Effect of electroacupuncture at Sibai on the gastric myoelectric acitivities of denervated rats

AIM： To explore the mechanism of the exciting effects of electro-acupuncture （EA） at Sibai on the gastric myoelectric activities. METHODS： A total of 32 rats were randomly divided into four groups. Through intraperitoneal injection with atropine （the anti-cholinergic agent by blockade of muscarinic receptors）, hexarnethonium （automatic nerve ganglion-blocking agent） and reserpine （anti-adrenergic agent by depleting the adrenergic nerve terminal of its norepinephrine store）, effects of EA at Sibai on the gastric myoelectric activities of the denervated rats were observed. RESULTS： After intraperitoneal injection of atropine and hexamethonium, the average amplitude and ratio of period to time in the phase of high activity of gastric myoelectric slow wave, and the average numbers of the peaks of gastric myoelectric fast wave were significantly decreased （P 〈 0.01, P 〈 0.05, P 〈 0.01）, while after intraperitoneal injection of reserpine, the aforementioned three parameters were increased （P 〈 0.01, P 〈 0.05, P 〈 0.01）. EA at Sibai point partially relieved the inhibitory effect of atropine and hexamethonium on the gastric myoelectric activities in the rats （P 〈 0.05 or P 〉 0.05）. CONCLUSION： Cholinergic and adrenergic nervous systems and autonomic nerve ganglion participate in the peripheral passage of the controlling effects of EA at Foot Yangming Channel on gastrointestinal tract.

Gastric electrical stimulation for gastroparesis:A goal greatly pursued,but not yet attained

The lack of an effective medical treatment for gastroparesis has pushed the research of new techniques of gastric electrical stimulation (GES) for nearly half a century of experimentation with a large variety of electrical stimuli delivered to the gastric wall of animals and patients with gastroparesis. Three principal methods are currently available: gastric low-frequency/high-energy GES with long pulse stimulation, high-frequency/low-energy GES with short pulse stimulation and neural sequential GES. The first method aims to reset a regular slow wave rhythm, but has variable effects on contractions and requires devices with large and heavy batteries unsuitable for implantation. High-frequency/low-energy GES, although inadequate to restore a normal gastric electro-mechanical activity, improves dyspeptic symptoms, such as nausea and vomiting, giving patients a better quality of life together with a more satisfactory nutritional status and is suitable for implantation. Unfortunately, the numerous clinical studies using this type of GES, with the exception of two, were not controlled and there is a need for definitive verification of the effectiveness of this technique to justify the cost and the risks of this procedure. The last method, which is neural sequential GES, consists of a microprocessor-controlled sequential activation of a series of annular electrodes along the distal two thirds of the stomach and is able to induce propagated contractions causing forceful emptying of the gastric content. The latter method is the most promising, but has been used only in animals and needs to be tested in patients with gastroparesis before it is regarded as a solution for this disease.

Experimental gastric dysrhythmias and its correlation with in vivo gastric muscle contractions

AIM： To study the direct correlation between gastric dysrhythrnias and in vivo gastric muscle tone. METHODS： Five healthy dogs were implanted with 4 pairs of electrodes along the greater curvature, with a strain gauge （SG） being sutured parallel to the distal electrodes （2 cm above the pylorus）. Intravenous vasopressin was given to induce gastric dysrhythrnia. The percentage of regular slow waves and SG energy were calculated. RESULTS： （1） the regularity of gastric rnyoelectric activity （GMA） was reduced during and after infusion of vasopressin; （2） SG energy was significantly decreased during the infusion of vasopressin; （3） the decrease in SG energy was well correlated with the reduction in GMA regularity; （4） SG energy was negatively correlated with bradygastria and tachygastria. CONCLUSION： Vasopressin inhibits gastric contractions and impairs gastric slow waves; gastric dysrhythrnias are associated with the reduced antral muscle contractions, and are indicative of antral hypornotility.

Environmental noise alters gastric myoelectrical activity:Effect of age

AIM: To evaluate the effect of age and acoustic stress on gastric myoelectrical activity (GMA) and autonomic nervous system function. METHODS: Twenty-one male subjects (age range 22-71 years, mean 44 years) were recruited and exposed, in random order, to three auditory stimuli (Hospital noise, conversation babble and traffic noise) after a 20-min baseline. All periods lasted 20 min and were interspersed with a 10 min of recovery. GMA was obtained using a Synectics Microdigitrapper. Autonomic nerve function was assessed by monitoring blood pressure and heart rate using an automatic recording device. RESULTS: Dominant power tended to decrease with increase of age (P < 0.05). The overall percentage of three cycle per minute (CPM) activity decreased during exposure to hospital noise (12.0%, P < 0.05), traffic noise (13.9%, P < 0.05), and conversation babble (7.1%). The subjects in the younger group (< 50 years) showed a consistent reduction in the percentage of 3 CPM activity during hospital noise (22.9%, P < 0.05), traffic noise (19.0%, P < 0.05), and conversation babble (15.5%). These observations were accompanied by a significant increase in bradygastria: hospital noise (P < 0.05) and traffic noise (P < 0.05). In contrast, the subjects over 50 years of age did not exhibit a significant decrease in 3 CPM activity. Regardless of age, noise did not alter blood pressure or heart rate. CONCLUSION: GMA changes with age. Loud noise can alter GMA, especially in younger individuals. Our data indicate that even short-term exposure to noise may alter the contractility of the stomach.