Effect of two-channel gastric electrical stimulation with trains of pulses on gastric motility

AIM： To investigate the effect of two-channel gastric electrical stimulation （GES） with trains of pulses on gastric emptying and slow waves.METHODS： Seven dogs implanted with four pairs of electrodes and equipped with a duodenal cannula were involved in this study. Two experiments were performed.The first experiment included a series of sessions in the fasting state with trains of short or long pulses, each lasted 10 min. A 5-min recording without pacing was made between two sessions. The second experiment was performed in three sessions （control, single-channel GES, and two-channel GES）. The stimulus was applied via the 1st pair of electrodes for single-channel GES （GES via one pair of electrodes located at 14 cm above the pylorus）, and simultaneously via the 1st and 3rd channels for two-channel GES （GES via two pairs of electrodes located at 6 and 14 cm above the pylorus）, Gastric liquid emptying was collected every 15 min via the cannula for 90 min.RESULTS： GES with trains of pulses at a pulse width of 4 ms or higher was able to entrain gastric slow waves. Two-channel GES was about 50% more efficient than single-channel GES in entraining gastric slow waves. Two-channel but not single-channel GES with trains of pulses was capable of accelerating gastric emptying in healthy dogs. Compared with the control session, two-channel GES significantly increased gastric emptying of liquids at 15 rain （79.0% ± 6.4% vs 61.3% ± 6.1%, P 〈 0.01）, 30 min （83.2% ± 6.3 % vs 68.2% ± 6.9%, P 〈 0.01）, 60 min （86.9% ± 5.5 % vs 74.1% ± 5.9%, P 〈 0.01）, and 90 rain （91.0% ± 3.4% vs 76.5% ± 5.9%, P 〈 0.01）.CONCLUSION： Two-channel GES with trains of pulses accelerates gastric emptying in healthy dogs and may have a therapeutic potential for the treatment of gastric motility disorders.     

胃电刺激对顺铂诱导的犬呕吐症状的影响

目的 研究顺铂(cisplatin,DDP)对胃肌电活动的影响,并探讨胃电刺激(GES)对化疗药物引起的犬呕吐和消化不良症状的治疗效应.方法 7只比格犬的胃浆膜均被植入4对电极,每只犬均先后进行两阶段实验.(1)DDP阶段:给予DDP(1.5 mg/kg),自给药开始持续记录胃电活动及动物症状;(2)GES+DDP阶段:自DDP给药开始,经近端胃体部电极持续给予串脉冲GES,给药剂量、胃电活动及症状记录同DDP阶段.结果 (1)DDP能诱导犬恶心呕吐症状及胃电紊乱:DDP阶段动物均出现频繁呕吐,呕吐次数为(5.5±1.2)次,总症状评分为31.83±2.75.通过胃电记录发现,基线水平时正常胃慢波占(96.50±1.14)%,而呕吐期间正常胃慢波占(69.61±5.81)%(P=0.003),并且胃电过速和胃电过缓发生的百分比均明显高于基线水平(P=0.020和P=0.031).(2)GES能减轻DDP诱导的呕吐和消化不良症状:GES+DDP阶段比格犬的症状评分较DDP阶段明显降低(24.50±1.45比31.83±2.75,P=0.028),并且呕吐次数也明显减少(3.7±0.8比5.5±1.2,P=0.028).但GES对DDP引起的胃电紊乱无明显影响.结论 DDP能诱导犬呕吐和胃电紊乱.串脉冲GES能明显减轻DDP引起的呕吐和消化不良症状,但对胃电紊乱无明显影响.     

