Changes in Dendritic Spine Density and Inhibitory Perisomatic Connectivity onto Medium Spiny Neurons in L-Dopa-Induced Dyskinesia.

Using bacterial artificial chromosome-double transgenic mice expressing tdTomato in D1 receptor-medium spiny neurons (MSNs) and enhanced green fluorescent protein in D2 receptor-MSNs, we have studied changes in spine density and perisomatic GABAergic boutons density in MSNs of both the D1R and D2R pathways, in an experimental model of parkinsonism (mouse injected with 6-hydroxydopamine in the medial forebrain bundle), both in the parkinsonian and dyskinetic condition induced by L-DOPA treatment. To assess changes in perisomatic GABAergic connectivity onto MSNs, we measured the number of contacts originated from parvalbumin (PV)-containing striatal "fast-spiking" interneurons (FSIs), the major component of a feed-forward inhibition mechanism that regulates spike timing in MSNs, in both cell types as well as the number of vesicular GABA transporter (VGAT) contacts. Furthermore, we determined changes in PV-immunoreactive cell density by PV immunolabeling combined with Wisteria floribunda agglutinin (WFA) labeling to detect FSI in a PV-independent manner. We also explored the differential expression of striatal activity-regulated cytoskeleton-associated protein (Arc) and c-Fos in both types of MSNs as a measure of neuronal activation. Our results confirm previous findings of major structural changes in dendritic spine density after nigrostriatal denervation, which are further modified in the dyskinetic condition. Moreover, the finding of differential modifications in perisomatic GABAergic connectivity and neuronal activation in MSNs suggests an attempt by the system to regain homeostasis after denervation and an imbalance between excitation and inhibition leading to the development of dyskinesia after exposure to L-DOPA.

Assessing the non-motor symptoms of Parkinson's disease: MDS-UPDRS and NMS Scale.

BACKGROUND AND PURPOSE: Although Parkinson's disease (PD) is characterized by typical motor manifestations, non-motor symptoms (NMS) are an outstanding part of the disease. At present, several specific instruments for assessment of NMS are available. The objective of our study was to determine the performance of the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS): Part I - Non-Motor Aspects of Experiences of Daily Living (nM-EDL) compared with the Non-Motor Symptoms Scale (NMSS). METHODS: To this purpose, 434 consecutive patients with PD were included in an international, observational, cross-sectional study. The association between scores of both scales was determined by the Spearman rank correlation coefficient. Equations for transformation of total score of a scale to the other were constructed from weighted regression models and both, transformed and observed score, contrasted by means of the Lin's Concordance Correlation Coefficient (LCCC) and Bland-Altman plot. RESULTS: As a whole, the prevalence of the NMS according to each scale was quite similar, and most of the correlations between their corresponding components were high (r(S) > 0.60). The total score correlation of the MDS-UPDRS Part I with the NMSS was high (r(S) = 0.81). Concerning the transformed scores, estimated scores only partially approach the observed ones (sharing about 60-64% of the variance) because residual variance increased with increasing magnitudes of the scores, i.e. the most severe patients (Bland-Altman plot; LCCC < 0.60 for severe patients). CONCLUSIONS: (i) MDS-UPDRS Part I (nM-EDL) and NMSS showed a strong convergent validity; (ii) however, transformed scores using the equations from weighted regression models showed that for patients with the most severe NMS they are not concordant.

Relationship between the MDS-UPDRS domains and the health-related quality of life of Parkinson's disease patients.

