility that lipopolysaccharide deprived from Helicobacter pylori may alter gastric motility. To address the question, we examined the effect of H. pylori lipopolysaccharide on gastric emptying in conscious rats. Gastric emptying was evaluated by the phenol red method. Time-course and dose-related effects of intraperitoneal administration of H. pylori lipopolysaccharide were investigated. Intraperitoneal injection of H. pylori lipopolysaccharide significantly suppressed gastric emptying of a liquid meal in a dose-dependent manner. The inhibitory action of H. pylori lipopolysaccharide was observed 2, 4, 8, or 12 hr after the injection. These results suggest for the first time that H. pylori lipopolysaccharide may suppress gastric emptying in a long-lasting fashion. It is also suggested that H. pylori may influence gastric function through its cell wall structure named lipopolysaccharide.

The effect of nitric oxide synthase blockade and indomethacin on gastric emptying and gastric contractility.

The aim of the present study was to investigate the effect of nitric oxide (NO) synthase inhibition on gastric emptying rate in conscious rats and on gastric muscle contractility. The involvement of NO was also investigated in indometacin-induced (25 mg/kg, s.c.) changes in gastric emptying rate and smooth muscle contractility. L-NAME (NG-nitro-L-arginine methyl ester; 10 mg/kg, i.v.) inhibited the gastric emptying rate compared to controls and this effect was abolished by L-arginine (300 mg/kg, i.v.). Similarly, indometacin treatment led to a significant delay of gastric emptying rate with respect to vehicle-treated rats. Gastric longitudinal and circular muscle strips of L-NAME or indometacin-treated rats showed a reduction in contractile responses to carbachol. The results demonstrate that NO synthase blockade and indometacin treatment delay gastric emptying in conscious rats, concomitant with reduced responsiveness to carbachol, in vitro.

Effects of KSG-504, a new CCK-A receptor antagonist, on gallbladder and gastrointestinal functions

We investigated the interaction of KSG-504 with CCK-8- or pentagastrin-induced gallbladder and gastrointestinal responses in vitro and in vivo. KSG-504 (10(-7)-10(-4) M) inhibited CCK-8-induced contractions of both isolated guinea pig gallbladder and rabbit terminal cavity of the bile duct in a concentration-dependent manner. Furthermore, intravenous administration of KSG-504 also dose-dependently inhibited CCK-8-induced gallbladder contraction in anesthetized guinea pigs with an IC50 value of 0.23 mg/kg. In conscious mice, KSG-504 inhibited both CCK-8- and egg yolk-stimulated gallbladder emptying in a dose-dependent manner (IC50: 13.3 and 9.6 mg/kg, respectively). The CCK-8-induced delay of gastric emptying in conscious rats was also antagonized by KSG-504 with an IC50 value of 3.78 mg/kg, i.v., whereas pentagastrin-stimulated gastric acid secretion in anesthetized rats was not affected by KSG-504 at all. KSG-504 (1 mg/kg, i.v.) also inhibited CCK-8-induced duodenal and jejunal contractions in anesthetized rabbits. These results indicate that KSG-504 exerts an antagonistic effect on CCK-A receptors in the gastrointestinal tract, but not on gastrin receptors in the stomach.

P-384 - The measurement of gastric emptying in conscious rats by monitoring serial changes in serum acetaminophen level.

P-384 - The measurement of gastric emptying in conscious rats by monitoring serial changes in serum acetaminophen level.

Effect of sauvagine on gastric emptying in conscious rats

Sauvagine, a linear peptide with forty amino acid residues isolated from the skin of Phyllomedusa sauvagei, was injected s.c. and i.c.v. in conscious rats to determine its effect on gastric emptying (G.E.). Both i.c.v. and s.c. administration of the peptide produced a significant decrease in G.E. time. This effect was dose-related and lasted for 4 h following the injection. The potency of the peptide and its presence in the central nervous system suggest a physiological role in the mediation of gastrointestinal motility.

Bombesin delays gastric emptying in the rat.

Bombesin, administered by the intraperitoneal route, delayed gastric emptying in conscious rats in a dose-dependent fashion (1--16 microgram/kg). This effect is unlikely to depend on systemic effects of the peptide and is most probably connected with the direct spasmogenic action on the gastroduodenal junction already pinpointed in previous investigations.