Is All Radiation-Induced Emesis Ameliorated by 5-HT3 Receptor Antagonists

Abstract : Exposing ferrets to gamma rays or X-rays produces vomiting that can be attenuated by 5-HT3 receptor antagonists and by subdiaphragmatic vagotomy. The present experiments evaluated the effectiveness of these treatments on emesis evoked by exposure to other types of radiation, fast neutrons from a nuclear reactor and high-energy protons (200 MeV), which differ in the relative effectiveness with which they produce vomiting. The results indicated that higher doses of 5-HT3 receptor antagonists Eusatron (0.03 and 0.30 mg/kg, s.c.) and Ondansetron (0.10 and 0.30 mg/kg, s.c.) prevented emesis following neutron irradiation. Lower doses of these 5-HT3 receptor antagonists and subdiaphragmatic vagotomy attenuated neutron-induced emesis, increasing the latency and decreasing the severity of the emetic episodes. Ondansetron (0.50 and 1.00 mg/kg, s.c.) completely prevented vomiting following exposure to high- energy protons. The results are interpreted as indicating that similar 5-HT3- dependent mechanisms mediate emesis produced by exposure to different types of radiation, despite differences in their relative effectiveness.