[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.