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Petramfar P, Jankovic J. Medication refractory restless legs syndrome: Real-world experience. J Neurol Sci 2024; 463:123121. [PMID: 38968665 DOI: 10.1016/j.jns.2024.123121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 06/22/2024] [Accepted: 07/01/2024] [Indexed: 07/07/2024]
Abstract
BACKGROUND Restless Legs Syndrome (RLS), impacting 5-13% of the population, poses challenges in long-term management. A knowledge gap exists in predicting resistance to first-line therapies. OBJECTIVE To identify demographic and clinical factors predictive of refractory cases. METHODS This retrospective study, conducted at the Parkinson's Disease Center and Movement Disorders Clinic, Baylor College of Medicine, Houston, Texas (January 2018 to September 2023) identified all patients with RLS evaluated during the pre-specified period and compared clinical and demographic data between medication-refractory ("malignant") group and "benign" cohort. RESULTS Among 132 patients with RLS, 23 (17.4%) were categorized as medication-refractory. This cohort was characterized by a significantly lower mean age at onset (39.3 vs. 53.5 years, p = 0.0005), longer disease duration (26.7 vs. 14.0 years), and a higher prevalence of a positive family history of RLS among first-degree relatives compared to the "benign" group (56.5% vs. 15.5%, p = 0.003). Furthermore, compared to the "benign" group, in the refractory group dopamine agonists were initiated as the primary medication at a significantly higher rate (p = 0.006). CONCLUSION Our study found that a younger age at disease onset, prolonged disease duration, initial use of dopamine agonists, and a positive family history increased the likelihood of refractory RLS. We caution against the use of dopamine agonists, especially in young patients with RLS. Additionally, botulinum toxin might be considered a viable second-line treatment, especially for patients with otherwise medically-refractory RLS.
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Affiliation(s)
- Peyman Petramfar
- Parkinson's Disease Center and Movement Disorders Clinic, Department of Neurology, Baylor College of Medicine, Houston, TX, USA
| | - Joseph Jankovic
- Parkinson's Disease Center and Movement Disorders Clinic, Department of Neurology, Baylor College of Medicine, Houston, TX, USA.
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Chenini S, Barateau L, Dauvilliers Y. Restless legs syndrome: From clinic to personalized medicine. Rev Neurol (Paris) 2023; 179:703-714. [PMID: 37689536 DOI: 10.1016/j.neurol.2023.08.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/11/2023]
Abstract
Restless legs syndrome (RLS) is a common neurological sensorimotor disorder that impairs sleep, mood and quality of life. RLS is defined by an urge to move the legs at rest that increases in the evening and at night, and is frequently associated with metabolic and cardiovascular diseases. Symptoms frequency, age at RLS onset, severity, familial history and consequences of RLS vary widely between patients. A genetic susceptibility, iron deficiency, dopamine deregulation, and possible hypo-adenosinergic state may play a role in the pathophysiology of RLS. Polysomnographic recordings found often periodic leg movements during sleep and wakefulness in patients with RLS. RLS can be classified as primary or comorbid with major diseases: iron deficiency, renal, neurological, rheumatological and lung diseases. First-line treatments are low-dose dopamine agonists, and alpha-2-delta ligands depending on the clinical context, and second/third line opiates for pharmacoresistant forms of RLS. Augmentation syndrome is a serious complication of dopamine agonists and should be prevented by using the recommended low dose. Despite an increase in knowledge, RLS is still underdiagnosed, poorly recognized, resulting in substantial individual health burden and socioeconomic coast, and education is urgently needed to increase awareness of this disabling disorder.
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Affiliation(s)
- S Chenini
- National Reference Centre for Orphan Diseases Narcolepsy and Rare Hypersomnias, Sleep Unit, Department of Neurology, CHU Montpellier, University of Montpellier, Montpellier, France; Institute for Neurosciences of Montpellier (INM), University of Montpellier, INSERM, Montpellier, France.
| | - L Barateau
- National Reference Centre for Orphan Diseases Narcolepsy and Rare Hypersomnias, Sleep Unit, Department of Neurology, CHU Montpellier, University of Montpellier, Montpellier, France; Institute for Neurosciences of Montpellier (INM), University of Montpellier, INSERM, Montpellier, France
| | - Y Dauvilliers
- National Reference Centre for Orphan Diseases Narcolepsy and Rare Hypersomnias, Sleep Unit, Department of Neurology, CHU Montpellier, University of Montpellier, Montpellier, France; Institute for Neurosciences of Montpellier (INM), University of Montpellier, INSERM, Montpellier, France.
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3
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Ferré S, Köfalvi A, Ciruela F, Justinova Z, Pistis M. Targeting corticostriatal transmission for the treatment of cannabinoid use disorder. Trends Pharmacol Sci 2023; 44:495-506. [PMID: 37331914 PMCID: PMC10524660 DOI: 10.1016/j.tips.2023.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 05/17/2023] [Accepted: 05/19/2023] [Indexed: 06/20/2023]
Abstract
It is generally assumed that the rewarding effects of cannabinoids are mediated by cannabinoid CB1 receptors (CB1Rs) the activation of which disinhibits dopaminergic neurons in the ventral tegmental area (VTA). However, this mechanism cannot fully explain novel results indicating that dopaminergic neurons also mediate the aversive effects of cannabinoids in rodents, and previous results showing that preferentially presynaptic adenosine A2A receptor (A2AR) antagonists counteract self-administration of Δ-9-tetrahydrocannabinol (THC) in nonhuman primates (NHPs). Based on recent experiments in rodents and imaging studies in humans, we propose that the activation of frontal corticostriatal glutamatergic transmission constitutes an additional and necessary mechanism. Here, we review evidence supporting the involvement of cortical astrocytic CB1Rs in the activation of corticostriatal neurons and that A2AR receptor heteromers localized in striatal glutamatergic terminals mediate the counteracting effects of the presynaptic A2AR antagonists, constituting potential targets for the treatment of cannabinoid use disorder (CUD).
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Affiliation(s)
- Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, USA.
| | - Attila Köfalvi
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Francisco Ciruela
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, Barcelona, Spain; Neuroscience Program, Bellvitge Institute for Biomedical Research, L'Hospitalet de Llobregat, Spain
| | - Zuzana Justinova
- Division of Pharmacology, Physiology, and Biological Chemistry (PPBC), National Institute of General Medical Sciences, National Institutes of Health, Bethesda, MD, USA
| | - Marco Pistis
- Department of Biomedical Sciences, Section of Neuroscience and Clinical Pharmacology, University of Cagliari, Cagliari, Italy; Neuroscience Institute, Section of Cagliari, National Research Council of Italy (CNR), Cagliari, Italy
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Madhaw G, Gupta R, Dhamija P, Kumar N. A Randomized, Open Label, Exploratory Trial Comparing Efficacy of Amantadine and Ropinirole in Restless Legs Syndrome. Sleep Sci 2023; 16:174-182. [PMID: 37425973 PMCID: PMC10325843 DOI: 10.1055/s-0043-1770810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/11/2023] Open
Abstract
Objective Amantadine has both anti-glutamatergic and dopaminergic action and may improve restless legs syndrome (RLS). We compared the efficacy and adverse-effect profile of amantadine and ropinirole in RLS. Methods In this randomized, open-label, 12-week flexible-dose exploratory study, RLS patients with international RLS study group severity scale score (IRLSS) > 10 were randomized to receive either amantadine(100-300mg/day) or ropinirole (0.5-2mg/day). Drug dose was increased until week-6 if IRLSS failed to improve by ≥10% of previous visit score. IRLSS change from baseline at week-12 was the primary outcome. Secondary outcomes included change in RLS-related quality of life (RLS-QOL) and insomnia severity index (ISI), along with clinical-global-impression of change/improvement (CGI-I), and proportion of patients with adverse-effects and resulting discontinuation. Results Twenty-four patients received amantadine and 22 received ropinirole. Both groups had a significant effect for visit*treatment arm (F (2.19,68.15) =4.35;P = 0.01). With a similar baseline IRLSS, both intention-to-treat (ITT) and per-protocol analyses revealed comparable IRLSS until week-8, with ropinirole appearing superior from week-10 to week-12 (week-12 IRLSS, amantadine vs ropinirole:17.0 ± 5.7 vs 9.0 ± 4.4;P < 0.001). ITT analysis at week-12 showed comparable proportion of responders (≥10% IRLSS reduction) in both groups (P = 0.10). Both drugs improved sleep and QOL, but week-12 scores favoured ropinirole [(ISI:14.4 ± 5.7 vs 9.4 ± 4.5; P = 0.001) ;(RLS-QOL:70.4 ± 17.9 vs 86.5 ± 9.8; P = 0.005)]. CGI-I at week-12 favoured ropinirole (Mann-Whitney U = 35.50, S. E = 23.05;P = 0.01). Four patients in amantadine and two in ropinirole group developed adverse effects, with resulting discontinuation in two patients on amantadine. Conclusions The present study reports equivalent reduction in RLS symptoms with both amantadine and ropinirole until week-8, with the latter being superior from week-10 onwards. Ropinirole was better tolerated.
