Hippocampal Development And Expression Of ItsNGF, BDNF And SYN1 In Bactrian Camel

The Bactrian camel is a kind of large mammals, living in Gobi, desert and semi-desert areas. It can not only endure thirst and drought, but also resistant wind and sand. Bactrian camel’s smell sensitive and has a good sense of direction. It can has a long time walk in the desert and never get lost. The good sense of direction and strong cognitive skills are closely related to its good learning and memory formation during growth and development. As we all know, the hippocampus plays an important role in learning and memory. Synaptic plasticity and LTP during the hippocampal development is the molecular basis of the formation of learning and memory. Therefore, the study about morphological and ultrastructural changes of neurons as well as the expression of some related protein during hippocampal development in Bactrian camel is helpful to understand that for what reason its direction recognition and cognitive abilities can be formed.Objective:To investigate the morphological and ultrastructural changes of main neurons and the expression of NGF, BDNF and SYN1 in different areas during the hippocampal development of Bactrian camel.Methods:Nissl staining was used to observe the structure changes of pyramidal cells and granule cells. And, immunohistochemistry was used to detect the expression of NGF, BDNF and SYN1 of neurons in fetal, young and adult Bactrian camels.Results:Nissl staining showed that the width of the pyramidal cell layer and granular cell layer gradually broadened during the hippocampal development of Bactrian camel. The numerical value is from (38.87±7.05～53.17±7.46) μm to (58.27±8.30～67.60±13.97) μm (P<0.05). Pyramidal cells in CA1-CA3 areas and granular cells of dentate gyrus enlarged in volume, the numerical value of Pyramidal cells is from (1,337.77±131.51～2,086.18±374.92)μm3 to (2,729.24±334.09～5,107.28±336.59)μm3 (P<0.001), the numerical value of granular cells is from 302.57±46.30 μm3 to 577.38±44.23 μm3 (P<0.001).While gradually decrease in density, the numerical value of Pyramidal cells is from (607.35±65.06～726.76±74.59) per/mm2 to (311.29±67.55～422.47±67.16) per/mm2 (P<0.001), the numerical value of granular cells is from 2,117.88±235.51 per/mm2 to 1632.88±197.15 per/mm2 (P<0.001). The proportion of nucleus in neuron also decreased, the numerical value of Pyramidal cells is from (3.57%±0.002～3.99%±0.006) to (2.32%±0.002～2.73%±0.005) (P<0.001), the numerical value of granular cells is from (7.57%±0.006) to (4.87%±0.330) (P<0.001). Immunohistochemical analysis revealed that the level of the NGF and BDNF in pyramidal cells of adult camel were higher than the other two periods (P<0.01). However, the level of these two proteins in granule cells were consistently increasing from fetal camel to adult camel. From fetal Bactrian camel to young Bactrian camel, the expression of SYN1 in pyramidal cells and granular cells increased significantly (P<0.05), while from young camel to adult camel, the expression of SYN1 increased less. The result of TEM showed that compared with fetal Bactrian camel, the number of synapses in hippocampal CA1 and CA3 areas of young Bactrian camel increased significantly and the structure of synapses is more complete. But compared with young Bactrian camel and adult Bactrian camel, the number of synapses in CA1 and CA3 areas of hippocampus changed little. In addition, the number of mitochondria in hippocampal CA1 and CA3 areas of young Bactrian camel is the most. While compared with young Bactrian camel, the number of mitochondria in hippocampal CA1 and CA3 areas of adult Bactrian camel is less.Conclusion:The main neurons continuously migrate and become mature with the hippocampal development of Bactrian camel. During this time, cells change from small, global, with little cytoplasm neurons to neurons which has distinct dendrites and axons. The high levels of NGF and BDNF in adult hippocampus indicate that NGF and BDNF can regulate functions of differentiated neurons which contribute to the learning and memory in hippocampal development of Bactrian camel. The expression of SYN1 is consistent with the results of ultrastructure of hippocampal neurons, it idicates that in the period of youth, the number of synapses in hippocampus of Bactrian camel is the most and in this period,it also requires the largest amount of energy.