Imad Ghorayeb

Phenotypical characterization of the neurons expressing the D1 and D2 dopamine receptors in the monkey striatum

The striatum is regulated by dopaminergic inputs from the substantia nigra. Several anatomical studies using in situ hybridization have demonstrated that in rodents, dopamine D1 and D2 receptors are segregated into distinct striatal efferent populations: dopamine D1 receptor into γ‐aminobutyric acid (GABA)/substance P striatonigral neurons, and dopamine D2 receptor into GABA/enkephalin striatopallidal neurons. The existence of such a segregation has not been investigated in primates. Therefore, to quantify the efferent striatal GABAergic neurons in the adult Cynomolgus monkey, we detected GAD67 mRNA expression while considering that only a minority of the GABAergic population is composed of interneurons. To characterize the peptidergic phenotype of the neurons expressing dopamine D1 or D2 receptors, we examined the mRNA coding for these receptors in the striatum at the cellular level using single‐ and double in situ hybridization with digoxigenin and 35S ribonucleotide probes. Double in situ hybridization demonstrated a high coexpression of dopamine D1 receptor and substance P mRNAs (91–99%) as well as dopamine D2 receptor and preproenkephalin A mRNAs (96–99%) in medium‐sized neurons throughout the nucleus caudatus, putamen, and nucleus accumbens. Only a small subpopulation (2–5%) of the neurons that contained dopamine D1 receptor mRNA also expressed dopamine D2 receptor mRNA in all regions. Large‐sized neurons known to be cholinergic expressed D2R mRNA. However, within the nucleus basalis of Meynert, the large cholinergic neurons expressed D2R mRNA, but the neurons producing enkephalin expressed neither D1R nor D2R mRNA. These results demonstrate that the striatal organizational pattern of D1 and D2 receptor segregation in distinct neuronal populations described in rodent also exists in primate. J. Comp. Neurol. 418:22–32, 2000.

Sleep disorders in Parkinson's disease: The contribution of the MPTP non-human primate model

To replicate the sleep-wake disorders of Parkinsons disease (PD) and to understand the temporal relationship between these sleep disturbances and the occurrence of parkinsonism, we performed long-term continuous electroencephalographic monitoring of vigilance states in unrestrained rhesus monkeys using an implanted miniaturized telemetry device and tested the effect of MPTP intoxication on their sleep-wake organization. MPTP injection yielded a dramatic disruption of sleep-wake architecture with reduced sleep efficacy that persisted years after MPTP administration. Primary deregulation of REM sleep and increased daytime sleepiness occurring before the emergence of motor symptoms were a striking feature of the MPTP effect. This was concomitant with a breakdown of dopaminergic homeostasis, as evidenced by decreased dopamine turnover measured after a single MPTP injection. In the long term, partial re-emergence of REM sleep paralleled the partial adaptation to parkinsonism, the latter being known to result from compensatory mechanisms within the dopaminergic system. Altogether, these findings highlight the suitability of the MPTP model of PD as a tool to model the sleep/wake disturbances of the human disease. Ultimately, this may help in deciphering the specific role of dopamine depletion in the occurrence of these disorders.

Progression of multiple system atrophy (MSA): A prospective natural history study by the European MSA study group (EMSA SG)

The disease‐specific Unified Multiple System Atrophy Rating Scale (UMSARS) has been developed recently and validated for assessing disease severity in multiple system atrophy (MSA). Here, we aimed at (1) assessing rates of disease progression in MSA and (2) validating UMSARS for sensitivity to change over time. Impairment was assessed at two time points 12 months apart using UMSARS Part I (historical review), UMSARS Part II (motor examination), as well as measures of global disease severity, including UMSARS Part IV, Hoehn and Yahr (HY) Parkinsons disease staging, Schwab England Activities of Daily Living (SE ADL), and a three‐point global Severity Scale (SS3). Fifty patients (male:female ratio, 1:0.9; possible MSA, 16%; probable MSA, 84%; MSA‐parkinsonian, 58%; MSA‐cerebellar, 42%) were assessed twice with an interval of 12.3 months. UMSARS II scores progressed by 57.3% (P < 0.0001) and UMSARS I scores by 35.6% (P < 0.0001) in relation to the respective baseline scores with no differences between motor subtypes, diagnostic categories and gender. Significant inverse correlations between (1) UMSARS I or UMSARS II progression and (2) baseline disability measures (i.e., the respective UMSARS or SS3 scores) and disease duration were found. Furthermore, the increases in HY staging, SE ADL and SS3 correlated significantly with UMSARS I, UMSARS II, and UMSARS IV progression. This report is the first prospective study showing rapid annual UMSARS rates of decline in MSA. Our data contribute to the ongoing validation process of UMSARS, and they facilitate the planning and implementation of future neuroprotective intervention trials.