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Affiliation(s)
- Govind Madhaw
- Department of Neurology, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
| | - Ravi Gupta
- Division of Sleep Medicine, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
- Department of Psychiatry, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
| | - Puneet Dhamija
- Department of Pharmacology, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
| | - Niraj Kumar
- Department of Neurology, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
- Division of Sleep Medicine, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India
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Ferré S, Sarasola LI, Quiroz C, Ciruela F. Presynaptic adenosine receptor heteromers as key modulators of glutamatergic and dopaminergic neurotransmission in the striatum. Neuropharmacology 2023; 223:109329. [PMID: 36375695 DOI: 10.1016/j.neuropharm.2022.109329] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 11/01/2022] [Accepted: 11/03/2022] [Indexed: 11/12/2022]
Abstract
Adenosine plays a very significant role in modulating striatal glutamatergic and dopaminergic neurotransmission. In the present essay we first review the extensive evidence that indicates this modulation is mediated by adenosine A1 and A2A receptors (A1Rs and A2ARs) differentially expressed by the components of the striatal microcircuit that include cortico-striatal glutamatergic and mesencephalic dopaminergic terminals, and the cholinergic interneuron. This microcircuit mediates the ability of striatal glutamate release to locally promote dopamine release through the intermediate activation of cholinergic interneurons. A1Rs and A2ARs are colocalized in the cortico-striatal glutamatergic terminals, where they form A1R-A2AR and A2AR-cannabinoid CB1 receptor (CB1R) heteromers. We then evaluate recent findings on the unique properties of A1R-A2AR and A2AR-CB1R heteromers, which depend on their different quaternary tetrameric structure. These properties involve different allosteric mechanisms in the two receptor heteromers that provide fine-tune modulation of adenosine and endocannabinoid-mediated striatal glutamate release. Finally, we evaluate the evidence supporting the use of different heteromers containing striatal adenosine receptors as targets for drug development for neuropsychiatric disorders, such as Parkinson's disease and restless legs syndrome, based on the ability or inability of the A2AR to demonstrate constitutive activity in the different heteromers, and the ability of some A2AR ligands to act preferentially as neutral antagonists or inverse agonists, or to have preferential affinity for a specific A2AR heteromer.
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Affiliation(s)
- Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Baltimore, MD, USA.
| | - Laura I Sarasola
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, 08907, L'Hospitalet de Llobregat, Spain; Neuropharmacology and Pain Group, Neuroscience Program, Institut d'Investigació Biomèdica de Bellvitge, IDIBELL, 08907, L'Hospitalet de Llobregat, Spain
| | - César Quiroz
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Baltimore, MD, USA
| | - Francisco Ciruela
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, School of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, 08907, L'Hospitalet de Llobregat, Spain; Neuropharmacology and Pain Group, Neuroscience Program, Institut d'Investigació Biomèdica de Bellvitge, IDIBELL, 08907, L'Hospitalet de Llobregat, Spain.
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6
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Tang M, Sun Q, Zhang Y, Li H, Wang D, Wang Y, Wang Z. Circadian rhythm in restless legs syndrome. Front Neurol 2023; 14:1105463. [PMID: 36908590 PMCID: PMC9995399 DOI: 10.3389/fneur.2023.1105463] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 02/07/2023] [Indexed: 02/25/2023] Open
Abstract
Restless legs syndrome (RLS) is a sensorimotor disorder with a obvious circadian rhythm, as its symptoms often occur or worsen only in the evening or at night. The mechanisms behind the rhythms of RLS have not yet been fully elucidated. This review explores possible causes for the circadian fluctuations of the symptomatology, including the levels of iron, dopamine, melatonin, melanocortin, and thyroid-stimulating hormone in the brain, as well as conditions such as peripheral hypoxia and microvascular function disorders. The metabolic disturbances of the substances above can create a pathological imbalance, which is further aggravated by physiological fluctuations of circadian rhythms, and results in the worsening of RLS symptoms at night. The review concludes with the suggestions for RLS treatment and research directions in the future.
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Affiliation(s)
- Mingyang Tang
- Sleep Center, Department of Neurology, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Qingqing Sun
- Sleep Center, Department of Neurology, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Yanan Zhang
- Sleep Center, Department of Neurology, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Huimin Li
- Sleep Center, Department of Neurology, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Dong Wang
- Sleep Center, Department of Neurology, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Ying Wang
- Sleep Center, Department of Neurology, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Zan Wang
- Sleep Center, Department of Neurology, The First Hospital of Jilin University, Changchun, Jilin, China
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Silvani A, Ghorayeb I, Manconi M, Li Y, Clemens S. Putative Animal Models of Restless Legs Syndrome: A Systematic Review and Evaluation of Their Face and Construct Validity. Neurotherapeutics 2023; 20:154-178. [PMID: 36536233 PMCID: PMC10119375 DOI: 10.1007/s13311-022-01334-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/02/2022] [Indexed: 12/24/2022] Open
Abstract
Restless legs syndrome (RLS) is a sensorimotor disorder that severely affects sleep. It is characterized by an urge to move the legs, which is often accompanied by periodic limb movements during sleep. RLS has a high prevalence in the population and is usually a life-long condition. While its origins remain unclear, RLS is initially highly responsive to treatment with dopaminergic agonists that target D2-like receptors, in particular D2 and D3, but the long-term response is often unsatisfactory. Over the years, several putative animal models for RLS have been developed, mainly based on the epidemiological and neurochemical link with iron deficiency, treatment efficacy of D2-like dopaminergic agonists, or genome-wide association studies that identified risk factors in the patient population. Here, we present the first systematic review of putative animal models of RLS, provide information about their face and construct validity, and report their role in deciphering the underlying pathophysiological mechanisms that may cause or contribute to RLS. We propose that identifying the causal links between genetic risk factors, altered organ functions, and changes to molecular pathways in neural circuitry will eventually lead to more effective new treatment options that bypass the side effects of the currently used therapeutics in RLS, especially for long-term therapy.
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Affiliation(s)
- Alessandro Silvani
- Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum - University of Bologna, Ravenna Campus, Ravenna, Italy
| | - Imad Ghorayeb
- Département de Neurophysiologie Clinique, Pôle Neurosciences Cliniques, CHU de Bordeaux, Bordeaux, France
- Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, UMR 5287, Université de Bordeaux, Bordeaux, France
- Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, UMR 5287, CNRS, Bordeaux, France
| | - Mauro Manconi
- Sleep Medicine Unit, Neurocenter of Southern Switzerland, EOC, Ospedale Civico, Lugano, Switzerland
- Department of Neurology, University Hospital, Inselspital, Bern, Switzerland
- Faculty of Biomedical Sciences, Università della Svizzera Italiana, Lugano, Switzerland
| | - Yuqing Li
- Department of Neurology, College of Medicine, Norman Fixel Institute for Neurological Diseases, University of Florida, Gainesville, FL, USA
| | - Stefan Clemens
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, NC, USA.
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Sarasola LI, del Torrent CL, Pérez-Arévalo A, Argerich J, Casajuana-Martín N, Chevigné A, Fernández-Dueñas V, Ferré S, Pardo L, Ciruela F. The ADORA1 mutation linked to early-onset Parkinson’s disease alters adenosine A1-A2A receptor heteromer formation and function. Biomed Pharmacother 2022; 156:113896. [DOI: 10.1016/j.biopha.2022.113896] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 10/17/2022] [Accepted: 10/17/2022] [Indexed: 01/14/2023] Open
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Earley CJ, Jones BC, Ferré S. Brain-iron deficiency models of restless legs syndrome. Exp Neurol 2022; 356:114158. [PMID: 35779614 PMCID: PMC9357217 DOI: 10.1016/j.expneurol.2022.114158] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 06/24/2022] [Accepted: 06/25/2022] [Indexed: 11/04/2022]
Abstract
Restless legs syndrome (RLS) is a common sensorimotor disorder for which two main pathological elements are fairly well accepted: Brain iron deficiency (BID) and an altered dopaminergic system. The ability to better understand the causal and consequential factors related to these two pathological elements, would hopefully lead to the development of better therapeutic strategies for treating, if not curing, this disease. The current understanding of the relationship between these two elements is that BID leads to some alterations in neurotransmitters and subsequent changes in the dopaminergic system. Therefore, rodent models based on diet-induced BID, provide a biological substrate to understand the consequences of BID on dopaminergic pathway and on alternative pathways that may be involved. In this review, we present the current research on dopaminergic changes found in RLS subjects and compare that to what is seen in the BID rodent model to provide a validation of the BID rodent model. We also demonstrate the ability of the BID model to predict changes in other neurotransmitter systems and how that has led to new treatment options. Finally, we will present arguments for the utility of recombinant inbred mouse strains that demonstrate natural variation in brain iron, to explore the genetic basis of altered brain iron homeostasis as a model to understand why in idiopathic RLS there can exist a BID despite normal peripheral iron store. This review is the first to draw on 25 years of human and basic research into the pathophysiology of RLS to provide strong supportive data as to the validity of BID model as an important translational model of the disease. As we will demonstrate here, not only does the BID model closely and accurately mimic what we see in the dopaminergic system of RLS, it is the first model to identify alternative systems from which new treatments have recently been developed.
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Affiliation(s)
- Christopher J Earley
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Byron C Jones
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Sergi Ferré
- Integrative Neurobiology Section, National Institutes of Health/National Institute on Drug Abuse, Baltimore, MD, USA
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10
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Kalampokini S, Poyiadjis S, Vavougios GD, Artemiadis A, Zis P, Hadjigeorgiou GM, Bargiotas P. Restless legs syndrome due to brainstem stroke: A systematic review. Acta Neurol Scand 2022; 146:440-447. [PMID: 36063288 DOI: 10.1111/ane.13702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 08/05/2022] [Accepted: 08/21/2022] [Indexed: 11/28/2022]
Abstract
Restless Legs Syndrome (RLS) is a sleep-related movement disorder, which can also result from brainstem pathology. A systematic review of articles published in the electronic databases PubMed and Web of Science was conducted to summarize the existent literature on RLS associated with a brainstem stroke. We identified eight articles including 19 subjects with RLS due to brainstem ischemic lesion. The symptoms occurred simultaneously with the infarction (66.7%) or few days after (33.3%). The most common location of infarction was pons and less commonly medulla. In most cases (68.4%), symptoms were unilateral. In the majority of those cases (92.3%), the contralateral limb was affected due to a lateral pons infarction. RLS symptoms after infarction improved or resolved in almost 90% of cases within a few days up to 3 months. In almost all patients who received dopaminergic treatment (11 out of 13, 91.7%), the symptoms improved significantly or resolved completely. Screening for RLS has to be considered in patients suffering a brainstem stroke, particularly anteromedial pontine infarction. The appearance of acute unilateral RLS symptoms, usually in association with other sensorimotor deficits, should prompt the clinician to consider a vascular event in the brainstem. RLS in these cases seem to have a favorable outcome and respond well to dopaminergic treatment.
