The remarkable hypoxia tolerance in Brandt's voles (Lasiopodomys brandtii).

Oxygen (O2 ) is essential for the survival of most animal species; however, O2 levels are lower than normal in certain spatiotemporal circumstances. Therefore, animals have to develop some strategies to face and adapt to this plight. This study compared the differences in survival, behavior, and hippocampal neurons under hypoxic conditions between Brandt's voles (Lasiopodomys brandtii) and Kunming mice (Mus musculus). Brandt's voles had longer survival times than did Kunming mice in 5%-6.5% O2 levels. Significant differences were observed in mortality between Brandt's voles and Kunming mice after 6 hr of exposure to 5%-7% O2 levels. The novel object recognition test (NORT) and neuronal nuclei staining revealed the presence of species-dependent learning deficits and neuron loss under hypoxic conditions. NORT and neuronal nuclei staining showed that the Kunming mice exposed to 7.5% O2 levels had significant learning deficits and neuronal loss compared with normoxia Kunming mice. Conversely, Brandt's voles exposed to 7.5% O2 levels had no significant learning deficits and neuronal loss compared with the normoxia group. Therefore, hypoxia showed significant effects on survival, cognitive behavior, and neuronal loss of the two species. Moreover, Brandt's voles showed stronger hypoxia tolerance than Kunming mice, and Brandt's voles hypoxia tolerance may root in their adaptive evolution to highland habitat environment. This research is meaningful for studying hypoxic adaptation in animals, and will promote the development of therapies for some illnesses such as stroke and cardiac arrest.