Neuroinhibition of xylazine induced emesis

Xylazine produces retching and vomiting presumably by activation of the chemoreceptor trigger zone (CTZ). The purpose of this project was to investigate whether neuroinhibition can prevent xylazine vomiting. Inhibitory neurons in the cervical vagus nerve of cats were stimulated with implanted cuff electrodes. Female cats, weighing from 3 to 4 kg, were anaesthetized with pentobarbital for surgical implantation of electrodes. After full recovery from surgery, animals were tested in weekly sessions. Stimulation was via a pulse generator connected to photon coupled linear isolator supplying constant current. Videotape was used to record observations. The range of effective stimulation was 1-10 ma, 4-100 Hz and 0.3-0.6 msec. Stimulation was initiated thirty sec. after subcutaneous injection of xylazine, 0.66 mg/kg. Stimulation of the inhibitory nerve group of the cervical vagus was effective in preventing vomiting in over 85% of the experimental trials. In addition to preventing emesis during stimulation, the latency of xylazine emesis was increased over control values. Repeated experimental trials of stimulation coupled with xylazine injection could result in the complete absence of emesis.