Preliminary Study On The Improvement Of Spatial Learning And Memory Ability Of AD Model Mice And Its Mechanism By Light Flicker Stimulation

Alzheimer’s disease(AD)is a neurodegenerative disease characterized by cognitive dysfunction and behavioral impairment with insidious onset and progressive progression.Currently,there is no specific medicine or method to cure AD or reverse the process of it.Physical therapy is one of the important treatment methods for AD,among which light stimulation therapy has attracted attention because of its noninvasive,safe and low cost,and has potential therapeutic value for AD.In this study,the effects of 40 Hz light flicker stimulation on the cholinergic system and neurons of AD model mouse are studied,and the therapeutic effect and safety of 40 Hz light flicker stimulation on AD are explored,so as to provide experimental basis for the development of light flicker stimulation therapy for AD.This subject had developed an LED light stimulator controlled by mobile phone APP.After testing and debugging,the frequency is 40 Hz and the duty cycle is 50%,which meets the experimental requirements.Wild type(WT)C57BL/ 6J mouse and APP/PS1 double transgenic AD model mouse under homologous background were used as experimental animals.They were divided into 6 groups,6 months old WT,6 months old AD and 9 months old AD stimulation groups and their control groups.The light stimulation groups were exposed to the light environment with flashing frequency of40 Hz,illuminance of 250-750 lux and color temperature of 4346.8±31.98 K,while the control groups were exposed to the dark environment of 0 Lux for 30min/day,with 5days of exposure and 2 days of rest as a course of treatment,a total of two courses.The black and white box test was used to test the visual discrimination ability of mouse;The Morris water maze and Y maze experiments were used to observe the changes of spatial learning and memory ability of mouse;Immunohistochemistry and western blot were used to quantitatively analyzed the changes of choline acetyltransferase(ChAT),neuronal nuclear antigen(NeuN)and β-amyloid protein(Aβ)in the hippocampus and Primary visual cortex(V1 region)of mouse.In the black and white box experiment,there was no significant difference in residence time of ADL6 group and AD6 group in the black box.In the Morris water maze experiment,the number of platform crossing and the latency time in the target quadrant of ADL6 group increased.In the Y maze experiment,there were significantly differences in the latency time and the number of entries between the ADL6 group of mice in the novel arm and other arms.Compared with the model control group,ChAT and NeuN positive cells in the hippocampus of ADL6 and ADL9 groups were significantly increased.The Aβ plaque load in hippocampus of ADL6 group was significantly decreased by 65.99%,and that in V1 group was significantly decreased by78.49%.There was no significant difference in Aβ plaque load in the hippocampus of ADL9 group,while the plaque load in V1 region increased.The protein levels of ChAT and NeuN in the V1 area of the light stimulation group increased slightly,and the NeuN of the ADL9 group increased significantly.The results showed that the 40 Hz light flicker stimulation did not cause significant damage to the spatial vision of mice,but improved the spatial learning and memory ability of APP/PS1 mice.The effect of light flicker stimulation may be related to the increase of NeuN positive neurons and neurotransmitter ChAT in the hippocampus and V1 region,and the decrease of Aβ plaque precipitation in the hippocampus and V1 region.The results showed that the 40 Hz light flicker stimulation did not cause significant damage to the spatial vision of mice,but improved the spatial learning and memory ability of APP/PS1 mice.The effect of light flicker stimulation may be related to the increase of NeuN-positive neurons and neurotransmitter ChAT,as well as the decrease of Aβ plaque load in hippocampus and V1 region.