Postnatal Organellogenesis in Pyramidal Neurons in the Cerebral Cortex in Rats

Abstract

We report here quantitative structural and histochemical evaluation of the postnatal development of organelles in neurons in the inner pyramidal layer of the frontal cortex in rat pups aged 5, 20, and 45 days form birth (four animals of each age). Growth of the perikaryon was seen during postnatal ontogeny, along with the consistent development of organelles within neurons. With age there was a progressive increase in the number of mitochondria, which became more extended in shape. Mitochondria showed progressive increases in the number and lengths of cristae. These changes were accompanied by increases in the activities of mitochondrial marker enzymes SDH and NADHDH. On day 5 after birth, the neuron cytoplasm was dominated by free ribosomes and then by rough endoplasmic reticulum. Cistern size increased progressively. Golgi complexes were not yet formed on day 5 after birth, though they were present by day 20. Lysosome numbers and size increased significantly by day 20; the activity of the lysosomal marker enzyme acid phosphatase showed a similar pattern.