Morphology of the ependymal lining of the rabbit third ventricle following intraventricular administration of synthetic luteinizing hormone‐releasing hormone (LH‐RH): A scanning electron microscopic investigation

The morphology of the ependymal surface of the rabbit third ventricle was studied following intraventricular injections of an ovulatory dose of synthetic LH‐RH. Identically treated rabbits that received injections of saline, only, served as controls. Animals from both groups were killed 5 minutes and 15 minutes after the injections. The ependyma of the dorsolateral ventricular wall and transitional zone maintained a constant appearance from animal to animal regardless of treatment or time of autopsy. The uniformly non‐ciliated ependyma of the ventrolateral wall and floor (infundibular and mammillary recesses) of the ventricle, however, not only exhibited an appearance quite distinct from either the dorsolateral wall or transitional zone, but also exhibited a transient responsiveness to LH‐RH treatment. In the controls, most ependymal cells of this region bulged conspicuously into the ventricle. Numerous pleomorphic knob‐ of bleb‐like protrusions and occasional microvilli characterized their apical membranes. In contrast, marked changes were seen in the character of the ependymal surface of animals killed five minutes following LH‐RH administration. These changes, which principally took the form of numerous irregular microvillous eruptions of the apical membrane, pervaded the rostrocaudal extent of the infundibular and mammillary recesses. Equivalent regions of the ependymal surface in animals killed 15 minutes after LH‐RH administration, however, were similar to those of the controls. These transient morphological changes observed in the ependymal surface of the ventrolateral wall and floor of the ventricle five minutes after LH‐RH injection may reflect structural modifications associated with absorption of the hormone across the ependymal‐CSF interface.