急性低氧下中枢加压素对循环活动的效应

ROLE OF CENTRAL VASOPRESSIN IN THE MAINTENANCE OF CARDIOVASCULAR ACTIVITIES DURING ACUTE HYPOXIA

为了解中枢加压素是否参与了低氧下循环活动的维持,本实验在同步监测麻醉大鼠血压(BP)、心率(HR)、左、右心室压(LVP,RVP)及其dP/dt的条件下,观察侧脑室注射(icv.)加压素V_1-、V_2-受体拮抗剂(各4μg)及同体积人工脑脊液(ACSF)(8μl)三组不同处理大鼠在低氧下循环指标的变化。于侧脑室注射药物10min后,让大鼠吸入含氧9％的氮氧混合气体15min,然后复氧。实验中观察到三组大鼠在低氧期间,循环活动各指标均下降。但icv.V_1-受体拮抗剂一组大鼠MBP,HR,左心室压峰值(LVSP)、左心室压力变化率最大值(LV+dp/dt_(max))等循环指标下降幅度显著大于对照组(P<0.01);复氧后两组间循环指标差异逐渐消失。常氧下icv,4μg V_1-受体拮抗剂及8μl ACSF对循环活动无影响。常氧下icv.V_2-受体拮抗剂导致大鼠HR,MBP,LVSP,LV+dp/dt_(max)出现一过性升高,但在低氧、复氧期间,该组与对照组循环活动各指标间无显著性差异。上述实验结果提示低氧应激期间,中枢内源性AVP对大鼠循环功能的维持具有重要作用。该效应是通过其V_1-受体介导的,与其V_2-受体无关。在正常情况下,中枢AVP对心血管活动无紧张性影响。

To investigate whether central vasopressin play a role in the maintenance of cardio-vascular activities of rats exposed to acute hypoxia, blood pressure, heart rate, pres-sures of left and right ventricles and their dp/dt were monitored in rats anesthetizedwith urethane. The rats were divided into three groups, each of which received intrac-erebroventricular injection (icv.) of V_1--and V_2--vasopressinergic antagonists (4 μg,each) and equivolumetric vehicle (8 μl, served as control group). Ten min after icv.three groups of rats were exposed to acute hypoxia (9% O_2 in N_2) for 15 min beforereoxygenation. During hypoxia, MBP, HR, LVSP and LV+dp/dt_(max) of V_1--antago-nist treated group decreased more significantly than those of the control group (P<0.01). After reoxygenation there were no significant differences between both groups.V_1--antagonist and the vehicle had no detectable effect on the cardiovascular parametersduring normoxia. Although icv. V_2--antagonist caused a transient augmentations of HR,MBP, LVSP and LV+dp/dt_(max)except for RVSP and RV+dp/dt_(max), there were no sig-nificant differences in cardiovascular activities between V_2--antagonist treated group andcontrol group during hypoxia and reoxygenation. These results indicate that central endogenous vasopressin play an important role inthe maintenance of cardiovascular activities during hypoxia via its V_1--receptor withoutinvolving V_2--receptor. The central vasopressin does not have a tonic effect on cardiovas-cular activities under normal conditions.