A Study On Cerebral Neurons And Cholinergic Neurons Mechanism Of Cognitive Deficits After Brain Concussion In Rats

Objective: To establish model of brain concussion rats, observe the feature of cognitive dysfunction and morphologic changes of cerebral cortex, dorsal hippocampus, dentate fornix and brainstem reticular formation, and cholinergic neurons changes of basal forebrain and brainstem reticular formation in brain concussion rats, to study the relationship between cognitive deficits and histopathologic changes of cerebral neurons and cholinergic neurons in brain concussion rats , and provide objective hispathologic bases for clinical diagnosis, treatment and forensic identification related to brain concussion.Methods: A brain concussion was produced in rats using a simple pendulum device model. One control (n=12) and six experimental groups were used(n=12 in each group). The cerebral concussion groups were assigned to sacrifice times ranging from 1 day to 24days after injury.A Morris Water Maze(MWM) memory paradigm was used to assess learning and memory function. Pycnosis degeneration or necrosis neurons in the locus cerebral cortex, dorsal hippocampus, dentate fornix and brainstem reticular formation were observed and counted after brain concussion. Cholinergic neurons in the basal forebrain and brainstem reticular formation were identified and quantitated using choline acetyltransferase(ChAT).Results: The latency to find the platform of the Morris Water Maze test in the lst~7thday post-BC was much longer than that in the control on days 1~3 post injury. There were no statistically differences between the 8th~ 14thday, the 15th -21th day post-BC and the control group. During the rt~24tkday post-BC , pycnosis degeneration or necrosis neurons of the locus cerebral cortex, dorsal hippocampus, dentate fornix were significantly increased, then decreased gradually, but recovered to normal by the 24thday after BC, and especially in parietal cortex and piriform cortex the necrosis neurons were significantly increased than temporal cortex , and there were no statistically difference berween the left and the right side. Pycnosis degeneration or necrosis neurons in the brainstem reticular formation were markedly increased in the 4thday after BC, and there were no statistically difference among the other groups and the control group. Compared with the control group, the number and the activity of ChAT expression in cholinergic neurons in the basal forebrain were outstandingly decreased after injury, then increased gradually, but recovered to normal at the 24thday, and the activity of ChAT expression in cholinergic neurons in the brainstem reticular formation rose at the T'day and declined at the 2thday post injury, then rose gradually, to the peak at the 24thday.Conclusions: 1. The model of brain concussion of rat can be established successfully using iron pendulum hitting device;2. The spatial learning and memory deficits of the rats are detected by MWM in early period post-BC(from 1 to 3 days after BC);3. Pycnosis degeneration or necrosis neurons of the cerebral cortex, dorsal hippocampus, dentate fornix and brainstem reticular formation are identified in BC rats;4. There are significantly changes in the number and activity of cholinergic neurons in the basal forebrain and brainstem reticular formation after BC;5. The change of cerebral neurons and cholinergic neurons correlate with cognitive deficits in BC rats .