Long-pulse gastric electrical stimulation at tachygastrial frequency reduces food intake by inhibiting proximal gastric tone

Objective. To investigate the effects of long pulse gastric electrical stimulation (GES) at a tachygastrial frequency on food intake, gastric tone and gastric myoelectrical activity (GMA). Material and methods. Of twelve dogs implanted with electrodes and a gastric cannula, 6 underwent truncal vagotomy. Stimulus consisted of long pulses with a frequency of 9 cycles/min. Experiment one was performed in all dogs to test for food intake with or without GES. Experiment two on six normal dogs consisted of baseline, GES and recovery periods. Gastric volume and GMA were recorded. Results. 1) GES reduced food intake in both normal (398.5±111.7 g versus 573.0±97.9 g; p<0.02) and vagotomized dogs (170.6±100.4 g versus 401.0±97.3 g; p<0.05). 2) Gastric volume was increased with stimulation from 168.4±17.7 ml to 301.1±34.1 ml (p<0.02 ANOVA) and maintained at 271.8±27.6 ml. 3) The percentages of normal slow waves before, during and after GES were 83.3±4.6%, 38.0±3.5% and 61.0±12.5%, respectively (p=0.02 ANOVA). Conclusion. Long-pulse GES at tachygastrial frequency substantially reduces food intake, and is not mediated by the vagal pathway but attributed to relaxation of the stomach and impairment of intrinsic GMA.     

Cutaneous gastric electrical stimulation alters gastric motility in dogs: New option for gastric electrical stimulation?

Background and Aim:  We investigated the effects of cutaneous gastric electrical stimulation (CGES) on gastric myoelectrical activity, postprandial antral contractions and gastric tone in dogs.
Methods:  CGES was carried out via abdominal surface electrodes over the stomach. After an overnight fast, gastric slow waves were recorded from the serosal electrodes in six dogs at a frequency of 4.4 cycles/min (c.p.m.) or 10 c.p.m. Nine dogs were used for the measurement of postprandial antral contractions. Gastric tone at baseline and during CGES was measured in six of the dogs.
Results:  We found that: (i) CGES at 4.4 c.p.m. decreased slow wave frequency (5.1 vs 4.6 c.p.m., P  < 0.05) and increased slow wave power (−6.2 vs 2.7 c.p.m., P  < 0.05); CGES at 10 c.p.m. increased slow wave frequency (5.1 vs 9.2 dB, P  < 0.05) and decreased normal slow waves (85.4% vs 60.0%, P  < 0.05); (ii) CGES at 10 c.p.m. significantly suppressed postprandial antral contractions ( P  < 0.01); (iii) CGES had no effects on gastric tone.
Conclusions:  CGES is capable of altering gastric slow waves and inhibiting gastric motility. It may have therapeutic potential for treating eating disorders, such as obesity. However, clinical studies are needed to explore the potential of CGES.     

Two-Channel Gastric Electrical Stimulation Accelerates Delayed Gastric Emptying Induced by Vasopressin

The aim of this study was to investigate the effects of two-channel gastric electrical stimulation (GES) on delayed gastric emptying, gastric dysrhythmias, and motion sickness-like symptoms induced by vasopressin. Seven dogs implanted with four pairs of gastric electrodes and a duodenal cannula were studied in four randomized sessions (saline, vasopressin, single-channel GES, and two-channel GES). The experiment in each session was conducted sequentially as follows: 30-min baseline, ingestion of a liquid meal, 30-min iv infusion of vasopressin or saline, and two 30-min postprandial recordings. In the GES sessions, GES was applied via the first pair of electrodes for single-channel GES or the first and third pairs of electrodes for two-channel GES. Gastric emptying was collected every 15 min via the cannula for a period of 90 min. Results were as follows. (1) Vasopressin induced gastric dysrhythmias, motion sickness-like symptoms, and delayed gastric emptying (P < 0.01, ANOVA). (2) GES normalized gastric dysrhythmias (P < 0.01) but showed no effects on vasopressin-induced emetic response. (3) Two-channel GES improved delayed gastric emptying induced by vasopressin. In comparison with the vasopressin session, two-channel GES, but not single-channel GES, significantly increased gastric emptying at 30 min (43.9 ± 12.6 vs. 27.5 ± 7.7%; P < 0.03), 60 min (75.3 ± 15.1 vs. 54.0 ± 17.8%; P < 0.05), and 90 min (91.6 ± 9.8 vs. 80.3 ± 9.0%; P < 0.05). GES with long pulses is able to normalize gastric dysrhythmias. Two-channel GES improves delayed gastric emptying induced by vasopressin.     

