BACKGROUND: The paired vestibular end organs lie within the semicircular canal of the inner ear in the temporal bones. It plays a role on the control of posture through the vestibuloocular reflex and the vestibulo-spinal reflex. Motion sickness-like symptoms induced by the abnormal stimulation of the vestibular system suggested that the vestibular system participate in the autonomic nervous function. The present study was carried out to determine the role of the vestibular system on the control of blood pressure by way of the autonomic nervous system. METHODS: Blood pressure was measured by means of pressure transducer during stimulation of the vestibular system or following bilateral labyrinthectomies in Sprague-Dawley rats weighing from 200 to 300g. RESULTS: 1) Blood pressure was elevated by electrical stimulation of the vestibular nerve. 2) Also, the pressure was elevated when the vestibular system was excited or inhibited by rotatory stimulation or galvanic stimulation. 3) The pattern of elevation in blood pressure which induced by electrical stimulation of the vestibular nucleus showed a dynamic response at stimulation frequency of 200Hz and a static response at 50Hz. 4) Elevation of blood pressure induced by vestibular sitmulation was more inhibited following bilateral cervical sympathectomies than following bilateral vagotomies. 5) Decreasing the blood pressure induced by positional change of the body was reinforced following bilateral labyrinthectomies. CONCLUSION: These results suggest that the vestibular system plays a role on the control of blood pressure by way of the autonomic nervous system as well as on the control of posture, therefore, the vestibular system prevents blood pressure from decreasing by positional change of the body.
Animals ; Autonomic Nervous System ; Blood Pressure* ; Ear, Inner ; Electric Stimulation ; Posture ; Rats* ; Rats, Sprague-Dawley ; Reflex ; Reflex, Vestibulo-Ocular ; Semicircular Canals ; Sympathectomy ; Temporal Bone ; Transducers, Pressure ; Vagotomy ; Vestibular Nerve