Effect of dopamine on pentagastrin-stimulated gastric antral motility in dogs with gastric fistula

Gastric feed intolerance is not increased in critically ill patients with type II diabetes mellitus

OBJECTIVE

To examine the occurrence of feed intolerance in critically ill patients with previously diagnosed type II diabetes mellitus (DM) who received prolonged gastric feeding.

DESIGN AND SETTING

Retrospective study in a level 3 mixed ICU.

PATIENTS

All mechanically ventilated, enterally fed patients (n = 649), with (n = 118) and without type II DM (n = 531) admitted between January 2003 and July 2005.

INTERVENTIONS

Patients with at least 72 h of gastric feeding were identified by review of case notes and ICU charts. The proportion that developed feed intolerance was determined. All patient received insulin therapy.

RESULTS

The proportion of patients requiring gastric feeding for at least 72 h was similar between patients with and without DM (42%, 50/118, vs. 42%, 222/531). Data from patients with DM were also compared with a group of 50 patients matched for age, sex and APACHE II score, selected from the total non-diabetic group. The occurrence of feed intolerance (DM 52% vs. matched non-DM 50% vs. unselected non-diabetic 58%) and the time taken to develop feed intolerance (DM 62.6 +/- 43.8 h vs. matched non-DM 45.3 +/- 54.6 vs. unselected non-diabetic 50.6 +/- 59.5) were similar amongst the three groups. Feed intolerance was associated with a greater use of morphine/midazolam and vasopressor support, a lower feeding rate and a longer ICU length of stay.

CONCLUSIONS

In critically ill patients who require prolonged enteral nutrition, a prior history of DM type II does not appear to be a further risk factor for feed intolerance.

Identification and regional distribution of the dopamine D(1A) receptor in the gastrointestinal tract

Dopamine (DA) is regarded as an important modulator of enteric function. Recent experiments have suggested that newly cloned DA receptor subtypes are widely expressed in peripheral organs, including the gastrointestinal tract. In the present studies, the D(1A) receptor subtype was identified in rat gut regions through localization of receptor protein by means of light microscopic immunohistochemistry and Western blot analysis and receptor mRNA by RT-PCR and in situ amplification and hybridization (3SR in situ). D(1A) receptor immunoreactivity was shown to have a diverse distribution in the gastrointestinal tract, being present in the gastroesophageal junction, stomach, pylorus, small intestine, and colon. The receptor has a transmural distribution present in both epithelial and muscle layers as well as in blood vessels and lamina propria cells of different gastrointestinal regions. Western blot analysis demonstrated a single 50-kDa band for esophagus, stomach, duodenum, jejunum, and colon. The in situ hybridization signal was localized to the same sites revealed by D(1A) receptor immunoreactivity. RT-PCR revealed an appropriate sized signal in similar regions. This study is the first to identify expression of the central D(1A) receptor throughout the normal mammalian gastrointestinal tract.

Gastroprokinetic effect of a new benzamide derivative itopride and its action mechanisms in conscious dogs

The novel benzamide derivative itopride was assayed for its effect on gastrointestinal motility in conscious dogs when it was administered intraduodenally (i.d.). Gastrointestinal motility was measured by means of chronically implanted force transducers, and itopride at a dose of 10 mg/kg, i.d. or more increased the gastric contractile force during the digestive state. Intraduodenal cisapride, domperidone and metoclopramide also stimulated gastric motility, and their threshold doses were 1, 3 and 1 mg/kg, respectively. Dopamine infusion (1 mg/kg/hr, i.v.) caused the postprandial gastric motility to disappear, but it was immediately restored by itopride at a dose of 3 mg/kg, i.d. With itopride at 1 and 3 mg/kg, i.d., acetylcholine (0.05 mg/kg/min)-induced contractions were greatly enhanced. In addition to its gastric stimulation, itopride at doses of 10-100 mg/kg, p.o. inhibited apomorphine (0.1 mg/kg, s.c.)-induced vomiting in dogs. In conclusion, intraduodenal itopride stimulates gastric motility through both anti-dopaminergic and anti-acetylcholinesterase actions. Its gastroprokinetic threshold dose was as large as 3-10 times those of cisapride, domperidone and metoclopramide. These findings suggest that itopride is an orally active gastroprokinetic with a moderate anti-emetic action.

Inhibitory effect of dopamine on gastric motility in rats

BACKGROUND

There is disagreement with regard to the involvement of dopamine (DA) receptors in gastric motility. The mechanisms of the inhibitory effect of DA on rat gastric motility was investigated in association with acetylcholine (Ach) release in the present study.

