CHANGES IN THE NUCLEOLAR ORGANIZER REGIONS IN THE TUBEROMAMMILLAR REGION AFTER DEHYDRATION

The existence of efferent connections between tuberomammillary (TM) an d the supraoptic (SON) nuclei led us to study the morphological change s at these levels during dehydration induced in rats by repeated admin istration of hypertonic saline. The dehydration effects are evaluated by three parameters: nucleus area, argyrophilic nucleolar organizer re gions (Ag-NOR) area, and mean number of Ag-NORs. These parameters refl ect the level of transcriptional activity of the rRNA genes, which in turn is closely related to the protein synthesis activity of the cell. The technique used is argyrophilic staining which labels the nucleola r organizer regions (NORs) of the nucleoli in the neurons and their ar ea, permitting their quantification with an image analysis system. The statistical analysis reflects the sensitivity to dehydration of these structures at TM level. Our results support the regulatory role of va sopressin secretion by SON through the histaminergic pathways arising from TM in rat dehydration processes.