Effect of Localized Brain Stem Lesions and Supradiaphragmatic Vagotomy on X-Irradiation Emesis in the Monkey

¹ From the Department of Anatomy, University of Utah College of Medicine, Salt Lake City, Utah

Bilateral ablation of area postrema by thermal coagulation resulted in loss of the normal early emetic response to total body x-irradiation in three monkeys (Macaca irus). Similar lesions in the lower descending vestibular nucleus with some damage to area postrema eliminated the vomiting reaction in one animal, but failed to do so in two others. Bilateral lesions in the dorsal sensory vagal nucleus without involvement of area postrema or other structures failed to inhibit vomiting to the standard dose of x-irradiation. In two other animals with similar lesions, but with extensive damage to area postrema or the nucleus of the tractus solitarius on one side, no vomiting occurred. Two animals with bilateral lesions in the superficial (ventricular) portion of the hypoglossal nuclei vomited during x-irradiation or in the usual interval following radiation. Supradiaphragmatic vagotomy resulted in complete inhibition of vomiting in five animals.