Alterations of Heart Rate Variability by Vestibular Stimulation in Rabbits

ABSTRACT

BACKGROUND: There is a substantial evidence that anatomical connections and functional interactions exist between vestibular and autonomic systems. The nature of these interactions, however, is complex and has not been fully defined. Heart rate variability (HRV) was used to investigate the physiological role of the vestibular system on control of heart rate. METHODS: HRV including mean, standard deviation, coefficient of variation (CV), power spectrum was analyzed from R-R intervals of ECG during vestibular stimulation in rabbits. RESULTS: Urethane anesthesia increased heart rate and maintained regular R-R intervals, however, low frequency region/high frequency region (LF/HF) was not changed. In anesthetized rabbits, electrical stimulation of the vagus nerve decreased heart rate and decreased LF/HF by increasing HF. On the contrary, electrical stimulation of the cervical sympathetic nerve increased heart rate and increased LF/HF by increasing LF. Atropine, cholinergic blocker, increased heart rate and increased LF/HF by reducing HF, and propranolol, beta-adrenergic blocker, decreased heart rate and decreased LF/HF by reducing LF. In unanesthetized rabbits, stimulation of the vestibular system induced by rotation or caloric increased heart rate and increased LF/HF by increasing LF. Also electrical stimulation of the vestibular nerve produced the same effects as rotation or caloric in anesthetized rabbits. CONCLUSION: These results suggest that stimulation of the vestibular system increased heart rate not by inhibiting the parasympathetic nerve but by activating the sympathetic nerve.