Organization of the human paraventricular hypothalamic nucleus

The cyto- and chemoarchitecture of the human paraventricular hypothalamic n ucleus (Pa) was studied with the aid of three-dimensional computer reconstr uction. The adult human Pa is a vertically elongated structure that abuts t he wall of the third ventricle (3V) medially and is indented dorsolaterally by the descending fornix. Chemoarchitecture revealed the following five su bnuclei in the human Pa. The most prominent of these is the magnocellular s ubnucleus (PaM) occupying the ventrolateral quadrant of the Pa and comprise d of a concentration of large arginin-vasopressin (AVP)- and acetylcholines terase (AChE)-positive cells, and small calbindin (Cb)-positive neurons. Ro strally, the PaM is succeeded by the small anterior parvicellular subnucleu s (PaAP), which contains small AChE-, AVP- and tyrosin hydroxylase (TH)-pos itive cells. Dorsal to the PaM is found the dorsal subnucleus (PaD), contai ning large spindle-shaped TH-, oxytocin (OXY)-, and AChE-positive cells, as well as a population of small Cb-positive neurons. Abutting the wall of th e 3V and medial to PaM and PaD is the parvicellular subnucleus (PaP). The P aP contains small cells immunoreactive for corticotropin-releasing factor ( CRF), neuromedin K receptor (NK3), and nonphosphorylated neurofilament prot ein (SMI32). The posterior subnucleus (PaPo) is situated posterior to the d escending column of the fornix; it replaces all above-mentioned subdivision s caudally, and is a chemoarchitectonic amalgam that includes dispersed lar ge AChE-, OXY-, AVP- and TH-positive cells, as well as small NK3-, CRF-, SM I32- and Cb-immunoreactive neurons. The present findings suggest that the h uman PaM and PaD are homologues to the magnocellular subnuclei of the rat P a, whereas the human PaP and PaPo correspond to the rat medial parvicellula r and posterior subnuclei, respectively. J. Comp. Neurol. 423:299-318, 2000 . (C) 2000 Wiley-Liss, Inc.