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Affiliation(s)
- Stefania Kalampokini
- Department of Neurology, Nicosia General Hospital and Medical school, University of Cyprus, Nicosia, Cyprus
| | | | - George D Vavougios
- Department of Neurology, Nicosia General Hospital and Medical school, University of Cyprus, Nicosia, Cyprus
| | - Artemios Artemiadis
- Department of Neurology, Nicosia General Hospital and Medical school, University of Cyprus, Nicosia, Cyprus
| | - Panagiotis Zis
- Department of Neurology, Nicosia General Hospital and Medical school, University of Cyprus, Nicosia, Cyprus
| | - Georgios M Hadjigeorgiou
- Department of Neurology, Nicosia General Hospital and Medical school, University of Cyprus, Nicosia, Cyprus
| | - Panagiotis Bargiotas
- Department of Neurology, Nicosia General Hospital and Medical school, University of Cyprus, Nicosia, Cyprus
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Salminen AV, Clemens S, García-Borreguero D, Ghorayeb I, Li Y, Manconi M, Ondo W, Rye D, Siegel JM, Silvani A, Winkelman JW, Allen RP, Ferré S. Consensus guidelines on the construct validity of rodent models of restless legs syndrome. Dis Model Mech 2022; 15:dmm049615. [PMID: 35946581 PMCID: PMC9393041 DOI: 10.1242/dmm.049615] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 07/10/2022] [Indexed: 12/16/2022] Open
Abstract
Our understanding of the causes and natural course of restless legs syndrome (RLS) is incomplete. The lack of objective diagnostic biomarkers remains a challenge for clinical research and for the development of valid animal models. As a task force of preclinical and clinical scientists, we have previously defined face validity parameters for rodent models of RLS. In this article, we establish new guidelines for the construct validity of RLS rodent models. To do so, we first determined and agreed on the risk, and triggering factors and pathophysiological mechanisms that influence RLS expressivity. We then selected 20 items considered to have sufficient support in the literature, which we grouped by sex and genetic factors, iron-related mechanisms, electrophysiological mechanisms, dopaminergic mechanisms, exposure to medications active in the central nervous system, and others. These factors and biological mechanisms were then translated into rodent bioequivalents deemed to be most appropriate for a rodent model of RLS. We also identified parameters by which to assess and quantify these bioequivalents. Investigating these factors, both individually and in combination, will help to identify their specific roles in the expression of rodent RLS-like phenotypes, which should provide significant translational implications for the diagnosis and treatment of RLS.
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Affiliation(s)
- Aaro V. Salminen
- Institute of Neurogenomics, Helmholtz Zentrum München GmbH - German Research Center for Environmental Health, 85764 Neuherberg, Germany
- Institute of Human Genetics, Klinikum rechts der Isar, Technische Universität München, 81675 Munich, Germany
| | - Stefan Clemens
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
| | | | - Imad Ghorayeb
- Département de Neurophysiologie Clinique, Pôle Neurosciences Cliniques, CHU de Bordeaux, 33076 Bordeaux, France
- Université de Bordeaux, Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, UMR 5287, 33076 Bordeaux, France
- CNRS, Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, UMR 5287, 33076 Bordeaux, France
| | - Yuqing Li
- Department of Neurology, Norman Fixel Institute for Neurological Diseases, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Mauro Manconi
- Sleep Medicine Unit, Regional Hospital of Lugano, Neurocenter of Southern Switzerland, 6900 Lugano, Switzerland
- Faculty of Biomedical Sciences, Università della Svizzera Italiana, 6900 Lugano, Switzerland
- Department of Neurology, University Hospital Inselspital, 3010 Bern, Switzerland
| | - William Ondo
- Houston Methodist Hospital Neurological Institute, Weill Cornell Medical School, Houston, TX 77070, USA
| | - David Rye
- Department of Neurology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Jerome M. Siegel
- Neuropsychiatric Institute and Brain Research Institute, University of California, Los Angeles, CA 90095, USA
- Neurobiology Research, Veterans Administration Greater Los Angeles Healthcare System, North Hills, CA 91343, USA
| | - Alessandro Silvani
- Department of Biomedical and Neuromotor Sciences Alma Mater Studiorum, Università di Bologna, 48121 Ravenna Campus, Ravenna, Italy
| | - John W. Winkelman
- Departments of Psychiatry and Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
| | - Richard P. Allen
- Department of Neurology, Johns Hopkins University, Baltimore, MD 21224, USA
| | - Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
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Khachatryan SG, Ferri R, Fulda S, Garcia‐Borreguero D, Manconi M, Muntean M, Stefani A. Restless legs syndrome: Over 50 years of European contribution. J Sleep Res 2022; 31:e13632. [PMID: 35808955 PMCID: PMC9542244 DOI: 10.1111/jsr.13632] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 04/21/2022] [Accepted: 04/22/2022] [Indexed: 11/28/2022]
Abstract
Restless legs syndrome (RLS) is a sensorimotor neurological disorder characterised by an urge to move the limbs with a circadian pattern (occurring in the evening/at night), more prominent at rest, and relieved with movements. RLS is one of the most prevalent sleep disorders, occurring in 5%-10% of the European population. Thomas Willis first described RLS clinical cases already in the 17th century, and Karl-Axel Ekbom described the disease as a modern clinical entity in the 20th century. Despite variable severity, RLS can markedly affect sleep (partly through the presence of periodic leg movements) and quality of life, with a relevant socio-economic impact. Thus, its recognition and treatment are essential. However, screening methods present limitations and should be improved. Moreover, available RLS treatment options albeit providing sustained relief to many patients are limited in number. Additionally, the development of augmentation with dopamine agonists represents a major treatment problem. A better understanding of RLS pathomechanisms can bring to light novel treatment possibilities. With emerging new avenues of research in pharmacology, imaging, genetics, and animal models of RLS, this is an interesting and constantly growing field of research. This review will update the reader on the current state of RLS clinical practice and research, with a special focus on the contribution of European researchers.
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Affiliation(s)
- Samson G. Khachatryan
- Department of Neurology and NeurosurgeryNational Institute of HealthYerevanArmenia
- Sleep Disorders CenterSomnus Neurology ClinicYerevanArmenia
| | | | - Stephany Fulda
- Sleep Medicine UnitNeurocenter of Southern Switzerland, Ospedale CivicoLuganoSwitzerland
| | | | - Mauro Manconi
- Sleep Medicine UnitNeurocenter of Southern Switzerland, Ospedale CivicoLuganoSwitzerland
- Department of NeurologyUniversity HospitalInselspitalBernSwitzerland
| | - Maria‐Lucia Muntean
- Center for Parkinson's Disease and Movement DisordersParacelsus‐Elena KlinikKasselGermany
| | - Ambra Stefani
- Sleep Disorders Clinic, Department of NeurologyMedical University of InnsbruckInnsbruckAustria
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Rodrigues MS, Ferreira SG, Quiroz C, Earley CJ, García-Borreguero D, Cunha RA, Ciruela F, Köfalvi A, Ferré S. Brain Iron Deficiency Changes the Stoichiometry of Adenosine Receptor Subtypes in Cortico-Striatal Terminals: Implications for Restless Legs Syndrome. Molecules 2022; 27:1489. [PMID: 35268590 PMCID: PMC8911604 DOI: 10.3390/molecules27051489] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 02/19/2022] [Accepted: 02/21/2022] [Indexed: 01/01/2023] Open
Abstract
Brain iron deficiency (BID) constitutes a primary pathophysiological mechanism in restless legs syndrome (RLS). BID in rodents has been widely used as an animal model of RLS, since it recapitulates key neurochemical changes reported in RLS patients and shows an RLS-like behavioral phenotype. Previous studies with the BID-rodent model of RLS demonstrated increased sensitivity of cortical pyramidal cells to release glutamate from their striatal nerve terminals driving striatal circuits, a correlative finding of the cortical motor hyperexcitability of RLS patients. It was also found that BID in rodents leads to changes in the adenosinergic system, a downregulation of the inhibitory adenosine A1 receptors (A1Rs) and upregulation of the excitatory adenosine A2A receptors (A2ARs). It was then hypothesized, but not proven, that the BID-induced increased sensitivity of cortico-striatal glutamatergic terminals could be induced by a change in A1R/A2AR stoichiometry in favor of A2ARs. Here, we used a newly developed FACS-based synaptometric analysis to compare the relative abundance on A1Rs and A2ARs in cortico-striatal and thalamo-striatal glutamatergic terminals (labeled with vesicular glutamate transporters VGLUT1 and VGLUT2, respectively) of control and BID rats. It could be demonstrated that BID (determined by measuring transferrin receptor density in the brain) is associated with a selective decrease in the A1R/A2AR ratio in VGLUT1 positive-striatal terminals.
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Affiliation(s)
- Matilde S. Rodrigues
- CNC-Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; (M.S.R.); (S.G.F.); (R.A.C.); (A.K.)
| | - Samira G. Ferreira
- CNC-Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; (M.S.R.); (S.G.F.); (R.A.C.); (A.K.)
| | - César Quiroz
- Integrative Neurobiology Section, National Institute on Drug Abuse, Baltimore, MD 21224, USA;
| | | | | | - Rodrigo A. Cunha
- CNC-Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; (M.S.R.); (S.G.F.); (R.A.C.); (A.K.)
- Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Francisco Ciruela
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, 08907 L’Hospitalet de Llobregat, Spain;
- Neuropharmacology and Pain Group, Neuroscience Program, Institut d’Investigació Biomèdica de Belvitge, Idibell, 08907 L’Hospitalet de Llobregat, Spain
| | - Attila Köfalvi
- CNC-Center for Neuroscience and Cell Biology of Coimbra, University of Coimbra, 3004-504 Coimbra, Portugal; (M.S.R.); (S.G.F.); (R.A.C.); (A.K.)
| | - Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Baltimore, MD 21224, USA;
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14
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Wang XX, Feng Y, Tan EK, Ondo WG, Wu YC. Stroke-related restless legs syndrome: epidemiology, clinical characteristics and pathophysiology. Sleep Med 2022; 90:238-248. [DOI: 10.1016/j.sleep.2022.02.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 01/23/2022] [Accepted: 02/01/2022] [Indexed: 12/24/2022]
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15
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Drakatos P, Olaithe M, Verma D, Ilic K, Cash D, Fatima Y, Higgins S, Young AH, Chaudhuri KR, Steier J, Skinner T, Bucks R, Rosenzweig I. Periodic limb movements during sleep: a narrative review. J Thorac Dis 2022; 13:6476-6494. [PMID: 34992826 PMCID: PMC8662505 DOI: 10.21037/jtd-21-1353] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 10/20/2021] [Indexed: 01/02/2023]
Abstract
Objective Using narrative review techniques, this paper evaluates the evidence for separable underlying patho-mechanisms of periodic limb movements (PLMs) to separable PLM motor patterns and phenotypes, in order to elucidate potential new treatment modalities. Background Periodic limb movement disorder (PLMD) is estimated to occur in 5–8% of the paediatric population and 4–11% of the general adult population. Due to significant sleep fragmentation, PLMD can lead to functional impairment, including hyperactivity and delayed language development in children, and poor concentration and work performance in adults. Longitudinal data demonstrate that those with PLMD are at greater risk of depression and anxiety, and a 4-fold greater risk of developing dementia. PLMD has been extensively studied over the past two decades, and several key insights into the genetic, pathophysiological, and neural correlates have been proposed. Amongst these proposals is the concept of separable PLM phenotypes, proposed on the basis of nocturnal features such as the ratio of limb movements and distribution throughout the night. PLM phenotype and presentation, however, varies significantly depending on the scoring utilized and the nocturnal features examined, across age, and co-morbid clinical conditions. Furthermore, associations between these phenotypes with major neurologic and psychiatric disorders remain controversial. Methods In order to elucidate potential divergent biological pathways that may help clarify important new treatment modalities, this paper utilizes narrative review and evaluates the evidence linking PLM motor patterns and phenotypes with hypothesised underlying patho-mechanisms. Distinctive, underlying patho-mechanisms include: a pure motor mechanism originating in the spinal cord, iron deficiency, dopamine system dysfunction, thalamic glutamatergic hyperactivity, and a more cortical-subcortical interplay. In support of the latter hypothesis, PLM rhythmicity appears tightly linked to the microarchitecture of sleep, not dissimilarly to the apnoeic/hypopneic events seen in obstructive sleep apnea (OSA). Conclusions This review closes with a proposal for greater investigation into the identification of potential, divergent biological pathways. To do so would require prospective, multimodal imaging clinical studies which may delineate differential responses to treatment in restless legs syndrome (RLS) without PLMS and PLMS without RLS. This could pave the way toward important new treatment modalities.
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Affiliation(s)
- Panagis Drakatos
- Sleep and Brain Plasticity Centre, CNS, IoPPN, King's College London, London, UK.,Sleep Disorders Centre, Guy's and St Thomas' Hospital, GSTT NHS, London, UK.,Faculty of Life and Sciences Medicine, King's College London, London, UK
| | - Michelle Olaithe
- School of Psychological Science, University of Western Australia, Perth, Western Australia, Australia
| | - Dhun Verma
- Sleep and Brain Plasticity Centre, CNS, IoPPN, King's College London, London, UK
| | - Katarina Ilic
- Sleep and Brain Plasticity Centre, CNS, IoPPN, King's College London, London, UK.,BRAIN, Imaging Centre, CNS, King's College London, London, UK
| | - Diana Cash
- Sleep and Brain Plasticity Centre, CNS, IoPPN, King's College London, London, UK.,BRAIN, Imaging Centre, CNS, King's College London, London, UK
| | - Yaqoot Fatima
- Institute for Social Science Research, University of Queensland, Brisbane, Australia.,Centre for Rural and Remote Health, James Cook University, Mount Isa, Australia
| | - Sean Higgins
- Sleep and Brain Plasticity Centre, CNS, IoPPN, King's College London, London, UK.,Sleep Disorders Centre, Guy's and St Thomas' Hospital, GSTT NHS, London, UK
| | - Allan H Young
- School of Academic Psychiatry, King's College London, London, UK
| | - K Ray Chaudhuri
- King's College London and Parkinson's Foundation Centre of Excellence, King's College Hospital, London, UK
| | - Joerg Steier
- Sleep Disorders Centre, Guy's and St Thomas' Hospital, GSTT NHS, London, UK.,Faculty of Life and Sciences Medicine, King's College London, London, UK
| | - Timothy Skinner
- Institute of Psychology, University of Copenhagen, Copenhagen, Denmark.,La Trobe Rural Health School, La Trobe University, Bendigo, Victoria, Australia
| | - Romola Bucks
- School of Psychological Science, University of Western Australia, Perth, Western Australia, Australia.,The Raine Study, University of Western Australia, Perth, Australia
| | - Ivana Rosenzweig
- Sleep and Brain Plasticity Centre, CNS, IoPPN, King's College London, London, UK.,Sleep Disorders Centre, Guy's and St Thomas' Hospital, GSTT NHS, London, UK
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16
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Ferré S, Belcher AM, Bonaventura J, Quiroz C, Sánchez-Soto M, Casadó-Anguera V, Cai NS, Moreno E, Boateng CA, Keck TM, Florán B, Earley CJ, Ciruela F, Casadó V, Rubinstein M, Volkow ND. Functional and pharmacological role of the dopamine D 4 receptor and its polymorphic variants. Front Endocrinol (Lausanne) 2022; 13:1014678. [PMID: 36267569 PMCID: PMC9578002 DOI: 10.3389/fendo.2022.1014678] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 09/14/2022] [Indexed: 11/13/2022] Open
Abstract
The functional and pharmacological significance of the dopamine D4 receptor (D4R) has remained the least well understood of all the dopamine receptor subtypes. Even more enigmatic has been the role of the very prevalent human DRD4 gene polymorphisms in the region that encodes the third intracellular loop of the receptor. The most common polymorphisms encode a D4R with 4 or 7 repeats of a proline-rich sequence of 16 amino acids (D4.4R and D4.7R). DRD4 polymorphisms have been associated with individual differences linked to impulse control-related neuropsychiatric disorders, with the most consistent associations established between the gene encoding D4.7R and attention-deficit hyperactivity disorder (ADHD) and substance use disorders. The function of D4R and its polymorphic variants is being revealed by addressing the role of receptor heteromerization and the relatively avidity of norepinephrine for D4R. We review the evidence conveying a significant and differential role of D4.4R and D4.7R in the dopaminergic and noradrenergic modulation of the frontal cortico-striatal pyramidal neuron, with implications for the moderation of constructs of impulsivity as personality traits. This differential role depends on their ability to confer different properties to adrenergic α2A receptor (α2AR)-D4R heteromers and dopamine D2 receptor (D2R)-D4R heteromers, preferentially localized in the perisomatic region of the frontal cortical pyramidal neuron and its striatal terminals, respectively. We also review the evidence to support the D4R as a therapeutic target for ADHD and other impulse-control disorders, as well as for restless legs syndrome.
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Affiliation(s)
- Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Baltimore, MD, United States
- *Correspondence: Sergi Ferré,
| | - Annabelle M. Belcher
- Division of Addiction Research and Treatment, Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Jordi Bonaventura
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Baltimore, MD, United States
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, L'Hospitalet de Llobregat, Spain
- Neuropharmacology & Pain Group, Neuroscience Program, Bellvitge Institute for Biomedical Research, L'Hospitalet de Llobregat, Spain
| | - César Quiroz
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Baltimore, MD, United States
| | - Marta Sánchez-Soto
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Baltimore, MD, United States
| | - Verònica Casadó-Anguera
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Barcelona, Spain
| | - Ning-Sheng Cai
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Baltimore, MD, United States
| | - Estefanía Moreno
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Barcelona, Spain
| | - Comfort A. Boateng
- Department of Basic Pharmaceutical Sciences, Fred Wilson School of Pharmacy, High Point, NC, United States
| | - Thomas M. Keck
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ, United States
| | - Benjamín Florán
- Departament of Physiology, Biophysics and Neurosciences, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Mexico City, Mexico
| | - Christopher J. Earley
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Francisco Ciruela
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, L'Hospitalet de Llobregat, Spain
- Neuropharmacology & Pain Group, Neuroscience Program, Bellvitge Institute for Biomedical Research, L'Hospitalet de Llobregat, Spain
| | - Vicent Casadó
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Barcelona, Spain
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas and, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Nora D. Volkow
- National Institute on Drug Abuse, National Institutes of Health, Rockville, MD, United States
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17
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Abstract
Restless Legs Syndrome (RLS) is a sensorimotor disorder that severely affects sleep. It is characterized by an urge to move the legs that is often accompanied by periodic limb movements during sleep (PLMS). RLS has a high prevalence in the population and is usually a life-long condition. While its origins remain unclear, RLS is initially highly responsive to treatment with dopaminergics that target the D3 receptor. However, over time patients often develop a gradual tolerance that can lead to the emergence of adverse effects and the augmentation of the symptoms. While the basal ganglia and the striatum control leg movements, the lumbar spinal cord is the gateway for the sensory processing of the symptoms and critical for the associated leg movements. D3 receptors are highly expressed in nucleus accumbens (NAc) of the striatum and the sensory-processing areas of the spinal dorsal horn. In contrast, D1 receptors are strongly expressed throughout the entire striatum and in the ventral horn of the spinal cord. Long-term treatment with D3 receptor full agonists is associated with an upregulation of the D1 receptor subtype, and D3 and D1 receptors can form functional heteromers, in which the D3R controls the D1R function. It is conceivable that the switch from beneficial treatment to augmentation observed in RLS patients after prolonged D3R agonist exposure may be the result of unmasked D1-like receptor actions.
