Emetic action of xylazine on the chemoreceptor trigger zone for vomiting in cats.

Xylazine is an effective sedative analgesic that induces vomiting in the cat. A consistently effective intramuscular emetic dose of xylazine was established in normal cats in this laboratory. Animals in which the area postrema of the medulla oblongata had been chronically destroyed did not exhibit emesis in response to the standard test dose of xylazine but continued to show sedation. By contrast, sham-operated cats responded normally. Refractoriness to deslanoside, a known specific emetic drug, was used as functional proof for successful ablation of area postrema, and the lesions were also validated histologically. We conclude that xylazine exerts its emetic action on the chemoreceptor trigger zone of the area postrema. It is suggested that this action may be mediated by an opiate type of molecular receptors.