Fig. 14

Effects of sinoaortic denervation on Gz-induced hypotensions. Typical responses in arterial pressure at the level of the brain (brain AP) of baroreceptor-intact and -denervated rats with anti-G equipment exposed to +5.0 Gz acceleration for 15 s. Sinoaortic denervation (SAD) was performed by cutting bilateral aortic nerves and carotid sinus nerves with application of 10 % phenol [6, 24]. AP arterial pressure at the level of the rat heart, HR heart rate. Upper panels to confirm denervation, no reflexive HR response was observed even when hypertension was induced by intravenous bolus phenylephrine (PE) in SAD rats (Left baroreceptor-intact, Right baroreceptor-denervated). Lower panels acceleration of +5.0 Gz induced greater deceleration hypotension than acceleration hypotension in a baro-intact rat with anti-G equipment, whereas it produced significantly deeper acceleration hypotension to the similar level of the deceleration hypotension in an SAD rat with anti-G equipment. The data from nine rats resulted in a significant difference in acceleration hypotension but not in deceleration hypotension between in intact and SAD rats, indicating that greater deceleration hypotension may be caused by failure of baroreflex function in the deceleration phase [24]