Gastric Slow Waves Research Articles

T1323 Do Different Types of Patients with Functional Dyspepsia in ROME III Criteria Vary in Related Pathophysiological Mechanisms?

BACKGROUND: In Rome III criteria, patients with functional dyspepsia (FD) are divided into: epigastric pain syndrome (EPS), postprandial discomfort syndrome (PDS) and EPS+PDS. Now, it remains unknown whether differences in the FD related pathophysiological mechanisms exit among them. If the differences are detected, it will be very helpful to treat different types of FD patients according to their special pathophysiologies. AIMS: To investigate the differences in FD related pathophysiologies including gastric solid emptying (GE), gastric muscular electrical activity (GME), autonomic nerve system function (ANS), gastric accommodation/sensitivity and abnormal psychological factors among EPS, PDS and EPS+PDS types of FD patients. METHODS: 77 FD patients according to Rome III criteria (57F, mean age 44.8yrs, EPS 17, PDS 34, EPS+PDS 26) were enrolled in this study. GE, GME, ANS, gastric accommodation/sensitivity and abnormal psychological factors were measured by GE test (radionuclide and radiopaque maker methods), multi-channel electrogastrography, heart rate variability analyzer, liquid nutrient load test (LNLT) and Zung Anxiety/Depression Scale, respectively. The study was approved by the ethics committee of PUMC Hospital. RESULTS: 1. No significant differences exited in age, sex and course of FD among the three types (P>0.05). 2. Delayed GE%: EPS vs. PDS vs. EPS+PDS 33.3% vs. 36.7% vs. 40.0% (P= 0.912). 3. GME: Normal percentage of 2-4cpm gastric slow waves: fasting 78.9±10.6% vs. 75.2±15.0% vs. 69.9±19.0% (P=0.209) and postprandial 71.0±14.0% vs. 71.6±15.2% vs. 62.6±17.3% (P=0.097). Percentage of slow wave coupling%: fasting 67.5±17.0% vs. 64.9±21.2% vs. 61.5±23.3% (P=0.684) and postprandial 62.0±15.7% vs. 59.2±19.6% vs. 50.9±18.1% (P=0.138). 4. LNLT: Maximal Intake Volume: 511±140 vs. 451±129 vs. 480±148ml (P=0.431). 5. ANS: Sympathetic Activity: fasting 0.46±0.28 vs. 0.36±0.19 vs. 0.45±0.14 (P=0.174) and postprandial 0.51±0.17 vs. 0.51±0.19 vs. 0.54±0.13 (P=0.821). Vagal Activity: fasting 0.62±0.17 vs. 0.64±0.19 vs. 0.55±0.14 (P=0.156) and postprandial 0.49±0.17 vs. 0.49±0.19 vs. 0.46±0.13 (P=0.821). 6. Zung Anxiety Scale: 45.6±9.4 vs. 48.4±10.1 vs. 49.7±9.5 (P=0.430) and Zung Depression Scale: 49.5±10.4 vs. 55.1±10.4 vs. 55.8±8.6 (P=0.112). CONCLUSIONS: No differences in the FD related pathophysiologies including GE, GME, ANS, gastric accommodation/sensitivity and abnormal psychological factors were detected among EPS, PDS and EPS+PDS types of FD patients, which suggests that the sub-grouping method of EPS, PDS and EPS+PDS is helpless to the treatment strategy“to treat different types of FD patients according to their special pathophysiologies”.

Multichannel electrogastrography under a magnifying glass – an in‐depth study on reproducibility of fed state electrogastrograms

We checked on reproducibility of parameters of a multichannel electrogastrogram in adults after intake of typical, applied in electrogastrography, test meals. Recordings of multichannel electrogastrograms were accomplished in four blocks comprising 18 subjects (nine healthy volunteers and nine patients with functional GI disorders) each. Every subject had two examinations taken 1-2 days apart, and a third one was accomplished at least 2 weeks before or after the two other sessions. The registration involved a 30-min fasted and a 2-h postprandial period after one of the meal stimuli tested within a given block: 400 mL water, 400 g yoghurt (378 kcal), a scrambled eggs sandwich (370 kcal), a pancake (355 kcal). From among the parameters reflecting the propagation of the gastric slow waves, the average percentage of slow wave coupling (APSWC) exhibited a good (coefficient of variation for paired examinations CV(p) < or = 10%) to moderate (10 < CV(p) < or = 30%) reproducibility. On the other hand, the reproducibility of the maximum dominant frequency difference and the spatial dominant power difference was found to be unsatisfactory. The reproducibility of the multichannel electrogastrographic parameters did not differ between healthy volunteers and patients with functional GI disorders. Gender or the kind of a test meal did not affect the reproducibility of the electrogastrographic parameters either. The medium-term reproducibility was not any worse than the short-term one. From among the parameters of a multichannel electrogastrogram intended to quantify the propagation of slow waves, only the APSWC offers a reproducibility potentially good enough for clinical applications.

