Basal Ganglia Neurophysiology during DBS in Rats

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DESCRIPTION (provided by applicant): Parkinson's disease (PD) is a degenerative neurological disorder affecting millions of patients all around the world. Renewed use of the deep brain stimulation (DBS) method provides a new opportunity for treating PD. A key issue to improve the treatment is to fully understand the neural mechanisms underlying the therapeutic effects of DBS. In this proposed study, two unique techniques developed in our laboratory: the chronic multiple-channel single unit recording and rat model of DBS, will be employed to study the neural responses in multiple basal ganglia regions during behaviorally effective DBS in rat model of Parkinsonism. A first objective is to establish a rodent model of DBS in Parkinsonian conditions. The effects of DBS will be evaluated in dopamine lesioned rats performing treadmill locomotion and limb use asymmetry tests. Locomotor d deficits during treadmill walking and imbalance usage of forelimb in vertical exploratory behaviors will develop after unilateral dopamine lesion. High frequency stimulation (HFS) of the subthalamic nucleus (STN) and the substantia nigra pars reticulata (SNr) will then be applied to alleviate these motor abnormalities. The degree of dopamine depletion in the basal ganglia will be detected by immunohistochemical staining of dopamine marker and this result will be correlated with the severity of motor deficits and DBS effects. Second, the basal ganglia neural responses following a dopamine lesion and during behaviorally effective HFS will be examined. Single neural activity and local field potential in the striatum globus pallidus, STN and SNr will be recorded simultaneously in a 64 channel recording system in the rat performing these behavioral tests. Neural responses following dopamine lesion will help us to understand the pathophysiologic process of developing Parkinsonian syndromes while the neural responses during behaviorally effective HFS will shed light on how DBS can restore normal information processing in the basal ganglia neural circuits that are disrupted following dopamine lesion. Several important improvements on recording and stimulation techniques will be made in cooperation with Biographic Inc. to achieve optimal conditions for high frequency stimulation and artifact free recording. The goal of this study is to explore the basic neural mechanism underlying the therapeutic effects of DBS and the knowledge obtained form this study will help us to improve the clinical treatment of PD with DBS method.