Morphological Characteristics Of Hippocampus In Yak And Primary Exploration On It’s Adult Neurogenesis

The morphology and cell types of the hippocampus in adult yak were observed by the traditional staining of HE and Golgi-Cox, and the neural stem cells and newborn neurons which located in SGZ of dentate gyrus were observed with DAB immunoperoxidase staining and immunofluorescence double-labeling for DCX/NeuN and GFAP/NeuN. It showes that the yak’s hippcampus mainly contains dentate gyrus and hippocampus proper, and both of them stratify clearly. Granular cells, mossy cells and pyramidal cells are the three major cell types of the hippocampus formation. The somas of pyramidal cells in CA3region are much bigger than those in CA1region, while the average length of apical dendrites of latter are more longer than former’s. The pyramidal cells in CA1region are obviously divided into two sublayers, but the pyramidal cells in CA3region form a close uniform layer. The somas of most DCX-positive cells, which distribute individually or together, mainly locates in the deepest part of the granule cell layer closing to hilus. The branched DCX-positive dentries which issued by these somas pass through granular layer and insert into molecular layer. A layer of GFAP-expressing radial glia-like cells are observed in the subgranular zone of the dentate gyrus, and their cytoplasms and single polarity processes are GFAP-positive, while the nucleis are negative. A large number of star GFAP-positive cells scatter in the whole hippocampal tissue, and specially, the density of GFAP-positive cells in molecular layer and the boundary of hilus closing to granular layer are much higher than those in other zones. The morphological characteristics of hippocampus in yak is similar to sheep’s, while be different from those small mammals’, such as rat、mouse、cat and rabbit. The two kinds of DCX immunostaining indicate that newborn neurons surely exist in yak’s hippocampus. And the immunofluorescence labeling for GFAP marker shows that the GFAP-positive cells locating in SGZ of dentate gyrus are very likely radial glias, that the astrocytes scatter in the whole hippocampal formation of yak.