PARTIAL COEXISTENCE OF NADPH-DIAPHORASE AND ACETYLCHOLINESTERASE IN THE HYPOTHALAMIC MAGNOCELLULAR SECRETORY NUCLEI OF THE RAT

Co-localization of NADPH-diaphorase (ND) and acetylcholinesterase (ACh E) activities were explored in the magnocellular secretory nuclei of t he rat hypothalamus by means of a double histochemical staining of the same sections. Partial co-existence was found in all the nuclei studi ed (paraventricular, supraoptic, fornicals and circular nuclei). No pa rticular location of the neurons expressing both markers was found, al though in the paraventricular nucleus all of them (ND+, AChE+ and neur ons expressing both markers) were preferentially located in the magnoc ellular subdivisions whereas in the parvicellular ones only some neuro ns belonging to all three types were detected, mainly located in the p eriventricular and medial subdivisions. The lowest degree of co-existe nce was found at the level of the main magnocellular nuclei (supraopti c and paraventricular) when compared with the accessory magnocellular nuclei, especially the posterior fornical and the circular nuclei. The se results extend previous data on the chemical nature of the neurons producing nitric oxide in the neurosecretory nuclei and the possible f unctional role of this atypical messenger in the hypothalamus. (C) 199 8 Elsevier Science B.V. All rights reserved.