Quantitative cellular description of gastric slow wave activity

Interstitial cells of Cajal (ICC) are responsible for the spontaneous and omnipresent electrical activity in the stomach. A quantitative description of the intracellular processes whose coordinated activity is believed to generate electrical slow waves has been developed and is presented here. In line with recent experimental evidence, the model describes how the interplay between the mitochondria and the endoplasmic reticulum in cycling intracellular Ca(2+) provides the primary regulatory signal for the initiation of the slow wave. The major ion channels that have been identified as influencing slow wave activity have been modeled according to data obtained from isolated ICC. The model has been validated by comparing the simulated profile of the slow waves with experimental recordings and shows good correspondence in terms of frequency, amplitude, and shape in both control and pharmacologically altered conditions.

Effects of audio stimulation on gastric myoelectrical activity and sympathovagal balance in healthy adolescents and adults

The primary aim of this study was to investigate the effects of different audio stimulations on gastric myoelectrical activity and sympathovagal balance in adolescents compared with adults. The study was performed in 11 adults and 12 adolescents. Each subject underwent two sessions, one for classical music, and the other for noise. Each session consisted of 30 min of baseline, 30 min of fasting audio stimulation, a test meal, 30 min of fed audio stimulation, and 30 min of recovery. Electrocardiogram and electrogastrogram were both recorded throughout each session. (i) In the fasting state, both classical music and noise impaired gastric slow wave activity in adolescents. In adults, noise had no effects while classical music moderately improved slow wave rhythmicity. (ii) In the fed state, neither noise nor music had any effects on gastric slow waves. (iii) In the fasting state, both noise and music increased the sympathovagal balance in adolescents; in adults only noise had such an effect. (iv) The test meal increased the sympathovagal balance in all groups. Gastric slow waves and the sympathovagal balance are more strongly affected by audio stimulation in adolescents than in adults. The test meal normalizes the audio stimulation-induced differences between the groups.

Two-channel gastric pacing with a novel implantable gastric pacemaker accelerates glucagon-induced delayed gastric emptying in dogs

Background The aim of the current study was to investigate the efficacy of 2-channel gastric electrical stimulation (GES) with a custom-made implantable pacemaker on delayed gastric emptying and gastric dysryhthmia induced by glucagon in dogs. Methods Six dogs were studied in 4 randomized session (saline, glucagon, glucagon with single-channel or 2-channel GES). GES was applied via the first pair of electrodes for single-channel GES or the first and third pairs of electrodes for 2-channel GES. Gastric emptying was assessed for 90 minutes and gastric slow waves were recorded at the same time. Results Both single-channel and 2-channel GES improved gastric dysryhthmia ( P < .05 vs glucagon session). Two-channel GES but not single-channel GES improved glucagon-induced delayed gastric emptying at 30 minutes, 45 minutes, 60 minutes, 75 minutes, and 90 minutes. Conclusion Two-channel GES with a novel implantable pacemaker is more efficient and effective than single-channel GES in improving delayed gastric emptying induced by glucagon. This implantable multipoint pacemaker may provide a new option for treatment of gastric motility disorders.

Effects and mechanisms of vaginal electrical stimulation on gastric tone in dogs

Electrical stimulation of one part of the gut may have beneficial or adverse effects on another region. We hypothesized that electrical stimulation of a visceral organ in one system might have an effect on another visceral organ system. That is, disorders of one system may be treated by interventions of another system and this may lead to a more convenient or less invasive therapies in some cases. The aim of this study was to evaluate the effects and mechanisms of vaginal electrical stimulation (VES) with different parameters on gastric tone and gastric slow waves in conscious dogs. Seven dogs were studied in two experiments. Experiment 1 was to study effects of VES on gastric tone and slow waves. Experiment 2 was performed in two sessions (long pulse VES plus guanethidine and VES with trains of long pulse plus guanethidine) to study involvements of possible sympathetic mechanisms. The results of our experiments were: (i) VES increased the gastric volume in a dose-dependent manner with the increase of stimulation frequency, amplitude or pulse width; (ii) VES had no effects on gastric slow waves; (iii) the inhibitory effect of VES with long pulses or trains of long pulses on gastric tone was abolished by guanethidine; and (iv) few or mild symptoms were noted with stimulation. VES decreases proximal gastric tone in an energy-dependent manner without affecting gastric slow waves. The inhibitory effect of VES is mediated by a sympathetic pathway. Hypertensive gastric tone might be treated using electrical stimulation of the vagina which is minimally invasive.