BACKGROUND AND PURPOSE: The Movement Disorder Society sponsored version of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) is a comprehensive instrument for assessing Parkinson's disease (PD). The present study was aimed at determining the relationships between MDS-UPDRS components and health-related quality of life (HRQoL) evaluations in PD patients. METHODS: An international, multicenter, cross-sectional study was carried out of 435 PD patients assessed with the MDS-UPDRS, Hoehn and Yahr (HY), Clinical Impression Severity for PD, EQ-5D and PD Questionnaire - eight items (PDQ-8). Spearman's rank correlation coefficients, exploratory factor analysis and multiple linear regression models (dependent variables EQ-5D and PDQ-8) were performed. RESULTS: The participants' age was 66.71 ± 10.32 years (51.5% men). PD duration was 8.52 ± 6.14, and median HY was 2 (range 1-5). The correlation between the EQ-5D index and the MDS-UPDRS ranged from -0.46 (Part IV) to -0.72 (Part II) and for the PDQ-8 index from 0.47 (Part III) to 0.74 (Part II). In multiple regression models with the MDS-UPDRS domains as independent variables, the main determinant for both the EQ-5D index and the PDQ-8 was Part II followed by Part I. After factorial grouping of the cardinal PD manifestations embedded in the MDS-UPDRS Parts III and IV for inclusion into multiple regression models, a factor formed by M-EDL, nM-EDL and fluctuations was the main determinant for both the EQ-5D and PDQ-8 indexes. CONCLUSIONS: The MDS-UPDRS component most tightly related with the HRQoL measures was a combination of motor and non-motor experiences of daily living.

The relationship between executive functions and fluid intelligence in Parkinson's disease.

BACKGROUND: We recently demonstrated that decline in fluid intelligence is a substantial contributor to frontal deficits. For some classical 'executive' tasks, such as the Wisconsin Card Sorting Test (WCST) and Verbal Fluency, frontal deficits were entirely explained by fluid intelligence. However, on a second set of frontal tasks, deficits remained even after statistically controlling for this factor. These tasks included tests of theory of mind and multitasking. As frontal dysfunction is the most frequent cognitive deficit observed in early Parkinson's disease (PD), the present study aimed to determine the role of fluid intelligence in such deficits. METHOD: We assessed patients with PD (n=32) and control subjects (n=22) with the aforementioned frontal tests and with a test of fluid intelligence. Group performance was compared and fluid intelligence was introduced as a covariate to determine its role in frontal deficits shown by PD patients. RESULTS: In line with our previous results, scores on the WCST and Verbal Fluency were closely linked to fluid intelligence. Significant patient-control differences were eliminated or at least substantially reduced once fluid intelligence was introduced as a covariate. However, for tasks of theory of mind and multitasking, deficits remained even after fluid intelligence was statistically controlled. CONCLUSIONS: The present results suggest that clinical assessment of neuropsychological deficits in PD should include tests of fluid intelligence, together with one or more specific tasks that allow for the assessment of residual frontal deficits associated with theory of mind and multitasking.

Moving from continuous dopaminergic stimulation to continuous drug delivery in the treatment of Parkinson's disease.

Motor fluctuations and motor complications are a major consequence of the treatment and progression of Parkinson's disease (PD) and they have, in particular, been linked to L-dopa therapy. Using continuous dopaminergic stimulation (CDS) by employing longer acting dopaminergic drugs has been proposed as a means of avoiding or lowering their occurrence. However, both the preclinical and clinical evidence base suggest that this concept does not fully explain the differences between L-dopa and dopamine (DA) agonist drugs and that their pharmacological profiles may also be important. In addition, the way in which drugs are delivered in PD appears to have a marked influence on both efficacy and side-effect profile. As a consequence, the concept of continuous drug delivery (CDD) has arisen to explain the differences between the intermittent and continuous delivery of both L-dopa and DA agonists. This review presents the evidence for using CDD as a working concept for the early and later stages of PD and in the treatment of motor complications and motor fluctuations. CDD as an approach to the treatment of PD may improve the outcome of therapy and explain the differences between drug classes and the delivery systems employed.

Behavioral sensitization to different dopamine agonists in a parkinsonian rodent model of drug-induced dyskinesias.

