[Influence of chronic intermittent hypoxia on sympathetic nerve activity in rats and effect of the antioxidant Tempol].

ABSTRACT

OBJECTIVE: To study the role of sympathetic nerve activity during the development of hypertension resulting from chronic intermittent hypoxia, and whether or not elevated sympathetic nerve activity is related to oxidative stress, and to investigate the preventive effect and possible mechanism of Tempol. METHODS: Forty-eight male Wistar rats were randomly divided into 6 groups of 8 each, including normoxic control group (NC), intermittent hypoxia group (IH) and 4 treatment groups (IHT1, IHT2, IHN1, IHN2). Among the treatment groups, IHT1, IHT2 groups were treated with 10% Tempol 100 mg × kg(-1)× d(-1) by intraperitoneal injection before exposed to IH and on day 28 after exposed to IH respectively, while IHN1 and IHN2 groups were treated with NS as controls. RESULT: There was no statistic difference in artery systolic blood pressure (SBP) between IH group, IHN1 group [(114 ± 6) mm Hg, 1 mm Hg = 0.133 kPa], and IHN2 group [(128 ± 6) mm Hg, P < 0.05] at the end of 6(th) week. SBP in the all IH groups was significantly elevated compared with NC group (P < 0.05) and the baseline SBP (P < 0.05) except of the group IHT1. SBP in the 2 tempol treatment groups was lower than the NS groups [(138 ± 10) mm Hg, both P < 0.05], while SBP of IHT2 group was higher than the IHT1 group (P < 0.01). No significant changes were found in the NC group. There were no statistic difference of NE and E in plasma and MDA in adrenal gland tissues between IH groups, IHN1 group and IHN2 group. The levels in NE and E and MDA in the 2 tempol treatment groups were lower than the NS groups (P < 0.05 or P < 0.01), but those in the IHT2 group were higher than the NC group (P < 0.05 or P < 0.01) and IHT1 groups (P < 0.05 or P < 0.01). No significant difference were found between IHT1 group and NC group. CONCLUSION: CIH could generate ROS by causing oxidative stress, which results in elevated sympathetic nerve activity. This may be one of the important mechanisms for CIH-induced hypertension. Tempol may be useful for prevention and treatment of OSAS-induced hypertension.