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Affiliation(s)
- Stefan Clemens
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, NC, USA.
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18
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Abstract
Restless legs syndrome (RLS) is a common sensorimotor disorder characterized by an urge to move that appears during rest or is exacerbated by rest, that occurs in the evening or night and that disappears during movement or is improved by movement. Symptoms vary considerably in age at onset, frequency and severity, with severe forms affecting sleep, quality of life and mood. Patients with RLS often display periodic leg movements during sleep or resting wakefulness. RLS is considered to be a complex condition in which predisposing genetic factors, environmental factors and comorbidities contribute to the expression of the disorder. RLS occurs alone or with comorbidities, for example, iron deficiency and kidney disease, but also with cardiovascular diseases, diabetes mellitus and neurological, rheumatological and respiratory disorders. The pathophysiology is still unclear, with the involvement of brain iron deficiency, dysfunction in the dopaminergic and nociceptive systems and altered adenosine and glutamatergic pathways as hypotheses being investigated. RLS is poorly recognized by physicians and it is accordingly often incorrectly diagnosed and managed. Treatment guidelines recommend initiation of therapy with low doses of dopamine agonists or α2δ ligands in severe forms. Although dopaminergic treatment is initially highly effective, its long-term use can result in a serious worsening of symptoms known as augmentation. Other treatments include opioids and iron preparations.
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19
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Garcia-Borreguero D, Garcia-Malo C, Granizo JJ, Ferré S. A Randomized, Placebo-Controlled Crossover Study with Dipyridamole for Restless Legs Syndrome. Mov Disord 2021; 36:2387-2392. [PMID: 34137476 PMCID: PMC8530834 DOI: 10.1002/mds.28668] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 04/26/2021] [Accepted: 04/29/2021] [Indexed: 01/25/2023] Open
Abstract
Background New pharmacological targets are needed for restless legs syndrome. Preclinical data suggest that a hypoadenosinergic state plays an important pathogenetic role. Objective The objective of this study was to determine whether inhibitors of equilibrative nucleoside transporters, for example, dipyridamole, could provide effective symptomatic treatment. Methods A 2‐week double‐blind, placebo‐controlled crossover study assessed the efficacy of dipyridamole (possible up‐titration to 300 mg) in untreated patients with idiopathic restless legs syndrome. Multiple suggested immobilization tests and polysomnography were performed after each treatment phase. Severity was assessed weekly using the International Restless Legs Rating Scale, Clinical Global Impression, and the Medical Outcomes Study Sleep scale. The primary end point was therapeutic response. Results Twenty‐eight of 29 patients recruited were included. International Restless Legs Rating Scale scores improved from a mean ± standard deviation of 24.1 ± 3.1 at baseline to 11.1 ± 2.3 at the end of week 2, versus 23.7 ± 3.4 to 18.7 ± 3.2 under placebo (P < 0.001). Clinical Global Impression, Medical Outcomes Study Sleep, and Multiple Suggested Immobilization Test scores all improved (P < 0.001). The mean effective dose of dipyridamole was 217.8 ± 33.1 mg/d. Sleep variables improved. The mean periodic leg movement index at the end of treatment with dipyridamole was 8.2 ± 3.5 versus. 28.1 ± 6.7 under placebo. Side effects (dipyridamole vs placebo) included abdominal distension (18% vs. 7%), dizziness (10.7% vs 7.1%), diarrhea, and asthenia (each 7.1% vs 3.6%). Conclusions Dipyridamole has significant therapeutic effects on both sensory and motor symptoms of restless legs syndrome and on sleep. Our findings confirm the efficacy of dipyridamole in restless legs syndrome predicted from preclinical studies and support a key role of adenosine in restless legs syndrome. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society
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Affiliation(s)
| | | | - Juan José Granizo
- Department of Clinical Epidemiology, Hospital Universitario Infanta Cristina, Instituto de Investigaciones Sanitarias Puerta de Hierro, Madrid, Spain
| | - Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, Maryland, USA
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20
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Lai YY, Kodama T, Hsieh KC, Nguyen D, Siegel JM. Substantia nigra pars reticulata-mediated sleep and motor activity regulation. Sleep 2021; 44:5893883. [PMID: 32808987 DOI: 10.1093/sleep/zsaa151] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 08/01/2020] [Indexed: 12/20/2022] Open
Abstract
STUDY OBJECTIVES The substantia nigra pars reticulata (SNR) is a major output nucleus of the basal ganglia. Animal studies have shown that lesions of the SNR cause hyposomnia and motor hyperactivity, indicating that the SNR may play a role in the control of sleep and motor activity. METHODS Eight 8- to 10-week-old adult male Sprague-Dawley rats were used. After 3 days of baseline polysomnographic recording, dialysates were collected from the lateral SNR across natural sleep-wake states. Muscimol and bicuculline were microinfused into the lateral SNR. RESULTS We found that GABA release in the lateral SNR is negatively correlated with slow wave sleep (SWS; R = -0.266, p < 0.01, n = 240) and positively correlated with waking (R = 0.265, p < 0.01, n = 240) in rats. Microinfusion of muscimol into the lateral SNR decreased sleep time and sleep quality, as well as eliciting motor hyperactivity in wake and increased periodic leg movement in SWS, while bicuculline infused into the lateral SNR increased sleep and decreased motor activity in SWS in rats. Muscimol infusion skewed the distribution of inter-movement intervals, with most between 10 and 20 s, while a flat distribution of intervals between 10 and 90 s was seen in baseline conditions. CONCLUSIONS Activation of the lateral SNR is important for inducing sleep and inhibiting motor activity prior to and during sleep, and thus to the maintenance of sleep. Abnormal function of the lateral SNR may cause hyposomnia and motor hyperactivity in quiet wake and in sleep.
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Affiliation(s)
- Yuan-Yang Lai
- Department of Psychiatry & Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, CA.,VA Greater Los Angeles HealthCare System, North Hills, CA.,Greater Los Angeles Veterans Research and Education Foundation, Los Angeles, CA
| | - Tohru Kodama
- Department of Psychiatry & Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, CA.,Physiological Psychology Lab, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan
| | - Kung-Chiao Hsieh
- VA Greater Los Angeles HealthCare System, North Hills, CA.,Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA
| | - Darian Nguyen
- Department of Psychiatry & Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, CA
| | - Jerome M Siegel
- Department of Psychiatry & Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles, CA.,VA Greater Los Angeles HealthCare System, North Hills, CA
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21
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Ferré S, Guitart X, Quiroz C, Rea W, García-Malo C, Garcia-Borreguero D, Allen RP, Earley CJ. Akathisia and Restless Legs Syndrome: Solving the Dopaminergic Paradox. Sleep Med Clin 2021; 16:249-267. [PMID: 33985651 DOI: 10.1016/j.jsmc.2021.02.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Akathisia is an urgent need to move that is associated with treatment with dopamine receptor blocking agents (DRBAs) and with restless legs syndrome (RLS). The pathogenetic mechanism of akathisia has not been resolved. This article proposes that it involves an increased presynaptic dopaminergic transmission in the ventral striatum and concomitant strong activation of postsynaptic dopamine D1 receptors, which form complexes (heteromers) with dopamine D3 and adenosine A1 receptors. It also proposes that in DRBA-induced akathisia, increased dopamine release depends on inactivation of autoreceptors, whereas in RLS it depends on a brain iron deficiency-induced down-regulation of striatal presynaptic A1 receptors.
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Affiliation(s)
- Sergi Ferré
- Integrative Neurobiology Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Triad Building, 333 Cassell Drive, Baltimore, MD 21224, USA.
| | - Xavier Guitart
- Integrative Neurobiology Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Triad Building, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - César Quiroz
- Integrative Neurobiology Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Triad Building, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - William Rea
- Integrative Neurobiology Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Triad Building, 333 Cassell Drive, Baltimore, MD 21224, USA
| | - Celia García-Malo
- Sleep Research Institute, Paseo de la Habana 151, Madrid 28036, Spain
| | | | - Richard P Allen
- Department of Neurology, Johns Hopkins University, Johns Hopkins Bayview Medical Center, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA
| | - Christopher J Earley
- Department of Neurology, Johns Hopkins University, Johns Hopkins Bayview Medical Center, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA
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22
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Lv Q, Wang X, Asakawa T, Wang XP. Pharmacologic Treatment of Restless Legs Syndrome. Curr Neuropharmacol 2021; 19:372-382. [PMID: 33380302 PMCID: PMC8033969 DOI: 10.2174/1570159x19666201230150127] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 10/24/2020] [Accepted: 12/19/2020] [Indexed: 01/14/2023] Open
Abstract
Restless legs syndrome (RLS)/Willis-Ekbom disease is a neurologic disorder characterized by a strong desire to move when at rest (usually in the evening) and paraesthesia in their lower legs. The most widely used therapies for first-line treatment of RLS are dopaminergic drugs; however, their long-term use can lead to augmentation. α2δ Ligands, opioids, iron, glutamatergic drugs, adenosine, and sleep aids have been investigated as alternatives. The pathogenesis of RLS is not well understood. Despite the efficacy of dopaminergic drugs in the treatment of this disorder, unlike in Parkinson's disease dopaminergic cell loss in the substantia nigra has not been observed in RLS. The etiology of RLS is likely complex, involving multiple neural pathways. RLS-related genes identified in genome-wide association studies can provide insight into the mechanistic basis and pathophysiology of RLS. Here we review the current treatments and knowledge of the mechanisms underlying RLS.
