RESUMO
Immunohistochemical method was used to investigate the morphology and distribution of the oxytocin immunoreactive (OXT-ir) neurons and their dendrites in the subependymal plexus (SEP) around the third ventricle (OXT-SEP). The OXT-ir neurons were of magnocellular neurosecretory type which often intercalated between the ependymal cells, their dendrites were generally long and straight and mostly paralleled to or traveled within the ependyma,some of them could protrude into the ventricle, and most of them appeared heavily vacuous and have a strong tendency of grouping into fascicles. The plexus was composed of dorsal and ventral parts, the former corresponding to the extent of the magnocellular paraventricular nuclei and was extensive and dense, the dendrites were well organized; the latter was more sparse. The cell bodies and dendrites within and between different parts might mix or contact with each other. The functional significance of the plexus is discussed.