Studies of the effect of 0.4-Gy and 0.6-Gy prenatal X-irradiation on postnatal adult behavior in the Wistar rat

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Abstract
Thirty‐four pregnant Wistar rats were X‐irradiated on the 9th or 17th day of gestation at a dosage level 0.4 Gy or 0.6 Gy or were sham‐irradiated. All mothers were allowed to deliver their offspring, and litters were limited to a maximum of eight on day 2. On day 30, 224 offspring were weaned and raised until 60 days of age, at which time testing began. Each rat randomly received, in random order, three of the following six behavioral tests: Water T‐maze, Conditioned Avoidance Response, Forelimb Hanging, Activity Wheel, Swimming, and Open Field. There were no statistically significant differences between the irradiated and control groups for maternal weight or weight gain or mean litter size, although the litter size of the 17th day 0.6‐Gy group was slightly lower. Among offspring irradiated with 0.6 Gy on the 17th day, 3‐day‐old neonates' weights were significantly reduced. Offspring irradiated on the 17th day with 0.6 Gy exhibited higher Conditioned Avoidance Response 5th‐day and retest avoidance scores than did the controls. There were also significant sex differences in responses within the irradiated and control groups for several tests, which were unrelated to radiation exposure. The results of this study indicate that low‐level X‐irradiation during the fetal period of rat gestation results in neonatal growth retardation and subtle behavioral alterations that may be manifested in adult life. Growth retardation may be the most sensitive indicator of suble effects that result from low‐level prenatal exposure to X‐rays.