Pre- and postjunctional effects of angiotensin II in hypertension due to adenosine receptor blockade

Abstract

Prejunctional facilitation of [3H]noradrenaline release induced by sympathetic nerve stimulation and postjunctional contractile effects of angiotensin II were studied in the mesenteric artery and vein of 1,3-dipropyl-8-sulfophenylxanthine (DPSPX)-hypertensive rats. Male Wistar rats received infusions of saline or DPSPX (90 microg/kg/h) i.p.. Blood pressure was determined by tail-cuff. The prejunctional effect of angiotensin II was similar in artery and vein preparations of control rats and was increased in DPSPX-hypertensive rats. In contrast, the contractile effect of angiotensin II was much more pronounced in the mesenteric vein than in the mesenteric artery of control rats and was markedly reduced in DPSPX-hypertensive rats. We conclude that (1) the increased prejunctional effect of angiotensin II may contribute to, while (2) the decreased contractile effect of angiotensin II may attenuate DPSPX-induced hypertension. This study also supports the hypothesis that pre- and postjunctional angiotensin II receptors are different.