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ABSTRACT: The aim of this study was to investigate the effects and mechanisms of gastric electrical stimulation (GES) on proximal stomach distention-induced visceral sensitivity. Isobaric gastric distention was performed using a barostat system in 8 normal and 6 vagotomized dogs and animal behaviors were noted and graded. The normal dogs were studied in 4 sessions: control (no GES), short pulse GES, long pulse GES, and dual-pulse GES, and the vagotomized dogs were studied in three sessions: control (no GES), long pulse GES and guanethidine. It was found that: 1) proximal stomach distention-induced behavioral changes were mediated by vagal and sympathetic pathways. The total behavior score (TBS) was 40.6 ± 7.4 in the controls, 15.3 ± 8.9 in vagotomized dogs (P=0.006 vs. control) and 8.8 ± 0.9 in the vagotomized dogs with guanethidine (P=0.04 vs. vagotomy). The behavioral changes were mediated via the vagal pathway at distention pressures below 20 mmHg, but mediated via both the vagal and sympathetic pathways at distention pressures equal to and above 20 mmHg. 2) GES with long pulses or dual pulses but not short pulses reduced the distention-induced behavioral score (P=0.003, P=0.006 and P=0.7, respectively) and the effects of GES of long pulses might be mediated via the vagal and sympathetic pathways. In conclusion, gastric distention-induced visceral sensitivity is mediated via the vagal pathway at low distention pressures but via both vagal and sympathetic pathways at high distention pressures. GES with long but not short pulses reduces distention-induced visceral sensitivity.
Autonomic neuroscience: basic & clinical 02/2011; 160(1-2):16-20. · 1.82 Impact Factor
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ABSTRACT: The aims of this study were to determine optimal pacing parameters of electrical stimulation on different gut segments and to investigate effects and possible mechanisms of gastrointestinal electrical stimulation on gut slow waves. Twelve female hound-mix dogs were used in this study. A total of six pairs of electrodes were implanted on the stomach, duodenum, and ascending colon. Bilateral truncal vagotomy was performed in six of the dogs. One experiment was designed to study the effects of the pacing frequency on the entrainment of gut slow waves. Another experiment was designed to study the modulatory effects of the vagal and sympathetic pathways on gastrointestinal pacing. The frequency of slow waves was 4.88 +/- 0.23 cpm (range, 4-6 cpm) in the stomach and 19.68 +/- 0.31 cpm (range, 18-22 cpm) in the duodenum. There were no consistent or dominant frequencies of the slow waves in the colon. The optimal parameters to entrain slow waves were: frequency of 1.1 intrinsic frequency (IF; 10% higher than IF) and pulse width of 150-450 ms (mean, 320.0 +/- 85.4 ms) for the stomach, and 1.1 IF and 10-20 ms for the small intestine. Electrical stimulation was not able to alter colon slow waves. The maximum entrainable frequency was 1.27 IF in the stomach and 1.21 IF in the duodenum. Gastrointestinal pacing was not blocked by vagotomy nor the application of an alpha- or beta-adrenergic receptor antagonist; whereas the induction of gastric dysrhythmia with electrical stimulation was completely blocked by the application of the alpha- or beta-adrenergic receptor antagonist. Gastrointestinal pacing is achievable in the stomach and small intestine but not the colon, and the maximal entrainable frequency of the gastric and small intestinal slow waves is about 20% higher than the IF. The entrainment of slow waves with gastrointestinal pacing is not modulated by the vagal or sympathetic pathways, suggesting a purely peripheral or muscle effect.
AJP Regulatory Integrative and Comparative Physiology 09/2009; 297(5):R1392-9. · 3.34 Impact Factor
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ABSTRACT: 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.
Digestive Diseases and Sciences 03/2008; 53(3):630-5. · 2.12 Impact Factor
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ABSTRACT: Gastric electrical stimulation (GES) is known to improve vomiting with short pulses, normalize dysrhythmia with long pulses, and accelerate gastric emptying with 2 channels. The aim of this study was to assess the effects of a new method GES, namely, 2-channel GES with dual pulses on gastric emptying of solids as well as gastric dysrhythmia and emetic responses.
Seven beagle dogs implanted with 4 pairs of electrodes were studied. A novel method of GES was proposed: 2-channel dual-pulse GES in which each stimulus was composed of a short pulse followed with a long pulse, and stimulation was delivered at 2 different locations. The study was performed to test the effects of this new method of GES on vasopressin-induced delayed gastric emptying of solids, gastric dysrhythmia, and emetic responses.
(1) Vasopressin-induced gastric dysrhythmia and emetic responses, as well as delayed gastric emptying of solids (P < .01). (2) Two-channel, but not 1-channel, dual-pulse GES was able to accelerate vasopressin-induced delayed gastric emptying of solids. (3) Both 1- and 2-channel dual-pulse GES was capable of improving dysrhythmia and emetic responses (P < .01).
The novel method of 2-channel dual-pulse GES is capable of accelerating gastric emptying of solids and improving dysrhythmia and emetic responses induced by vasopressin. This new method of GES may have a potential for gastroparesis.
Surgery 02/2008; 143(1):72-8. · 3.10 Impact Factor
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ABSTRACT: 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.
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.
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.
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.
American journal of surgery 08/2007; 194(1):122-7. · 2.36 Impact Factor
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ABSTRACT: To investigate the effects of acute and chronic partial restraint stress (PRS) on visceral sensitivity to colorectal distention and the neuroendocrine response in rats.
Male Sprague-Dawley rats were used in this study. The abdominal withdrawal reflex score was assessed before stress, immediately after acute or chronic PRS, and 7 days after the first stress. The plasma levels of corticosterone (CORT) and adrenocorticotropic hormone (ACTH) were detected by radioimmunoassay at different time points.
The abdominal withdrawal reflex scores of the rats with acute or chronic PRS were significantly higher immediately after stress than those before and 7 days after the stress (P < 0.05). The levels of CORT (25.35 +/- 6.03 ng/mL) and ACTH (312.47 +/- 50.76 pg/mL) in rats with acute PRS showed a significant elevation immediately after stress compared to rats without PRS (7.24 +/- 2.97 ng/mL, 97.00 +/- 23.33 pg/mL, P < 0.05). However, these hormones returned to the baseline value 7 days after acute PRS. The levels of CORT (20.84 +/- 2.19 ng/mL) and ACTH (200.41 +/- 78.10 pg/mL) in rats with chronic PRS were significantly higher after stress than in rats without PRS (P < 0.05), and these hormones remained elevated 7 days after chronic PRS.
Both acute and chronic PRS induce reversible visceral hypersensitivity. Acute PRS transiently elevates the plasma levels of CORT and ACTH, whereas chronic PRS has a longer term effect.
Chinese Journal of Digestive Diseases 02/2006; 7(3):149-55.