A nationwide survey of excessive daytime sleepiness in Parkinson's disease in France

To determine the prevalence of excessive daytime sleepiness (EDS) and that of dozing and sudden onset of sleep episodes (SOS) while driving in ambulatory patients with Parkinsons disease (PD) in France, a national sample of private and public neurologists was asked to recruit the first 10 consecutive nondemented PD patients. Each patient completed a questionnaire including the Epworth Sleepiness Scale (ESS) and the likelihood of dozing off and experiencing SOS episodes behind the wheel. Clinical and demographic data were collected. One thousand six hundred and twenty‐five patients with PD were included in the survey. Twenty‐nine percent of the patients suffered from EDS (ESS score ≥10) but only 0.8% declared a high chance of dozing while driving and 0.5% reported totally unpredictable SOS episodes while driving. Risk factors for EDS were male gender, reduced activity of daily living, and a high daily levodopa equivalent dosage. Risk factors for SOS episodes while driving were an ESS score ≥10, male gender, and low Hoehn and Yahr staging. EDS is common in ambulatory patients with PD and is a major risk factor for dozing and for SOS episodes behind the wheel in patients who drive.

Determinants of sleepiness in automobile drivers

Governmental agencies do not systematically investigate the presence of daytime sleepiness as a determinant of driving accidents. We surveyed automobile drivers traveling on summer vacations and driving long distances on a European highway. We evaluated their subjective daytime sleepiness while driving and any sleep deprivation just prior to departure. Five-hundred sixty-seven automobile drivers (mean age 37.7 +/- 11 years) were interviewed at a roadside rest-stop. Questions covered the sleep/wake schedule during the year, sleep habits, and the presence of symptoms frequently associated with sleep-disordered breathing. Sleep behavior just prior to departure was compared to the usual sleep schedule during the year. Fifty percent of the responders had a sleep restriction just prior to departure (mean -203 minutes) compared to usual total sleep time during the year; 10% had no nocturnal sleep prior to departure. Drivers younger than 30 years were significantly more acutely sleep deprived than other drivers. Economic migrants (subjects with low economic status) also experienced significant acute sleep restriction.

The European Multiple System Atrophy-Study Group (EMSA-SG)

Summary.Introduction. The European Multiple System Atrophy-Study Group (EMSA-SG) is an academic network comprising 23 centers across Europe and Israel that has constituted itself already in January 1999. This international forum of established experts under the guidance of the University Hospital of Innsbruck as coordinating center is supported by the 5th framework program of the European Union since March 2001 (QLK6-CT-2000-00661). Objectives. Primary goals of the network include (1) a central Registry for European multiple system atrophy (MSA) patients, (2) a decentralized DNA Bank, (3) the development and validation of the novel Unified MSA Rating Scale (UMSARS), (4) the conduction of a Natural History Study (NHS), and (5) the planning or implementation of interventional therapeutic trials. Methods. The EMSA-SG Registry is a computerized data bank localized at the coordinating centre in Innsbruck collecting diagnostic and therapeutic data of MSA patients. Blood samples of patients and controls are recruited into the DNA Bank. The UMSARS is a novel specific rating instrument that has been developed and validated by the EMSA-SG. The NHS comprises assessments of basic anthropometric data as well as a range of scales including the UMSARS, Unified Parkinson’s Disease Rating Scale (UPDRS), measures of global disability, Red Flag list, MMSE (Mini Mental State Examination), quality of live measures, i.e. EuroQoL 5D (EQ-5D) and Medical Outcome Study Short Form (SF-36) as well as the Beck Depression Inventory (BDI). In a subgroup of patients dysautonomic features are recorded in detail using the Queen Square Cardiovascular Autonomic Function Test Battery, the Composite Autonomic Symptom Scale (COMPASS) and measurements of residual urinary volume. Most of these measures are repeated at 6-monthly follow up visits for a total study period of 24 months. Surrogate markers of the disease progression are identified by the EMSA-SG using magnetic resonance and diffusion weighted imaging (MRI and DWI, respectively). Results. 412 patients have been recruited into the Registry so far. Probable MSA-P was the most common diagnosis (49% of cases). 507 patients donated DNA for research. 131 patients have been recruited into the NHS. There was a rapid deterioration of the motor disorder (in particular akinesia) by 26.1% of the UMSARS II, and – to a lesser degree – of activities of daily living by 16.8% of the UMSARS I in relation to the respective baseline scores. Motor progression was associated with low motor or global disability as well as low akinesia or cerebellar subscores at baseline. Mental function did not deteriorate during this short follow up period. Conclusion. For the first time, prospective data concerning disease progression are available. Such data about the natural history and prognosis of MSA as well as surrogate markers of disease process allow planning and implementation of multi-centre phase II/III neuroprotective intervention trials within the next years more effectively. Indeed, a trial on growth hormone in MSA has just been completed, and another on minocycline will be completed by the end of this year.

Sleep disorders in multiple system atrophy

Summary.Complaints about sleep disorders and excessive daytime sleepiness are common among patients with multiple system atrophy. The diffuse neurodegenerative process that encompasses the key structures involved in the regulation of the sleep/wake transition and respiratory function may account for these complaints and for the most frequent polysomnographic findings in MSA, i.e., sleep-related breathing disturbances and REM sleep behaviour disorder, which are both treatable conditions. Nocturnal stridor is an inspiratory sound produced by complex vocal cord muscle dysfunction. Often occurring with sleep apnoea, stridor is associated with decreased survival. REM sleep behaviour disorder, a parasomnia characterized by loss of normal skeletal muscle atonia during REM sleep with prominent motor activity, is detected in almost all patients. The pathophysiology of both disorders is partially elucidated but increasing evidence points to the role of basal ganglia dysfunction.