METHODS

In vivo vagotomized, splanchnicectomized rats and control rats were used, and gastric movement was determined as the gastric motility index after DA administration. In vitro study of Ach release from the circular muscle strips of the gastric corpus was investigated after administration of domperidone, SCH23390, phentolamine, or propranolol.

RESULTS

In the in vivo study DA inhibited gastric motility in a dose-dependent manner. Vagotomy and splanchnicectomy had no effect on the inhibitory effect of DA. In vitro study DA inhibited [3H]-Ach release in a dose-dependent manner. The inhibitory effect of DA was antagonized by domperidone but not by phentolamine, propranolol, or SCH23390.

CONCLUSIONS

Inhibition of gastric motility by dopamine is independent of extrinsic innervation and seems to be mediated by DA2 receptors in the gastric wall.

The effect of dopamine on rat gastric motility

The inhibitory mechanism of dopamine (DA) on rat gastric motility was investigated in association with DA receptors. Gastric movement was assessed according to the method of Jacoby et al and was expressed with the system of Ludwick et al. (1968). DA inhibited gastric movement in both the corpus and antrum in a dose-dependent manner. Domperidone, a specific antagonist of DA2 receptor, suppressed DA-induced inhibition of gastric movement in a dose-dependent manner. SCH23390, a specific antagonist of DA1 receptor did not affect DA-induced inhibition of gastric movement. LY171555, a specific agonist of DA2 receptor, inhibited gastric movement in both the corpus and antrum in a dose-dependent manner. SKF38393, a specific agonist of DA1 receptor, did not affect gastric movement. These results indicate that DA plays an important role in the inhibitory regulation of gastric motility, through DA2 receptor but not DA1 receptor.

A novel water-soluble dopamine-2 antagonist with anticholinesterase activity in gastrointestinal motor activity. Comparison with domperidone and neostigmine

A novel water-soluble dopamine-2 antagonist, N-[4-[2-(dimethylamino) ethoxy]benzyl]-3,4-dimethoxybenzamide hydrochloride (HSR-803) was synthesized and assayed for its gastrointestinal smooth muscle stimulating activity in vivo and in vitro. In the in vivo study, gastrointestinal contractile activity was measured by means of chronically implanted force transducers in conscious dogs; it was found that HSR-803 at 3.0 mg/kg IV probably stimulated gastric contractile force twice during the digestive state and significantly antagonized dopamine-(1.0 mg/kg per hour) inhibited gastric contractions in doses of 0.3, 1, and 3 mg/kg IV. With a background IV infusion of HSR-803 at 3 mg/kg per hour, the contraction-stimulating activity of acetylcholine (0.05 mg/kg per minute) was greatly enhanced while the response to bethanechol was not changed. As a result, HSR-803 was found to have a strong anticholinesterase activity besides the antidopamine-2 activity; i.e., the anticholinesterase activity of HSR-803 at 3 mg/kg per hour was equivalent to that of neostigmine at 10 micrograms/kg per hour, and dopamine-2 antagonistic activity of HSR-803 was similar to that of domperidone on a weight basis. No symptom suggesting actions on the central nervous system was noticed in HSR-803 up to 10 mg/kg IV in conscious dogs. In the in vitro study, HSR-803 inhibited cholinesterase dose-dependently, and IC50 was 2.9 x 10(-6) mol/L, while those of neostigmine and domperidone were 2.3 x 10(-8) mol/L and 1.7 x 10(-5) mol/L, respectively. In conclusion, HSR-803 stimulates endogenous acetylcholine release by antagonizing the dopamine-2 receptor on the postsynaptic cholinergic neurons, and the anticholinesterase activity of HSR-803 may cause the released acetylcholine to accumulate at cholinergic receptor sites. Thus, HSR-803 is potentially capable of enhancing cholinergic activity in the gastrointestinal region.

Cisapride offsets dopamine-induced slowing of fasting gastric emptying

The effect of cisapride, a new gastrokinetic drug, on gastroduodenal motility was tested in six healthy volunteers. In order to obtain a model for slowed gastric emptying, dopamine was infused at a rate of 8 micrograms/kg/min. Dopamine significantly slowed the fractional emptying rate of fasting gastric contents from 5.14 +/- 0.37 to 1.45 +/- 0.67 %/min. Injection of either 10 mg of cisapride or 10 mg of metoclopramide restored emptying rate to normal (5.87 +/- 0.56 and 5.62 +/- 0.61 %/min, respectively). When cisapride was given without dopamine background, emptying was only moderately enhanced. Reflux of bile salts was not significantly affected by either cisapride or dopamine alone. When given on a dopamine background, however, both metoclopramide and cisapride decreased bile salt reflux below control values without any active treatment. It is concluded that emptying of fasting gastric contents can be speeded by cisapride, particularly when emptying is slowed by dopamine. A clear effect on bile salt reflux cannot be demonstrated.

