Effects of prenatal exposure to gamma rays on circling and activity behavior in prepubertal and postpubertal rats

The study departs from the finding that postural asymmetries in low-weight female neonates are greatly increased following prenatal lesions inflicted by gamma irradiation at day 15. Given that amphetamine-induced rotation in adult rats could be predicted by their infantile axial asymmetry we expecte d a greater tendency for circling in rats exposed at day 15. To examine thi s prediction, Sprague-Dawley rats were exposed to a single dose of gamma ra diation at 1.5 Gy with a dose-rate of 0.15 Gy/min. The dose was delivered o n one of the embryonic days (E15, 17 or 19) throughout the whole body of pr egnant dams. Sham prenatal exposure of controls consisted of placing pregna nt rats in the same environment for 10 min. All rats were tested during the active part of the circadian cycle. At postnatal day 27 (P27) exposed pups did not differ in rates of either spontaneous or d-amphetamine-induced cir cling from the shams. At P57, in keeping with our prediction, E15 rats mani fested enhanced rotation and higher net asymmetry. However, E17 also showed higher gyration tendency compared to their shams while exposed E19 rats di d not differ from their shams. The role of intrinsic DAergic imbalance pres umably sharpened by irradiation at E15 and of neocortical deficit inflicted at E15 and E17 are discussed. (C) 1999 Elsevier Science B.V. All rights re served.