[Autoradiographic studies of the neurogenesis and morphogenesis of the cingulate region in the rat. I. Proliferation patterns in different pre- and postnatal stages].

The proliferation of the matrix-cells in the limbic cortex of 219 embryonic rats has been investigated by means of autoradiographs, after injection of tritiated thymidine at different stages of foetal life. The course of the labeling index indicates that matrix-cells represent a cell population in which cell multiplication is both rapid and continuous. Moreover the number of labeled cells decreases following the migration of labeled neuroblasts to another site. Because the beginning of migration retards after a division a proliferative compartment and a differentiating compartment were found in the subventricular and the ventricular zone. The migration appears in waves not before 24 hours after division of cells. We have found that, between the second and the third day and between the third and the fourth day after injection, migrating cells arise with 1/2 or 1/4 of the number of silver grains respectively. Cell division and migration both indicate in the brain a sequential nature; after each mitosis only one of the daughter-cells retains their proliferative capacity, the other becomes differentiated into neuroblast and leaves the proliferative compartment.