Wistar rats were exposed to 10, 20 and 40 sGy of gamma-irradiation. Maximal activity of 2-oxoglutarate- and succinate dehydrogenases, as well as of aspartate-2-oxoglutarate and pyruvate-2-oxoglutarate in the brain tissue was measured within 30 days after the exposure. Dehydrogenase activity was measured in the brain cortex, limbic system and in the cerebellum; transaminase activity was determined in the brain cortex, diencephalic zone and in the hypophysis. It was found that small doses of irradiation resulted in an oscillating increase of dehydrogenase activity with a decrease of the amplitude by the 30th day of the experiment. As the dose of irradiation increases, the periods of normal activity change into phases of inhibition of dehydrogenase action, the period of oscillations diminishes. Transaminase activity, as a rule, changes in a phase in a reversible manner as compared with dehydrogenase activity. These observations are discussed from the point of view of structural relations between these two systems in the intramitochondrial supramolecular structures, the so-called metabolons.