[K(ATP) channel opener facilitates carotid sinus baroreflex in anesthetized rats]

The effects of cromakalim (Cro), a K(ATP) channel opener, on the carotid baroreflex were studied in 32 anesthetized rats with perfused isolated carotid sinus. The results obtained are as follows. (1) By perfusing the isolated carotid sinus with Cro (10 micromol/L), the functional curve of the baroreflex was shifted to the left and downward, with a peak slope (PS) increasing from 0.36+/-0.01 to 0.48+/-0.01 kPa/kPa (P<0.001), whereas the reflex decrease in mean arterial pressure (RD) was increased from 5.78+/-0.14 to 7.87+/-0.12 kPa (P<0.001). Meanwhile, the threshold pressure (TP), equilibrium pressure (EP) and saturation pressure (SP) were all significantly decreased from 8.34+/-0.35 to 6.41+/-0.09 kPa (P<0.01), 12.71+/-0.25 to 11.78+/-0.24 kPa (P<0.01) and 24.89+/-0.25 to 22.56+/-0.16 kPa (P<0.001), respectively. Among the functional parameters of carotid baroreflex, the changes in RD, PS and TP induced by Cro were dose-dependent. (2) By pretreatment with glibenclamide (10 micromol/L), a K(ATP) channel blocker, the above effects of Cro on the carotid baroreflex were abolished. (3) The Cro-induced change in the baroreflex was enhanced by preperfusing with adenosine (125 micromol/L). On the basis of the above results, it is concluded that Cro facilitates the carotid baroreflex, an effect attributable to the enhanced stretch of baroreceptors by dilation of sinus wall as a result of K(ATP) channel activation.