The subthalamic activity and striatal monoamine are modulated by subthalamic stimulation

Not all the mechanisms by which subthalamic nucleus deep brain stimulation (STN-DBS) alleviates parkinsonian symptoms have been clarified as yet. The levels of striatal monoamine and the subthalamic beta activity might contribute to its efficacy. However, their direct relationship is unclear. We aimed to examine the correlation between the striatal monoamine and the STN beta activity induced by STN-DBS.

Experiments were performed under urethane anesthesia in normal (n=4) and 6-hydroxydopamine hemi-lesioned Parkinson's disease (PD) model rats (n=5). STN-DBS was applied to the left STN, and local field potential (LFP) was recorded before and after STN-DBS. Striatal extracellular fluid was collected before, during, and after STN-DBS. Spectral analysis of STN-LFP was performed, and the levels of monoamine were measured.

The levels of 3-4-dihydroxyphenylacetic acid (DOPAC) were significantly decreased after the cessation of stimulation in PD model rats. The levels of none of the monoamines were significantly affected in normal rats. The STN beta power was significantly elevated after the cessation of stimulation in normal rats but was significantly decreased in PD model rats. The STN beta power and the levels of DOPAC and 5-HT was positively correlated in PD model rats, whereas the levels of dopamine and 5-HT showed positive correlation and the levels of DOPAC and Homovanillic acid (HVA) showed negative correlation in normal rats.

STN-DBS could decrease the levels of DOPAC and the STN beta power in a PD model rat. The STN beta power and the levels of striatal monoamine might be differentially correlated between normal and PD model rats.