Beyond tremor and rigidity: non-motor features of Parkinson’s disease

Does WOQ-9 help to recognize symptoms of non-motor wearing-off in Parkinson's disease?

EWO (Epidemiology of Wearing-Off symptoms among the population of Parkinson's disease (PD) patients on L-DOPA) is a multicentric, non-interventional, epidemiological and exploratory trial, focused on patients with PD who are treated with L-DOPA. The primary objective is the estimation of wearing-off symptoms (based on WOQ-9 questionnaire and assessment by neurologists) among PD patients who are treated with L-DOPA. From September 30, 2007 to June 30, 2008 altogether 563 valid records of PD patients were collected in movement disorders centers (Level A and Level B centers). Wearing-off symptoms were observed in 66.7% of PD patients (neurologists' assessment) and in 90.6% of PD patients (WOQ-9 questionnaire). The biggest discrepancy was found in PD patients treated with L-DOPA for 0-2 years. The probability of detecting wearing-off by the neurologists strongly correlated with the highest number of positive responses in the WOQ-9 marked by PD patients. There was significant difference in the diagnosis of wearing-off between Level A centers (77.7%) and Level B centers (62.0%). When motor and non-motor symptoms in the WOQ-9 were considered, the difference between neurologists came from the detection of non-motor symptoms (lower in the Level B centers). The neurologists' assessment of wearing-off symptoms and PD patients' subjective evaluation of the WOQ-9 is based on the experience of the neurologist and on the detection of the non-motor symptoms of wearing-off. Careful explanation of the WOQ-9 questionnaire and improved awareness of the non-motor symptoms of wearing-off is strongly suggested.

In vivo effect of 5-HT₇ receptor agonist on pyramidal neurons in medial frontal cortex of normal and 6-hydroxydopamine-lesioned rats: an electrophysiological study

The 5-hydroxytryptamine (5-HT)-7 receptor began to be cloned and pharmacologically characterized close to 20 years ago. It couples positively via G-proteins to adenylyl cyclase and activation of this receptor increases neuronal excitability, and several studies have shown that degeneration of the nigrostriatal pathway leads to an impairment of 5-HT system. Here we reported that systemic and local administration of 5-HT₇ receptor agonist AS 19 produced excitation, inhibition and no change in the firing rate of pyramidal neurons in medial prefrontal cortex (mPFC) of normal and 6-hydroxydopamine-lesioned rats. In normal rats, the mean response of the pyramidal neurons to AS 19 by systemic and local administration in mPFC was excitatory. The inhibitory effect by systemic administration of AS 19 was reversed by GABA(A) receptor antagonist picrotoxinin. Systemic administration of picrotoxinin excited all the neurons examined in normal rats, and after treatment with picrotoxinin, the local administration of AS 19 further increased the firing rate of the neurons. In the lesioned rats, systemic administration of AS 19, at the same doses, also increased the mean firing rate of the pyramidal neurons. However, cumulative dose producing excitation in the lesioned rats was higher than that of normal rats. Systemic administration of AS 19 produced inhibitory effect in the lesioned rats, which was partially reversed by picrotoxinin. The local administration of AS 19, at the same dose, did not change the firing rate of the neurons in the lesioned rats. Systemic administration of picrotoxinin and the local administration of AS 19 did not affect the firing rate of the neurons in the lesioned rats. These results indicate that activity of mPFC pyramidal neurons is regulated through activation of 5-HT₇ receptor by direct or indirect action, and degeneration of the nigrostriatal pathway leads to decreased response of these neurons to AS 19, suggesting dysfunction and/or down-regulation of 5-HT₇ receptor on the pyramidal neurons and GABA interneurons in the lesioned rats.

