Morphometric study on the development of magnocellular neurons of the supraoptic nucleus utilising immunohistochemical methods.

Vasopressin (VP)- and oxytocin (OXY)-producing neurons, components of the rat supraoptic nucleus, have been located with immunohistochemical methods, with the purpose of studying their morphofunctional characteristics during different phases of life (embryonic, juvenile, adult and senile). To carry out this study, an IBAS I (Kontron) computerised image analyser has been utilised. The hormone VP is first detected in the neuronal cytoplasm of 21 days old rat embryos and the hormone OXY appears in the neuronal cytoplasm later, in the newborn phase. The neuronal area with a positive reaction for the two neurohormones has been evaluated and it has been found that the quantity of reaction substance is proportional to the age. In the adult period, VP neurons possess a reaction area (198 microns 2) greater than that of OXY neurons (153 microns 2). In the SON, there are two neuronal shapes, fusiform and round; these shapes coexist in both hormonal types of neurons. Until Day 15 of postnatal development, the SON neurons are intermixed in the interior of the nucleus but in this period a neuronal redistribution is initiated. In the adult phase, OXY neurons are situated preferentially in the anterior, posterior and dorsal parts and VP neurons in the ventral and posterior parts, with both neurons being present in the intermediate part of the SON.