Neuroprotective effects of subthalamic nucleus high-frequency stimulation on substantia nigra neurons in a Parkinson's disease rat model

BACKGROUND:Deep-brain stimulation has proven to be beneficial in the treatment of Parkinson’s disease(PD) patients.OBJECTIVE:To investigate the effects of high-frequency stimulation(HFS) to the subthalamic nucleus(STN) on neuronal apoptosis and apoptosis-related gene expression in the substantia nigra pars compacta,and to analyze the neuroprotective effect of HFS-STN.DESIGN,TIME AND SETTING:Neuronal morphology experiments were performed in the Beijing Neurosurgical Institute from May to December in 2005.MATERIALS:Forty healthy,adult,Sprague Dawley rats were used to establish a PD model with a unilateral microinjection of 6-hydroxydopamine into two target areas of the right medial forebrain bundle.6-hydroxydopamine was purchased from Sigma(USA);high-frequency electrical stimulator was produced by World Precision Instruments(USA);Terminal deoxynucleotidyl transferase dUTP nick end labeling(TUNEL) kit was a product of Nanjing Jiancheng Technology Co.,Ltd.(China);and Bcl-2 and Bax protein assay kit were purchased from Wuhan Boster Bioengineering Co.,Ltd.(China).METHODS:Forty rats were randomly divided into three groups.The stimulation group(n = 15) received HFS-STN on the day of PD modeling.The PD model group(n = 15) was used to establish the PD model.The control group(n = 10) was injected with normal saline containing 0.2 g/L ascorbic acid into two areas of the right medial forebrain bundle.MAIN OUTCOME MEASURES:Survival of dopaminergic neurons in the substantia nigra pars compacta was determined using Nissl staining.Apoptosis of dopaminergic neurons was detected using TUNEL techniques.Expression of anti-apoptotic protein,Bcl-2,and pro-apoptotic protein,Bax,were assayed by immunohistochemistry.RESULTS:Following 6-hydroxydopamine injection,the number of substantia nigra pars compacta neurons was reduced in the stimulation and PD model groups,compared to the control group.At 2 and 4 weeks post-surgery,the grey value of Nissl stained images was significantly less in the PD model and stimulation groups(P < 0.05),and the stimulation group exhibited greater grey values compared to the model group(P < 0.05).At 2 and 4 weeks post-surgery,the number of apoptotic neurons was significantly less in the stimulation group compared to the model group(P < 0.05).In addition,Bcl-2 and Bax expression,as well as the Bcl-2/Bax ratio,was much higher in the stimulation group compared to the model group(P < 0.05).CONCLUSION:HFS-STN has a neuroprotective effect on dopaminergic neurons in the substantia nigra pars compacta of PD rats by promoting Bcl-2 expression,inhibiting Bax expression,and reducing the number of apoptotic dopaminergic neurons.