To establish the closed moderate traumatic brain injury animal model.

Eighty male SD rats were randomly divided into 4 groups, 20 in each group, including three groups with different degrees of brain injury (A, B, C) and sham operation (N). Referring to Marmarou injury model, group A, B and C made the steel bar weighing 450 g fall freely and hit the rat head to establish TBI according to the designed strike height (1.0, 1.5, 2.0 m). The general condition, neurobehavioral and brain histomorphological changes were observed.

Within 14 d after injury, the mortality rates of group N, A, B and C were 0%, 5%, 20% and 60%, respectively. With the increase of the amount of injury, the mortality rate increased (P<0.05). With the increase of the number of injuries, the neurological deficit score (mNSS) increased at each time point after injury (P<0.05), which was higher than that in group N. The results of HE staining showed that, compared with group N, with the increase of wound volume, HE staining showed matrix loosening, widening of pericellular space and vascular space of neurons, disordered arrangement and degeneration of neurons and swelling and degeneration of glia were more obvious under light microscope. The results of immunohistochemical staining showed that the positive expression of β-APP and NF-L in cerebral cortex of group A, B and C was higher than that of group N.

The steel bar weighted 450 g felled from the height of 1.5 m that hit against the middle of head of rat have established a relatively stable moderate closed TBI animal model with obviously pathological features changes and more stable and repeatable than other groups.