Effects of Prenatal X-Irradiation on Activity, Emotionality, and Maze-Learning Ability in the Rat

Gravid albino rats of the Sprague-Dawley strain received 25, 50, or 100 r of whole-body x irradiation on either day 5, 10, 15, or 20 of gestation. Controls were sham-irradiated. Offspring were evaluated for activity and emotionality on the inclined-plane and open-field test and for maze-learning ability on the Lashley III maze, The results show that prenatal radiation exposure alters activity, emotionality, and learning ability as measured by these tests. On the inclined-plane test, a generalized depression of activity was observed, with a more pronounced effect seen in groups irradiated late in gestation. On the openfield test, activity of the early irradiated groups continued to be depressed, with an increase in activity observed in the late irradiated groups. Emotionality was generally reduced in most radiation groups. Dose-response relationships were not consistently evident, On the maze-learning test, the female offspring that were irradiated early (day 5 or 10) during fetal development learned the maze faster, whereas female offspring receiving radiation later (day 15 or 20) during fetal development showed adverse effects. For male offspring, there were no clear dose-response or stage-dependent effects, with radiation groups in general showing a facilitation in maze-learning ability as compared to the controls. These results are discussed with reference to previous findings in this area, and various biological mechanisms are presented to account for these data.