Abstract:

The development of cerebral cortex neurons has been studied in different stages of pre- and postnatal periods of rats. In order to show the neuronal processes, the Golgi-Cox impregnation technique was used. The first neuronal process development was observed in the cranial and caudal poles of the cerebral cortex during the 15th prenatal day and continued spreading from the lateral regions and poles towards the dorsocentral regions of the hemispheres. The cells which showed the first impregnation in the cerebral cortex, were bipolar cells and their bodies were located in the deep regions of the hemisphere wall. Primitive multipolar cells, which were seen in the superficial regions on the 17th prenatal day, dispersed to the deeper regions during the following days of gestation. The neurons showing impregnations formed cell groups during the 19th prenatal day. These cells were arranged on an axis; whose perikaryons were touching each other. At the beginning of the postnatal period, they often appeared to be in the deeper regions, laminae V-VI of the cortex, later they were observed in the upper regions. Probably, a "starter cell" created cellular inductive effects, resulting in these celular accumulations. After birth, cells separated from these groups according to the maturation level of their cellular and neuropilic contents, cerebral growth and the increase in number and length of neuron processes. As a result, in the course of the prenatal development of the cerebral cortex, consisting of cell proliferation and migration, we observed differentiation and maturation activities. The periods, in which differentiation and maturation occur, are predominantly late prenatal and postnatal periods. In addition, functionally related cells differentiate and mature in the same cell groups.

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