COEXISTENCE OF NADPH-DIAPHORASE WITH TYROSINE-HYDROXYLASE IN HYPOTHALAMIC MAGNOCELLULAR NEURONS OF THE RAT

The presence and distribution of NADPH-diaphorase (ND) neurons as well as tyrosine hydroxylase-immunoreactive (TH) neurons in the hypothalam us are well established. Previous studies have shown the coexistence o f ND with neuroactive substances such as calbindin, somatostatin, vaso pressin and oxytocin in neurons of this region of the brain. As the to pographical patterns of distribution of ND and TH coincide in many cas es, the aim of this study was to determine the possible coexistence of both substances in the main hypothalamic magnocellular nuclei of the albino rat. Histochemical-immunocytochemical double labelling was empl oyed on the same sections as well as a morphometric study. NADPH-diaph orase and tyrosine hydroxylase neurons were observed in all the nuclei under study (supraoptic, paraventricular and accessory nuclei), altho ugh most neurons showing the coexistence of both substances were mainl y located in the supraoptic nucleus, isolated neurons with double labe lling being found in the magnocellular parts of the paraventricular nu cleus and in same of the accessory nuclei. Although both substances ha ve previously been shown to be modified in hypothalamic neurons after osmotic stimuli, the range of functions of ND in the CNS is only begin ning to be understood. Further studies are needed to elucidate the fun ctional role that ND/TH neurons play in the nervous system.