Effects of muscarinic receptor stimulation and nitric oxide synthase inhibition on gastric tone and gastric myoelectrical activity in canines

Aims:  This study was designed to assess whether the muscarinic receptor stimulation and nitric oxide synthase inhibition were equally effective on gastric fundic tone or gastric myoelectrical activity (GMA) in canines, and the correlation between gastric fundic tone and GMA.
Methods:  Gastric fundic tone and GMA were recorded on seven dogs implanted with serosal electrodes and a gastric cannula.
Results:  Bethanechol and L-nitro-N-arginine (L-NNA) significantly increased gastric fundic tone; gastric volume was decreased with bethanechol or L-NNA ( P  < 0.05). Increased spike activities were observed after both bethanechol and L-NNA. The percentage of slow waves superimposed with spikes was increased with bethanechol ( P  < 0.001) and L-NNA ( P  < 0.05). There was a significant reduction in dominant frequency (DF) ( P  < 0.05), dominant power (DP) ( P  < 0.05) and percentage of normal slow waves (%N) ( P  < 0.05) with bethanechol, while no significant change was observed with L-NNA. The variation of gastric tone was not correlated with parameters of GMA.
Conclusions:  Muscarinic receptor stimulation and nitric oxide synthase inhibition have similar effects on gastric tone and gastric spike activities, but different effects on gastric slow waves. Gastric fundic tone does not correlate with gastric slow waves.     

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

Aims: 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. Methods: 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. Results: (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. Conclusion: 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. Xiaohua Hou and Geng-Qing Song contributed equally to this work.     

Anti-dysrhythmic effects of long-pulse gastric electrical stimulation in dogs

BACKGROUND/AIM: The aim of this study was to investigate the anti-dysrhythmic effect of long-pulse gastric electrical stimulation (GES) in dogs. METHODS: The study was performed in 7 healthy dogs implanted with 4 pairs of serosal gastric electrodes. Each dog was studied in three sessions on 3 separate days in a randomized order with recordings of gastric slow waves. In session 1 or 2, infusion of either saline or glucagon (0.1 U/kg in 20 ml saline instilled in 40 min) was given during the 2nd and 3rd 20-min periods. The protocol of session 3 was the same as that of session 2 except that GES was performed during the 2nd 20-min period. RESULTS: (1) Glucagon induced gastric dysrhythmia and decreased gastric slow-wave coupling (ANOVA, p < 0.001). The long-pulse GES normalized glucagon-induced gastric dysrhythmia and the uncoupling of slow waves. (2) Glucagon induced symptoms and behaviors suggestive of nausea and the symptoms were not improved by long-pulse GES. CONCLUSION: (1) Glucagon induces gastric dysrhythmias, slow-wave uncoupling and symptoms, and (2) long-pulse GES normalizes glucagon-induced gastric dysrhythmia and slow-wave uncoupling with no improvement in symptoms.     

Long-pulse gastric electrical stimulation at tachygastrial frequency reduces food intake by inhibiting proximal gastric tone

OBJECTIVE: To investigate the effects of long pulse gastric electrical stimulation (GES) at a tachygastrial frequency on food intake, gastric tone and gastric myoelectrical activity (GMA). MATERIAL AND METHODS: Of twelve dogs implanted with electrodes and a gastric cannula, 6 underwent truncal vagotomy. Stimulus consisted of long pulses with a frequency of 9 cycles/min. Experiment one was performed in all dogs to test for food intake with or without GES. Experiment two on six normal dogs consisted of baseline, GES and recovery periods. Gastric volume and GMA were recorded. RESULTS: 1) GES reduced food intake in both normal (398.5+/-111.7 g versus 573.0+/-97.9 g; p<0.02) and vagotomized dogs (170.6+/-100.4 g versus 401.0+/-97.3 g; p<0.05). 2) Gastric volume was increased with stimulation from 168.4+/-17.7 ml to 301.1+/-34.1 ml (p<0.02 ANOVA) and maintained at 271.8+/-27.6 ml. 3) The percentages of normal slow waves before, during and after GES were 83.3+/-4.6%, 38.0+/-3.5% and 61.0+/-12.5%, respectively (p=0.02 ANOVA). CONCLUSION: Long-pulse GES at tachygastrial frequency substantially reduces food intake, and is not mediated by the vagal pathway but attributed to relaxation of the stomach and impairment of intrinsic GMA.     

