Morphological aspects of the hypothalamic-hypophyseal system

Summary The reaction of neural structures of the medial basal hypothalamus (MBH) to its complete deafferentation was studied in male rats by means of enzyme-histochemical and histoautoradiographic methods. Particular attention was paid to nerve cells of the arcuate nucleus and to the tanycytes. The metabolic activity of these cells increased upon the whole.According to the indices of metabolic activity in normal conditions and following deafferentation, the authors distinguish among the ependymal cells of the recessus infundibularis in rats, -tanycytes, which correspond to the ependymal lining at the level of the arcuate nucleus, and -tanycytes, which correspond to the ependyma of the median eminence. In normal conditions both were marked by a sufficiently high level of metabolism, which did not exclude the possibility of protein synthesis. Following deafferentation, -tanycytes seemed most reactive. The most active elements among the -tanycytes were the ependymal cells of the lateral part of the median eminence (¹-tanycytes).The metabolic peculiarities of the nerve cells of the arcuate nuclei and the tanycytes, revealed in normal conditions and after deafferentation, are discussed in connection with the modern concepts of the role of these cells in hypothalamic-hypophyseal transmission.