Functional State of the Heart during Spontaneous Nonconvulsive Seizure Activity at Various Times of the Day.

Circadian peculiarities of HR regulation and functional capacities of the heart in WAG/Rij rats with genetically determined absence epilepsy are related to spike-wave activity of the brain. The number of spike-wave discharges (SWD) is maximum at night, early morning, and evening time and decreases to minimum at 08.00-16.00. At night, functional capacities of the heart are reduced and stress test at night induces ischemic changes in the myocardium at a lower functional load than in the daytime (low level of SWD activity). The decrease in the number of SWD and spike-wave index during the daytime contributes to the central mechanisms of autonomic regulation of the heart. However, these capacities are reduced against the background of increased seizure activity during nighttime.