M 3 cholinoceptors and P 2y purinoceptors mediating relaxation of arteries in spontaneously hypertensive rats at prehypertensive stages

Abstract

Muscarinic eholinoeeptor and purinoceptor subtypes were determined in femoral and mesenterie artery strips from spontaneously hypertensive rats (SHR) at prehypertensive stages. Acetylcholine (ACh), earbachol and oxotremorine induced endothelium-dependent relaxations during contractions evoked by 5-hydroxytryptamine. The order of relative potency of the agonists was ACh > earbachol = oxotremorine in the prehypertensive SHR and Wistar Kyoto rats (WKY). Schild plot data for muscarinic eholinoeeptor antagonists obtained with earbachol or oxotremorine as agonist indicated that the arteries of prehypertensive SHR and WKY possessed M 3 cholinoceptors mediating relaxation. The relaxation responses of the prehypertensive SHR and WKY arteries to ATP were inhibited by reactive blue 2 but not altered after P 2x purinoceptors had been desensitized by α,β-methylene ATP, which suggests that the arteries possessed P 2y, purinoceptors mediating relaxation. The responses of the femoral and mesenteric arteries from prehypertensive SHR to ACh, earbachol and ATP were similar to those of WKY arteries, although the response of the prehypertensive SHR artery to oxotremorine was significantly increased compared to that of the WKY artery. The results suggest that M 3 eholinoeeptor- and P 2y purinoceptor-mediated relaxations are not changed in prehypertensive SHR arteries as compared to those in WKY arteries.