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Affiliation(s)
| | | | - Tetsuya Asakawa
- Address correspondence to these authors at the Department of Neurology, TongRen Hospital, Shanghai Jiao Tong University School of Medicine, No.1111 Xianxia Road, 200336, Shanghai, China; Tel: +86-021-52039999-72223; Fax: +86-021-52039999-72223; E-mail: and Department of Neurosurgery, Hamamatsu University School of Medicine, Handayama, 1-20-1, Higashi-ku, Hamamatsu-city, Shizuoka 431-3192, Japan; Tel: + 81-53-435-2283; Fax: + 81-53-435-2282;, E-mail:
| | - Xiao Ping Wang
- Address correspondence to these authors at the Department of Neurology, TongRen Hospital, Shanghai Jiao Tong University School of Medicine, No.1111 Xianxia Road, 200336, Shanghai, China; Tel: +86-021-52039999-72223; Fax: +86-021-52039999-72223; E-mail: and Department of Neurosurgery, Hamamatsu University School of Medicine, Handayama, 1-20-1, Higashi-ku, Hamamatsu-city, Shizuoka 431-3192, Japan; Tel: + 81-53-435-2283; Fax: + 81-53-435-2282;, E-mail:
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Lyu S, Xing H, Liu Y, Girdhar P, Zhang K, Yokoi F, Xiao R, Li Y. Deficiency of Meis1, a transcriptional regulator, in mice and worms: Neurochemical and behavioral characterizations with implications in the restless legs syndrome. J Neurochem 2020; 155:522-537. [PMID: 32910473 PMCID: PMC7894994 DOI: 10.1111/jnc.15177] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 08/04/2020] [Accepted: 08/28/2020] [Indexed: 12/21/2022]
Abstract
Restless legs syndrome is a sleep-related sensorimotor neurological disease affecting up to 10% of the population. Genetic analyses have identified Myeloid Ecotropic viral Integration Site 1 (MEIS1), a transcriptional regulator, to be associated with not only the restless legs syndrome but also self-reported symptoms of insomnia and sleep. This study is to determine if Meis1 deficiency in mice can lead to restless legs syndrome-like phenotypes, and if it is the case, what the underlying mechanisms are. We used two genetic model systems, Caenorhabditis elegans and mice. Egg retention assay and fluorescent reporters were used with C. elegans. For mice, we performed behavioral tests, serum and brain iron detection, qRT-PCR, western blot, immunohistochemistry, and in vitro brain-slice recording. Our results showed that with C. elegans, the function of dop-3, an orthologue of DRD2, was diminished after the knockdown of unc-62, an ortholog of MEIS1. Additionally, unc-62 knockdown led to enhanced transcription of the orthologue of tyrosine hydroxylase, cat-2. Meis1 knockout mice were hyperactive and had a rest-phase-specific increased probability of waking. Moreover, Meis1 knockout mice had increased serum ferritin and altered striatal dopaminergic and cholinergic systems. Specifically, Meis1 knockout mice showed an increased mRNA level but decreased protein level of tyrosine hydroxylase in the striatum. Furthermore, Meis1 knockout mice had increased striatal dopamine turnover and decreased spontaneous firing regularity of striatal cholinergic interneurons. Our data suggest that Meis1 knockout mice have restless legs syndrome-like motor restlessness and changes in serum ferritin levels. The symptoms may be related to dysfunctional dopaminergic and cholinergic systems.
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Affiliation(s)
- Shangru Lyu
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, University of Florida, Gainesville, FL, USA
| | - Hong Xing
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, University of Florida, Gainesville, FL, USA
| | - Yuning Liu
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, University of Florida, Gainesville, FL, USA
| | - Pallavi Girdhar
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, University of Florida, Gainesville, FL, USA
| | - Keer Zhang
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, University of Florida, Gainesville, FL, USA
| | - Fumiaki Yokoi
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, University of Florida, Gainesville, FL, USA
| | - Rui Xiao
- Department of Aging and Geriatric Research, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Yuqing Li
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, University of Florida, Gainesville, FL, USA
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Garcia-Malo C, Peralta SR, Garcia-Borreguero D. Restless Legs Syndrome and Other Common Sleep-Related Movement Disorders. Continuum (Minneap Minn) 2020; 26:963-987. [PMID: 32756231 DOI: 10.1212/con.0000000000000886] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
PURPOSE OF REVIEW In this article, the different sleep-related movement disorders are discussed with special attention given to restless legs syndrome (RLS). RECENT FINDINGS The differential diagnosis of sleep-related movement disorders can often be challenging; therefore, it is essential to have accurate information to make a correct diagnosis. This article focuses on RLS, highlighting the change in the paradigm of initial treatment, the role played by iron (pathophysiologic and therapeutic), and how to approach possible complications occurring with long-term treatment. SUMMARY RLS is one of the most common neurologic conditions, and it is common in clinical practice to find patients experiencing symptoms suggestive of RLS. Neurologists must be careful and thorough in the diagnosis, excluding RLS mimics. The decisions regarding which specific sleep-related movement disorder is present and how it should be treated are important because in certain cases, especially in RLS, adverse effects and long-term complications are frequently reported with the use of certain drugs.
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Kosmowska B, Ossowska K, Wardas J. Pramipexole Reduces zif-268 mRNA Expression in Brain Structures involved in the Generation of Harmaline-Induced Tremor. Neurochem Res 2020; 45:1518-1525. [PMID: 32172399 PMCID: PMC7297825 DOI: 10.1007/s11064-020-03010-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 02/11/2020] [Accepted: 03/04/2020] [Indexed: 11/25/2022]
Abstract
Essential tremor is one of the most common neurological disorders, however, it is not sufficiently controlled with currently available pharmacotherapy. Our recent study has shown that pramipexole, a drug efficient in inhibiting parkinsonian tremor, reduced the harmaline-induced tremor in rats, generally accepted to be a model of essential tremor. The aim of the present study was to investigate brain targets for the tremorolytic effect of pramipexole by determination of the early activity-dependent gene zif-268 mRNA expression. Tremor in rats was induced by harmaline administered at a dose of 15 mg/kg ip. Pramipexole was administered at a low dose of 0.1 mg/kg sc. Tremor was measured by Force Plate Actimeters where four force transducers located below the corners of the plate tracked the animal's position on a Cartesian plane. The zif-268 mRNA expression was analyzed by in situ hybridization in brain slices. Harmaline induced tremor and increased zif-268 mRNA levels in the inferior olive, cerebellar cortex, ventroanterior/ventrolateral thalamic nuclei and motor cortex. Pramipexole reversed both the harmaline-induced tremor and the increase in zif-268 mRNA expression in the inferior olive, cerebellar cortex and motor cortex. Moreover, the tremor intensity correlated positively with zif-268 mRNA expression in the above structures. The present results seem to suggest that the tremorolytic effect of pramipexole is related to the modulation of the harmaline-increased neuronal activity in the tremor network which includes the inferior olive, cerebellar cortex and motor cortex. Potential mechanisms underlying the above pramipexole action are discussed.
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Affiliation(s)
- Barbara Kosmowska
- Department of Neuropsychopharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna Street, 31-343, Kraków, Poland
| | - Krystyna Ossowska
- Department of Neuropsychopharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna Street, 31-343, Kraków, Poland
| | - Jadwiga Wardas
- Department of Neuropsychopharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, 12 Smętna Street, 31-343, Kraków, Poland.
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Lyu S, Xing H, DeAndrade MP, Perez PD, Yokoi F, Febo M, Walters AS, Li Y. The Role of BTBD9 in the Cerebellum, Sleep-like Behaviors and the Restless Legs Syndrome. Neuroscience 2020; 440:85-96. [PMID: 32446853 DOI: 10.1016/j.neuroscience.2020.05.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 04/27/2020] [Accepted: 05/14/2020] [Indexed: 12/28/2022]
Abstract
Recent genome-wide association studies (GWAS) have found cerebellum as a top hit for sleep regulation. Restless legs syndrome (RLS) is a sleep-related sensorimotor disorder characterized by uncomfortable sensations in the extremities, generally at night, which are often relieved by movements. Clinical studies have found that RLS patients have structural and functional abnormalities in the cerebellum. However, whether and how cerebellar pathology contributes to sleep regulation and RLS is not known. GWAS identified polymorphisms in BTBD9 conferring a higher risk of sleep disruption and RLS. Knockout of the BTBD9 homolog in mice (Btbd9) and fly results in motor restlessness and sleep disruption. We performed manganese-enhanced magnetic resonance imaging on the Btbd9 knockout mice and found decreased neural activities in the cerebellum, especially in lobules VIII, X, and the deep cerebellar nuclei. Electrophysiological recording of Purkinje cells (PCs) from Btbd9 knockout mice revealed an increased number of non-tonic PCs. Tonic PCs showed increased spontaneous activity and intrinsic excitability. To further investigate the cerebellar contribution to RLS and sleep-like behaviors, we generated PC-specific Btbd9 knockout mice (Btbd9 pKO) and performed behavioral studies. Btbd9 pKO mice showed significant motor restlessness during the rest phase but not in the active phase. Btbd9 pKO mice also had an increased probability of waking at rest. Unlike the Btbd9 knockout mice, there was no increased thermal sensation in the Btbd9 pKO. Our results indicate that the Btbd9 knockout influences the PC activity; dysfunction in the cerebellum may contribute to the motor restlessness found in the Btbd9 knockout mice.