Dopamine-induced migrating myoelectrical complex-like activity in human duodenum

The effect of dopamine on human gastric and small intestinal interdigestive motility was investigated in 12 subjects. Intestinal motility was recorded by means of a four-lumen polyvinyl probe with four open tips located 15 cm apart, continuously perfused with distilled water. In each subject during the same study, after recording two consecutive spontaneous phase III of migrating myoelectrical complexes and when a phase II appeared, dopamine was infused intravenously twice in a dose of 5 micrograms/kg/min for 15 min with an interval of 20 min between each infusion. In six subjects, the second dopamine infusion was preceded by a treatment with sulpiride (10 mg, intravenously, as bolus) or domperidone (10 mg, intravenously, as bolus), each considered a highly selective dopamine antagonist. The results show that dopamine stimulates duodenal motility producing a pattern similar to that observed in phase III of spontaneously occurring migrating myoelectrical complexes. The second dopamine infusion reproduced in all cases the same pattern of motility as observed during the first infusion. Sulpiride and domperidone prevented the effect of dopamine in all cases. It is therefore suggested that dopamine-induced duodenal motility may involve specific dopaminergic receptors.

Prevention of recurrent ulcer bleeding, a multicentre study of the effect of ranitidine and trimipramine over one year

Short term studies of the prevention of bleedings from peptic ulcers and erosions have been reported by a number of authors following treatment with antacids (1), H2-receptor blockers, cimetidine (2-15), a combination of cimetidine and tranexamic acid (16), cimetidine and somatostatin (17), cimetidine and sucralfate or secretion (18, 19, 20), cimetidine compared to antacid (21), and cimetidine compared to antacid and pirenzepine (22). The H2-blocker rantitidine has been compared to placebo (24, 25, 26). An uncontrolled study has been performed using proglumide (27), a controlled study with vasopressin (28) and with secretin versus somatostatin (28). In the studies with H2-receptor antagonists conflicting results have been obtained. No report has been published concerning the effect over more than a few days or weeks.

Inhibitory effect of dopamine on canine gastric fundus

The mechanism of the inhibitory effect of dopamine on canine stomach fundus was studied in longitudinal and circular muscle fundus strips, contracted by transmural electrical stimulation or by methacholine. Results obtained for longitudinal and circular strips were similar. Dopamine (1 X 10(-6)-1 X 10(-4) M) concentration-dependently inhibited frequency-response curves to electrical stimulation; these concentrations did not change the resting tone of the strips. Dopamine (1 X 10(-4) M), tested on contractions of similar amplitude induced in the same strips by electrical stimulation at 0.5 Hz and by methacholine, inhibited the electrically induced contractions but had little influence on the contractions induced by methacholine. The inhibition of the electrically induced contractions by dopamine 1 X 10(-4) M was not influenced by the presence of cocaine 3 X 10(-5) M or hydrocortisone 3 X 10(-5) M. The alpha 1- and alpha 2-adrenoceptor antagonist phentolamine and the alpha 2-adrenoceptor antagonist rauwolscine markedly antagonized the inhibitory effect of dopamine on the response to electrical stimulation at 0.5 Hz. The alpha 1-adrenoceptor antagonist prazosin and the dopamine receptor antagonists haloperidol and domperidone had no effect. The dopamine receptor antagonist metoclopramide decreased the inhibitory effect of dopamine but had a similar effect on the inhibition caused by noradrenaline. These results indicate that the inhibitory effect of dopamine in the dog gastric fundus is mainly mediated by an interaction with alpha 2-adrenoceptors on the intramural cholinergic neurons; this effect is largely direct since it was not influenced by cocaine.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of isoprenaline on bethanechol-stimulated gastric antral motility in dogs with gastric fistula

The purpose of the present study was to evaluate the effect of isoprenaline on gastric antral motility in conscious dogs with gastric fistula, using intraluminal strain-gauge transducers. Infusion of bethanechol increased the motility for both frequency and strength. Isoprenaline, a beta 1- and beta 2-agonist, was used alone and in conjunction with selective blockade of beta 1 and beta 2 receptors. The stimulated antral motility was dose-dependently inhibited by isoprenaline. The effect was significantly blocked by the beta 1 + beta 2-adrenoceptor blocker propranolol and by using in conjunction the beta 1-adrenoceptor blocker practolol and the beta 2-adrenoceptor blocker H 35/25. H 35/25 and particularly practolol reduced the effect of isoprenaline to some extent, but the reduction was not of statistical significance. This indicates that isoprenaline acts on antral motility through both beta 2 and beta 1 receptors. Dose-response experiments with five logarithmically increasing doses of bethanechol and one dose of isoprenaline showed inhibition of a non-competitive type.

