| Objective To investigate the influence of acetylcholine characteristic infro-low frequency transcranial magnetic stimulation(ACh-TMS)on the spatial learning and memory function of rat model of Alzheimer’s disease(AD)induced by β-amyloid(Aβ)1-42,and its possible mechanisms.Methods Sprague-Dawley rats were randomly divided into six groups,namely,normal(N),model(M),pseudo-operation(P),fake stimulation(M+P),acetylcholine characteristic infro-low frequency transcranial magnetic stimulation(ACh-TMS)and Donepezil(Donepezil).The rat model of AD was established by bilateral injection of Aβ1-42 into the hippocampus.Morris water maze test was used to evaluate the spatial learning and memory function of all rats.The content of brain derived neurotrophic factor(BDNF)was measured with enzyme-linked immuno sorbent assay(ELISA),and the level of acetylcholine(ACh),the activities of acetylcholinesterase(AChE)and choline acetyltransferase(ChAT)in the tissue of rat hippocampus were detected by spectrophotometry method.The local field potential of the rat hippocampus CA1 area was recorded by the multi-channel recording techniques in vivo and its component of theta rhythm activity was abstracted and analyzed.The modified Highman congo red staining was used to observe the accumulation of amyloid in the rat hippocampus.Results(1)Compared with N group,the mean escaped latency of rats in M group and M+P group in hidden platform test increased,the time in target quadrant(%)and the number of crossing platform in probe test decreased obviously(P < 0.05).Compared with the M+P group,the spatial learning and memory function of rats in ACh-TMS and Donepezil groups were significantly improved,with the mean escape latency shortened,the time in target quadrant(%)and the number of crossing platform increased remarkably(P < 0.05),but there was no difference between ACh-TMS group and Donepezil group(P > 0.05).The levels of BDNF,ACh and the activity of ChAT were significantly increased in ACh-TMS group compared with those of M+P group.(2)The peak power of theta rhythm of CA1 area in rat hippocampus of M group and M+P group decreased when compared to the N group(P < 0.05)and the power increased after treated with ACh-TMS(P < 0.05);the peak power frequency of theta rhythm in M+P group and Donepezil group declined compared with these of other groups(P < 0.05).(3)The amyloid deposit was found in the dentate gyrus(DG)of hippocampus in all groups,except for N group and P group.Conclusions Injection of Aβ1-42 into rat hippocampus results in impairment of spatial learning and memory function,and also the suppression of theta rhythm.ACh-TMS on this kind of AD rat shows an ability to improve the spatial learning and memory function,and the theta suppression in the hippocampus.These effects might be related to its upregulating the expression of BDNF,modifying the neuronal activity and elevating the level of cholinergic neurotransmitter in the hippocampus. |
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