Changes in autonomic control of the cardiovascular system in the Wistar audiogenic rat (WAR) strain, an experimental model of epilepsy

Abstract

This study aimed to evaluate autonomic cardiovascular modulation and baroreflex control of heart rate (HR) in Wistar audiogenic rats (WAR), an epileptic rat strain. We studied spontaneous baroreflex (sequence method) as well as reflex changes in HR evoked by phenylephrine or nitroprusside‐induced changes in arterial pressure (AP). Blockers of autonomic receptors (atropine and propranolol) were used to measure cardiac autonomic tone. Pulse interval (PI) and AP variability analyses were performed by FFT spectral analysis to evaluate cardiovascular sympathovagal modulation. In WAR, AP and HR were higher (109±2 mmHg and 366±9 bpm) as compared with Wistar rats (101±2 mmHg and 326±10 bpm). Power in the low frequency (0.2–0.8 Hz) band, a marker of sympathetic activity, was higher in the AP and PI spectra of WAR than in those of Wistar rats. High frequency (0.8–3 Hz) power of PI spectra, which is linked to cardiac vagal modulation, was lower in WAR. Both strains showed similar vagal tone (91±13 vs. 94±11 bpm) but sympathetic tone was higher in WAR (30±4 vs. 14±4 bpm). No differences were found in the gains of evoked (1.32±0.1 vs. 1.35±0.2 ms/mmHg) or spontaneous (1.34±0.2 vs. 2.04±0.2 ms/mmHg) baroreflex sensitivity. Higher AP and HR are well known to be associated with sympathetic predominance and with threatening cardiovascular events, which are typical causes of sudden unexpected death in epilepsy. Support: FAPESP, CNPq.