Hyperkinetic Rat Model Induced by Optogenetic Parafascicular Nucleus Stimulation

The parafascicular nucleus (PF) plays important roles in controlling the basal ganglia. It is not well known whether the PF affects the development of abnormal involuntary movements. This study was aimed to find a role of the PF in development of abnormal involuntary movements (AIMs) using optogenetic methods in an animal model.Fourteen rats were underwent stereotactic operation, in which they were injected with an adeno-associated virus with channelrhodopsin (AAV2-hSyn-ChR2- mCherry) to the lateral one third of the PF. Behavior test was performed with and without optical stimulation 14 days after the injection of the virus. AIM of rat was examined using AIM score. After the behavior test, rat's brain was carefully extracted and the section was examined using a fluorescence microscope to confirm transfection of the PF.Of the 14 rats, 7 rats displayed evident involuntary abnormal movements. Abnormal involuntary movement scores were increased significantly after the stimulation compared to those at baseline. In rats with abnormal involuntary movements, mCherry expression was prominent in the PF, while the rats without AIM lacked with the mCherry expression.Abnormal involuntary movements could be reversibly induced by stimulating the PF through an optogenetic method.