Abstract
We reported sinusoidal acceleration induced heart rate (HR) modulation synchronized to the acceleration frequency in case of human and rat. The synchrony may be caused by a sinusoidal fluid pressure change or by a vestibulo-cardiovascular reflex, however the detail was not well evaluated. We examined the contribution of the vestibular system using goldfish in water where the body fluid may not be directly affected by external acceleration due to the neutral buoyancy. The fish was subjected to linear and rotational accelerations with various frequencies and amplitudes in different postures. Two types of goldfish with and without vestibular function were also tested to verify the vestibular contribution. The off-centered rotation was applied in two different postures relative to the rotation vector keeping a constant maximum radial acceleration and varying the tangential acceleration. The synchrony was evaluated by cross correlation power spectra of HR. In case of linear acceleration fixing body in both horizontal and vertical positions, a synchrony was observed in the HR power spectrum at the acceleration frequency as well as the off-centered rotational stimulation. When the head was on the rotational axis, the synchrony was not observed in neither of two directions. The synchrony was diminished without vestibular function. It strongly implied that the input from vestibular system may play an important role in the heart rate variability. [J Physiol Sci. 2007;57 Suppl:S194]
