Impairment of electrical functions of CNS and alterations in cell populations associated with irradiation

Two types of cell injury have been described in the gyrus dentatus of the hippocampus. The first (pycnotic cells) located in the proliferative subgranular zone, allowed the quantification of damage and calculation of the RBE of fast neutrons as 3.1 to 3.3. The second (light spots) located in the mature granule cells suggested the hypothesis: the granular layer being the major entrance to the hippocampus could contain the target cells for injury which may explain some electrical disturbances in the downstream pyramidal cells and even perhaps some of the functional disorders which are known to happen in the first days after acute irradiation (of 1 or a few Gy). This hypothesis is based on the fact that early functional disturbances and cellular lesions have the same threshold (1 Gy) and the same time course. (UK)