Clinical application prospects of gastric pacing for treating postoperative gastric motility disorders

Similar to the heartbeat, gastric peristalsis is regulated by an electrical rhythm generated by a pacemaker. Thus, electrical dysrhythmia of gastric slow waves will inevitably affect gastric peristalsis and emptying. The recurrence of postoperative gastroparesis is thereby closely related to the abnormalities of electrical dysrhythmia and ectopic pacemakers, resulting in postoperatively persistent gastric motility disorders in some severe cases, despite the use of prokinetic and antiemetic drugs. Recent studies have demonstrated that gastric pacing, analogous to pacing the human heart, is an attractive and promising therapy that is both feasible and safe. Gastric pacing has been shown to be strikingly effective in normalizing gastric dysrhythmia, increasing the activity of the gastric slow wave and thereby prompting gastric dynamia and emptying. Furthermore, the long-term utilization of gastric pacing can (i) relieve patients from clinical symptoms, such as nausea and vomiting; (ii) release patients with severe postoperative gastroparesis from relying on prokinetic drugs and the jejunal feeding tube; (iii) return patients to normal oral nutritional intake and provide a more satisfactory nutritional status and most importantly; and (iv) give patients a better quality of life. Overall, research focused on gastric pacing has demonstrated excellent prospects for clinical application in the treatment of postoperative gastroparesis disorders, especially for those unresponsive to prokinetic drugs.

The TANTALUS™ System for Obesity: Effect on Gastric Emptying of Solids and Ghrelin Plasma Levels

Gastric electrical stimulation (GES), using the implantable TANTALUS System, is being explored as a treatment for obesity. The system delivers nonstimulatory electrical signals synchronized with gastric slow waves, resulting in stronger contractions. We hypothesized that this GES may enhance gastric emptying and as a result affect plasma ghrelin and insulin homeostasis. The aim was to test the effect of GES on gastric emptying of solids and on ghrelin and insulin blood levels in obese subjects. The system consists of 3 pairs of gastric electrodes connected to an implantable pulse generator. Gastric emptying test (GE) of solids was performed twice, on separate days, a few weeks after implantation, before and after initiation of stimulation. Blood samples for ghrelin and insulin were taken at baseline and at 15, 30, 60 and 120 min after the test meal. There were 11 females, 1 male, mean age 39.1 +/- 8.9 years, mean BMI 41.6 +/- 3.4. Data is available from 11 subjects; GE was normal in 9 subjects and accelerated in 2 subjects. GES significantly accelerated GE compared to control: percent retention at 2 hours 18.7 +/- 12.2 vs 31.9 +/- 16.4, respectively (P < 0.01). Overall, there was no significant change in ghrelin or insulin profile after food intake. Ghrelin levels fell significantly at 60 min compared to baseline during stimulation (P = 0.014) and control (P = 0.046). GES results in a significant acceleration of gastric emptying of solids in obese subjects. GES did not have a significant effect on postprandial ghrelin levels when compared to control.

Feasibility of gastric electrical stimulation by use of endoscopically placed electrodes

Gastric electrical stimulation (GES), which has been reported to have therapeutic potentials for gastroparesis and obesity, involves the surgical placement of electrodes with the patient under general anesthesia. New methods are needed for implanting GES electrodes in a safer and more feasible way. Our purpose was to investigate the safety and feasibility of placing electrodes endoscopically for GES. A pilot study. Six female hound dogs that weighed 13 to 22 kg. Endoscopically placed electrodes passed through the abdomen and the stomach wall. The study was performed in dogs surgically implanted with gastric serosal electrodes and endoscopically implanted electrodes. The experiment consisted of a 30-minute baseline, a 30-minute GES, and a 30-minute recovery. GES was performed through endoscopically placed electrodes. Gastric slow waves were simultaneously recorded with the serosal electrodes and the endoscopically placed electrodes. (1) The slow wave frequency recorded from the endoscopically placed electrodes was significantly correlated with that from the serosal electrodes (r = 0.97, P < .002). (2) GES through the endoscopically placed electrodes was able to entrain gastric slow waves. (3) No gastric leakage into the abdominal cavity was noted and the dogs were healthy and comfortable. (4) The endoscopically placed electrodes remained for 2 to 3 weeks. The fixation of the electrodes needs to be improved for longer-term uses. GES may be accomplished without surgery by inserting the electrode wire through the abdomen under endoscopy. The study results indicate that the endoscopically placed electrodes are effective for GES and do not result in any adverse events.