The pyramidal neurons in the medial prefrontal cortex show decreased response to 5-hydroxytryptamine-3 receptor stimulation in a rodent model of Parkinson's disease

In the present study, effect of SR 57227A, a selective 5-hydroxytryptamine-3 (5-HT(3)) receptor agonist, on the firing activity of pyramidal neurons in the medial prefrontal cortex (mPFC) was studied in normal rats and rats with 6-hydroxydopamine lesions of the substantia nigra pars compacta by using extracellular recording. Systemic administration of SR 57227A (40-640 μg/kg, i.v.) decreased the mean firing rate of pyramidal neurons in normal and the lesioned rats. This inhibition was significant only at doses higher than 320 μg/kg and 640 μg/kg in normal and the lesioned rats, respectively, and was reversed by i.v. administration of 5-HT(3) receptor antagonist tropisetron or GABA(A) receptor antagonist bicuculline. Furthermore, local application of SR 57227A (0.01 μg) in the mPFC inhibited the firing rate of pyramidal neurons in normal rats while having no effect on firing rate in the lesioned rats. The i.v. administration of bicuculline excited the pyramidal neurons in normal rats, and then local application of SR 57227A did not alter the mean firing rate of these neurons. However, these two drugs did not affect the activity of the pyramidal neurons in the lesioned rats. We conclude that activation of 5-HT(3) receptors inhibited pyramidal neurons in the mPFC of normal rats via GABAergic interneurons, and degeneration of the nigrostriatal pathway decreased response of the pyramidal neurons to SR 57227A, suggesting the dysfunction of 5-HT(3) receptors and/or down-regulation of the expression on GABAergic interneurons in the lesioned rats.

Parkinson's disease dementia

Dementia associated with Parkinson's disease (PDD) is a common problem and one that is associated with significant morbidity and mortality. Over the past decade, increasing research efforts and funding have been directed toward an improved understanding of PDD. Despite these efforts, fundamental gaps remain in our knowledge. Consequently, therapeutic progress has been frustratingly slow and incomplete. To significantly affect PDD, novel "disease-modifying" agents, rather than more traditional neurotransmitter replacement approaches, likely will be required.

Genes regulated in MPTP-treated macaques and human Parkinson's disease suggest a common signature in prefrontal cortex

The presymptomatic phase of Parkinson's disease (PD) is now recognized as a prodromal phase, with compensatory mechanism masking its progression and non-motor early manifestations, such as depression, cognitive disturbances and apathy. Those mechanisms were thought to be strictly dopamine-mediated until recent advances have shed light upon involvement of putative outside-basal ganglia, i.e. cortical, structures. We took advantage of our progressive 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated macaque model to monitor whole genome transcriptional changes in several brain areas. Our data reveals that transcriptomic activity changes take place from early stages, suggesting very early compensatory mechanisms or pathological activity outside the basal ganglia, including the PFC. Specific transcriptomic changes occurring in the PFC of fully parkinsonian MPTP-treated macaques have been identified. Interestingly, a large part of these transcriptomic changes were also observed in human post-mortem samples of patients with neurodegenerative diseases analysed by quantitative PCR. These results suggest that the PFC is able to detect the progression of dopamine denervation even at very early time points. There are therefore mechanisms, within the PFC, leading to compensatory alterations and/or participating to pathophysiology of prodromal PD manifestations.

Parkinson disease: an update

BACKGROUND

Over the past decade, the treatment of Parkinson disease (PD) has undergone tremendous changes. New drugs have been introduced to manage the cardinal motor symptoms of PD, and other agents have been borrowed to treat the nonmotor manifestations of the illness. For neurologists faced with the task of treating PD patients, the available array of medications may be confusing and intimidating.

REVIEW SUMMARY

In this review, I summarize the newest approved medications for the treatment of PD, including the new dopamine agonists and catechol-O-methyl-transferase inhibitors. I also describe agents that are used to treat common problems in PD patients, including hallucinations, orthostasis, nausea, erectile dysfunction, depression, and memory loss. Guidelines for handling common scenarios in PD patients will be illustrated by 10 case histories. Finally, the most promising PD drugs that are currently in development will be reviewed.

CONCLUSIONS

Neurologists have a vast armamentarium to treat both motor and nonmotor manifestations of PD. Understanding this array allows the astute clinician to improve the lives of their patients with PD.