Angiotensin II-norepinephrine relationship in the central nervous system

Abstract

The effects of angiotensin II (All) and bilateral nephrectomy on [³H] norepinephrine (NE) uptake in hypothalamus and medulla oblongata were studied in male rats. The endogenous NE content in hypothalamus increased 4, 24 and 48 h after nephrectomy with a simultaneous decreasing of plasma renin activity. Intraventriculary infused [³H] NE uptake increased in hypothalamus and medulla oblongata of nephrectomized animals in cytoplasmatic compartment as in granular stores, while it decreased in hypothalamus of All-infused animals. [³H] NE metabolites radioactivity decreased in nephrectomized animals if they are compared with All-infused ones. These changes were independent of systolic arterial pressure that was not modified in none of the groups. The study of the ratio granular/cytoplasmatic [³H] NE and metabolites radioactivity shows that All probably acts on cellular membrane uptake of NE. The modification of metabolites/NE ratio in both stores would be due to All action on MAO activity. The effects of All and nephrectomy on [³H] NE uptake can explain the inverse relationship between circulating All levels and NE content in the central nervous system (CNS).