[Circadian rhythms in the functional activity of rat brain capillaries]

Diurnal density of the capillary network and the activity of butyrilcholinesterase and alkaline phosphatase in the capillary wall of the rat medulla oblongata and mesencephalon have been studied. Maximum activity of butyrilcholinesterase has been stated to be in the day time (12--15 a. m.) and minimum--at night (24 p. m.). In the activity of alkaline phosphatase two peaks are noted: in the morning (9--12 a. m.) and in the evening (21 p. m.). Decrease in the activity of the two substances is observed at 24 p. m. Since these two enzymes participate, to a certain degree, in metabolic and barrier function of brain capillaries, a conclusion is made on diurnal fluctuations in the level of the brain capillary blood circulation. It is recommended to take into account the circadian rhythms of the capillary blood circulation while investigating brain capillary circulation in practice.