The Effects of Neonatal Irradiation on Postnatal Activity and Elimination

Abstract

It has been demonstrated that neonatal irradiation has diverse anatomical and neurological effects on the nervous system (1-3). These studies have uniformly indicated, first, that the nervous system of the developing organism is radiosensitive, and, second, that the amount of damage is directly related to dosage and inversely related to the age of the organism at the time of exposure. Studies on the behavioral effects of radiation have produced less definitive results than the neurological and anatomical studies (4-6). Of these studies, relatively few have investigated the behavioral effects of irradiation delivered to the organism at birth (5). Therefore, this study focuses on irradiation delivered to the neonate and the effects of this treatment on activity and elimination. Emotional behavior has been inferred from a variety of dependent variables (open field activity, elimination, home cage emergence, food consumption in open field, etc.), and no consensus appears to have been reached with regard to its exact meaning (7). Thus, in this report we shall not use the term emotionality. Only descriptive terms such as activity, elimination, and latency will be employed. Furchtgott and Echols (8) studied the effects of X-radiation on activity and elimination in rats and found that: (1) neonatal irradiation (300 R) tended to depress tilt cage activity, whereas fetal irradiation significantly increased such activity; (2) open field motility was, relative to controls, significantly greater for fetally irradiated animals and significantly less for neonatally irradiated animals; (3) neonatally irradiated animals seemed to defecate less frequently in the open field than controls. Thus, neonatally irradiated animals responded in an aberrant manner when compared to the fetally irradiated (in late gestation) subjects as well as the control subjects. These investigators concluded that X-irradiation results in hyperemotionality.