CHANGES IN MEMORY ELECTROPHYSIOLOGY NEUROCHEMISTRY AND NEURONAL ULTRASTRUCTURE AFTER DEUTERON IRRADIATION OF BRAIN IN C57B1/10 MICE

Abstract— Changes in memory, electrocorticograms (ECoG), protein, DNA, RNA, neurotransmitters, enzyme activity and neuronal ultrastructure were examined after deuteron irradiationof the brain in C57B1/10 mice. Twenty animals served as sham‐irradiated controls, while three irradiated groups received a dose of either 500, 5000 or 10,000 rads covering an area of 9 × 5 mm over the dorsal surface of the brain and extending to a depth of 2 mm from the skull. The 10,000 rad group differed significantly in retention of spontaneous locomotor performance and dark maze exploration during a 16‐month post‐irradiation period. Desynchronization with an overall amplitude reduction of both spontaneous and light evoked ECoG was observed in the 10,000 rad group. There was a dose‐dependent decrease in protein, DNA and RNA content but not in their concentrations. Brain irradiation resulted in a significant change in content as well as concentration of 5‐HT and in acetylcholinesterase activity both per brain and per gram fresh weight. Morphologically, there was a significant reduction in brain and pituitary weight. Histochemical observations indicated a uniform and dose‐dependent reduction in vascular alkaline phosphatase activity and a selective decrease in staining for cellular DNA and RNA in different regions of the irradiated tissue of the brain. Electron microscopic comparisons of nuclear and cytoplasmic changes indicated serration of some nuclear membranes in the 10,000 rad group, accumulation of glycogen, numerous phagocytes and formation of multi‐lamellar intraneuronal membranes. Prominent synaptic changes were not observed in the remaining neurons within the irradiated tissue of the brain. From the multidisciplinary comparisons it was concluded that deuteron irradiation of the CNS can be used as another approach for relating changes in such unique functions as learning and memory to subcellular and cellular changes in specific regions of the brain. Copyright © 1968, Wiley Blackwell. All rights reserved