内皮素对麻醉大鼠颈动脉窦压力感受器活动的影响

在麻醉大鼠隔离灌流颈动脉窦区条件下记录窦神经传入放电,观察内皮素（ＥＴ－１）对动脉压力感受器活动的影响。结果如下：（１）在颈动脉窦区灌流１ｎｍｏｌ／Ｌ ＥＴ－１时,压力感受器机能曲线向左上方移位,曲线的最大斜率（ＰＳ）增加,窦神经传入放电最大积分值（ＰＩＶ）增大。由此提示,这一剂量的ＥＴ－１对压力感受器活动有易化作用。（２）用１０ｎｍｏｌ／Ｌ ＥＴ－１灌流时,压力感受器机能曲线则向右下方移位,ＰＳ

Effects of endothelin on carotid baroreceptor activity in anesthetized rats

The effects of endothelin (ET-1) on carotid baroreceptor activity were examined in 33 anesthetized rats with perfused isolated carotid sinus by recording sinus nerve afferent discharge. The results obtained were as follows: (1) By perfusing with 1 nmol/L ET-1, the functional curve of carotid baroreceptor (FCCB) was shifted to the left and upward with increase of peak slope (PS), while the peak integral value of carotid sinus nerve discharge (PIV) was increased, indicating that the carotid baroreceptor activity was facilitated. (2) On the contrary, by perfusing with 10 nmol/L ET-1, FCCB was shifted to the right and downward with a decrease of PS and PIV. In response to perfusion with 100 nmol/L ET-1, FCCB was further shifted to the right and downward with a marked decrease of PS and PIV. These results showed that ET-1 at 10 or 100 nmol/L exerted an inhibitory action on the baroreceptor activity. (3) Selective ETA receptor blocker-BQ-123 (0.15 mumol/L) could abolish the inhibitory effects of ET-1 (10 nmol/L) on baroreceptor. (4) Preperfusing with KATP channel antagonist-glibenclamide (10 mumol/L) could also eliminated the effects of ET-1. All the above results suggested that ET-1 exerts the dual effects on baroreceptor, facilitation at low doses and inhibition at high doses. The later effect may be mediated by ETA through KATP channels.