Enhanced monoamine release in the median preoptic area following reduced extracellular fluid volume in rats

The role of monoaminergic neural inputs to fluid regulatory systems in the median preoptic nucleus (MnPO) was investigated by examination of monoamine metabolism during reduction of systemic extracellular fluid volume in freely moving rats. Extracellular fluid volume was decreased iso-osmotically by subcutaneous polyethylene glycol (PEG), and extracellular noradrenaline (NA), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) were measured using intracerebral microdialysis techniques. PEG treatments significantly increased NA, DA and DOPAC release in the MnPO area. The results suggest that monoaminergic neural systems in the region of the MnPO are important in the control of extracellular fluid balance.