Age related changes in the endocrine hypothalamus: I. Tanycytes and the blood-brain-cerebrospinal fluid barrier.

The fine structural organization of the floor of the third cerebral ventricle (dorsum of the median eminence of the hypothalamus) of 2 normal adult mice Fisher 344 rats was compared and contrasted with that of 2 aged rats 30 months old. Closely juxtaposed tanycytes (specialized ependymal cells) of normal young adults in the lower walls and floor of the third ventricle. In contrast, tanycytes in aged rats demonstrated significant intracellular separations, with only fine cytoplasmic processes remaining to interlink them. The phenomenon of mechanical separation between tanycytes in aged animals is discussed with respect to a potential impairment in the integrity of the blood-brain-cerebrospinal fluid barrier.