THE PARAVENTRICULAR AND SUPRAOPTIC NUCLEI OF FETAL AND NEONATAL OFFSPRING OF RATS TREATED WITH DEXAMETHASONE DURING GESTATION

We have. investigated the development and differentiation of the parav entricular (PVN) and supraoptic (SON) nuclei in 20-day-old male offspr ing (3- and 14-day-old pups) of rats treated with dexamethasone (Dx) ( 0.3 mg/kg b.w./day) from day 16-20 of gestation. The analyses were mad e in serial frontal hypothalamic sections by measuring the maximum dia meter (Dmax) and area of neurosecretory cell nuclei in five subgroups of PVN (anterior parvocellular and magnocellular, medial parvocellular and magnocellular and posterior magnocellular) at eight levels. Prolo nged Dx-treatment of pregnant rats resulted in a significant decrease of Dmax and the area of PVN neurosecretory cell nuclei of their offspr ing at levels 3, 4, 5, 6 and 7 where anterior and medial parvo cellula r subgroups of neurons were present or dominant. Morphometrical data w ere in accordance with the histological appearance of parvocellular ne urons where nuclei were visibly diminished. Dx-treatment of pregnant r ats resulted in a significant decrease of Dmax and the area of SON neu rosecretory cell nuclei of fetuses and 3-day-old rat pups. Our finding s about the differentiation of hypothalamic nuclei indicate that Dr-tr eatment of pregnant rats lowers the synthesizing activity of PVN and S ON neurosecretory neurons of fetuses and neonatal offspring.