Effect of l-DOPA on local field potential relationship between the pedunculopontine nucleus and primary motor cortex in a rat model of Parkinson’s disease

• Alterations of the LFP activities in PPN and M1 caused by dopamine loss can be mostly corrected by l-DOPA.
• l-DOPA can partly reverse the altered relationship between PPN and M1 of 6-OHDA lesioned rats.
• There are differences of alterations and the therapeutic effects on LFP activities and synchronization in PPN and M1 between resting state and walking state.

Levodopa (l-DOPA) has been proved to reverse the pathologic neuron activities in many brain regions related to Parkinson’s disease (PD). But little is known about the effect of l-DOPA on the altered electrophysiological coherent activities between pedunculopontine nucleus (PPN) and motor cortex. To investigate this, local field potentials (LFPs) of PPN and primary motor cortex (M1) were recorded simultaneously in control, 6-hydroxydopamine lesioned and lesioned rats with l-DOPA chronic treatment. The results revealed that in resting state, chronic l-DOPA treatment could correct the suppressed power of LFPs in PPN and M1 in low-frequency band (1–7 Hz) and the enhanced power in high-frequency band (7–70 Hz in PPN and 12–70 Hz in M1) of lesioned rats. In locomotor state, l-DOPA treatment could correct the alterations in most of frequency bands except the δ band in PPN and α band in M1. Moreover, l-DOPA could also reverse the altered coherent relationships caused by dopamine depletion in resting state between PPN and M1 in β band. And in locomotor state, l-DOPA had therapeutic effect on the alterations in δ and β bands but not in the α band. These findings provide evidence that l-DOPA can reverse the altered LFP activities in PPN and M1 and their relationships in a rat model of PD, which contributes to better understanding the electrophysiological mechanisms of the pathophysiology and therapy of PD.