Immediate arousal response and adaptation to low-dose x-rays in mouse and its disappearance by olfactory bulbectomy and nitric oxide inhibitor.

The effects of low-dose x-rays (4 cGy) on mouse brain were examined. EEG recording were made on sleeping mice before, during and after exposure. Exposure to x-rays induced the immediate change in EEG pattern from a low-frequency and high-amplitude (sleep) to a high-frequency and low-amplitude (arousal). Repeated exposure caused a decrease in number of mice showing arousal, suggesting that adaptation to x-ray stimuli was acquired by mice. In the olfactory bulbectomized mice, no arousal response could be noticed. When mice were injected with N-nitro-L-arginine or N-monomethyl-L-arginine, nitric oxide inhibitor, no decrease in the arousal mouse number occurred, even after the repeated exposure. These results indicate clearly that olfactory bulbs play an important role in immediate detection of x-rays and a possible involvement of NO in the adaptation to x-ray stimuli by mouse.