Noninvasive assessment of the effects of glucagon on the gastric slow wave

Hyperglycemic effects on the gastric slow wave are not well understood, and no studies have examined the effects that hyperglycemia has on gastric slow wave magnetic fields. We recorded multichannel magnetogastrograms (MGGs) before and after intravenous administration of glucagon and subsequent modest hyperglycemia in 20 normal volunteers. Normal slow waves were evident in baseline MGG recordings from all 20 subjects, but within 15 min after glucagon had been given, we noted significant effects on MGG signals. In addition to an overall decrease in the slow wave frequency from 2.9 +/- 0.5 cycles per min (cpm) to 2.2 +/- 0.1 cpm (P < 0.05), we observed significant changes in the number and range of spectral peaks recorded. Furthermore, the propagation velocity determined from surface current density maps computed from the multichannel MGG decreased significantly (7.1 +/- 0.8 mm/s to 5.0 +/- 0.3 mm/s, P < 0.05). This is the first study of biomagnetic effects of hyperglycemia in normal subjects. Our results suggest that the analysis of the MGG provides parameter quantification for gastric electrical activity specific to and characteristic of slow wave abnormalities associated with increased serum glucose by injection of glucagon.

Seasonal variation in gastric myoelectrical activity in young Japanese females

In order to test our hypothesis that there is seasonal variation in digestion and absorption of dietary carbohydrate from the intestine, we previously determined the amount of unabsorbed carbohydrate after breakfast by the breath hydrogen test in the four seasons. In pursuing our hypothesis further, we also recorded gastric myoelectrical activity before and after the breakfasts. In the current report, we describe the seasonality of gastric myoelectrical activity. Twenty-six Japanese female subjects were studied in winter, spring, summer and autumn. The cutaneous electrogastrogram was analysed by spectral analysis to compute the pre- and post-prandial dominant slow wave frequency (DF), and percentage of the 2 – 4 cpm gastric slow wave (Normal %). Two-factor ANOVA indicated that there was no significant seasonal variation in DF and Normal %. These results indicate that seasonal variations in digestion and absorption of dietary carbohydrate are caused by factors other than gastric and small intestinal motility.

Effects of Gastric Electrical Stimulation with Short Pulses and Long Pulses on Gastric Dysrhythmia and Signs Induced by Vasopressin in Dogs

This study was to investigate the effect of gastric electrical stimulation (GES) with short pulses, long pulses, short-pulse trains or long-pulse trains on gastric dysrhythmia and motion-sickness signs induced by vasopressin. Seven male beagle dogs implanted with four pairs of electrodes on gastric serosa were studied. The study was performed in six sessions in a randomized order. In session 1 or 2, either saline or vasopressin was infused without GES. In session 3, 4, 5 and 6, GES with short pulses, long pulses, trains of short pulses or trains of long pulses was performed before and during vasopressin infusion. Gastric slow waves and motion-sickness signs were recorded in each session. (1) Vasopressin induced gastric dysrhythmia and motion sickness-like signs (ANOVA, P < 0.001). (2) GES with short pulses or trains of short pulses was capable of preventing vasopressin-induced emetic response (P < 0.001), but did not normalize gastric dysrhythmia. (3) GES with long pulses or trains of long pulses was able to normalize gastric dysrhythmia induced by vasopressin (P < 0.001), but showed no effects on vasopressin-induced motion-sickness signs. GES with short pulses or trains of short pulses prevents vasopressin-induced emetic response with no improvement in gastric dysrhythmia. GES with long pulses or trains of long pulses normalizes gastric dysrhythmia induced by vasopressin with no effects on signs.

