Abstract
Parkinson's disease (PD) is a common neurodegenerative disease characterized by the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc), thereby leading to severe deprivation of dopaminergic input from SNc to the striatum. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective medical therapy in alleviating motor symptoms in moderate to sever PD patients. However, the mechanism of how DBS works remains unclear. In this study, I used c-Fos immunocytochemical staining to identify the motor cortex neurons whose activity were changed after STN-DBS and then characterized those cells exhibiting STN-DBS-dependent changes in their activities. I observed a group of larger and dark c-Fos positive cells (gaint c-Fos positive cell) in the layer Vb of the ipsilateral motor cortex after ipsilateral STN-DBS in PD rats, while similar neurons were not found in normal rats subjected to STN-DBS or in PD rats subjected to contralateral STN-DBS. The results of double-staining with the antibodies of c-Fos and of NeuN, GABA or SMI 32 indicated that most of the giant c-Fos positive cells were pyramidal tract type (PT-type) neurons whose descending axons could send out collaterals to and innervate STN. On the basis of my data, I propose that STN-DBS antidromically excited afferent axons which originated from the PT-type neuron and the therapeutic effects of STN-DBS may be due to, at least partly, by the activation of these afferent axons.