| Objective: The combination of behavioal studies andpathomorphological testing, to observe the effect castration anddihydrostestosterone (DHT) replacement therapy on hippocampal CA1regionin senescence accelerated mouse-prone/8(SAMP8) as the model of mildcognitive impairment (MCI). Further investigate the effect of DHT to improvemechanism of Alzheimer’s disease (AD) and to provide some experimentalproof.Methods:415-month-old male SAMP8were randomly divided intosham-operation control group (P8group), castrated group, anddihydrostestosterone replacement therapy with castrated group (DHT group).Castrated group and DHT group was removed twin testis. DHT group wasinjected hypodermically DHT [1mg/(kg day)] after1day. Other groups wereinjected equal asepsis medical maize oil. All groups were injected for60days,and all mice were kept under normal conditions.17males SAMR1werechosen as normal contrast of the consanguinity group (R1group).1. Determine the level of serum testosterone: Using the125I testosteroneradioimmunoassay kit, we determined the level of serum testosterone of R15-months group, P85-months group, R17-months group, P87-months group,castrated group, and DHT group.5mice were in each group.2. Morris water maze test：The mice were raised2days under theenvironment of labyrinth laboratory first. Training was progressed from thethird day and in every morning between9:00~11:00. The fixed positionlocation underway trials: the Morris water maze was dividing equally for4quadrants, the plat was put into the first quadrant. The mouse went into waterfrom the first quadrants midpoint towards the wall in pond, and the videofrequency acquisition system tracked and recorded escape latency. This test continued5days. Space exploring trial: the sixth day, removed the plat andtaken notes the times that the mouse acrossing span flat roof in120s.3. Tissue preparation and staining observation: After Morris water mazetest, all mice were injected6%chloral hydrate to abdominal, anesthesiaed themice, broken right auricle and perfused quickly with normal saline andsubsequently fixed with4%paraform via left ventricle. From superiorcolliculus to optic chiasma segment, the brain made the same two partsthrough middle sagittal viewing by razor blade. One was made use for Golgistaining, the other was made of paraffin sections using for nissl staining,anti-Aβ immunohistochemical staining and negative control.Results:1. Serum testosterone levels in these groups：Serum testosterone levels ofR1group were higher than that of the same month P8group. Serumtestosterone levels of7-months group were decreased than that of5-mouthsgroup, but the decrease level of P8group (28%) were higher than R1group(5%).2. In the MWM test, the escape latency of P8group was significantlonger than that in R1group (P<0.05), the escape latency of castrated groupwas significant longer than that in P8group and DHT group (P<0.05), butthere wasn’t significant difference in the escape latency comparing with P8group and DHT group (P>0.05). The times of span flat roof of R1groupincreased comparing with P8group (P<0.05), the times of span flat roof ofcastrated group was significant less than that in P8and DHT group (P<0.05),but there wasn’t significant difference comparing with P8group and DHTgroup (P>0.05).3. With HE staining, in R1group, hippocampal neuron arranged in order,and the structure of CA1region was normal. Neuronal cells in P8groupbecame sparse and the cell layer became less. In castrated group, neurons inhippocampal CA1region were sparse and presented karyopyknosis. But inDHT group, the pathological change of neuronal cells have been improved.4. With Nissl staining, neuronal Nissl bodies of R1group were rich and dense, with significant difference in the number of neurons compared with theother groups (P<0.05). Neuronal Nissl bodies in P8group became sparse andsmaller, and some nuclei processed pyknosis. Neurons in hippocampal CA1region of castrated group were much fewer and presented karyopyknosis, withless and even desolved Nissl bodies. The number of neurons of DHT groupincreased and has significantly statistical difference compared with castratedgroup (P<0.05). But there were no significant difference in the number ofneurons between DHT group with P8group (P>0.05).5. With anti-Aβ immunohistochemistry, the number of Aβ-immunepositive neurons and the optical density in hippocampal CA1region of R1group decreased compared with P8group (P<0.05), and the number and theoptical density of Aβ-immune positive neurons in DHT group were markedlyless than that of castrated group (P<0.05). But there were no difference in thenumber of neurons between DHT group with P8group (P>0.05).6. With Golgi staining, the dendritic spines in hippocampal CA1regionof R1group were morphology regulation and well-arranged, the number of theapical dendritic thorns density was1.30±0.17/μm, and with significantdifference compared with the other groups (P<0.05). The number of dendriticspines of P8group was1.16±0.09/μm. The number of dendritic spine of DHTgroup (1.15±0.07/μm) decreased obviously comparing with that of castratedgroup (0.78±0.04/μm)(P<0.05), but there were no difference between DHTgroup with P8group.Conclusions:1. From MCI stage (5months) to AD stage (7months), the decrease levelof testosterone in SAMP8mice is higer than that in SAMR1mice, whichindicate the decrease of androgen may be in part the risk factor of dementia.2. In castrated SAMP8mice of MCI stage, the ability of memoryacquisition and storage capacity declined obviously, neurons in hippocampalCA1region were sparse and presented karyopyknosis, and the number and theoptical density of Aβ-immune positive neurons were increased. These resultsdetermine that androgen deficiency can accelerate the development of AD. 3. In castrated SAMP8mice, androgen treatment could raise the ability ofmemory and storage and the pathological change of hippocampus, andpostpone the development of AD. |
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