[Adenosine facilitates carotid baroreceptor activity in rats]

The effects of adenosine (Ado) on the carotid baroreceptor were studied in 36 anesthetized rats with isolated carotid sinus perfusion by recording the sinus nerve afferent activity. The results obtained were as follows: (1) By perfusing the isolated carotid sinus with 75 mumol/L Ado, the functional curve for intrasinus pressure(ISP)-integral of sinus nerve activity (ISNA) relation was shifted to the left and upward with peak slope (PS) increased from (18.75 +/- 0.12)%/kPa to (22.21 +/- 0.11)%/kPa (P < 0.001) and the peak integral value (PIV) enhanced from (209.83 +/- 2.57)% to (239.17 +/- 1.75)% (P < 0.001), while the threshold pressure (TP) and saturation pressure (SP) were significantly decreased from 8.57 +/- 0.24 to 7.15 +/- 0.23 kPa (P < 0.001) and from 22.99 +/- 0.34 to 21.21 +/- 0.43 kPa (P < 0.01). By perfusing with high concentrations of Ado (125 and 175 mumol/L), the curves for ISP-ISNA relation were shifted to the left and upward further and the changes of the functional parameters such as PS, TP and SP were dose-dependent. (2) By pretreatment with 8-cyclopentyl-1,3-dipropylxanthine (0.134 mmol/L), a selective adenosine A1-receptor antagonist, the above mentioned effects of Ado on carotid baroreceptor activity were abolished. (3) The Ado-induced increase in sinus nerve afferent activity could be eliminated by pretreatment with KATP channel blocker glibenclamide (10 mumol/L). The above results suggest that Ado exerts a facilitatory action on the isolated carotid baroreceptor and such an action of Ado may be attributed to the opening of KATP channels, which is mediated by A1-receptors.