Radiation chemistry of the hippocampal brain slice

Abstract

The in vitro hippocampal brain slice is a 0.4 mm thick neural network that can be used to study brain responses to radiation and related injuries. This preparation is unique in that it responds to ionizing radiation within minutes after exposure without complications from changes in vascularity, blood flow, blood pressure, etc. Electrophysiological studies have shown that x- and γ-rays alter synaptic transmission and spike generation, elements of normal brain activity. To evaluate the role of hydroxyl free radicals ( ·OH) in these changes, slices were exposed to dilute H 2O 2 solutions. EPR spin trapping experiments verified that ·OH is produced. Neural responses, while similar, were not identical to those due to radiation, possibly because of a different distribution of ·OH. Although H 2O 2 is freely diffusible, it produces ·OH at specific sites where, e.g. iron reduces it. In contrast, x- and γ-rays produce ·OH more uniformly throughout the tissue. H 2O 2 may provide a better model for high-LET radiation where yields of radical products of water radiolysis are decreased and peroxide reactions predominate.