1995 Volume 47 Issue 1-2 Pages 13-19
To investigate effects of irradiation on brain monoaminergic neurons, we measured the contents and synthetic rate of noradrenaline (NA), dopamine (DA) and 5-hydroxytryptamine (5-HT) in the cerebral cortex, brain stem and hippocampus of the rat brain one and eight weeks after 60Co irradiation (1.5 and 10Gy) to the head. With 1.5 Gy-irradiation, the NA and DA contents in the brain stem only increas ed over one week. By week g, these contents had decreased in the cortex while the 5-HT content in the brain stem and hippocampus increased. Neither one nor eitht weeks after the dose, the others were unchanged. With 10Gy-irradiation, the DA content in the brain stem increased but that in the cortex and 5-HT content in all the three regions decreased on day 7, and the rest was unchanged. In week 8, the NA, DA and the 5-HT contents in all the three regions decreased. Since the monoamine contents were markedly affected with 10Gy-irradiation, we measured accumulation of dihydroxyphenylalanine (DOPA)and 5-hydroxytryptophan (5-HTP) after NSD-1015 administration, which represents syntheses of catecholamines and 5-HT, respectively. In all brain regions tested, irradiation had no effect on the accumulation in week 8. Accumulation of 5-HTP decreased after irradiation on both day 7 and week 8 in all the brain regions except for the cerebral cortex on day 7. These results suggest that cobalt irradiation impairs monoaminergic neuronal activities in the brain through the inhibition of monoamine synthesis.
