Study For Discharge Patterns Of The Pedunculopontine Nucleus After Dopamine Lesioning In Rats

Interest in the pedunculopontine nucleus (PPN), a new deep brain stimulation (DBS) targetfor Parkinson’s disease(PD), has increased in recent years，but little is known about the firingpattern alterations of PPN in PD. In this study,multi-channel in vivo recording technique wereperformed in normal rats and6-hydroxydopamin (6-OHDA) lesioned rats just when theywere freezing or moving to observe the changes of spikes and local field potentials occuring inPPN neurons. Adult male Wistar rats were randomly divided into control group and experimentgroup．A rat PD model was established using6-OHDA injecting into SNc and VTA these twobrain areas．Spike and LFP signals were collected from the two groups.The sort of neurons wereanalyzed with Offline Sorter. Their firing rate and firing pattern were analyzed withNeuroExplorer and their Spectrogram and Power Spectral Density and Spectral Decompositionwere analyzed with MATLAB software to investigate the changes in neuronal activities andlocal field potentials of the pedunculopontine nucleus after unilateral6-OHDA lesioning of thestriatum in rats.Experimental finding：By applying microdrive array, whether freezing or moving, the invivo recording in unilateral rat pedunculopontine nucleus demonstrated that neurons with twodifferent waveforms and firing patterns can be observed. NeuronⅠ have wider waveforms andlower firing rates while NeuronⅡ have narrower waveforms and higher firing rates.While freezing the firing rate of NeuronⅠ significantly increased from5.6±0.5Hz innormal rats to7.2±0.9Hz in PD rats(P＜0.05) while Neuron Ⅱsignificantly increased from11.7±1.3Hz in normal rats to14.7±1.8Hz in PD rats(P＜0.01). The interspike intervals ofNeuronⅠ significantly decreased from0.21±0.05s in normal rats to0.15±0.03s in PD rats (P＜0.01)while Neuron Ⅱ significantlydecreased from0.09±0.02s in normal rats to0.06±0.02s in PD rats(P＜0.01). The coefficient of variation of NeuronⅠ increased from1.16±0.13in normal rats to1.23±0.16in PD rats(P＞0.05) while Neuron Ⅱsignificantly increased from1.15±0.14in normal rats to1.49±0.21in PD rats(P＜0.01). The mode of ISI in s of NeuronⅠsignificantly decreased from0.052±0.012in normal rats to0.036±0.010in PD rats (P＜0.05)while Neuron Ⅱ significantlydecreased from0.035±0.010in normal rats to0.019±0.005in PD rats(P＜0.01). While moving the firing rate of NeuronⅠ significantly increased from5.7±0.6Hz innormal rats to7.6±1.0Hz in PD rats while Neuron Ⅱ significantly increased from14.6±1.5Hz in normal rats to17.4±2.1Hz in PD rats. The interspike intervals of NeuronⅠ significantlydecreased from0.20±0.04s in normal rats to0.14±0.03s in PD rats (P＜0.05) while NeuronⅡ significantlydecreased from0.08±0.02s in normal rats to0.05±0.02s in PD rats(P＜0.05).The coefficient of variation of NeuronⅠ increased from1.18±0.13in normal rats to1.25±0.15in PD rats(P＞0.05) while Neuron Ⅱ significantly increased from1.17±0.15in normalrats to1.45±0.25in PD rats(P＜0.01). The mode of ISI in s of NeuronⅠ decreased from0.046±0.012in normal rats to0.035±0.008in PD rats(P＞0.05) while Neuron Ⅱsignificantlydecreased from0.033±0.009in normal rats to0.015±0.004in PD rats(P＜0.01).Whether freezing or moving, the LFPs signals at0.7～12Hz were much more(P＜0.05)than while those at30～100Hz were much less in experiment group than in control group (P＜0.01)．Conclusion: These results prove that injecting6-OHDA into SNc and VTA these two brainareas is an ideal method to construct PD rat model and the neurons in the pedunculopontinenucleus are overactive in6-OHDA lesioned rats, and their firing is becoming more irregular,which suggests that the firing activity of neurons are overactive in6-OHAD lesioned rats,indicating the participation of this nucleus in the pathophysiology of parkinsonism.