Experiments on 35 rabbits were made to study the time course of the function of the dorsal hippocamp, reticular formation of the midbrain, ventromedial hypothalamus, caudate nucleus and anteromedial thalamus in the course of prolonged adaptation to exercise and during deadaptation. It was determined that the most considerable changes in excitability and brain blood circulation were recorded within the first 10 days of exercise. From the 20th day of the experiment, abnormalities in the function of the structures under study, except those in the hypothalamus, got stabilized, which is regarded as adaptive reaction. In the course of adaptation the periodicity of the function of the brain structures was defined.