Effects of enhanced viscosity on canine gastric and intestinal motility

BACKGROUND AND AIM: The aim of this study was to investigate the effect of enhanced viscosity on gastric emptying and gastrointestinal motor and myoelectrical activities in dogs. METHOD: The study was performed in eight healthy female hound dogs chronically implanted with four pairs of gastric and two pairs of intestinal serosal electrodes and a duodenal fistula. Each dog was studied in three sessions and fed with three test meals with different viscosity. Gastric emptying was monitored for 2 h simultaneously with gastric and intestinal myoelectrical recordings. RESULTS: The liquid test meal containing either 0.78% or 1.21% of galactomannan significantly delayed gastric emptying but had no effect on postprandial blood glucose levels in comparison with the meal containing no galactomannan. The liquid test meal containing either 0.78% or 1.21% of galactomannan significantly increased the frequency and strength of intestinal motility but had no effect on intestinal slow wave rhythms. The product with enhanced viscosity had no effect on gastric motor activity or gastric slow waves. CONCLUSION: It was concluded that enhanced viscosity delays gastric emptying, increases postprandial intestinal but not gastric motility, and has no effects on gastric or intestinal slow waves.     

Treatment of gastroparesis with electrical stimulation

Electrically stimulating the stomach to treat gastroparesis has been proposed by investigators for decades. With the development of techniques of implantable pacing devices and electrodes and promising preliminary results in chronic pacing studies, gastric electrical stimulation (GES) has received increasing attention recently among researchers and clinicians. A number of studies have been performed to investigate the effects of GES on gastric motility, gastric emptying, and gastrointestinal symptoms in both dogs and humans. Based on the frequency of the electrical stimulus used for chronic treatment of gastroparesis, gastric electrical stimulation can be classified into low-frequency stimulation (LFS) and high-frequency stimulation (HFS). Although some of the results are still controversial, the majority of these studies seem to indicate that LFS is able to normalize gastric dysrhythmias and entrain gastric slow waves and accelerate gastric emptying. On the other hand, HFS has no effect on gastric emptying but is able to significantly reduce symptoms of nausea and vomiting in gastroparetic patients. GES has provided an exciting new advance in the treatment of gastroparesis and management of upper gastrointestinal symptoms. This paper will review the available studies of GES in the treatment of gastroparesis and current status of this field.     

Cisplatin-Induced Gastric Dysrhythmia and Emesis in Dogs and Possible Role of Gastric Electrical Stimulation

The aim of this study was to investigate the effect of cisplatin on gastric myoelectrical activity and the role of gastric electrical stimulation in the treatment of cisplatin-induced emesis in dogs. Seven dogs implanted with electrodes on the gastric serosa were used in a two-session study. Cisplatin was infused in both the control session and the gastric electrical stimulation session, and gastric electrical stimulation was applied in the gastric electrical stimulation session. Gastric slow waves and emesis, as well as behaviors suggestive of nausea, were recorded during each session. The results were as follows: (1) cisplatin induced vomiting and other symptoms and induced gastric dysrhythmia. The percentage of normal slow waves decreased significantly during the 2.5 h before vomiting (P = 0.01) and the period of vomiting (P < 0.001). (2) Gastric electrical stimulation reduced emesis and the symptoms score. The total score in the control session was higher than that in the gastric electrical stimulation session (P = 0.02). However, gastric electrical stimulation had no effects on gastric dysrhythmia. It is concluded that cisplatin induces emesis and gastric dysrhythmia. Gastric electrical stimulation may play a role in relieving chemotherapy-induced emetic responses and deserves further investigation.     

