Impact of electrical stimulation of the stomach on gastric distension‐induced emesis in the musk shrew

Abstract

Background Gastric electrical stimulation (GES) is implicated as a potential therapy for difficult-to-treat nausea and vomiting; however, there is a lack of insight into the mechanisms responsible for these effects. The current study tested the relationship between acute GES and emesis in musk shrews, an established emetic model system. Methods Urethane-anesthetized shrews were used to record emetic responses (monitoring intra-tracheal pressure and esophageal contractions), respiration rate, heart rate variability, blood pressure, and gastrointestinal electromyograms. We investigated the effects of acute GES pulse duration (0.3, 1, 5, and 10 ms), current amplitude (0.5, 1, and 2 mA), pulse frequency (8, 15, 30, and 60 Hz), and electrode placement (antrum, body, and fundus) on emesis induced by gastric stretch, using a balloon. Key results There were four outcomes: (1) GES did not modify the effects of gastric stretch-induced emesis; (2) GES produced emesis, depending on the stimulation parameters, but was less effective than gastric stretch; (3) other physiological changes were closely associated with emesis and could be related to a sub-threshold activation of the emetic system, including suppression of breathing and rise in blood pressure; and (4) a control experiment showed that 8-OH-DPAT, a reported 5-HT1A receptor agonist that acts centrally as an antiemetic, blocked gastric stretch-induced emesis. Conclusions & Inferences These results do not support an antiemetic effect of acute GES on gastric distension-induced emesis within the range of conditions tested, but further evaluation should focus on a broader range of emetic stimuli and GES stimulation parameters.

Machine learning prediction of emesis and gastrointestinal state in ferrets

“…After the tracheotomy, anesthesia was delivered through the intratracheal tube. Intratracheal airway pressure was monitored using an air pressure transducer (SAR-830/AP Small Animal Ventilator, CWE, Inc., Ardmore, Pennsylvania, USA), which was used to measure respiratory rate and the occurrence of emetic episodes [18]. Blood pressure was monitored and recorded using a fluid-filled catheter inserted through the left Ventral surface images were used to determine electrode location by drawing a triangle on top of the fat pad of the lesser curvature of the stomach (Fig.…”

“…For this ferret, the overall testing accuracy was above chance (82%). For animals [16][17][18][13][14][15][16][17][18], and 15-18 the classifiers were trained on 3 gastric states therefore chance level for prediction was 33% while testing accuracy for all 3 animals was above 80%. Similar to data from acute anesthetized experiments there was substantial inter-subject variability in terms of the optimal features and GI myoelectric activity signals required to detect gastric state.…”

“…The filtered signal was then downsampled to 10 Hz and a second low-pass Butterworth filter with a cut-off frequency of 0.3 Hz (18 cpm, 2 nd order) was applied. In one ferret(13)(14)(15)(16)(17)(18) non-physiological high amplitude transients that lasted 10-20 seconds were observed across all channels. These artifacts were removed by blanking the 1-min window around the artifact, prior to filtering and down-sampling.…”

Estimation of body surface area in the musk shrew (Suncus murinus): a small animal for testing chemotherapy-induced emesis

“…Although many studies of emesis use large animals, such as dogs and ferrets 3 , there has been a growing interest in the use of smaller animals, particularly musk shrews 4, 5 (Fig.1A). Rodents (rats and mice) lack an emetic reflex and, therefore, are not suitable for emetic testing 6 .…”

“…Shrews were euthanized at the end of other, primary, studies using: (1) CO 2 (rising); or (2) intracardiac injection of Beuthanasia-D (0.2 ml = 78 mg sodium pentobarbital, Henry Schein), under general anesthesia (urethane, 1 g/kg, ip) 5 . Euthanization was confirmed by cervical dislocation.…”