Effects of low dose heavy particle radiation to central nervous system (CNS) were studied using mouse neonatal brain cells in culture exposed to heavy ions and X ray at fifth days of the culture. The applied dose varied from 0.05Gy to 2.0Gy. The subsequent biological effects were evaluated by an induction of apoptosis and the survivability of neurons focusing on the dependencies of (1) the animal strains with different genetic types, and (2) LET of the different nucleons. Of the three mouse strains tested, SCID, B6 and C3H, for brain cell culture, SCID was the most sensitive and C3H the least sensitive to both X-ray and carbon ion (290MeV/n) when compared by 10 % apoptotic induction. However, the sensitivity differences among the strains were much smaller in case of carbon ion comparing to that of X-ray. The LET dependency was compared with using C3H and B6 cells exposing to different ions, proton (H, C, Ne, Ar, and Fe). Although no detectable LET dependency was observed at higher dose than 1 Gy, an enhancement was observed in the high LET (85 -200 KeV/_m) and low dose (<0.5 Gy) regions. The survivability profiles of the neurons were different in the mouse strains and ions.14th IAA Humans in Space Symposi