Origins and patterns of spontaneous and drug-induced canine gastric myoelectrical dysrhythmia

The aim of this study was to investigate the characteristics and orientation of gastric dysrhythmia using multichannel serosal recordings in dogs. Ten dogs chronically implanted with four to eight pairs of electrodes were studied. Gastric slow waves were recorded in four sessions: postsurgical and after atropine, vasopressin, and glucagon. A total of 554.7 min of bradygastria, 201 min of tachygastria and 22.3 min of arrhythmia were observed in the recordings. The majority of bradygastria (80.5 ± 9.4%) originated in the proximal stomach (P < 0.04, vs other locations) and propagated all the way to the distal antrum. In contrast, tachygastria mainly originated in the distal antrum (80.6 ± 8.8%) (P < 0.04, vs other locations) and propagated partially or all the way to the proximal stomach. Dysrhythmia appeared intermittently with normal gastric slow waves. In all recordings, normal slow waves were present 38.0 ± 5.3% of the time, while bradygastria, tachygastria, and arrhythmia were present 35.9 ± 5.3%, 23.0 ± 1.6%, and 2.4 ± 0.5% of the time, respectively. The prevalence of dysrhythmia was highest in the distal antrum (80.4%) (P < 0.01) and lowest in the proximal part of the stomach. In conclusion, tachygastria originates from an ectopic pacemaker in the distal antrum. It may completely or partially override the normal slow waves. Bradygastria is attributed to a decrease in the frequency of the normal pacemaker in the corpus. The prevalence of gastric dysrhythmia is different in different locations of the stomach and is highest in the distal antrum.     

Inhibitory effects of gastric electrical stimulation on ghrelin-induced excitatory effects on gastric motility and food intake in dogs

Objective. To investigate the effects of ghrelin on food intake, gastric motility and whether gastric electrical stimulation (GES) is capable of reversing these effects of ghrelin in dogs. Material and methods. Seven healthy dogs were equipped with a gastric cannula and electrodes for the measurement of antral motility and gastric myoelectrical activity (GMA). Both food intake and gastric motility studies were performed in three sessions (control, ghrelin, 20 µg and ghrelin plus GES) in randomized order, respectively. After a 28-h fast, the animals were provided with unlimited solid food for 1.5?h, 30?min after saline or ghrelin injection. Recordings of antral contractions and GMA in each session were recorded for 30?min at baseline and 45?min after ghrelin/saline injection in the fasting state. GES was performed throughout the experiment initiated 30?min prior to the injection. Results. 1) Ghrelin significantly increased food intake from 475.6±75.5?g in the controls to 535.9±90.3?g with ghrelin (p=0.04); this excitatory effect was reversed by GES. 2) Ghrelin significantly increased the motility index from 8.6±1.6 in the controls to 16.1±2.4 with ghrelin (p=0.01) and this effect was also reversed by GES. 3). There were no effects of ghrelin on GMA. Conclusions. Ghrelin induces antral contractions and increases food intake. GES is capable of blocking these excitatory effects of ghrelin. These findings suggest that GES may inhibit the resistant effect of ghrelin on weight loss.     

The Effect on Gastric Tone of Gastric Electrical Stimulation with Trains of Short Pulses Varies with Sites and Stimulation Conditions

