Center for Medical Siences, Ibaraki Prefectural University of Health Sciences
Abstract
The distribution and cell morphology of the cells which contribute to the supra-ependymal plexus in the rat were studied by retrograde labeling technique using cholera toxin subunit B(CTB), as a tracer. After injection of CTB into the lateral ventricle, highly labeled profiles were seen in the supra-ependymal plexus, while tanycytes of the third ventricle and a large number of cells in the dorsal raphe nucleus were also strongly labeled. Ependymocytes, subependymal glial cells and a few neurons in the subfornical organ and the hypothalamus (including the paraventricular hypothalamic nucleus) exhibited l[?]ow levels of labeling. Labeled cells of the dorsal raphe nucleus were most commonly located in the caudal half of the nucleus. They formed two cell groups; as a ventral group near the medial longitudinal fascicle and the dorsal one just beneath the aqueduct. Labeled cells in the dorsal group extended their dendrites to dorsomedially or dorolaterally, while the dendrites of labeled cells in the ventral group were oriented dorsally and ventrally. Dorsally, dorsomedially or dorsolaterally oriented dendrites from both groups run just beneath the aqueduct. The results or the present study show that almost all of the cells of origin of the supra-ependymal plexus extend their dendrites toward the ependyma. We assume that this peculiar dendritic organization allows the cells to monitor the ventriculor milieu
