Abstract

Objective: The vestibular system contributes control of blood pressure during postural changes through the vestibulosympathetic reflex. In the vestibulosympathetic reflex, afferent signals from the peripheral vestibular receptors are transmitted to the vestibular nuclei, rostral ventrolateral medullary nuclei, and then to the intermediolateral cell column of the thoracolumbar spinal cord. Physiological characteristics of the vestibulosympathetic reflex in terms of neurogenic and humoral control of blood pressure were investigated in this study.
Methods
Conscious rats with sinoaortic denervation were used for removal of baroreceptors in reflex control of blood pressure, and hypotension was induced by intravenous infusion of sodium nitroprusside (SNP). Expression of c-Fos protein was measured in the medial vestibular nuclei (MVN), rostral vestrolateral medullary nuclei (RVLM), and intermediolateral cell column (IMC) in T4-7, and levels of blood epinephrine were measured following SNP-induced hypotension.
Results
SNP-induced hypotension significantly increased expression of c-Fos protein in the MVN, RVLM, and IMC, also significantly increased level of blood epinephrine compared to normotensive control animals.
Conclusion
These results suggest that the vestibulosympathetic reflex regulates blood pressure through neurogenic control including MVN, RVLM, and IMC, also through humoral control including epinephrine secretion by the adrenal medulla following SNP-induced hypotension. The physiological characteristics of the reflex may contribute to basic treatment of impairment of blood pressure control during postural changes.

• Keywords: Vestibulosympathetic reflex;Hypotension;c-Fos protein;Epinephrine;Intermediolateral cell column