Long term effects of prenatal exposure to low level gamma rays on spontaneous circadian motor activity of male mice.

The spontaneous circadian motor activity of first generation (F1) hybrid male C57BL/6xC3H mice irradiated with gamma rays on the 14th day of gestation was studied at the following ages: young (6-7 months), adult (12-13 months), and old (19-20 months). Doses were 0.1, 0.2, 0.5 or 1.0 Gy. A 12-hour day-night cycle was maintained with light on a at 6:00 hr. Spontaneous circadian motor activity was recorded with a capacitance-induction motility monitor for 48 consecutive hours. Activity was measured at 2-hour intervals, and the data stored on computer discs. The activity of the 1.0 Gy group recorded at 22:00 and 2:00 hr for young mice and at 2:00 hr for adult ones was significantly higher than that of the age-matched control group. Results suggest that male mice irradiated with 1.0 Gy at gestational day 14 show nocturnal hyperactivity in the young and adult stages.