Effect of irradiation at the early foetal stage on adult brain function of mouse: Learning and memory

Purpose: To study the long-term effect of early foetal irradiation on the learning and memory in the adult mouse. Materials and methods: The abdominal area of pregnant Swiss albino mice was exposed to a single dose of 0.25-1.5 Gy γ-radiation on the 14th day of gestation and the mice were left to deliver their offspring. At 6 months of age, the learning and memory functions of the F₁ mice were tested by hole-board activity, conditioned avoidance response and radial arm maze performance. The animals were again subjected to the radial arm maze test at 12 and 18 months of age. Results: There was a significant dose-dependent decrease in the learning ability and memory retention of 6-month-old mice at doses >0.25 Gy. The significant changes persisted to 18 months of age in mice exposed to ≥0.5 Gy. All changes showed a linear dose-response at doses <1 Gy. Conclusions: The gestational day 14 of Swiss albino mice is a sensitive stage in brain development to γ-ray-induced impairment of learning and memory during the adult life. Permanent deficits in these functions can be induced by a dose of ∼0.5 Gy at this stage, when the developmental activity of the cerebral cortex is at its peak.