Synchronized gastric electrical stimulation improves delayed gastric emptying in nonobese mice with diabetic gastroparesis

The aim of this study was to investigate the effect and mechanism of synchronized gastric electrical stimulation (SGES) on gastric emptying in nonobese mice with diabetic gastroparesis (DB-GP). Eight control mice and 48 nonobese diabetic (NOD) mice with two pairs of gastric electrodes were used in this study. The study included seven groups in a randomized order [control, diabetes (DB), DB-GP, DB + SGES, DB-GP + SGES, DB-GP + Atropine, and DB-GP + SGES + Atropine groups]. In the control, DB, DB-GP, and DB-GP + Atropine groups, gastric emptying was measured in BLAB/cJ mice (control group) or NOD mice with a duration of diabetes of 0-7 days (DB group) or 28-35 days (DB-GP or DB-GP + Atropine group). In the DB + SGES, DB-GP + SGES, and DB-GP + SGES + Atropine groups, the experiment was the same as the corresponding DB, DB-GP, and DB-GP + Atropine groups except that SGES was applied during the experiment. SGES was applied via the proximal pair of electrodes and synchronized with the intrinsic gastric slow waves. The following results were obtained: 1) gastric emptying was delayed in NOD mice with a duration of diabetes of 28-35 days; 2) SGES was able to significantly increase gastric emptying in both diabetic mice and diabetic gastroparetic mice; and 3) the excitatory effect of SGES was completely blocked by atropine. SGES accelerates gastric emptying in NOD mice with diabetic gastroparesis. The effect of SGES on gastric emptying is mediated via the cholinergic pathway. These findings suggest that SGES may have a therapeutic potential for treating patients with diabetic gastroparesis.

Effect of ghrelin on gastric myoelectric activity and gastric emptying in rats

Ghrelin is a recently discovered peptide in the endocrine cells of the stomach, which may stimulate gastric motility via the vagal nerve pathway. However, the mechanism of ghrelin-induced changes in gastrointestinal motility has not been clearly defined. The purpose of this study was to investigate the pharmacological effects of ghrelin on gastric myoelectrical activity and gastric emptying in rats, and to investigate whether cholinergic activity is involved in the effects of ghrelin. The study was performed on Sprague-Dawley rats implanted with serosal electrodes for electrogastrographic recording. Gastric slow waves were recorded from fasting rats at baseline and after injection of saline, ghrelin, atropine, or atropin + ghrelin. Gastric emptying of non-caloric liquid was measured by the spectrophotometric method in conscious rats. Intravenous administration of rat ghrelin (20 μg/kg) increased not only dominant frequency, dominant power and regularity of the gastric slow wave but also the gastric emptying rate when compared with the control rats ( P < 0.01, P < 0.05, P < 0.05, P < 0.001 respectively). These stimulatory actions of ghrelin on both gastric myoelectrical activity and gastric emptying were not fully eliminated by pretreatment with atropine sulphate. These results taken together suggest that ghrelin may play a physiological role in the enteric neurotransmission controlling gastric contractions in rats.

Gastric electric stimulation for the treatment of gastroparesis

Gastric electric stimulation is an emerging therapy for refractory gastroparesis. Several methods have been used to electrically stimulate the stomach. Initial studies used gastric electrical pacing, which entrains and paces the gastric slow waves at a slightly higher rate than the patient's normal myoelectric frequency of 3 cycles per minute (cpm). The technique currently practiced uses high-frequency, low-energy stimulation at four times the basal rate (12 cpm). Results from published studies with high-frequency stimulation reveal an improvement in symptoms, primarily of nausea and vomiting, and primarily in patients with diabetic gastroparesis, with only a modest change in gastric emptying. As treatment with gastric electric stimulation evolves, further delineation of its overall effectiveness, the type of patient that will likely respond, optimal electrode placement(s), and stimulus parameters should be explored.

Effects of retrograde gastric electrical stimulation with pulse trains on gastric emptying of solids and plasma hormones in dogs

Background Retrograde gastric electrical stimulation (RGES) is proposed as a novel therapy for obesity. However, mechanisms of RGES are not fully investigated. The aim of this study was to investigate the effects of RGES with trains of pulses on gastric slow waves, gastric emptying of solids, and plasma concentrations of satiety-related peptides and glucose. Methods Seven female beagle dogs implanted with 4 pairs of gastric electrodes on the gastric serosa were studied (control and RGES). Gastric emptying, gastric slow waves, and signs were recorded in each session. Plasma leptin, insulin, glucagons, and glucose were also measured. Results RGES with pulse trains (a pulse width of 2 milliseconds) significantly decreased gastric emptying of solids and plasma insulin but has no effect on plasma leptin, glucagons, and glucose. Conclusion Acute gastric electrical stimulation with pulse trains is able to decrease gastric emptying of solids and plasma insulin but has no effects on plasma leptin, glucagons, and glucose.

