[Study of the hypothalamus of neonatally castrated rats by the karyometric method].

The sensitivity of different hypothalamic regions to the effect of androgens has been studied during the period of the brain sex differentiation. The castration of animals during the first week of life was shown to result in the marked increase of size of the neuron nuclei in the preoptic, suprachiasmatic, arcuate and ventromedial nuclei of the hypothalamus; the size of neuron nuclei in the dorsomedial nucleus suffered no changes. The dynamics of size of the cell nuclei was followed in different hypothalamic regions with respect to the time of castration.