Depressive Effects of Chronic Intermittent Hypobaric Hypoxia on Renal Vascular Hypertension through Enhancing Baroreflex

Baroreflex function plays a critical role in the maintenance of cardiovascular homeostasis and is impaired in different types of hypertension in both human and animals. Chronic intermittent hypobaric hypoxia (CIHH) facilitates baroreflex in anesthetized rats. The aim of the present study was to investigate the effect of CIHH on arterial blood pressure (ABP) and baroreflex function in renal vascular hypertension (RVH) rats. Adult male Sprague-Dawley rats were randomly divided into four groups: Sham-operated (SHAM), RVH, CIHH treatment (CIHH), and RVH plus CIHH (RVH+CIHH) groups. RVH was induced by the 2-kidney-l-clip method. CIHH rats experienced 28-day (6 h per day) hypobaric hypoxia simulating 5,000 m altitude in a hypobaric chamber. Renal sympathetic nerve activity (RSNA), ABP and heart rate (HR) were recorded. Baroreflex was elicited by intravenous infu-sion of phenylephrine (PE, 25 g/kg) and sodium nitroprusside (SNP, 10 lug/KG), respectively. Baroreflex curves were plotted by using RSNA or HR v.s. mean arterial pressure (MAP). The systolic ABP measured by tail-cuff method was significantly higher in the RVH rats compared with the SHAM rats. Furthermore, RSNA-MAP baroreflex curves shifted to the right and upward with a decrease in baroreflex gain (Gmax) in RVH rats. CIHH treatment significantly decreased systolic ABP in RVH rats to the level in the SHAM rats and shifted RSNA-MAP baroreflex curves to the left and downward with a normalized Gmax. These data suggest that CIHH treatment produces an anti hypertensive effect in RVH rats, likely due to facilitating baroreflex function. Thus, CIHH represents a potential novel therapeutics to treat hypertension.