Ameliorating effects of sacral neuromodulation on gastric and small intestinal dysmotility mediated via a sacral afferent‐vagal efferent pathway

Abstract

Background/AimsIn a recent study of sacral nerve stimulation (SNS) for colonic inflammation, a possible spinal‐vagal pathway was implicated. The aim of this study was to provide evidence for such a pathway by investigating the effects of SNS on dysmotility of the stomach and duodenum that are not directly innervated by the sacral efferents.MethodsTwenty‐seven rats were chronically implanted with wire electrodes for SNS and gastrointestinal slow waves. SNS was performed in several acute sessions to investigate its effects on gastric/duodenal slow waves and emptying/transit impaired by glucagon and rectal distention (RD).Results(a) SNS increased the percentage of normal gastric slow waves impaired by glucagon (from 53.9% to 77.0%, P < .0001) and RD (from 64% to 78%, P = .037). This improvement was abolished by atropine. (b) Similar effects were observed with SNS on duodenal slow waves, which was also blocked by atropine. (c) SNS normalized delayed gastric emptying induced by glucagon (control: 61.3%, glucagon: 44.3%, glucagon + SNS: 65.8%) and RD (control: 61.3%, RD: 46.7%, RD + SNS: 64.3%). It also normalized small intestinal transit delayed by RD (P = .001, RD + SNS vs RD; P = .9, RD + SNS vs control). (4) Both glucagon and RD induced an increase in the sympathovagal ratio (P = .007, glucagon vs baseline; P < .001, RD vs baseline) and SNS decreased the ratio (P = .006, glucagon + SNS vs glucagon; P = .04, RD + SNS vs RD).ConclusionsNeuromodulation of the sacral nerve improves gastric and small intestinal pacemaking activity and transit impaired by glucagon and RD by normalizing the sympathovagal balance via a retrograde neural pathway from the sacral nerve to vagal efferents.

Auricular vagal nerve stimulation enhances gastrointestinal motility and improves interstitial cells of Cajal in rats treated with loperamide

“…Moreover, we found that aVNS also improved the impairments induced by loperamide in both gastric and intestinal slow waves. The impairments and changes in GI slow waves were comparable to that of FD rats and diabetic rats with delayed gastric emptying and dysrhythmia (decreased normal slow waves) 30,31 . Recently, Sukasem et al 56 reported that transcutaneous aVNS also effectively altered the frequency and amplitude of gastric slow waves in healthy pigs.…”

“…aVNS was performed using parameters of 25 Hz, 0.5 ms, 2 s on, 3 s off and amplitude of 90% motor threshold (range from 1 to 2 mA). The motor threshold was defined as the minimum amplitude of stimulation at which the animal's ear began to shake, and the motor threshold was determined at the beginning of each experiment 29,30 . Animals received aVNS at the conchae of the right ear for 1 h daily for 7 days (from D7 to D14).…”

“…Gastric slow waves and ISW were recorded for 30 min in the fasting state and 30 min after a test meal (2 g of food consumed within 10 min) using a Biopac system (EOG 100A; Biopac Systems Inc.) and previously established method 30 in Sham‐aVNS ( n = 8) and aVNS groups ( n = 8) at D0, D7, and D14. Special analyses were performed to derive following parameters 33 : (1) Dominant Frequency (DF), (2) Dominant Power (DP), and (3) the percentages of normal (N%), brady (B%), and tachy (T%) slow waves.…”

Ameliorating effects and mechanisms of transcutaneous auricular vagal nerve stimulation on abdominal pain and constipation

“…We speculated that this might be attributed to (a) possible innervation of the vagus nerve to the rectum and/or (b) a possible vagal afferent and sacral efferent pathway. In a few recent studies, sacral nerve stimulation was reported to alter functions of the gastrointestinal organs (stomach and small intestine) that are not innervated with the sacral nerve ( 77 , 78 ), and a spinal afferent and vagal efferent pathway was indicated with the sacral nerve stimulation ( 79 ).…”

Auricular Vagal Nerve Stimulation Improves Constipation by Enhancing Colon Motility via the Central-Vagal Efferent Pathway in Opioid-Induced Constipated Rats

“…aVNS was performed using parameters of 25 Hz, 0.5 msec, 2 sec on, 3 sec off, and amplitude of 90% motor threshold (range from 1 to 2 mA). The motor threshold was defined as the minimum amplitude of stimulation at which the animal's ear began to shake (29,30). Animals received aVNS unilaterally (right ear) in both acute and chronic study, but with different stimulation duration.…”