Central AII evokes a normal sodium appetite in the Fischer rat, but its low spontaneous sodium intake may be related to reduced excitation and increased inhibition in septo-preoptic AII neurons

Abstract

Fischer rats show a low or absent basal salt appetite and a reduced intake of salt solutions in response to peripherally administered angiotensin II (AII) when compared to other strains. We investigated spontaneous sodium intake, and sodium intake after intracerebroventricular (i.c.v.) AII and losartan, and septo-preoptic neuronal responses to AII and losartan, in age-matched male Fischer and Wistar rats. Spontaneous intake of 1.8% NaCl was lower in Fischers, but i.c.v. injection of 10 pmol AII produced similar 2 h intakes in a 2 h test period. Iontophoretic application of AII and losartan onto neurons in the septo-preoptic continuum revealed differences between the two strains of rat. In the Fischer rats only 11% of the spontaneously active neurons were sensitive to locally applied AII compared to approximately 30% in the Wistar. Local application of losartan produced neuronal inhibition in Fischer rats but neuronal excitation in Wistars. The central AII system appears to be regulated differently in these two strains, and may be related to the differences in their spontaneous sodium intake, but not to AII aroused sodium appetite.