NITRIC-OXIDE SYNTHASE INCREASES IN HYPOTHALAMIC MAGNOCELLULAR NEURONSAFTER SALT LOADING IN THE RAT - AN IMMUNOHISTOCHEMICAL AND IN-SITU HYBRIDIZATION STUDY

Magnocellular hypothalamic neurons of the paraventricular (PVN) and su praoptic (SON) nuclei have been shown to contain a wide variety of mes senger molecules in addition to vasopressin and oxytocin, including th e nitric oxide (NO)-synthesizing enzyme (NOS). In this paper we have i nvestigated the effects of salt loading on the expression of NOS by me ans of immunohistochemistry and in situ hybridization. The results sho w an increase in the number of NOS-immunoreactive (IR) neurons both in the PVN and the SON after 5 and 14 days of salt loading. Several of t hese neurons were double labelled with vasopressin antiserum. In situ hybridization showed a marked increase in the number of neurons expres sing NOS mRNA and a stronger signal in individual neurons. The present results suggest a role for NO in the magnocellular hypothalamic syste m after salt loading.