Low-dose X-ray-induced depression of sexual behavior in mice.

In recent years concern over the biological stimulatory-effect of low-dose noxiousness has been growing. In the course of a study of low dose X-rays effects, we found that male ICR white Swiss mice showed remarkable suppression of mounting behavior after whole body irradiation by 5 to 15 cGy X-rays. Higher doses (25-35 cGy), however, did not induce such effects. Irradiation of the mice head-portion produced these effects, suggesting the important role played by the brain in this phenomenon. Furthermore, we examined the difference between the presence and absence of psychological stress when the mice were exposed to radiation. The results showed that the depression of mounting behavior could be observed in stressed mice, which were housed in prolonged social-isolation, but not in non-stressed mice, that were allowed to socialize. The central nervous system of adult animals is usually considered to be extremely radioresistant. However, the results presented here clearly demonstrate that the brain is one of the most radiosensitive organs in terms of physiological changes.