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Affiliation(s)
- Shangru Lyu
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Hong Xing
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Mark P DeAndrade
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Pablo D Perez
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Fumiaki Yokoi
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Marcelo Febo
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Arthur S Walters
- Division of Sleep Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Yuqing Li
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, College of Medicine, University of Florida, Gainesville, FL, USA.
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27
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Romero-Peralta S, Cano-Pumarega I, García-Borreguero D. Emerging Concepts of the Pathophysiology and Adverse Outcomes of Restless Legs Syndrome. Chest 2020; 158:1218-1229. [PMID: 32247713 DOI: 10.1016/j.chest.2020.03.035] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 02/15/2020] [Accepted: 03/13/2020] [Indexed: 01/05/2023] Open
Abstract
Restless legs syndrome (RLS), also known as Willis-Ekbom disease (WED), is a common neurological disorder affecting up to 5% to 10% of the population, but it remains an underdiagnosed condition. RLS/WED is characterized by uncomfortable sensations, mainly in the legs, which appear during inactivity and worsen in the evening or at night. The prevalence of RLS/WED and periodic leg movements (PLMs) is increased in patients with sleep-disordered breathing, particularly in those with OSA, the most common sleep disorder encountered in sleep centers. New advances in the pathophysiology of RLS/WED have shown important implications for various genetic markers, neurotransmitter dysfunction, and iron deficiency. A practical approach to RLS/WED management includes an accurate diagnosis, the identification of reversible contributing factors, and the use of nonpharmacological therapies, including iron substitution (oral or IV) therapy. Many pharmacological agents are effective for the treatment of RLS/WED. Until recently, the first-line treatment of RLS/WED consisted of low-dose dopamine agonists (DA). However, given the fact that DAs cause high rates of augmentation of symptoms, international guidelines recommend that whenever possible the initial treatment of choice should be an α2δ ligand, and avoidance of dopaminergic agents unless absolutely necessary. If necessary, the lowest effective dose should be used for only the shortest possible time. The symptoms of RLS/WED can disrupt the quality of sleep as well as the quality of life. IV iron therapy may be considered in patients with refractory RLS. A better understanding of RLS/WED pathophysiology will allow patients to receive tailored therapy, resulting in an improved quality of life.
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Affiliation(s)
- Sofía Romero-Peralta
- Sleep Research Institute, Madrid; Sleep Unit, Respiratory Department, Hospital Universitario Guadalajara, Guadalajara
| | - Irene Cano-Pumarega
- Sleep Research Institute, Madrid; Sleep Unit, Respiratory Department, Hospital Universitario Ramón y, Madrid, Spain
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29
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Lai YY, Hsieh KC, Cheng YH, Chew KT, Nguyen D, Ramanathan L, Siegel JM. Striatal histamine mechanism in the pathogenesis of restless legs syndrome. Sleep 2020; 43:5610750. [PMID: 31671173 PMCID: PMC8491621 DOI: 10.1093/sleep/zsz223] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 03/07/2019] [Indexed: 11/13/2022] Open
Abstract
STUDY OBJECTIVES Restless legs syndrome (RLS) has been hypothesized to be generated by abnormal striatal dopamine transmission. Dopaminergic drugs are effective for the treatment of RLS. However, long-term use of dopaminergic drugs causes adverse effects. We used iron-deficient (ID) and iron-replacement (IR) rats to address the neuropathology of RLS and to determine if a histamine H3 receptor (H3R) antagonist might be a useful treatment. Histamine H3R antagonists have been shown to decrease motor activity. METHODS Control and ID rats were surgically implanted with electrodes for polysomnographic recording. After 3 days of baseline polysomnographic recordings, rats were systemically injected with the H3R agonist, α-methylhistamine, and antagonist, thioperamide. Recordings were continued after drug injection. Striatal H3R levels from control, ID, and IR rats were determined by western blots. Blood from control, ID, and IR rats was collected for the measurement of hematocrit levels. RESULTS α-Methylhistamine and thioperamide increased and decreased motor activity, respectively, in control rats. In ID rats, α-methylhistamine had no effect on motor activity, whereas thioperamide decreased periodic leg movement (PLM) in sleep. Sleep-wake states were not significantly altered under any conditions. Striatal H3R levels were highest in ID rats, moderate to low in IR rats, and lowest in control rats. Striatal H3R levels were also found to positively and negatively correlate with PLM in sleep and hematocrit levels, respectively. CONCLUSIONS A striatal histamine mechanism may be involved in ID anemia-induced RLS. Histamine H3R antagonists may be useful for the treatment of RLS.
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Affiliation(s)
- Yuan-Yang Lai
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, CA
| | - Kung-Chiao Hsieh
- Veterans Administration Greater Los Angeles HealthCare System (VAGLAHS), Sepulveda, Los Angeles, CA
| | - Yu-Hsuan Cheng
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, CA
| | - Keng-Tee Chew
- Veterans Administration Greater Los Angeles HealthCare System (VAGLAHS), Sepulveda, Los Angeles, CA
| | - Darian Nguyen
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, CA
| | - Lalini Ramanathan
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, CA
| | - Jerome M Siegel
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, CA.,Veterans Administration Greater Los Angeles HealthCare System (VAGLAHS), Sepulveda, Los Angeles, CA
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Köfalvi A, Moreno E, Cordomí A, Cai NS, Fernández-Dueñas V, Ferreira SG, Guixà-González R, Sánchez-Soto M, Yano H, Casadó-Anguera V, Cunha RA, Sebastião AM, Ciruela F, Pardo L, Casadó V, Ferré S. Control of glutamate release by complexes of adenosine and cannabinoid receptors. BMC Biol 2020; 18:9. [PMID: 31973708 PMCID: PMC6979073 DOI: 10.1186/s12915-020-0739-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 01/13/2020] [Indexed: 12/20/2022] Open
Abstract
Background It has been hypothesized that heteromers of adenosine A2A receptors (A2AR) and cannabinoid CB1 receptors (CB1R) localized in glutamatergic nerve terminals mediate the integration of adenosine and endocannabinoid signaling involved in the modulation of striatal excitatory neurotransmission. Previous studies have demonstrated the existence of A2AR-CB1R heteromers in artificial cell systems. A dependence of A2AR signaling for the Gi protein-mediated CB1R signaling was described as one of its main biochemical characteristics. However, recent studies have questioned the localization of functionally significant A2AR-CB1R heteromers in striatal glutamatergic terminals. Results Using a peptide-interfering approach combined with biophysical and biochemical techniques in mammalian transfected cells and computational modeling, we could establish a tetrameric quaternary structure of the A2AR-CB1R heterotetramer. This quaternary structure was different to the also tetrameric structure of heteromers of A2AR with adenosine A1 receptors or dopamine D2 receptors, with different heteromeric or homomeric interfaces. The specific quaternary structure of the A2A-CB1R, which depended on intermolecular interactions involving the long C-terminus of the A2AR, determined a significant A2AR and Gs protein-mediated constitutive activation of adenylyl cyclase. Using heteromer-interfering peptides in experiments with striatal glutamatergic terminals, we could then demonstrate the presence of functionally significant A2AR-CB1R heteromers with the same biochemical characteristics of those studied in mammalian transfected cells. First, either an A2AR agonist or an A2AR antagonist allosterically counteracted Gi-mediated CB1R agonist-induced inhibition of depolarization-induced glutamate release. Second, co-application of both an A2AR agonist and an antagonist cancelled each other effects. Finally, a CB1R agonist inhibited glutamate release dependent on a constitutive activation of A2AR by a canonical Gs-Gi antagonistic interaction at the adenylyl cyclase level. Conclusions We demonstrate that the well-established cannabinoid-induced inhibition of striatal glutamate release can mostly be explained by a CB1R-mediated counteraction of the A2AR-mediated constitutive activation of adenylyl cyclase in the A2AR-CB1R heteromer.
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Affiliation(s)
- Attila Köfalvi
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal
| | - Estefanía Moreno
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, and Institute of Biomedicine, University of Barcelona, 08028, Barcelona, Spain
| | - Arnau Cordomí
- Laboratori de Medicina Computacional, Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain
| | - Ning-Sheng Cai
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Victor Fernández-Dueñas
- Unitat de Farmacologia, Departament Patologia i Terapèutica Experimental, Facultat de Medicina, IDIBELL, Universitat de Barcelona, L'Hospitalet de Llobregat, Spain.,Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain
| | - Samira G Ferreira
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal
| | - Ramón Guixà-González
- Laboratori de Medicina Computacional, Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain
| | - Marta Sánchez-Soto
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Hideaki Yano
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Verònica Casadó-Anguera
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, and Institute of Biomedicine, University of Barcelona, 08028, Barcelona, Spain
| | - Rodrigo A Cunha
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal.,Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Ana Maria Sebastião
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.,Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Francisco Ciruela
- Unitat de Farmacologia, Departament Patologia i Terapèutica Experimental, Facultat de Medicina, IDIBELL, Universitat de Barcelona, L'Hospitalet de Llobregat, Spain. .,Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain.
| | - Leonardo Pardo
- Laboratori de Medicina Computacional, Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain.
| | - Vicent Casadó
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, and Institute of Biomedicine, University of Barcelona, 08028, Barcelona, Spain.
| | - Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA.
