POSTNATAL ORGANELLOGENESIS IN PYRAMIDAL NEURONS OF RAT CEREBRAL CORTEX

Quantitative ultrastructural and histochemical assessment of postnatal organellogenesis in internal pyramidal layer neurons was performed on rat brain frontal cortex 5, 20, and 45 days after birth (4 animals of each age). Enlargement of perikarya and orderly development of neuronal organelles was found in postnatal ontogenesis. With age, the number of mitochondria progressively increased and they became more elongated, in parallel with the continuous growth of the amount and length of their cristae. This was accompanied by the increase of the activity of mitochondrial marker enzymes succinate dehydrogenase and NADH dehydrogenase. At postnatal Day 5, free ribosomes prevailed in the cytoplasm of neurons, while later granular endoplasmic reticulum became more prominent with a progressive growth of the length of its cisterns. The Golgi complex was not yet organized at postnatal Day 5, its formation was completed by Day 20. The content of lysosomes and their size increased considerably by Day 20; the activity of lysosomal marker enzyme acid phosphatase changed in a similar manner.

organellogenesis, pyramidal neurons, frontal cortex