Dyskinesia is Closely Associated with Synchronization of Theta Oscillatory Activity Between the Substantia Nigra Pars Reticulata and Motor Cortex in the Off L-dopa State in Rats

Excessive theta(θ)frequency oscillation and synchronization in the basal ganglia(BG)has been reported in elderly parkinsonian patients and animal models of levodopa(L-dopa)-induced dyskinesia(LID),particularly theθoscillation recorded during periods when L-dopa is withdrawn(the off L-dopa state).To gain insight into processes underlying this activity,we explored the relationship between primary motor cortex(M1)oscillatory activity and BG output in LID.We recorded local field potentials in the substantia nigra pars reticulata(SNr)and M1 of awake,inattentive resting rats before and after L-dopa priming in Sham control,Parkinson disease model,and LID model groups.We found that chronic L-dopa increasedθsynchronization and information flow between the SNr and M1 in off L-dopa state LID rats,with a SNr-to-M1 flow directionality.Compared with the on state,θoscillational activity(θsynchronization and informationflow)during the off state were more closely associated with abnormal involuntary movements.Our findings indicate thatθoscillation in M1 may be consequent to abnormal synchronous discharges in the BG and support the notion that M1θoscillation may participate in the induction of dyskinesia.

Glutamatergic Neurons in the Caudal Zona Incerta Regulate Parkinsonian Motor Symptoms in Mice

Parkinson’s disease(PD)is the second most common and fastest-growing neurodegenerative disorder.In recent years,it has been recognized that neurotransmitters other than dopamine and neuronal systems outside the basal ganglia are also related to PD pathogenesis.However,little is known about whether and how the caudal zona incerta(ZIc)regulates parkinsonian motor symptoms.Here,we showed that specific glutamatergic but not GABAergic ZIc^(VgluT2) neurons regulated these symptoms.ZIc^(VgluT2) neuronal activation induced time-locked parkinsonian motor symptoms.In mouse models of PD,the ZIc^(VgluT2) neurons were hyperactive and inhibition of their activity ameliorated the motor deficits.ZIc^(VgluT2) neurons monosynaptically projected to the substantia nigra pars reticulata.Incerta-nigral circuit activation induced parkinsonian motor symptoms.Together,our findings provide a direct link between the ZIc,its glutamatergic neurons,and parkinsonian motor symptoms for the first time,help to better understand the mechanisms of PD,and supply a new important potential therapeutic target for PD.