Effect of dopamine on bethanechol-stimulated gastric antral motility in dogs with gastric fistula

The purpose of the present study was to evaluate the effect of dopamine on gastric antral motility in conscious dogs with gastric fistula, using intraluminal strain-gauge transducers. Infusion of bethanechol increased the motility with regard to both frequency and strength. Dopamine, an endogenous catecholamine, was used alone and in conjunction with selective blockade of adrenergic and dopaminergic receptors. The stimulated antral motility was dose-dependently inhibited by dopamine. The effect was significantly blocked by the peripherally acting dopaminergic blocker domperidone. The alpha-adrenoceptor blocker phentolamine reduced the effect of dopamine to some extent, but the reduction was not of statistical significance. The dopamine-inhibited motility was not altered by the beta 1-adrenoceptor blocker practolol or the beta 1 + beta 2-adrenoceptor blocker propranolol. This indicates that dopamine acts on gastric antral motility predominantly through dopaminergic receptors. beta-Adrenergic receptors, which are active in the impairment of gastric acid secretion, do not seem to be involved in the motility response. Dose-response investigations with five increasing doses of bethanechol and one dose of dopamine showed inhibition of a non-competitive type.

Effect of dopamine on bethanechol-stimulated gastric mucosal blood flow and gastric acid secretion in dogs with gastric fistula

The aim of the present study was to investigate the effect of Dopamine on bethanechol-stimulated gastric acid secretion and mucosal blood flow. dopamine was used alone and in conjunction with selective blockade of the alpha, beta, and dopaminergic receptors. An increasing and dose-dependent stimulation of gastric acid secretion was found for dopamine at 1, 5, and 10 micrograms/kg/min. A significant inhibition of gastric acid secretion was found with the highest dose of dopamine (40 micrograms/kg/min). the stimulatory effect seems to be mediated by more than one receptor, whereas the inhibition by high dopamine doses could be explained by a beta 1 stimulation. Dopamine (10 micrograms/kg/min) was found to increase the bethanechol-stimulated gastric mucosal blood flow. Phentolamine (alpha blackade) increased this dopamine-elevated blood flow further, with a significant increase in the ratio between blood flow and acid secretion, indicating a primary action of the alpha receptors on blood flow. Bethanechol stimulated the gastric acid secretion and blood flow in a parallel manner. It is concluded that alpha-receptor stimulation is the predominant directly acting factor in the regulation of gastric mucosal blood flow, whereas stimulation of beta, muscarinic, and 'gastrinergic' receptors mainly occurs indirectly via changes in parietal cell function. The main effect of dopamine seems to be on gastric motility, whereas the effect on gastric acid secretion is of minor importance.

Effect of dopamine on pentagastrin-stimulated gastric acid secretion and mucosal blood flow in dogs with gastric fistula

The purpose of this study was to elucidate the effect of intravenously administered dopamine on dopamine receptors and adrenergic receptors in terms of its effect on gastric acid secretion, the kinetic mechanism, blood flow, and antral motility. Dopamine was used alone and in conjunction with selective blockade of alpha-, beta-, and dopaminergic receptors. A significant inhibition of gastric acid secretion was found with the highest dose of dopamine used (40 micrograms/kg/min). The kinetic study showed characteristics of a non-competitive type. The anti-secretory effect dopamine was significantly blocked by non-selective beta-blockade or by selective beta-blockade but not by alpha- or dopaminergic receptor blockade. This suggests that the inhibitory effect of dopamine on gastric secretion is mediated by beta-receptors. There was no significant effect on gastric mucosal blood flow, but the ratio between blood flow and acid secretion was significantly elevated during dopamine infusion, indicating that the acid inhibition was not secondary to changes in blood flow. It is concluded that the dopamine inhibition of acid secretion is mediated by beta 1-receptors, unlike the effect on antral gastric motility, which is mediated by dopamine receptors.