[Autoradiography of the neurogenesis and morphogenesis of the regio cingularis in the rat. II. Proliferation kinetics in the area praecentralis agranularis].

The proliferation of the matrix-cells in the Area praecentralis agranularis 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 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 betw-en the third and the fourth day after injection, migrating cells arise with 1/2 or 1/4 of the number of silver grains respectively. A comparison with the values of the Regio cingularis mesoneocorticalis (RICHTER and KRANZ 1978) indicates that no differences exist between the both regions. Cell division and migration both indicate in the brain a sequential nature; after each mitosis only one of the daughtercells retains their proliferative capacity, the other becomes differentiated into neuroblast and leaves the proliferative compartment.