[The characteristics of the effect of anaprilin on the indices of the rat cardiac intervalogram at different phases of the circadian cycle].

At night a more effective attenuation of sympathetic activity by acute and chronic propranolol was observed. Single use of the drug in other daytime was accompanied by irregular changes in the neuronal control of heart activities. This irregularity was intensified after repeated treatment of beta-adrenoblocker and led to the stable increase of the sympathetic tone in the morning and day hours.