BACKGROUND: Gastric electrical stimulation (GES) can improve symptoms in patients with gastroparesis and induce weight loss in obese subjects. AIMS: To evaluate the effect on gastric tone of GES under different conditions at different sites of the stomach. METHODS: Eleven dogs were implanted with a gastric cannula and two pairs of stimulation electrodes (in the middle of the lesser curvature and of the greater curvature, 10 cm from the pylorus). Gastric tone was assessed with a barostat. GES was applied using: (1) Enterra conditions (14 Hz, 5 mA, 0.3 ms, 0.1 s on, 5 s off); (2) modified Enterra conditions (40 Hz, 5 mA, 0.3 ms, 0.1 s on, 5 s off); and (3) implantable gastric stimulation (IGS) conditions (40 Hz, 5 mA, 0.3 ms, 2 s on, 3 s off). Six sessions were performed randomly with each animal on six separate days. RESULTS: (1) At the lesser curvature, GES with modified Enterra conditions significantly elevated gastric volume from 96.9 +/- 8.3 ml at baseline to 133.9 +/- 11.7 ml (P = 0.015) and a similar effect was observed with IGS (91.3 +/- 7.1 ml vs. 186.3 +/- 27.1 ml, P = 0.013). GES with Enterra conditions had no such an effect. (2) At the greater curvature, GES with Enterra conditions significantly increased gastric volume from basal 94.1 +/- 4.4 ml to 122.1 +/- 11.3 ml (P = 0.032); modified Enterra conditions had the opposite effect (96.5 +/- 9.0 ml vs. 77.4 +/- 11.7 ml, P = 0.025) and no significant effect was observed with IGS conditions. CONCLUSION: The effects of GES on gastric tone vary with the conditions and sites of stimulation. These findings may help to explain the distinct effects of GES therapy in patients with gastroparesis and obesity.     

Gastric Electrical Stimulation With Parameters for Gastroparesis Enhances Gastric Accommodation and Alleviates Distention-Induced Symptoms in Dogs

Gastric electrical stimulation (GES) improves symptoms in patients with gastroparesis. We sought to determine if stimulation at fundus with parameters used for gastroparesis could affect gastric accommodation and distention-induced symptoms in dogs. Nine dogs were implanted with a gastric cannula at the anterior stomach and 1 pair of stimulation electrodes in the fundus. Assessment of gastric accommodation and a series of gastric distention were performed using a barostat. Stimulation parameters were of short pulse trains of 14 Hz, 5 mA, 0.3 ms, and 0.1 s on, 5 s off. GES at fundus significantly decreased fasting gastric tone. Fasting gastric volume was significantly increased from 56.3+/-10.4 mL at baseline to 102.4+/-23.1 mL with stimulation (P=.011). Postprandial gastric accommodation was significantly enhanced with stimulation. The extent of accommodation increased from 249.3+/-39.9 mL in the control session to 325.8+/-25.1 mL with stimulation (P=.011). Symptom scores induced by balloon distention of the stomach were significantly lower during stimulation in comparison with those of baseline (P=.016). In conclusion, GES with parameters for gastroparesis enhances postprandial gastric accommodation and reduces visceral perception in normal dogs. This effect, if seen also in humans, may explain in part the symptomatic improvement associated with GES therapy in patients with gastroparesis.     

正向低频长脉冲对逆向刺激模拟胃异位起搏点诱发胃电过速的治疗作用

目的探讨正向低频长脉冲胃电刺激对逆向高频长脉冲模拟胃异位起搏点诱发胃电过速的治疗作用。方法7条纯种雌性比格犬，依次沿胃大弯前壁浆膜层植入4对心脏起搏电极。通过距离幽门最近的1对电极输入高频长脉冲电信号诱导内源性胃肌电活动发生胃电过速，刺激参数为0．3mA、300ms、9cpm。刺激10min后，通过距离口端最近的1对电极输入不同振幅的低频长脉冲，直至纠正胃电过速，从而获得正向控制胃电过速的最小能量。观察电刺激前、刺激中和刺激后消化不良症状并进行评分。结果正向低频长脉冲能够完全控制逆向高频长脉冲模拟异位起搏点诱发的胃电过速，最小刺激振幅为（5．0±0．93）mA，最小刺激能量为（1500±277．75）（ms×mA）。获得完全控制的正向低频长脉冲与逆向高频长脉冲相比，正常胃慢波百分率升高（95．61％±3．78％ vs42．68％±19．74％，P=0．001），胃电过速百分率降低（3．58％±0．85％ vs40．29％±19．68％，P=0．001），主频降低（6．35±0．66 vs5．60±0．85，P=0．031），主功升高（-9．67±5．08 vs-2．26±1．03，P=0．001）。胃慢波基线期、高频长脉冲（RG-ES）期、完全控制的低频长脉冲（FGES＋RGES）期的消化不良症状评分均为1分，无明显差异。结论正向低频长脉冲能够完全纠正由高频逆向长脉冲模拟人工 异位起搏点引发的胃电过速，并恢复由此降低的胃动力。     

