Altered neuronal activity in the pedunculopontine nucleus: An electrophysiological study in a rat model of Parkinson’s disease

• The PPN neurons were hyperactive in 6-OHDA lesioned rats.
• The firing pattern of PPN neurons was changed due to the 6-OHDA lesion.
• The loss of dopamine in rats resulted in the changes of LFP activities.

The pedunculopontine nucleus (PPN) is a new deep brain stimulation target for treating Parkinson’s disease (PD). But the alterations of the PPN electrophysiological activities in PD are still debated. To investigate these potential alterations, extracellular single unit and local field potential (LFP) activities in the PPN were recorded in unilateral hemispheric 6-hydroxydopamine (6-OHDA) lesioned rats and in control rats, respectively. The spike activity results revealed two types of neurons (Type I and Type II) with distinct electrophysiological characteristics in the PPN. Both types of neurons had increased firing rate and changed firing pattern in lesioned rats when compared to control rats. Specifically, Type II neurons showed an increased firing rate when the rat state was switched from rest to locomotion. The LFP results demonstrated that lesioned rats had lower LFP power at 0.7–12 Hz and higher power at 12–30 Hz than did control animals in either resting or locomotor state. These findings provide a better understanding of the effects of 6-OHDA lesion on neuronal activities in the PPN and also provide a proof of the link between this structure and locomotion, which contributes to better understanding the mechanisms of the PPN functioning in the pathophysiology of PD.