NADPH-diaphorase activity in the paraventricular nucleus of the hypothalamus: distribution, coexiztence and functional implications

In mammals neurons of the hypothalamic para­ ventricular nucleus exhibir intense and selecrive sraining (mainly magnocellular component) for NAOPH-diaphorase. Several coexistcnces of this enzyme with neurobiological substances and func­ tional implications have been reponed. Additio­ nally, different experimental conditions such as salt loading, food deprivation, stress, lactation, hypophysectomy and hormonal treatments promo­ te changes in the expression of rhe enzyrne in the paraventricular nucleus. In the present paper xve analyze the inforrnation available about the distri­ bution of NADPH-diaphorase activity in the para­ ventricular nucleus, the coexistence with different bioactive molecules and its possible functional roles. \Xfe condude that 1.- There is a wiclespread expression of TADPH-cliaphorase activiry in the thrce different rypes of neurons located in rhe paraventricular nucleus (magno-, parvo- anclmediocellular (mes). However, the highest concen­p'alion of the neurons showing this activiry is situa­red at the level of the magnocellular component.2.- These NADPI-l-diaphorase neurons co-express neuropeptides and other neuroactive substances, although there is not el general correspondence with a specific onc suggesting that AOPH-cliap­ horase is not relared to general mechanisms invol­ ving rhese subsiances. 3.- NADPH-diaphorase acti­ vity in rhe paraventricular nucleus can be modulatcd hy differenr hormones and experimen­tal conditions. 4.- Basccl upon rhe foregoing, nitricoxide proclucing neurons in the paraventricular nucleus are an irnportant cellular population of rhis nucleus involved in multiple mechanisms, espe­ cially neuroendoerine funcrions. However, the exacr role of rhis messcnger molecule in rhe para­ ventricular nuclcus is not torally known.