Repeated treatment with dopamine (DA) receptor agonists strongly potentiates contralateral turning behavior due to selective stimulation of D1 or D2-class receptors in 6-hydroxydopamine (6-OHDA)-lesioned rats. This phenomenon, referred to as sensitization, is believed to be related to the motor response complications (dyskinesias, on-off states) that occur during chronic administration of levodopa in Parkinson's disease patients. In recent years a new method for the evaluation of abnormal involuntary movements (AIMs) secondary to dopaminergic stimulation in 6-OHDA-lesioned rats was described. These AIMs resemble dyskinesias as seen in parkinsonian patients under levodopa therapy. Our objective was to evaluate the effects of repeated treatment with different regimes of DA agonists on turning behavior and on an AIMs scale in 6-OHDA lesioned rats, with the aim of discriminating between drugs with different dyskinesia-inducing potential. In addition, we explored the effects of a previous exposure to a DA agonist (priming) on the behavioral response to the subsequent administration of a DA agonist with the same or different pharmacologic profile. Our results show that in apomorphine-treated rats, rotational behavior and AIMs run a parallel course of enhancement, while in those receiving quinpirole there is a dissociation, suggesting that they could be mediated by different mechanisms. The finding of a significant priming effect on subsequent testing of 6-OHDA lesioned rats should be borne in mind as the use of these pharmacological tests in the screening of well lesioned animals could lead to an erroneous interpretation of further results on dyskinesias and rotational behavior.

Effect of sleep deprivation on motor performance in patients with Parkinson's disease.

Animal research provides evidence that sleep deprivation influences the dopamine system. Knowledge about the effect of sleep deprivation on motor performance in patients with Parkinsons disease is scarce. This study examines the influence of total and partial sleep deprivation compared to normal sleep on motor state and performance in Parkinson's disease. Fifteen nondepressed patients with Parkinson's disease underwent one night of total sleep deprivation (TSD), one night of partial sleep deprivation (PSD) after 3 a.m., and one control night of normal sleep (S), performed in a random, nonconsecutive order. Over a period of 3 hours the following morning, motor evaluations (United Parkinson's Disease Rating Scale, [UPDRS] and tapping rate) were performed before and every 30 minutes after intake of the usual morning dopaminergic drug dose. All patients underwent polysomnography apart from the sleep deprivation protocol. Mean UPDRS motor scores and tapping velocities did not differ significantly after each of the schedules, but a subgroup of four patients improved their motor score after partial sleep deprivation. These data do not confirm previous findings of an overall positive influence of sleep deprivation on motor function in Parkinson's disease. However, the results indicate that different response types to sleep deprivation may exist and that a subgroup of patients could benefit from partial sleep deprivation.

Polysomnographic measures in Parkinson's disease: a comparison between patients with and without REM sleep disturbances.

STUDY OBJECTIVE: To assess the frequency of rapid eye movement (REM) sleep abnormalities in Parkinson's disease (PD) patients and compare polygraphic sleep measures in those with and without REM sleep disturbances. DESIGN: Polysomnographic recordings of 2 consecutive nights were performed in 45 patients with PD (mean age 65 years, mean Hoehn and Yahr stage 2.2). Twenty patients were treated with dopaminergic drugs, 10 were drug-free for two weeks and 15 had never been treated with L-dopa or dopamine agonists. According to the polysomnographic findings, the patients were divided into those with and without REM sleep abnormalities. Abnormal REM sleep features were defined as REM sleep without atonia (RWA) and REM sleep behavior disorder (RBD). RESULTS: Eighteen (40%) of the PD patients showed either RWA (24%; 6 men, 5 women) or RBD (16%; 6 men, 1 woman). Patients with REM sleep disturbances had a significantly longer duration of the disease (8.3 vs. 3.9 years), a more severe stage of the disease (2.6 vs. 2.0 Hoehn and Yahr stage) and were treated with a higher dosage of dopaminergic drugs (L-dopa, pergolide and bromocriptin). 67% of the patients with normal REM sleep were untreated at the time of the sleep study, but only 39% of those with REM sleep abnormalities. Sleep EEG measures (sleep efficiency, sleep onset latency, sleep period time, relative amounts of sleep stages) for the second night showed no significant differences between both groups apart from a significantly lower sleep period time in PD patients with RWA/RBD. CONCLUSIONS: Abnormal REM sleep features are a frequent finding in patients with PD. The prevalence seems to increase with a longer disease duration. Therefore, a careful follow-up is necessary. A sleep architecture not different from PD patients without RWA/RBD suggests that the underlying abnormality is confined to REM sleep.

