Role Of MTOR Signaling Pathway In Levodopa - Induced Dyskinesia And Its Mechanism

Objective:To Research the the role and mechanism of mammalian target of rapamycin(mTOR) signaling pathway in the Pathogenesis of levodopa-induced dyskinesia (L-dopa Induced Dyskinesia, LID) in striatum.Methods:Made hemi-parkinsomism rat models by6-OHDA microinjection stereotaxically into medial forebrain bundle (MFB),then establish LID rat models by intraperitoneal injection of L-dopa for a week,the sucessful high dyskinesia rats were randomly applied into LID group (n=12)and Rapa group(n=12),normal rats as while as shamed rats and PD rats were also used as control groups(n=12).The animals from the LID group were treated with chronic Administration with1-dopa+benseride injection for subsequent2weeks,while the animals from the RAPA group received equal RAPA treatment in the following2weeks.The abnormal involuntary movement(AIM) scores were evaluated using the rat AIM rating scale. Then animals were killed and the brain were colledted and processed for4usages:i)double labeling immunofluorescence to Detect the coexpression level of D1R, D2R with phospho-Ser65-4E-BPl and phospho-Thr389-S6K;ii transmission electron microscope(TEM) to distinguish the variations of the postsynaptic density; iii) immunohistochemical staining to determine the expression level of Cx36;and iv)Western Blotting to determine the expression level of phospho-p44/42MAPK-ERKl/2, phospho-Thr389-S6K, phospho-Ser235/236-S6, phospho-Ser240/244-S6, phospho-Ser65-4E-BP1, and phospho-Ser295-PSD95in striatum.Results:(1) the AIM scores of LID group are significantly increased compared with RAPA grpup(p<0.01).(2)Both D1R and D1R are activated, but the coexpression levels of DIR with phospho-Thr389-S6K and phospho-Ser65-4E-BP1has massive superiority compared with D2R in striatums of LID rats(p<0.001).(3)the length of synaptic activity density and expression levels of Cx36in striatal of LID group is extremely increased compared with RAPA grpup(p<0.001).(4)The expression levels of phospho-p44/42MAPK-ERK1/2, phospho-Thr389-S6K, phospho-Ser235/236-S6, phospho-Ser240/244-S6, phospho-Ser65-4E-BP1, and phospho-Ser295-PSD95in striatums of LID rats were significantly increased compared with rapamycin treatment group(p<0.001).Conclusion:mTOR signaling pathway in rat striatum activation of the LID formation, the mechanism is abnormal mTORC1pathway activity, leading to activation of its its downstream effector molecules p70S6K and4E-BP1, due to the increases of phosphorylation of ribsom protein S6and chemical synapses Ser295-PSD95levels and overexpression of electrical synapses connexin Cx36, leading to the changes of synaptic plasticity, and then dysfunction of the basal ganglia loops, resulting in the occurrence of LID.