Neuroanatomical Study of the A11 Diencephalospinal Pathway in the Non-Human Primate

Background The A11 diencephalospinal pathway is crucial for sensorimotor integration and pain control at the spinal cord level. When disrupted, it is thought to be involved in numerous painful conditions such as restless legs syndrome and migraine. Its anatomical organization, however, remains largely unknown in the non-human primate (NHP). We therefore characterized the anatomy of this pathway in the NHP. Methods and Findings In situ hybridization of spinal dopamine receptors showed that D1 receptor mRNA is absent while D2 and D5 receptor mRNAs are mainly expressed in the dorsal horn and D3 receptor mRNA in both the dorsal and ventral horns. Unilateral injections of the retrograde tracer Fluoro-Gold (FG) into the cervical spinal enlargement labeled A11 hypothalamic neurons quasi-exclusively among dopamine areas. Detailed immunohistochemical analysis suggested that these FG-labeled A11 neurons are tyrosine hydroxylase-positive but dopa-decarboxylase and dopamine transporter-negative, suggestive of a L-DOPAergic nucleus. Stereological cell count of A11 neurons revealed that this group is composed by 4002±501 neurons per side. A 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) intoxication with subsequent development of a parkinsonian syndrome produced a 50% neuronal cell loss in the A11 group. Conclusion The diencephalic A11 area could be the major source of L-DOPA in the NHP spinal cord, where it may play a role in the modulation of sensorimotor integration through D2 and D3 receptors either directly or indirectly via dopamine formation in spinal dopa-decarboxylase-positives cells.

Simultaneous Intrastriatal 6-Hydroxydopamine and Quinolinic Acid Injection: A Model of Early-Stage Striatonigral Degeneration

Animal models reproducing early stages of striatonigral degeneration (SND), the core pathology underlying parkinsonism in multiple system atrophy, are lacking. We have developed a new model of early-stage SND by using a simultaneous unilateral administration of quinolinic acid (QA) and 6-hydroxydopamine (6-OHDA) into the putaminal equivalent of the rat striatum. Spontaneous and drug-induced behavior, thigmotactic scanning, paw reaching deficits, and histopathology were studied in rat groups: group 1 (control), group 2 (QA), group 3 (6-OHDA), and group 4 (QA + 6-OHDA). The double toxin administration resulted in reduction of the spontaneous and the amphetamine-induced ipsiversive bias in the 6-OHDA group and in a reduction of the apomorphine-induced ipsiversive rotations in the QA group. Simultaneous QA and 6-OHDA also reduced the thigmotactic bias observed in the 6-OHDA rats. Combined toxin elicited a nonsignificant contralateral deficit in paw reaching but a significant deficit on the ipsilateral side. Histopathology revealed a significant reduction of the lesioned striatal surface (-27%) with neuronal loss and increased astrogliosis in group 4 compared to group 2, consistent with an exacerbation of QA toxicity by additional 6-OHDA. By contrast, the mean loss of the TH-positive neurons in the ipsilateral substantia nigra pars compacta (SNc) of group 4 was less marked (-15%) than in the 6-OHDA group (-36%), indicating a possible protective action of intrastriatal QA upon 6-OHDA retrograde SNc degeneration. This study shows that a combined unilateral intrastriatal administration of QA and 6-OHDA may serve as a model of early stage SND which is more suitable for early therapeutic interventions.

When gender matters: Restless legs syndrome. Report of the “RLS and woman” workshop endorsed by the European RLS Study Group

Sleep is an essential human behavior that shows prominent gender differences. Disturbed sleep, in particular, is much more prevalent in females than males. Restless legs syndrome (RLS) as one cause of disturbed sleep was observed to be somewhat more common among women than men in Ekboms 1945 seminal series of clinical cases with the disease. He, however, reported this gender difference mainly for those with more severe symptoms. Since then numerous studies have reported that women are affected by RLS about twice as often as males for mild as well as moderate to severe RLS. The present review focuses on RLS in females from the perspectives of both epidemiology and pathophysiology. RLS will generally become worse or might appear for the first time during pregnancy. Parity increases the risk of RLS later in life suggesting that pregnancy is a specific behavioral risk factor for developing RLS. Some evidence suggests that dysfunction in iron metabolism and high estrogen levels might contribute to RLS during pregnancy. But, menopause does not lower the incidence of RLS nor does hormone replacement therapy lead to an increase, suggesting a quite complex uncertain role of hormones in the pathophysiology of RLS. Therefore, further, preferably longitudinal studies are needed to unravel the factors causing RLS in women. These studies should include genetic, clinical and polysomnographic variables, as well as hormonal measures and variables assessing iron metabolism.