[Formation of structural and ultrastructural organization of striatum rat postnatal ontogenesis upon changes in their...

By light microscopy (by Nissl and Golgi), electron microscopy, and immunohistochemistry methods, formation of structure of the brain striatum dorsolateral part from birth to the 3-month age was studied in rats submitted to acute hypoxia at the period of embryogenesis. It has been established that hypoxia at the 13.5th day (E13.5) leads to a delay of neuronogenesis for the first two weeks of postnatal development as compared with control animals, while the majority of large neurons at this period are degenerated by the type of chromatolysis with swelling cell body and processes and lysis of cytoplasmic organoids. By the end of the 3rd week, shrunk hyperchromic or picnomorphic neurons with the electron-dense cytoplasm and enlarged tubules of endoplasmic reticulum and Golgi complex were also observed. An increased number of swollen processes of glial cells was detected in neuropil around degenerating neurons. By the 30th day as well as in adult rats there was observed destruction of mitochondrial apparatus, an increase of the number of lysosomes, and the appearance of bladed nuclei - signs of apoptotic cell death, which was also confirmed by an increased expression of proapoptotic p53 protein and its colocalization with caspase-3 in a part of neurons. Morphometrical analysis has shown a decrease of density of striatum cell arrangement and a change of ratio of different cell types in the rats submitted to hypoxia as compared with control group. At early stages of postnatal ontogenesis there was the greatest decrease (42.3% at the 5th day, 14.2% at the 10th day, p < 0.01) of the number of large neurons with the area more than 80 microm2. After 3 weeks of postnatal development the number of middlesize neurons (30-95 microm2) decreased (by 11.8-19.2%) as compared with control. The obtained data show that a change of conditions of embryogenesis (hypoxia) at the period of the most intensive proliferation of the forebrain neuroblasts leads to disturbances of the process of formation of the striatum nervous tissue. This can be the cause of delay of development and disturbances of behavior and learning observed in rats submitted to prenatal hypoxia.