Cytoarchitecture And Adult Neurogenesis In Telencephalon Of Scincella Tsinlingensis

Adult neurogenesis is a hot research topic in the field of life science. It is a dynamic controlled process, and easily affected by various factors. All mammals, including humans that have studied, possess the ability of neurogenesis in their lifetime, but its difference among different species. To investigate the adult neurogenesis of reptiles, has important significance in the research of the regularity and evolution of adult neurogenesis in non mammalian vertebrate. In the present study, we used Scincella tsinlingensis as materials. Gross anatomy, conventional histological and transmisson electron microscopy were used to observe and describe the histomorphology of telencephalon. Intraperitoneally injectioned with BrdU, immunohistochemical and laser scanning confocal microscopy were used to count and analysis the distribution and quantity of neural stem cells, characterization and seasonal differences of adult neurogenesis.1. The telencephalon of adult S. tsinlingensis showed elongated shape, it can be divided into the telencephalon, diencephalon, mesencephalon, cerebellum and medulla oblongata. Telencephalon consisted of hemicerebrum and olfactory bulb. Mesencephalon is well developed, has an optic chiasma in its belly. Medulla oblongata has an obvious bending, connected to the spinal cord.2. The telencephalon of S. tsinlingensis was divided into the main and accessory olfactory bulb, olfactory peduncle, anterior olfactory nucleu, rostral, pre-commissural, post-commissural and caudal telencephalon, has made great progress than amphibians. Compared with mammals and birds, S. tsinlingensis' cerebral cortex is thinner, dorsal cortex is the thinnest, and gradually thicken when extended to the medial and lateral cortex. The cortex is composed of the cell layer, the inner and outer plexiform layers. Hemisphere lateral ventricle with sulcus, and the surface of the lateral ventricle wall is the ependyma. In addition, cerebral substance contained dorsal ventricular ridge, spetum, striatum and hypothalamus. Post-commissural telencephalon has nucleus sphericus. Main-olfactory bulb can be divided into 7 layers, olfactory nerve fibers layer, glomerular layer, external plexiform layer, mitral layer, internal plexiform layer, granular layer and ependyma layer. The number of neurons in the medial cortex was the most, including multipolar cell, bitufted cell and monotufted cell.3. In olfactory bulb, there were a large number of filaments in the axons of the olfactory nerve fiber layer. The electron density of glomerular layer is high, and have many asymmetric synapses. There are many synapses in external plexiform layer, some dendrites have myelin sheaths. Mitral cell was larger, its nuclear margin was wavy and chromatin condensation. There are a large number of synapses in internal plexiform layer, and the number of axons was increased. Cells development in granular cell layer is different. Ependymal cells have obvious cilia. Hemicerebrum widely distributed neural cells, glial cells and ependymal cells. Immature nerve cells are abundant, shows the typical characteristics of immature nerve cells, elongated nuclei, spongy chromatin and centriole. Mature nerve cells are mainly located in the cortical cell layer, with large cell body, dendrites and axons were obvious, nuclear chromatin dispersion. Ependymal cells arranged in the ventricle, cell body was cuboidal and irregular, the surface has obvious cilia. In addition, a small number of apoptotic cells, astrocytes and microglia were also seen.4. BrdU positive cells were widely distributed in telencephalon, but the number of positive cells in each region showed significant difference. The density of BrdU positive cells in the AON was the highest, have a high level of adult neurogenesis. Adult neurogenesis has seasonal difference, showed the change trend of autumn> summer> spring> winter. GFAP positive cells were widely distributed in telencephalon, their thick fibrous projections extended in the brain parenchyma, finally anchored in the meninges. Morphological changes of DCX positive cells located the ventricular sulcus, inner plexiform layer and cortex showed that, the newborn nerve cells through into the brain parenchyma by radial migration, and eventually reached the cerebral cortex and developed in mature neural cells, finally joined the neural network.The morphology and histomorphology of adult S. tsinlingensis' telencephalon have no significant difference compared with other lizards'. Adult neurogenesis has obvious seasonal variation, may be related to the living environment and habits. Therefore, S. tsinlingensis'telencephalon can be used as a good model for the study of regeneration, migration and maturation of neurons in the central nervous system of the lizard.