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.