Abstract
The biological effects of ionizing radiation on learning have been studied over 50 years. However, it is still unknown how ionizing radiation affects a neuron network itself, although it has been reported that the radiation-induced learning and memory impairments are caused by suppression of hippocampal neurogenesis1). The nematode Caenorhabditis elegans is known as a model organism of which function is associated with individual neurons to some extent. The present study therefore aims to investigate responses of two functions of a neuron network induced by gamma irradiation, i.e. chemo-attraction to NaCl, and food-NaCl associative learning2) of C. elegans in the adult stage when neurogenesis does not occur.
The animals were irradiated with 60Co gamma-rays (0, 100, 500 and 1000 Gy). Chemo-attraction to NaCl was not significantly inhibited by gamma-irradiation (< 500 Gy). The decrease of chemo-attraction linked with food-NaCl associative learning was significantly enhanced than that of non-irradiated ones (100 – 500 Gy, i.e. at the dose range of no effects on chemo-attraction).
These results suggest that the sensitivity to gamma-rays is different between neural circuits related with chemo-attraction to NaCl and food-NaCl associative learning, even in the same neuron network.
References:
1) Raber et al., (2004) Radiat. Res. Vol. 162(1) 39-47
2) Saeki et al., (2001) J. Exp. Biol. Vol. 204 1757-1764
