Changes in autonomic control of the cardiovascular system in the Wistar audiogenic rat (WAR) strain

Abstract

We evaluated autonomic cardiovascular modulation and baroreflex control of heart rate (HR) in a particular epileptic rat strain, Wistar audiogenic rats (WARs). We studied spontaneous baroreflex sensitivity as well as reflex changes in HR evoked by phenylephrine/nitroprusside-induced changes in arterial pressure (AP). Atropine and propranolol were used to measure cardiac autonomic tone. AP and pulse interval (PI) variability analysis were performed in the time and frequency domains (FFT spectral analysis) to evaluate cardiovascular sympatovagal modulation in WARs. AP and HR were higher in WARs (109±2mm Hg and 366±9bpm) than in Wistar control rats (101±2mm Hg and 326±10bpm). The power of the low-frequency band of both AP and PI spectra, a marker of sympathetic modulation, was higher in WARs than in Wistar control rats. The high-frequency power of the PI spectra in normalized units, which is linked to cardiac vagal modulation, was lower in WARs. Both WARs and Wistar control rats had similar vagal tone (91±13bpm vs 94±11bpm, respectively), but sympathetic tone was higher in WARs (30±4bpm vs 14±4bpm). No differences were detected in the gain of evoked (1.32±0.1ms/mm Hg vs 1.35±0.2ms/mm Hg) or spontaneous (1.34±0.2ms/mm Hg vs 2.04±0.2ms/mm Hg) baroreflex sensitivity. The higher AP and HR and the autonomic imbalance (sympathetic predominance) in WARs might be associated with an increased risk of life-threatening cardiovascular events in this strain.