Response of associative learning and nervous system of to heavy ion beam irradiation

Sakashita, Tetsuya; Hamada, Nobuyuki*; Suzuki, Michiyo*; Kakizaki, Takehiko; Wada, Seiichi*; Funayama, Tomoo; Kobayashi, Yasuhiko

It has been reported that the radiation-induced impairments of learning and memory in mammals are mainly caused by suppression of hippocampal neurogenesis. On the other hand, alterations of neurotransmitter activity in rat brain after ionizing irradiation suggest impairments of function in the central nervous system (CNS) except for hippocampus. However, direct measurement of the impairments is difficult in mammals. Thus, our goal of the present study is to understand at the functional level when and how ionizing radiation affects CNS, using the adult stage of with no newborn neuron and a simple learning behavior, i.e. food-NaCl associative learning. The animals were irradiated with broad beams of C ions (0-500 Gy), which were included in cosmic rays. We observed a remarkable decrease of chemotaxis index just after irradiation in the food-NaCl associative learning conditioned animals. The result suggests that plastic parts of the nervous system related food-NaCl associative learning are sensitive to C ions. Microbeam irradiation experiments are in progress.