Effects of Removed Carotid Sinus Nerves Upon the Brainstem PO2 Autoregulation in Conscious Rabbit

Effects of removal of bilateral carotid sinus nerves upon the brain P02 autoregulation in conscious rabbit were studied. Following intravenous injections of phenylephrine (PE) and nitroglycein (NG), baroreflex sensitivity (BRS) was measured from changes in R-R interval per unit changes in arterial blood pressure.The reflex heart rate response to blood pressure modulation was profoundly impaired by denervation of carotid sinus nerve, and brainstem PO2 autoregulation was disturbed only when blood pressure was elevated by PE injection. In contrast, tissue P02 of normal animal was well preserved. Furthermore, passive head up tilt (45 degrees) was performed in normal and denervated rabbits. After postural changes, the transient decreases of brainstem PO2 were observed in denervated animals. However, in normal animals, PO2 showed minimum changes for tilting.Thus, our findings suggested that vertigo attack would be occurred by the ishemia in the brainstem due to an impairment of BRS.