Summary
The surface features of the ependymal lining of the habenular complex in rats, aged between three weeks and nine months, were studied by means of scanning and transmission electron microscopy.
The ependyma of the medial habenular nucleus is heavily ciliated, the cilia obscuring underlying substructure in SEM — preparations. On the habenular commissure most cilia are arranged in tufts. Cilia are provided with segmental indentations and occasional apical thickenings. Vesicular protrusions of the ependymal cytoplasm into the ventricular lumen and the frequent occurrence of homogeneous supraependymal globules were interpreted as signs of ependymosecretory activity of nucl. hab. med. Supraependymal cells are most numerous on the anterior and superior surface of the habenular commissure. Cells presenting features identical to Kolmer (epiplexus) cells were identified on the ventricular surface of nucl. hab. med. in one specimen showing degenerative changes of undetermined aetiology in the habenular nuclei. It is therefore suggested that such cells need not necessarily be restricted to the choroid plexus.
Supraependymal unmyelinated axons are particularly numerous on both nucl. hab. med. and commiss. hab. They make desmosome contacts (maculae adherentes) with the ependymal plasmalemma. Contacts presenting all features of typical synapses were not encountered. The vesicle population of the axonal profiles mainly comprises 35–50 nm translucent round vesicles besides small numbers of 60–100 nm dense-cored vesicles and large pleiomorphic vesicles. Most probably the axons belong to the well-established dense population of serotonergic axons in the dorsal part of the third ventricle.
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Cupédo, R.N.J. The surface ultrastructure of the habenular complex of the rat. Anat. Embryol. 152, 43–64 (1977). https://doi.org/10.1007/BF00341434
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DOI: https://doi.org/10.1007/BF00341434