Abstract: As the key factors related to neuroprotective function in the nervous system of vertebrates, neuroglobin (NGB) and hypoxia inducible factor-1α (HIF-1α) play important physiological functions in the process of hypoxic adaptation. This study aimed to explore the relationship between expression and distribution of NGB and HIF-1α in the process of adaptation to hypoxia of yak (Bos grunniens) hindbrain which plays an important regulatory function in animal movement, breathing, sensory and other physiological activities. RT-qPCR, Western blot and immunohistochemical methods were used to investigate the expression and localization characteristics of NGB and HIF-1α in different regions of yak hindbrain. The results showed that the expression trend characteristics between NGB and HIF-1α in yak hindbrain were basically consistent, the highest expression level was found in the archicerebellum which was significantly higher than those in the medulla oblongata, pons and other parts of cerebellum (P<0.05), the expression level in the cerebellar hemisphere cortex was less than that in the archicerebellum and the lowest expression level was found in the palaeocerebellum, there were also some differences in the expression levels of the two factors in other regions. The distribution characteristics of NGB and HIF-1α positive products were similar, and the overall intensity of the HIF-1α protein immunopositive response was higher than that of NGB protein. NGB and HIF-1α were mainly expressed in the cytoplasm of neurons in the medulla oblongata and pons. Scattered NGB and HIF-1α positive cells could be found in the molecular layer of the cerebellar cortex, archicerebellum, neocerebellum and palaeocerebellum. There were also a small number of positive expressions in the basket cells. The dendritic cell cytoplasm of Purkinje cells in the Purkinje cell layer showed a strong positive expression of NGB and HIF-1α. Strong positive expression of NGB and HIF-1α were also observed in the granular cell cytoplasm. The regions of white matter (medulla) showed rarely NGB and HIF-1α positive expression in the cytoplasm of the neurons. No expression was observed in the negative control. The above results suggested that there were selective differences between the expression of NGB and HIF-1α in different regions of yak hindbrain during the long-term adaptation to hypoxic environment. The archicerebellum has a higher tolerance to hypoxia, followed by the cerebellar hemisphere, and the weakest tolerance to hypoxia in the palaeocerebellum. The reason for the differences might be related to the specific functions undertaken by the relevant regions of the hindbrain in yak and the adaptive function of hypoxia in each region mainly depends on its specific neuronal structure.

Key words: neuroglobin, hypoxia inducible factor-1α, yak, hindbrain