[The effect of damage to the hypothalamic suprachiasmatic nuclei in rats on the restructuring of the dynamic indices of the cardiointervalogram induced by propranolol].

Daily variations in the heart rate were studied. Chronic treatment with propranolol attenuated the sympathetic tone only at night and promoted acrophase in the morning. The complete lesion of suprachiasmatic nuclei balanced the circadian rhythm of the heart rate variability and the effect of drug.