The Effects Of Fluoxetine On The Behavioral Changes And Cholinergic Neurons Of Early APP/PS1 Transgenic AD Mice

PART ONE THE EFFECTS OF FLUOXETINE ON THE BEHAVIORAL CHANGES OF EARLY APP/PS1 TRANSGENIC AD MICEObjective To investigate the effects of fluoxetine on the spatial learning and memory ability of early AD mice,in order to provide a theoretical basis for further study in the effects of fluoxetine on the pathological changes of AD and the application of fluoxetine in the clinical treatment of AD.Methods Twenty 8-month-old female APP/PS1 transgenic AD mice were randomly divided into the control group(APP/PS1,n = 10)and the intervention group(APP/PS1 + FLX,n = 10).The mice in the intervention group were intraperitoneally injected with FLX(10 mg/kg/d)and the control group mice were injected with the same dose of normal saline at the fixed time every morning for 9 weeks.During the intervention,all the AD mice were housed in a standard environment and weighed regularly(once a week).In the last week of intervention,Morris water maze was used to test the spatial learning ability and memory ability of mice at the same time.The test scheme consists of the first 5 days of position navigation tasks and the 6th day of spatial probe tasks.In the position navigation task,the time required to find the hidden platform was the escape latency time to be used as an indicator to evaluate the spatial learning ability.In the spatial probe tasks,the frequency of crossing the platform location and the target quadrant swimming time were used as indicators to assess the spatial memory ability.The trajectory,the escape latency,the frequency of crossing the platform location and the target quadrant swimming time were recorded in the tasks.Results 1.There was no significant difference on the body weight in the two groups before and after the intervention(p > 0.05).2.In the Morris water maze test,the results of the position navigation test showed that the escape latency of the intervention group was significantly shorter than that of the control group(p < 0.05).The escape latency of the mice in the intervention group on 1st,2nd,4th and 5th day was significantly shorter than that in the control group(p < 0.05).On the 3rd day,the escape latency of the intervention group was not statistically different from that of the control group(p > 0.05).3.The results of the spatial probe tasks showed that there was no significant difference in the frequency of crossing the platform location between the intervention group and the control group.The target quadrant swimming time in the intervention group was not significantly different from that in the control group(p > 0.05).Conclusions 1.After 9 weeks of fluoxetine intervention,the body weight of AD mice did not change significantly,suggesting that fluoxetine has no obvious toxic effects on the AD mice.2.After intervention,early AD mice significantly shortened the escape latency in the Morris water maze test,suggesting that fluoxetine can promote the spatial learning ability of AD mice.PART TWO THE EFFECTS OF FLUOXETINE ON THE CHOLINERGIC NEURONS IN HIPPOCAMPUS OF EARLY APP/PS1 TRANSGENIC AD MICEObjective To investigate the changes of the cholinergic neurotransmitters and the number of cholinergic neurons in the subregions of hippocampus of early AD mice after fluoxetine intervention,in order to further reveal the structural basis for fluoxetine-induced improvement of the spatial learning ability in AD mice and provide theoretical basis for the further clinical application of fluoxetine.Methods After Morris water maze test,5 mice were randomly selected from each group.After anesthesia,the mice were sacrificed,and the hippocampus tissue was dissected on ice.One side of the hemispheres was randomly chosen for the content of ACh and the activity of ChAT with enzyme linked immunosorbent assay(ELISA).The remained 5 mice in each group were anesthetized and perfused transcardially with 4% paraformaldehyde and normal saline.The brain was dissected and one side hemisphere was randomly selected.The hemispheres were dehydrated in sucrose dilution with gradient concentration,embedded in O.C.T and then sliced coronally at 50 ?m equidistant intervals on a cryostat microtome.According to the stereological equidistant random sampling principle,the hippocampus tissure sections were randomly sampled.5 groups of equidistant random sections containing hippocampus were obtained.One series of equidistant sections were randomly selected for immunofluorescence staining to observe cholinergic neurons.Another series of equidistant sections were randomly selected for immunohistochemical staining,and the number of cholinergic neurons in each subregion of the hippocampus was investigated using stereological methods.Results 1.After fluoxetine intervention,the ELISA results showed that the content of ACh in the intervention group was significantly higher than that of in the control group(p < 0.05).There was no significant difference in the activity of ChAT between the intervention group and the control group(p > 0.05).2.The immunofluorescence results showed that cholinergic neurons in the intervention group were denser than those in the control group.3.The stereological results showed that the number of cholinergic neurons in the DG region of hippocampus of the intervention group was significantly higher than that of the control group(p < 0.05).The number of cholinergic neurons in the CA1 region of hippocampus of the intervention group was significantly higher than the control group(p < 0.05);the number of cholinergic neurons in the CA2-3 region of the intervention group was not significantly different from the control group(p > 0.05).Conclusions 1.Continuous fluoxetine intervention for 9 weeks could increase the content of ACh in the hippocampus of AD mice,indicating that fluoxetine might promote the release of ACh in the hippocampus of the brain.2.Fluoxetine intervention could increase the number of cholinergic neurons in DG and CA1 regions of AD mice,indicating that fluoxetine might have a protective effect on cholinergic neurons.3.The present results that fluoxetine intervention increased the ACh content in the hippocampus of AD mice and the number of cholinergic neurons in DG and CA1 regions might be one of the structural basis for the fluoxetine-induced improvement of the spatial learning ability in AD mice.