Roles of putative neurotransmitters in the regulation of gastric and intestinal slow waves in conscious dogs

Slow waves play an important role in controlling the frequency and propagation of gastrointestinal contractions. However, mechanisms involved in the modulation of slow wave activity in vivo are still unclear. In this study, the roles of different neurotransmitters in the regulation of gastrointestinal slow waves were investigated in conscious dogs. Female dogs implanted with electrodes in the stomach and the small bowel were used in a seven-session study. Gastrointestinal myoelectrical activity was recorded at baseline and after i.v. saline, atropine, atropine methyl nitrate, guanethidine, Nomega-nitro-L-arginine (L-NNA), ondansetron or naloxone. Both atropine and atropine methyl nitrate induced tachygastria, bradygastria and arrhythmia. No difference was noted in the effects between atropine and atropine methyl nitrate. L-NNA increased the dominant frequency of small-intestinal slow waves but had no effect on gastric slow waves. Guanethidine, ondansetron and naloxone did not affect the dominant frequency, power or percentage of normal gastrointestinal slow waves. Acetylcholine acting at muscarinic receptors seems to play an important role in the regulation of gastric slow waves. Nitric oxide may play a role in modulating intestinal slow waves but not gastric slow waves. Sympathetic pathways, 5-HT(3) receptors and opioid receptors (especially micro-opioid receptors) do not play a role in the regulation of gastric or intestinal slow waves under normal physiological conditions.

Electrogastrogram extraction using independent component analysis with references

Electrogastrogram (EGG) is a noninvasive measurement of gastric myoelectrical activity cutaneously, which is usually covered by strong artifacts. In this paper, the independent component analysis (ICA) with references was applied to separate the gastric signal from noises. The nonlinear uncorrelatedness between the desired component and references was introduced as a constraint. The results show that the proposed method can extract the desired component corresponding to gastric slow waves directly, avoiding the ordering indeterminacy in ICA. Furthermore, the perturbations in EGG can be suppressed effectively. In summary, it can be a useful method for EGG analysis in research and clinical practice.

Robust propagation velocity estimation of gastric electrical activity by least mean p-norm blind channel identification

The propagation of the gastric slow wave is one of the most important spatial characteristics of gastric electrical activity (GEA). The time delay estimation (TDE) is an effective approach to quantitatively assessing the propagation velocity of GEA. Traditional TDE analyses are developed under the condition reported that the background noise in GEA analysis is Gaussian distributed. Due to the effects of spikes and/or motion artifacts, the GEA obtained from gastric serosal electrodes often contains sharp transitions. This paper proposes robust time delay estimation based on least mean p-norm blind channel identification (BCILMP) under alpha-stable noise condition. Compared with the least mean square time delay estimation (LMSTDE), the BCILMP provides better performance in the impulsive noise environments. The robustness of the proposed method is demonstrated through computer simulations in both Gaussian and alpha-stable noise environments. The results of the propagation velocity of real data obtained from gastric serosal electrodes in gastroparetic patients show that the propagation velocity in gastroparetic patients is slower than in the normal subjects reported in the literature, and the slow-wave propagation is directed proximally to distally from the corpus toward the pylorus but not all the variability of the propagation velocity increases monotonously.

Inhibitory effects of sildenafil on gastric motility and gastric slow waves in dogs

The aim of this study was to investigate the effects of sildenafil on gastric motility and gastric slow waves in dogs. The study was performed in healthy dogs and composed of three experiments. The first experiment was designed to study the effects of sildenafil on gastric emptying and gastric slow waves. The second experiment was used to investigate the effects of sildenafil on gastric tone. The third experiment was used to study the effects of sildenafil on postprandial antral contractions. (i) Sildenafil did not alter gastric emptying of liquid. (ii) Sildenafil had no effects on dominant frequency and percentage of normal gastric slow waves. The dominant power of gastric slow waves was, however, significantly reduced with sildenafil (P < 0.02). (iii) Fasting gastric volume with sildenafil was significantly higher than that at baseline (P < 0.0005) or in the control session (P < 0.002). However, the postprandial gastric volume was not altered with sildenafil. (iv) Sildenafil inhibited gastric antral motility. The contraction index was 338.5 +/- 39.99 at baseline and 122.5 +/- 20.3 after the injection of sildenafil (P = 0.003). Sildenafil inhibits fundic tone and antral motility but does not seem to delay gastric emptying of liquid in dogs. The amplitude but not the frequency or regularity of the gastric slow wave is inhibited by sildenafil.