Gastric Electrical Stimulation Does Not Significantly Affect Canine Gastric Acid Secretion and 24-Hour Gastric pH

Gastric electrical stimulation (GES) was shown to improve symptoms in patients with gastroparesis. However, the underlying mechanisms remain unclear. This study assessed the influence of various patterns of GES on fasting and postprandial gastric acid secretion and 24-hr gastric pH. Eight healthy dogs were studied and we found that in the fasting state, low-frequency, long-pulse (6/12-cpm, 375-msec, 4-mA) GES at the proximal stomach significantly inhibited the secretion of gastric juice (P < 0.05). No such effect was observed during GES (6/12 cpm) at the distal stomach. In the postprandial period, low-frequency, long-pulse GES at both proximal and distal sites and at both frequencies did not significantly affect gastric acid secretion. High-frequency, short-pulse GES, investigated for obesity (21 Hz, 8 mA, and 250 microsec, with 2 secs on, 3 sec off), at the proximal and distal stomach did not significantly affect the 24-hr gastric pH profile. In conclusion, GES with various stimulation parameters, and at various sites, has little effect on gastric acid secretion. The clinical effects induced by GES at these parameters may not be related to their effect on gastric acid homeostasis.     

Is There a One-to-One Correlation Between Gastric Emptying of Liquids and Gastric Myoelectrical or Motor Activity in Dogs?

The aim of this study was to investigate the correlation of gastric emptying with gastric myoelectrical activity recorded from internal serosal electrodes and with gastric motility measured from strain gauges. The study was performed in eight healthy dogs chronically implanted with four pairs of electrodes and two strain gauges on the gastric serosa and equipped with a duodenal fistula for the assessment of gastric emptying. Each dog was fed four liquid test meals on four separate days with identical calories (320 kcal) and volume (473 ml). A correlation was found between gastric emptying and the energy of contraction in the frequency band of 3.75–7.50 cycles/min during the first 30 min after the meal (r = 0.46, P < 0.05). While none of the parameters of gastric myoelectrical activity was correlated with gastric emptying, two major parameters, percentage of regular gastric slow waves and percentage of slow-wave coupling, were found to be associated with delayed gastric emptying. A significant correlation was found between the frequency of gastric slow waves and that of the contractions in both fasting (r = 0.83, P < 0.001) and fed state (r = 0.70, P < 0.001 at 30 min, r = 0.86, P < 0.001 at 60 min). It was concluded that gastric emptying is correlated with the strength of gastric contractions in a frequency range identical to that of the gastric slow waves, and there is no one-to-one correlation between gastric emptying of liquids and any parameters of gastric myoelectrical activity. However, major parameters of gastric myoelectrical activity are associated with gastric emptying.     

Vagal Afferent Is Involved in Short-Pulse Gastric Electrical Stimulation in Rats

This study investigated the effect of gastric electrical stimulation (GES) on vagal activity and its possible vagal afferent-mediated mechanisms. Sixty rats implanted with gastric serosal electrodes were divided into six groups (control, vehicle, local capsaicin, perivagal capsaicin, systemic capsaicin, and vagotomy). GES with six sets of parameters was performed in the control group; and GES with one set of effective parameters was performed in the other five groups. Spectral analysis of heart rate variability was used to assess vagal activity. Regular gastric slow waves were recorded in the control rats with a frequency of 4.8 cycles/min. Vagotomy significantly reduced the frequency of the gastric slow wave but did not induce dysrhythmia. Capsaicin did not alter the gastric slow wave. Short-pulse (300-microsec) GES significantly increased vagal activity at a frequency four times the intrinsic slow-wave frequency. Stimulation at a lower frequency or with a long pulse (300 msec) had no effect on vagal activity. Vagotomy or capsaicin administered perivagally, systemically, or locally abolished the effect of GES on the vagal activity. GES with short but not long pulses is capable of altering vagal activity. This effect is mediated by capsaicin-sensitive vagal afferent fibers.