Qin Li

Involuntary movements, or dyskinesia, represent a debilitating complication of levodopa therapy for Parkinson's disease. Although changes affecting D(1) and D(2) dopamine receptors have been studied in association with this condition, no causal relationship has yet been established. Taking advantage of a monkey brain bank constituted to study levodopa-induced dyskinesia, we report changes affecting D(1) and D(2) dopamine receptors within the striatum of normal, parkinsonian, ...

Appearance of dyskinesia is a common problem of long-term l-DOPA treatment in Parkinson's disease patients and represents a major limitation for the pharmacological management of the motor symptoms in advanced disease stages. We have recently demonstrated that dopamine released from serotonin neurons is responsible for l-DOPA-induced dyskinesia in 6-hydroxydopamine (6-OHDA)-lesioned rats, raising the possibility that blockade of serotonin neuron activity by combination of 5-HT(1A) and ...

Spinal cord injury disrupts the communication between the brain and the spinal circuits that orchestrate movement. To bypass the lesion, brain-computer interfaces have directly linked cortical activity to electrical stimulation of muscles, and have thus restored grasping abilities after hand paralysis. Theoretically, this strategy could also restore control over leg muscle activity for walking. However, replicating the complex sequence of individual muscle activation patterns underlying ...

The serotonin (5-hydroxytryptamine [5HT]) system has recently emerged as an important player in the appearance of l-3,4-dihydroxyphenylalanine (levodopa [l-dopa])-induced dyskinesia in animal models of Parkinson's disease. In fact, dopamine released as a false transmitter from serotonin neurons appears to contribute to the pulsatile stimulation of dopamine receptors, leading to the appearance of the abnormal involuntary movements. Thus, drugs able to dampen the activity of serotonin ...

Dyskinesias represent a debilitating complication of levodopa therapy for Parkinson's disease (PD). While we recently demonstrated that levodopa-induced dyskinesia results from increased dopamine D(1) receptor-mediated transmission, we also questioned the possible role of subcellular localization of D(1) and D(2) receptors in mediating these effects as we previously showed that D(1) receptors undergo differential trafficking in striatal neurons of non-dyskinetic PD patients. Taking ...

BACKGROUND: In rodents, the development of dyskinesia produced by L-DOPA in the dopamine-depleted striatum occurs in response to increased dopamine D1 receptor-mediated activation of the cAMP - protein kinase A and of the Ras-extracellular signal-regulated kinase (ERK) signalling pathways. However, very little is known, in non-human primates, about the regulation of these signalling cascades and their association with the induction, manifestation and/or maintenance of ...

BACKGROUND: A role for enhanced opioid peptide transmission has been suggested in the genesis of levodopa-induced dyskinesia. However, basal ganglia nuclei other than the striatum have not been regarded as potential sources, and the opioid precursors have never been quantified simultaneously with the levels of opioid receptors at the peak of dyskinesia severity.

METHODS: The levels of messenger RNA (mRNA) encoding the opioid precursors preproenkephalin-A and preproenkephalin-B in the ...

BACKGROUND: ΔFosB is a surrogate marker of L-DOPA-induced dyskinesia (LID), the unavoidable disabling consequence of Parkinson's disease L-DOPA long-term treatment. However, the relationship between the electrical activity of FosB/ΔFosB-expressing neurons and LID manifestation is unknown.

METHODS: We used the Daun02 prodrug-inactivation method associated with lentiviral expression of β-galactosidase under the control of the FosB promoter to investigate a causal link between the activity ...

Parkinson's disease is caused primarily by degeneration of brain dopaminergic neurons in the substantia nigra and the consequent deficit of dopamine in the striatum. Dopamine replacement therapy with the dopamine precursor l-dopa is the mainstay of current treatment. After several years, however, the patients develop l-dopa-induced dyskinesia, or abnormal involuntary movements, thought to be due to excessive signaling via dopamine receptors. G protein-coupled receptor kinases (GRKs) ...

The classic view of anatomofunctional organization of the basal ganglia is that striatopallidal neurons of the "indirect" pathway express D2 dopamine receptors and corelease enkephalin with GABA, whereas striatopallidal neurons of the "direct" pathway bear D1 dopamine receptors and corelease dynorphin and substance P with GABA. Although many studies have investigated the pathophysiology of the basal ganglia after dopamine denervation and subsequent chronic levodopa (L-dopa) treatment, ...

INTRODUCTION: Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the loss of dopaminergic neurons as well as the presence of proteinaceous inclusions named Lewy bodies. α-synuclein (α-syn) is a major constituent of Lewy bodies, and the first disease-causing protein characterized in PD. Several α-syn-based animal models of PD have been developed to investigate the pathophysiology of PD, but none of them recapitulate the full picture of the disease. ...

In the present study we investigated whether the neuropeptide nociceptin/orphanin FQ (N/OFQ), previously implicated in the pathogenesis of Parkinson's disease, also affects L-DOPA-induced dyskinesia. In striatal slices of naive rodents, N/OFQ (0.1-1 μm) prevented the increase of ERK phosphorylation and the loss of depotentiation of synaptic plasticity induced by the D1 receptor agonist SKF38393 in spiny neurons. In vivo, exogenous N/OFQ (0.03-1 nmol, i.c.v.) or a synthetic N/OFQ receptor ...

BACKGROUND: Involuntary movements, or dyskinesia, represent a debilitating complication of dopamine replacement therapy for Parkinson disease (PD). The transcription factor DeltaFosB accumulates in the denervated striatum and dimerizes primarily with JunD upon repeated L-3,4-dihydroxyphenylalanine (L-DOPA) administration. Previous studies in rodents have shown that striatal DeltaFosB levels accurately predict dyskinesia severity and indicate that this transcription factor may play a ...

Amantadine, an N-methyl-D-aspartate glutamate receptor antagonist, is currently the only pharmacological treatment for levodopa-induced dyskinesia (LID) in Parkinson's disease (PD), but causes adverse effects on the central nervous system at therapeutic doses. Fenobam, a negative modulator of metabotropic glutamate receptor subtype 5, has recently been reported to attenuate LID in MPTP-treated macaques. The aim of the current study was to investigate the treatment interactions of fenobam ...

Dyskinesia represents a debilitating complication of L-3,4-dihydroxyphenylalanine (L-dopa) therapy for Parkinson's disease. Such motor manifestations are attributed to pathological activity in the motor parts of basal ganglia. However, because consistent funneling of information takes place between the sensorimotor, limbic, and associative basal ganglia domains, we hypothesized that nonmotor domains play a role in these manifestations. Here we report the changes in 2-deoxyglucose (2-DG) ...