Selective increase of Nurr1 mRNA expression in mesencephalic dopaminergic neurons of D2 dopamine receptor-deficient mice.

The orphan nuclear receptor Nurr1 is critical for the survival of mesencephalic dopaminergic precursor neurons. Little is known about the mechanisms that regulate Nurr1 expression in vivo. Other members of this receptor family have been shown to be activated by dopamine. We sought to determine if Nurr1 expression is also regulated by endogenous dopamine through dopamine receptors. Consequently, we investigated the expression of Nurr1 mRNA in genetically modified mice lacking both functional copies of the D2 dopamine receptor gene and in their congenic siblings. Quantitative in situ hybridization demonstrated a significant increased expression of Nurr1 mRNA in the substantia nigra pars compacta and the ventral tegmental area of D2 dopamine receptor -/- mice. No change in Nurr1 expression was detected in other brain regions, such as the habenular nuclei and temporal cortex. Among the cell groups studied, mesencephalic dopaminergic neurons are unique in that they express both Nurr1 and the D2 dopamine receptor, and synthesize dopamine. Thus, it seems plausible that the selective increase in Nurr1 expression observed in D2 receptor-deficient mice is the consequence of an impaired dopamine autoreceptor function.

The indirect basal ganglia pathway in dopamine D(2) receptor-deficient mice.

Recent pathophysiological models of basal ganglia function in Parkinson's disease predict that specific neurochemical changes in the indirect pathway would follow the lack of stimulation of D(2) dopamine receptors. Post mortem studies of the basal ganglia in genetically modified mice lacking functional copies of the D(2) dopamine receptor gene allowed us to test these predictions. When compared with their congenic N(5) wild-type siblings, mice lacking D(2) receptors show an increased expression of enkephalin messenger RNA in the striatum, and an increased activity and expression of cytochrome oxidase I in the subthalamic nucleus, as expected. In addition, D(2) receptor-deficient mice display a reduced expression of glutamate decarboxylase-67 messenger RNA in the globus pallidus, as the basal ganglia model predicts. This reduction contrasts with the lack of change or increase in glutamate decarboxylase-67 messenger RNA expression found in animals depleted of dopamine after lesions of the mesostriatal dopaminergic system. Furthermore, D(2) receptor-deficient mice show a significant decrease in substance P messenger RNA expression in the striatonigral neurons which form the direct pathway. Finally, glutamate decarboxylase-67 messenger RNA expression in the basal ganglia output nuclei was not affected by mutations in the D(2) receptor gene, a fact that could probably be related to the absence of a parkinsonian locomotor phenotype in D(2) receptor-deficient mice. In summary, these findings provide compelling evidence demonstrating that the lack of endogenous stimulation of D(2) receptors is sufficient to produce subthalamic nucleus hyperactivity, as assessed by cytochrome oxidase I histochemistry and messenger RNA expression, and strongly suggest the existence of interactions between the basal ganglia direct and indirect pathways.

A combined pattern of movement disorders resulting from posterolateral thalamic lesions of a vascular nature: a syndrome with clinico-radiologic correlation.

We report a series of seven patients in whom a combined pattern of complex movement disorders restricted to one upper extremity emerged as a result of posterolateral thalamic lesions of vascular origin. This disorder was mainly characterized by choreiform and dystonic movements associated with variable, rhythmic, alternating movements of low frequency (myorhythmia). All cases showed, on computed tomography scan and/or magnetic resonance imaging, focal lesions involving the posterolateral quadrant of the thalamus. Review of similar cases reported with identical clinico-radiologic features allows us to conclude that it is possible to establish an accurate anatomoclinical correlation based on the clinical phenomenology, even before imaging studies are performed, in these cases. The opposite is not entirely possible, however, because lesions in the same quadrant of the thalamus are often associated with different patterns of abnormal movements or present without abnormal movements.

