[Participation of the tanycytes in the mechanisms of sex differentiation of the brain].

Enzymo-histochemical methods were applied to the study of the activity of a number of dehydrogenases of the specialized ependyma of the inferior-lateral walls and floor of the 3rd ventricle in rats of both sexes during the "critical" period of sexual differentiation of the hypothalamic region of the brain (the first week after birth). At the level of the arcuate nucleus (alpha2-tanycytes) and the medial portion of the medial eminence (beta2-tanycytes) the ependyma was characterized by similar metabolic activity indices in ratlings of both sexes at the decisive periods of the "critical" period (the 3rd, 5th, 7th days after birth). The metabolic activity was reduced on the 5th day in the cells of animals of both sexes. At the critical period the ependyma of the lateral portions of the median eminence (beta1-tanycytes) displayed marked sexual differences in the activity of the enzymes under study. On the 5th day beta1-tanycytes of male rats showed a reduction and of female rats - an elevation of the metabolic activity. The results obtained permit to suppose that beta1-tanycytes participated in the mechanisms of sexual differentiation of the brain.