Monoamine metabolism in the developing rat brain and effects of ionizing radiation.

Neonatal X-radiation induces profound changes in monoamine metabolism in the developing CNS. NE and 5-HT concentrations increase 7 days post-radiation in all CNS regions undergoing rapid axonal growth and proliferation, but not in the region of the cell bodies from which the respective neurotransmitters originate. The increase in NE and 5-HT levels is accompanied by a concomitant increase in the rate of synthesis. While these changes are evident as late as 22 days of age, the monoaminergic systems revert to normal by maturity. It is suggested that these alterations reflect an imbalance in the density of nerve endings to the region where these terminate. These regions are immature at birth and cell proliferation, a process which is affected by X-radiation, is still occurring at the time of exposure.