Studies on the distribution of vasopressin-immunoreactive neuronal perikarya and their fibers in the hypothalamus of Tupaia belangeri.

The distribution of vasopressin (VP)-immunoreactive neuronal perikarya and its fibers had been studied in the hypothalamus of Tupaia belangeri using the avidin-biotin complex (ABC) immunocytochemical technique. VP-immunoreactive neurons were found in the hypothalamic paraventricular nucleus (PVN), supraoptic nucleus (SON), accessory supraoptic nucleus (ASN), hypothalamic lateral nucleus (HLN), perifornical nucleus (PFN) and ansa peduncularis (AP) but not in the suprachiasmatic nucleus (SCN). VP neurons of the rostral PVN could be divided into three subnuclei and the caudal PVN could also be divided although not so distinctly into four subnuclei. The VP-immunoreactive neuronal perikarya of SON were divided into three parts, i.e., medioventral, mediodorsal and laterodorsal. Three types of VP neuronal perikarya, i.e., large, medium and small cells, existed in PVN and SON. Between PVN and SON, there were a large number of VP immunopositive nerve fibers. In addition, there were numerous immunopositive fibers projecting into the infundibulum and the neurohypophysis. VP-immunoreactive-positive products localized in the large granular vesicles and on the rough-surfaced endoplasmic reticulum could be seen under electron microscope.