The study of establishment of repetitive traumatic brain injury model in rats

Objective To establish a stable reproducible repeated traumatic brain injury (TBI) animal model to study the neuron loss after TBI. Methods Sixty-four male SD rats were randomly divided into single TBI control group, the single TBI group, repetitive TBI control group, and repetitive TBI group, and each group was divided into four subgroups: 3 d group, 7 d group, 14 d group and 30 d group, each subgroup of 4 rats. Single TBI group was hit only once after craniotomy, repetitive TBI group hit four times in intervals of 24 h, and the control group was only given anesthesia to remove bone flap. After TBI model was established, the modified neurological severity score (mNSS) was detected at 1st, 3rd, 7th, 14th and 30th day, and Morris water maze test was used to examine spatial learning and memory ability at 30th day. The hematoxylin and eosin (HE) staining was used to observe the brain damage after the injury, and immunofluorescence to test neurons NeuN missing after injury. Results (1) As compared with the single TBI group, the mNSS results showed that the neurobehavioral injury was more serious at different time points after injury (1, 3 d: P=0.013, 7 d: P=0.003, 14 d: P=0.008, 21, 30 d: P=0.000). Morris water maze latency training results showed that the time to reach the target platform was prolonged at the second day after the start of training when compared with single TBI group (P=0.000). The percentage of target quadrant showed that the single injury group [(33.33±6.80)%] was higher than that in the repeated injury group [(16.34±3.76)%] in the same injury time (P=0.029). (2) Immunofluorescence showed that the neurons in the repetitive TBI group around the damaged area and those in the area of hippocampal dentate gyrus were lost seriously over time, more significant than in single TBI group (damaged area: 14 d: P=0.007, 30 d: P=0.003; hippocampal dentate gyrus: 14 d: P=0.009, 30 d: P=0.007). Conclusion As compare with the single TBI group, repetitive TBI leads to severe neurological defect and neuron loss. This repetitive TBI model can provide replicable rat model to study the neuropathology mechanism of neurodegeneration after repetitive brain injury. Key words: Traumatic brain injury; Neurodegenerative disease; Rat; Neuron; Model, animal