Activation of the subfornical organ enhances extracellular noradrenaline concentrations in the hypothalamic paraventricular nucleus in the rat

Experiments were carried out to investigate whether angiotensinergic efferent pathways from the subfornical organ (SFO) regulate the noradrenergic system in the region of the hypothalamic paraventricular nucleus (PVN), Intracerebral microdialysis techniques were utilized to quantify the extracellular content of noradrenaline (NA) in the PVN area. In urethane-anaesthetized male rats, electrical stimulation (5-20 Hz, 600 CIA) of the SFO significantly increased the NA concentration in the region of the PVN, and the increase was significantly prevented by pretreatment with the angiotensin II (AAIG II) antagonist saralasin (Sar, 5 mug), into the third ventricle (3V), Injections of ANG II (5 mug) into the 3V significantly enhanced NA release in the PVN area. These results suggest that the angiotensinergic pathways from the SFO to the PVN may act to enhance NA release in the region of the PVN, (C) 2001 Elsevier Science Inc.