Establishment of brain ischemia model in tree shrew

Tree shrew, as a kind of small and inexpensive animal between insectivores and primates with the general anatomy being similar to human, could be considered as developed animal model for brain ischemia (BI) study. However, there is no neural behavior scores criterion from tree shrew with BI up to now.

To produce BI model of tree shrew, a novel systematic neurobehavioral assessment scale, named as neural behavior scores (NBS) including aggressive behavior, seeking behavior, gait, startle reflex, high jump and warped-tail phenomenon was firstly established and used in this study. Moreover, magnetic resonance imaging (MRI) was performed on the first day after the operation to detect the imaging changes caused by ischemia. Then TTC, HE staining and immunofluorescent staining for GFAP and NeuN, were performed 24 h after surgery respectively.

NBS in BI group were significantly higher than that of sham operation group at 1d, 3d, 5d and 7d after ischemia. Meanwhile, compared with the sham operation group, the T2 images demonstrated significant higher signal and local brain swelling after cerebral ischemia in tree shrews. The staining of TTC and HE showed apparent infarction and necrosis of the cerebral region, and most of neurons exhibited a shrink.

We have successfully established the BI model of tree shrew, confirmed by NBS (a new developed method), MRI, HE staining, TTC staining and immunofluorescence staining. It is the first time to report a novel neurobehavioral assessment scale for BI in tree shrew.