Development of paraventricular nucleus (PVN) associated with immunoreactivity to tyrosine hydroxylase (TH) in the second half of gestation.

The aim of this study was to shed more light on the developmental characteristics of human paraventricular nucleus (PVN) and hypothalamus in general, using modern immunohistochemical techniques to detect the activity of tyrosine hydroxylase (TH) in the synthesis of catecholamine (CA). Fetal brains were examined at 12, 16, 20 and 23 weeks gestation. Immunohistochemical staining used for sections is a qualitative method for detection and distribution of the chosen protein. The amplification of positive signals was carried out using AVIDIN/BIOTIN technique. The first positive results were obtained at 16th week of gestation and immunoreactivity) grew with the advencement of gestation and that there was no homogenisation of immunoreactivity in some parts of the nucleus. The PVN showed to be an oval formation. nearly parallel with the lateral wall of the 3rd cerebral ventricle, where the upper apex of the nucleus is situated closer to the ependymal ventricular layer. There was an ascendant dorsal movement of the nucleus in the embryonic phase of hypothalamus development.