Gamma Radiation (5-10 Gy) Impairs Neuronal Function in the Guinea Pig Hippocampus
ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD
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Guinea pigs were exposed to 5 and 10 Gy gamma radiation. Hippocampal brain slices were isolated 30 min. 1 day, 3 days and 5 days after irradiation or sham irradiation or sham irradiation and the electrophsio-logical characteristics of the neural tissue were evaluated. Both radiation doses elicited significant changes that were dependent on dose, dose rate and time. Synaptic efficacy decreased soon after exposure to 5 Gy at dose rates of both 1 and 20 Gymin. Recovery occurred by 5 days. Ten grays at 20 Gymin potentiated the postsynaptic potential 1 day after irradiation. By 3 days, synaptic efficacy was decreased and did not recover. The ability of the synaptic potentials to generate spikes was potentiated within 30 min after exposure to 5 Gy at 1 Gymin and persisted through 3 days, with recovery at 5 days. At the 20 Gymin dose rate, a similar potentiation did not result with 10 Gy and occurred only at 3 days after irradiation with 5 Gy. Rather, within 30 min and after 5 days, spike generation was significantly depressed by these exposures. Both synaptic efficacy and spike generation contribute to the net input-output relationship of the neuronal population. This relationship was profoundly decreased with 30 min with recovery at 1 day and subsequent decline with the higher dose rate in a dose-dependent manner. These persistent changes in neuronal function are likely to be a consequence of the actions of ionizing radiation on the physiological processes that influence the neuronal environment.
- Medicine and Medical Research
- Physical Chemistry