Topographic organization of the karyometric response to neonatal castration of the male mouse in the paraventricular and ventromedial hypothalamic nuclei.

We have analysed the karyometric development of four topographic subdivisions of the paraventricular nucleus (rostral, medial, lateral and caudal) and three topographic subdivisions of the ventromedial nucleus (ventral, central and dorsal) of the hypothalamus in neonatally castrated male mice. Castration at birth produces a decrease of the nuclear sizes from the 10th to the 35th postnatal day, but after this age, no differences were detected in comparison with the sizes of the control male mice. Neonatal gonadal hormone deprivation also produces changes in the nuclear shape of the nuclei, that tend to be more spherical in both centres, as we could establish after the study of the form factor parameter (perimeter/area ratio). We have found differences in the response of both hypothalamic nuclei to neonatal castration and differences in the response of the topographic subdivisions of both of them.