title: Altered Neuronal Firing Pattern of the Basal Ganglia Nucleus Plays a Role in Levodopa-Induced Dyskinesia in Patients with Parkinson's Disease.
abstract: BACKGROUND
  Levodopa therapy alleviates the symptoms of Parkinson's disease (PD), but long-term treatment often leads to motor complications such as levodopa-induced dyskinesia (LID).
  
  
  OBJECTIVE
  To explore the neuronal activity in the basal ganglia nuclei in patients with PD and LID.
  
  
  METHODS
  Thirty patients with idiopathic PD (age, 55.1 ± 11.0 years; disease duration, 8.7 ± 5.6 years) were enrolled between August 2006 and August 2013 at the Xuanwu Hospital, Capital Medical University, China. Their Hoehn and Yahr (1967) scores ranged from 2-4 and their UPDRS III scores were 28.5 ± 5.2. Fifteen of them had severe LID (UPDRS IV scores of 6.7 ± 1.6). Microelectrode recording was performed in the globus pallidus internus (GPi) and subthalamic nucleus (STN) during pallidotomy (n = 12) or STN deep brain stimulation (DBS; bilateral, n = 12; unilateral, n = 6). The firing patterns and frequencies of various cell types were analyzed by assessing single cell interspike intervals (ISIs) and the corresponding coefficient of variation (CV).
  
  
  RESULTS
  A total of 295 neurons were identified from the GPi (n = 12) and STN (n = 18). These included 26 (8.8%) highly grouped discharge, 30 (10.2%) low frequency firing, 78 (26.4%) rapid tonic discharge, 103 (34.9%) irregular activity, and 58 (19.7%) tremor-related activity. There were significant differences between the two groups (p < 0.05) for neurons with irregular firing, highly irregular cluster-like firing, and low-frequency firing.
  
  
  CONCLUSIONS
  Altered neuronal activity was observed in the basal ganglia nucleus of GPi and STN, and may play important roles in the pathophysiology of PD and LID.
authors.affiliation: Department of Neurosurgery, Xuanwu Hospital, Capital Medical University Beijing, China.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Li
authors.affiliation: Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University Beijing, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhuang
authors.affiliation: Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University Beijing, China.
authors.forename: Yongjie
authors.initials: Y
authors.lastname: Li
keywords: Parkinson’s disease; globus pallidus; levodopa; microelectrodes; movement disorders; subthalamic nucleus