Subfornical organ efferents enhance extracellular noradrenaline concentrations in the median preoptic area in rats

The present study was carried out to examine whether angiotensinergic pathways from the subfornical organ (SFO) regulate the noradrenergic system in the median preoptic nucleus (MnPO). Intracerebral microdialysis techniques were used to quantify the extracellular concentration of noradrenaline (NA) in the MnPO area. In urethane-anesthetized male rats, electrical stimulation (5-20 Hz, 0.6 mA) of the SFO significantly increased the NA concentration in the MnPO area, and the increase was significantly diminished by pretreatment with the angiotensin II (ANG II) antagonist saralasin (Sar; 5 mu g), into the third ventricle (3V). Injections of ANG II (5 mu g) into the 3V significantly enhanced NA release in the MnPO area. The data imply that the angiotensinergic pathways from the SFO to the MnPO may act to enhance NA release in the MnPO area. (C) 1997 Elsevier Science Ireland Ltd.