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BACKGROUND: Although experimental studies have utilized high-frequency stimulation in animal models, few reports have focused on long-term subthalamic nucleus deep brain stimulation (STN DBS) in Parkinson's disease (PD) animal models.OBJECTIVE: The present study simulated long-term DBS system and utilized microdialysis technology to study the influence of STN DBS on levels of extracellular dopamine (DA) and its metabolites, homovanillic acid (HVA) and dihydroxy phenyl acetic acid, in the corpus striatum of a hemiparkinsonian monkey model.DESIGN, TIME AND SETTING: A controlled animal study was performed at the Neurosurgery Laboratory, Changhai Hospital of the Second Military Medical University of Chinese PLA between January 2004 and December 2007.MATERIALS: 1-methy-4-phenyl-1, 2, 3, 6-tetrahydropyrindinewas (MPTP) purchased from Sigma,USA. Type-3389 DBS electrode and type-7246 pulse generator were provided by Medtronic, USA.METHODS: Hemiparkinsonism was induced in 2 male, adult Rhesus Macaque monkeys through unilateral internal carotid artery infusion of MPTP. Following model establishment, stimulation electrodes were implanted in the right STN, and chronic high-frequency stimulation (60 μs pulse width, 130 Hz frequency, and 1.5-2.0 V pressure) was performed.MAIN OUTCOME MEASURES: Prior to, and 2 hours, 8 hours, 1 week, 1 month, and 2 months after DBS, samples were collected from the caudate nucleus and putamen using microdialysis technology.Extracellular levels of DA and its metabolites were measured using high-performance liquid chromatography and electrochemical detection (HPLC-ECD) methods.RESULTS: At 8 hours, 1 week, 1 month, and 2 months after DBS, DA levels in the putamen and caudate nucleus were increased on the electrode-implanted side by 39%, 91%, 111%, and 114% and 31%, 91%, 106%, and 102%, respectively. The DA turnover rate (HVA/DA) was increased in the putamen and caudate nucleus by 186% and 91%, respectively, at 8 hours after DBS, while there was no significant difference at 1 week, 1 month, and 2 months after DBS.CONCLUSION: Effective, chronic, high frequency DBS increased extracellular DA levels in the corpus striatum, which could be one of mechanisms involved in the effects of STN DBS.