[Neo and postnatal development of the cerebral cortex in mice. Ultrastructural study].

Maturation in the Purkinje cell (Pk) of the cerebellar cortex of developing mice (from birth up to weaning) was investigated by structural and especially ultrastructural studies. In comparison to the adult neuron, four developmental stages were identified by studying selective morphological features (shape and size of the Pk, neuronal environment) as well as specific characteristics of neuronal constituants, particularly the "nucleus-ribosome system". The stages are: early, intermediate and late neuroblasts and young neuron. The neuronogenesis of the Purkinje cell can be summarized as follows: (a) the nuclear maturation occurs early in the development and markedly preceeds that of several organelles in the perikaryon; (b) the cytoplasmic maturation extends gradually until the young neuron state was reached. Some structures such as the granular mass and the "spotted body" in the nucleus, the nuclear envelop including its two membranes, and the ribosomal components either free or attached to the Endoplasmic Reticulum seem to exert an important role during neuronal development. Maturation processes in the Purkinje cell are generally similar in both mouse and rat and, except for some morphological and/or chronological variables, comparable in others developing nerve cells. This model of neuronal maturation is used alone or in comparison to another model of neuro-behavioral evolution which was established concommitantly. Both of these models reveal to be very useful for the evaluation of the effects induced in the developing animal following the administration of neuropsychotropic drugs such as Hallucinogens and Narcotics.