A Novel Approach in Spinal Cord Stimulation for Enhancing Gastric Motility: A Preliminary Study on Canines

Background/Aims@#Gastroparesis is commonly seen in patients with diabetes and functional dyspepsia with no satisfactory therapies. Dysautonomia is one of the main reasons for the imbalanced motility. We hypothesized that spinal cord stimulation (SCS) is a viable therapy for gastroparesis via the autonomic modulation to improve gastric motility. The aim is to find an optimal method of SCS for treating gastroparesis. @*Methods@#Eight healthy-female dogs were implanted with a gastric cannula, a duodenal cannula, 2 multi-electrode spinal leads, and an implantable pulse generator. Gastric motility index (MI) was used to determine the best stimulation location/parameters of SCS. Optimized SCS was used to improve glucagon-induced gastroparesis. @*Results@#With fixed parameters, SCS at Thoracic 10 (T10) was found most effective for increasing gastric MI (37.8%, P = 0.013). SCS was optimized with different parameters (pulse width: 0.05-0.6 msec, frequency: 5-500 Hz, motor threshold: 30-90%) on T10. Our findings revealed that 0.5 msec, 20 Hz with 90% motor threshold at T10 were the best parameters in increasing MI. Glucagon significantly delayed gastric emptying, and this inhibitory effect was partially blocked by SCS. Gastric emptying at 120 minutes was 25.6% in the control session and 15.7% in glucagon session (P = 0.007 vs control), while it was 22.9% with SCS session (P = 0.041 vs glucagon). SCS with the optimal parameters was found to maximally enhance vagal activity and inhibit sympathetic activity assessed by the spectral analysis of heart rate variability. @*Conclusions@#SCS with optimized stimulation location and parameters improves gastric motility in healthy-dogs and accelerates gastric emptying impaired by glucagon via enhancing vagal activity.

Ameliorating Effects of Electroacupuncture on Dysmotility, Inflammation, and Pain Mediated via the Autonomic Mechanism in a Rat Model of Postoperative Ileus

BACKGROUND/AIMS: Postoperative ileus increases healthcare costs and reduces the postoperative quality of life (QOL). The aim of this study is to investigate effects and mechanisms of electroacupuncture (EA) at ST36 and PC6 on gastrointestinal motility in rat model of postoperative ileus. METHODS: Laparotomy was performed in 24 rats (control [n = 8], sham-EA [n = 8], and EA [n = 8]) for the implantation of electrodes in the stomach and mid-jejunum for recording of gastric and small intestinal slow waves. Electrodes were placed in the chest skin for electrocardiogram (ECG). Intestinal manipulation (IM) was performed in Sham-EA and EA rats after surgical procedures. Small intestinal transit (SIT), gastric emptying (GE), postoperative pain, and plasma TNF-α were evaluated in all rats. RESULTS: (1) Compared with sham-EA, EA accelerated both SIT (P < 0.05) and GE (P < 0.05) and improved regularity of small intestinal slow waves. (2) Compared with the control rats (no IM), IM suppressed vagal activity and increased sympathovagal ratio assessed by the spectral analysis of heart rate variability from ECG, which were significantly prevented by EA. (3) EA significantly reduced pain score at 120 minutes (P < 0.05, vs 15 minutes) after the surgery, which was not seen with sham-EA. (4) Plasma TNF-α was increased by IM (P = 0.02) but suppressed by EA (P = 0.04) but not sham-EA. CONCLUSION: The postoperative ileus induced by IM, EA at ST36 and PC6 exerts a prokinetic effect on SIT and GE, a regulatory effect on small intestinal slow waves and an analgesic effect on postoperative pain possibly mediated via the autonomic-cytokine mechanisms.

Blunted Peripheral and Central Responses to Gastric Mechanical and Electrical Stimulations in Diet-induced Obese Rats

BACKGROUND/AIMS: The increase in the prevalence of obesity is attributed to increased food intake and decreased physical activity in addition to genetic factors. Altered gut functions have been reported in obese subjects, whereas, little is known on the possible alterations in brain-gut interactions in obesity. The aim of the study was to explore possible alterations in gastric myoelectrical activity, gastric emptying, autonomic functions and central neuronal responses to gastric stimulations in diet-induced obese rats. METHODS: Gastric myoelectrical activity, gastric emptying and heart rate variability were recorded in lean and obese rats; extracellular neuronal activity in the ventromedial hypothalamus and its responses to gastric stimulations were also assessed. RESULTS: (1) Gastric emptying was significantly accelerated but gastric myoelectrical activity was not altered in obese rats; (2) the normal autonomic responses to feeding were absent in obese rats, suggesting an impairment of postprandial modulation of autonomic functions; and (3) central neuronal responses to gastric stimulations (both balloon distention and electrical stimulation) were blunted in obese rats, suggesting impairment in the brain-gut interaction. CONCLUSIONS: In diet-induced obese rats, gastric emptying is accelerated, postprandial modulations of autonomic functions is altered and central neuronal responses to gastric stimulations are attenuated. These alterations in peripheral, autonomic and brain-gut interactions may help better understand pathogenesis of obesity and develop novel therapeutic approaches for obesity.

Electrogastrography: Methodology, Validation and Applications

Electrogastrography (EGG) is a non-invasive method for the measurement of gastric myoelectrical activity. It was first discovered in 1921 and popularized in 1990s. EGG is attractive because it is non-invasive. However, due to its non-invasive nature, there have also been controversies regarding validity and applications of EGG. The aim of this review is to discuss the methodologies, validation and applications of EGG. Pros and cons of EGG will also be discussed in detail. First, the gastric slow wave and its correlation with gastric motility are presented. The association between gastric dysrhythmia and impaired gastric motility is reviewed. Secondly the method for recording the electrogastrogram is presented in detail and pitfalls in the recording and analysis of EGG are discussed. Thirdly, findings reported in the literature demonstrating the accuracy of EGG in recording gastric slow waves and gastric dysrhythmia are reviewed and discussed. The correlation of the electrogastrogram with gastric contraction is carefully discussed. Finally, applications of EGG in a few major areas are reviewed.