Levodopa in Parkinson's disease: neurotoxicity issue laid to rest?

Orally administered levodopa remains the most effective symptomatic treatment for Parkinson's disease. The introduction of levodopa therapy is often delayed, however, because of the fear that it might be toxic for the remaining dopaminergic neurons, and thus accelerate the deterioration of the patient's condition. Evidence for levodopa toxicity comes mainly from in vitro studies which have demonstrated that levodopa can damage dopaminergic neurons by a mechanism that probably involves oxidative stress. It is widely accepted, however, that levodopa is not toxic for healthy animals and humans who do not have Parkinson's disease. It has been argued that the lesioned mesostriatal dopaminergic system could be more vulnerable to levodopa-induced toxicity, because the brain extracellular concentrations attained by levodopa are higher when the dopaminergic system is damaged, and remaining dopaminergic neurons experience a process of compensatory hyperactivity. Evidence for in vivo levodopa toxicity in animal models of Parkinson's disease is scarce and contradictory. A comprehensive recent study failed to find any evidence of levodopa toxicity in rats with either moderate or severe lesions of the mesostriatal dopaminergic system. Concerning the hypothesis of toxicity, some recent reports have shown that levodopa can have trophic effects on dopaminergic neurons in vitro, and our own work has shown that long term levodopa therapy promotes recovery of striatal dopaminergic markers in rats with moderate nigrostriatal lesions. Given that neither epidemiological nor clinical studies have ever provided evidence to support that long term levodopa administration can accelerate the progression of Parkinson's disease, we believe that levodopa therapy should not be delayed on the basis of an unconfirmed hypothesis.

D3 receptor knockdown through antisense oligonucleotide administration supports its inhibitory role in locomotion.

To study the specific contribution of the D3 dopamine receptor in the generation of locomotor activity, total or partially dopamine-depleted rats were pretreated with an antisense oligodeoxynucleotide for the D3 receptor (D3R-as) and locomotor activity induced by apomorphine was measured. A 35.7% increase in locomotor activity was seen in the totally dopamine-depleted rats pretreated with the D3R-as, whereas the same antisense, caused a significantly greater increase in the locomotor response (95%) in the partially dopamine-depleted rats compared with control groups (pretreated with a control oligodeoxynucleotide or vehicle). In situ autoradiography for D3 receptors showed a 27% fall in the density of D3 receptors in the islands of Calleja compared with control animals. Our results seem to confirm that D3 receptors exert an inhibitory effect on locomotor activity, through the stimulation of both pre- and postsynaptic components.

Increased [125I]sulpiride binding in the subthalamic nucleus of rats with nigrostriatal lesions.

Subthalamic nucleus (STN) hyperactivity follows lesions of mesencephalic dopaminergic neurons in animal models of Parkinson's disease. The mechanism leading to sustained STN hyperactivity in parkinsonism is not well understood, but it seems not to depend on the integrity of striato-pallido-subthalamic connections (the so called indirect pathway). Sustained STN hyperactivity could result from the loss of the direct dopaminergic innervation of the STN. Here we report increased [125I]sulpiride binding in the STN of rats with 6-hydroxydopamine (6-OHDA) lesions of mesencephalic dopaminergic neurons. Furthermore, we found that chronic oral treatment with levodopa reverted the lesion-induced increase in [125I]sulpiride binding. Our results demonstrate that most STN D2-class dopamine receptors are postsynaptic to afferent dopaminergic fibers. Furthermore, they suggest that alterations of local STN dopaminergic mechanisms could play a role in the pathophysiology of parkinsonism and mediate the therapeutic/adverse effects of chronic levodopa administration.

A clinical, pharmacologic, and polysomnographic study of sleep benefit in Parkinson's disease.

