Abstract
We have demonstrated that the vestibular system has a significant role in the arterial pressure (AP) response during gravitational change. The vestibular system is known to be highly plastic. It has been well reported the plasticity of the vestibulo-ocular and vestibulo-spinal reflex, however, it is still unclear the plasticity of the vestibulo-cardiovascular reflex. The aim of the present study was to examine whether the hypergravity environment alters the AP response via the vestibular system in conscious rats. As the gravitational input, the linear acceleration was employed. The AP and renal sympathetic nerve activity (RSNA) during ± 1 G linear acceleration was measured in conscious rats reared under usual 1 G environment (n = 12) or 2 weeks 3 G environment (n = 8). Six directions of the linear acceleration were employed; i.e., tail-to-nose, nose-to-tail, left-to-right, right-to-left, ventral-to-dorsal and dorsal-to-ventral. The AP of the 1 G rat was increased by 22 ± 1 mmHg (tail-to-nose), 17 ± 1 mmHg (nose-to tail), 19 ± 1 mmHg (left-to-right), 20 ± 1 mmHg (right-to-left), 14 ± 1 mmHg (ventral-to-dorsal) and 16 ± 1 mmHg (dorsal-to-ventral). This pressor response was significantly attenuated in the 3 G rat. However, there was no significant difference in the pressor response during air jet stimulation between 1 G and 3 G rats. These results indicate that the AP response via the vestibular system was specifically attenuated by maintaining under hypergravity environment. [J Physiol Sci. 2008;58 Suppl:S183]
