Ultrastructural changes in the ependymal lining of the median eminence following the intraventricular administration of catecholamine

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Abstract
Changes in the ependymal surfaces of the floor of the third ventricle and lateral recess have been studied in male rats by electron microscopy after the intraventricular administration of epinephrine or dopamine. In control rats the floor of the third ventricle has essentially a smooth contour interrupted only by occasional bleb‐like protrusions or microvilli. In the floor of the lateral recess this surface gradually becomes more irregular due to the appearance of increased surface modifications. A further increase in the number of complexly‐folded microvilli, pinocytotic vacuoles and coated vesicles occurs on the epen‐dymal surface of the roof of the lateral recess and adjacent ependyma. These morphological findings are consistent with the concept that the ependymal cells of the lateral recess may serve as important sites for the absorption of materials from the CSF.Increased numbers of bleb‐like protrusions were observed on the ependymal surface of the floor of the third ventricle five minutes after the intraventricular administration of either epinephrine or dopamine. The ependymal surface of the roof of the lateral recess also showed bleb‐like protrusions and a complexly‐folded microvillus border. Fifteen minutes after either the epinephrine or dopa‐mine administration all of the ependymal surfaces studied appeared as in control rats. The increase in bleb‐like protrusions noted in the floor of the third ventricle after the injection of epinephrine or dopamine are suggestive of a secretory process rather than a manifestation of an absorptive function in this region.