We assessed the effect of sleep benefit on motor performance in Parkinson's disease (PD) and analyzed its relation to pharmacologic and sleep measures. The sleep benefit phenomenon-motor improvement after sleep before drug intake-in patients with PD has been addressed by questionnaire studies, but objective data are scarce. Ten PD patients with sleep benefit were pairwisely matched to 10 PD patients without sleep benefit for gender, age, PD symptom duration, and medications. We examined motor performance at night before sleep, during morning baseline state immediately after spontaneous awakening, and continuously after intake of the usual levodopa dose. Plasma levodopa concentrations were measured serially and all-night polysomnography was performed. Between night and morning evaluations, motor state improved slightly in patients with sleep benefit and deteriorated slightly in patients without sleep benefit. The difference between both groups proved to be significant. After levodopa induced "on" state, patients with sleep benefit had more severe interdose "off" than those without. Levodopa concentrations and polysomnographic findings were similar in both conditions, although there was a trend toward more abnormal sleep measures in sleep benefit patients. Sleep benefit is a small but significant phenomenon. It does not clearly relate to a specific sleep variable; however, patients with sleep benefit showed a different response profile to levodopa. Subjective perception or possibly sensory mechanisms could play an additional role in sleep benefit in PD.

Opposite roles of D1 and D5 dopamine receptors in locomotion revealed by selective antisense oligonucleotides.

Contralateral rotations induced by the D1-like agonist SKF 38393 in unilaterally 6-hydroxydopamine-lesioned rats were completely prevented by the administration of the D1-like antagonist SCH 23390. A similar result was obtained after intracerebroventricular administration of an antisense oligodeoxynucleotide for the D1 receptor (D1R-as). Contrariwise, administration of a D5R-as potentiated the effects of SKF 38393, showing a 60% increase in the rotational scores. Both effects were reversible upon cessation of D1R-as or D5R-as treatment and were also specific since rotational scores in rats treated with vehicle or with a randomly designed oligodeoxynucleotide were not modified. These results suggest that whereas D1 receptors play a facilitatory role in locomotion, D5 receptors exert an inhibitory effect.

Chronic levodopa is not toxic for remaining dopamine neurons, but instead promotes their recovery, in rats with moderate nigrostriatal lesions.

Orally administered levodopa remains the most effective symptomatic treatment for Parkinson's disease (PD). The introduction of levodopa therapy is often delayed, however, because of the fear that it might be toxic for the remaining dopaminergic neurons and, thus, accelerate the deterioration of patients. However, in vivo evidence of levodopa toxicity is scarce. We have evaluated the effects of a 6-month oral levodopa treatment on several dopaminergic markers, in rats with moderate or severe 6-hydroxydopamine-induced lesions of mesencephalic dopamine neurons and sham-lesioned animals. Counts of tyrosine hydroxylase (TH)-immunoreactive neurons in the substantia nigra and ventral tegmental area showed no significant difference between levodopa-treated and vehicle-treated rats. In addition, for rats of the sham-lesioned and severely lesioned groups, immunoradiolabeling for TH, the dopamine transporter (DAT), and the vesicular monoamine transporter (VMAT2) at the striatal level was not significantly different between rats treated with levodopa or vehicle. It was unexpected that quantification of immunoautoradiograms showed a partial recovery of all three dopaminergic markers (TH, DAT, and VMAT2) in the denervated territories of the striatum of moderately lesioned rats receiving levodopa. Furthermore, the density of TH-positive fibers observed in moderately lesioned rats was higher in those treated chronically with levodopa than in those receiving vehicle. Last, that chronic levodopa administration reversed the up-regulation of D2 dopamine receptors seen in severely lesioned rats provided evidence that levodopa reached a biologically active concentration at the basal ganglia. Our results demonstrate that a pharmacologically effective 6-month oral levodopa treatment is not toxic for remaining dopamine neurons in a rat model of PD but instead promotes the recovery of striatal innervation in rats with partial lesions.