Establishment of an Animal Model for Radiation-induced Vomiting in Rats Using Pica

We investigated whether radiation-induced pica, a behavior characterized by the eating of a non-food substance, such as kaolin, can be used as an index of radiation-induced vomiting in rats. Since there was an individual difference in the susceptibility to pica, we selected rats that actually ate kaolin following X-ray irradiation, and used them for the experiment. The total-body irradiation (TBI) increased kaolin consumption in a dose-dependent manner (sham, 0.05 +/- 0.03 (SEM) g; 2 Gy, 0.38 +/- 0.11 g; 4 Gy, 1.54 +/- 0.28 g; 8 Gy, 3.55 +/- 0.67 g), and the increased kaolin consumption after 4 Gy of TBI was inhibited by a pretreatment with the serotonin 5-HT3 receptor antagonist ondansetron (2 mg/kg, i.p.) (saline, 1.49 +/- 0.33 g; ondansetron, 0.75 +/- 0.11 g). Furthermore, 4 Gy of abdominal irradiation was more effective to induce pica than that of head irradiation (abdomen: 0.37 +/- 0.05 g, head: 0.06 +/- 0.01 g). These findings suggested that peripheral serotonergic pathway is predominantly involved in the development of radiation-induced pica in rats and that the radiation-induced pica could be useful as a behavioral index for the severity of radiation-induced vomiting in rats.