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Why Are Women Prone to Restless Legs Syndrome? INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17010368. [PMID: 31935805 PMCID: PMC6981604 DOI: 10.3390/ijerph17010368] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 12/29/2019] [Accepted: 12/31/2019] [Indexed: 12/17/2022]
Abstract
Restless legs syndrome is a relatively common neurologic disorder considerably more prevalent in women than in men. It is characterized by an inactivity-induced, mostly nocturnal, uncomfortable sensation in the legs and an urge to move them to make the disagreeable sensation disappear. Some known genes contribute to this disorder and the same genes contribute to an overlapping condition—periodic leg movements that occur during sleep and result in insomnia. Dopamine and glutamate transmission in the central nervous system are involved in the pathophysiology, and an iron deficiency has been shown in region-specific areas of the brain. A review of the literature shows that pregnant women are at particular risk and that increased parity is a predisposing factor. Paradoxically, menopause increases the prevalence and severity of symptoms. This implies a complex role for reproductive hormones. It suggests that changes rather than absolute levels of estrogen may be responsible for the initiation of symptoms. Both iron (at relatively low levels in women) and estrogen (at relatively high oscillating levels in women) influence dopamine and glutamate transmission, which may help to explain women’s vulnerability to this condition. The syndrome is comorbid with several disorders (such as migraine, depression, and anxiety) to which women are particularly prone. This implies that the comorbid condition or its treatment, or both, contribute to the much higher prevalence in women than in men of restless legs syndrome.
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Lyu S, Xing H, DeAndrade MP, Perez PD, Zhang K, Liu Y, Yokoi F, Febo M, Li Y. The role of BTBD9 in the cerebral cortex and the pathogenesis of restless legs syndrome. Exp Neurol 2019; 323:113111. [PMID: 31715135 DOI: 10.1016/j.expneurol.2019.113111] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 10/09/2019] [Accepted: 11/07/2019] [Indexed: 01/18/2023]
Abstract
Restless legs syndrome (RLS) is a nocturnal neurological disorder affecting up to 10% of the population. It is characterized by an urge to move and uncomfortable sensations in the legs which can be relieved by movements. Mutations in BTBD9 may confer a higher risk of RLS. We developed Btbd9 knockout mice as an animal model. Functional alterations in the cerebral cortex, especially the sensorimotor cortex, have been found in RLS patients in several imaging studies. However, the role of cerebral cortex in the pathogenesis of RLS remains unclear. To explore this, we used in vivo manganese-enhanced MRI and found that the Btbd9 knockout mice had significantly increased neural activities in the primary somatosensory cortex (S1) and the rostral piriform cortex. Morphometry study revealed a decreased thickness in a part of S1 representing the hindlimb (S1HL) and M1. The electrophysiological recording showed Btbd9 knockout mice had enhanced short-term plasticity at the corticostriatal terminals to D1 medium spiny neurons (MSNs). Furthermore, we specifically knocked out Btbd9 in the cerebral cortex of mice (Btbd9 cKO). The Btbd9 cKO mice showed a rest-phase specific motor restlessness, decreased thermal sensation, and a thinner S1HL and M1. Both Btbd9 knockout and Btbd9 cKO exhibited motor deficits. Our results indicate that systematic BTBD9 deficiency leads to both functional and morphometrical changes of the cerebral cortex, and an alteration in the corticostriatal pathway to D1 MSNs. Loss of BTBD9 only in the cerebral cortex is sufficient to cause similar phenotypes as observed in the Btbd9 complete knockout mice.
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Affiliation(s)
- Shangru Lyu
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Hong Xing
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Mark P DeAndrade
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Pablo D Perez
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Keer Zhang
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Yuning Liu
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Fumiaki Yokoi
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Marcelo Febo
- Department of Psychiatry, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Yuqing Li
- Norman Fixel Institute for Neurological Diseases, Department of Neurology, College of Medicine, University of Florida, Gainesville, Florida, USA.
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The Role of BTBD9 in Striatum and Restless Legs Syndrome. eNeuro 2019; 6:ENEURO.0277-19.2019. [PMID: 31444227 PMCID: PMC6787346 DOI: 10.1523/eneuro.0277-19.2019] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 07/22/2019] [Accepted: 08/02/2019] [Indexed: 12/23/2022] Open
Abstract
Restless legs syndrome (RLS) is a sensory-motor neurological disorder characterized by uncomfortable sensations in the extremities, generally at night, which is often relieved by movements. Genome-wide association studies (GWAS) have identified mutations in BTBD9 conferring a higher risk of RLS. Knockout of the BTBD9 homolog in mice (Btbd9) and fly results in motor restlessness and sleep disruption. Clinical studies have found RLS patients have structural and functional abnormalities in the striatum; however, whether and how striatal pathology contributes to the pathogenesis of RLS is not known. Here, we used fMRI to map regions of altered synaptic activity in basal ganglia of systematic Btbd9 knock-out (KO) mice. We further dissected striatal circuits using patch-clamp electrophysiological recordings in brain slices. Two different mouse models were generated to test the effect of specific knockout of Btbd9 in either striatal medium spiny neurons (MSNs) or cholinergic interneurons (ChIs) using the electrophysiological recording, motor and sensory behavioral tests. We found that Btbd9 KO mice showed enhanced neural activity in the striatum, increased postsynaptic currents in the MSNs, and decreased excitability of the striatal ChIs. Knocking out Btbd9 specifically in the striatal MSNs, but not the ChIs, led to rest-phase specific motor restlessness, sleep disturbance, and increased thermal sensation in mice, which are consistent with results obtained from the Btbd9 KO mice. Our data establish the role of Btbd9 in regulating the activity of striatal neurons. Increased activity of the striatal MSNs, possibly through modulation by the striatal ChIs, contributes to the pathogenesis of RLS.
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Ferré S, Ciruela F. Functional and Neuroprotective Role of Striatal Adenosine A 2A Receptor Heterotetramers. J Caffeine Adenosine Res 2019; 9:89-97. [PMID: 31559390 PMCID: PMC6761580 DOI: 10.1089/caff.2019.0008] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In the striatum, adenosine A2A receptors (A2AR) are mainly expressed within the soma and dendrites of the striatopallidal neuron. A predominant proportion of these striatal postsynaptic A2AR form part of the macromolecular complexes that include A2AR-dopamine D2 receptor (D2R) heteromers, Golf and Gi/o proteins, and the effector adenylyl cyclase (AC), subtype AC5. The A2AR-D2R heteromers have a tetrameric structure, constituted by A2AR and D2R homomers. By means of reciprocal antagonistic allosteric interactions and antagonistic interactions at the effector level between adenosine and dopamine, the A2AR-D2R heterotetramer-AC5 complex acts an integrative molecular device, which determines a switch between the adenosine-facilitated activation and the dopamine-facilitated inhibition of the striatopallidal neuron. Striatal adenosine also plays an important presynaptic modulatory role, driving the function of corticostriatal terminals. This control is mediated by adenosine A1 receptors (A1R) and A2AR, which establish intermolecular interactions forming A1R-A2AR heterotetramers. Here, we review the functional role of both presynaptic and postsynaptic striatal A2AR heterotetramers as well as their possible neuroprotective role. We hypothesize that alterations in the homomer/heteromer stoichiometry (i.e., increase or decrease in the proportion of A2AR forming homomers or heteromers) are pathogenetically involved in neurological disorders, specifically in Parkinson's disease and restless legs syndrome.
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Affiliation(s)
- Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, Maryland
| | - Francisco Ciruela
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, School of Medicine, IDIBELL, University of Barcelona, L'Hospitalet de Llobregat, Barcelona, Spain.,Institute of Neurosciences, University of Barcelona, Barcelona, Spain
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Ferri R, DelRosso LM, Silvani A, Cosentino FII, Picchietti DL, Mogavero P, Manconi M, Bruni O. Peculiar lifespan changes of periodic leg movements during sleep in restless legs syndrome. J Sleep Res 2019; 29:e12896. [DOI: 10.1111/jsr.12896] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 06/24/2019] [Accepted: 06/25/2019] [Indexed: 12/15/2022]
Affiliation(s)
- Raffaele Ferri
- Department of Neurology I.C. Sleep Research Centre Oasi Research Institute ‐ IRCCS Troina Italy
| | - Lourdes M. DelRosso
- Seattle Children's Hospital Seattle WA USA
- University of California San Francisco CA USA
- Benioff Children's Hospital OaklandCA USA
| | - Alessandro Silvani
- Department of Biomedical and Neuromotor Sciences (DIBINEM) University of Bologna Bologna Italy
| | | | - Daniel L. Picchietti
- University of IllinoisSchool of Medicine and Carle Foundation HospitalUrbana IL USA
| | - Paola Mogavero
- Istituti Clinici Scientifici MaugeriIRCCSScientific Institute of Pavia Pavia Italy
| | - Mauro Manconi
- Faculty of Biomedical Sciences Department of Neurology Sleep and Epilepsy Center Neurocenter of Southern SwitzerlandCivic Hospital (EOC) of LuganoBern UniversityUniversità della Svizzera Italiana Lugano Switzerland
| | - Oliviero Bruni
- Department of Social and Developmental Psychology Sapienza University Rome Italy
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D3 and D1 receptors: The Yin and Yang in the treatment of restless legs syndrome with dopaminergics. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2019; 84:79-100. [PMID: 31229178 DOI: 10.1016/bs.apha.2019.01.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Dopaminergic treatments targeting the D3 receptor subtype to reduce the symptoms of RLS show substantial initial clinical benefits but fail to maintain their efficacy over time. Sensorimotor circuits in the spinal cord are the gateway for the sensory processing of the symptoms and critical for the associated leg movements that relieve the symptoms and the periodic limb movements that often develop during sleep. There is a high preponderance of the inhibitory D3 receptor in the sensory-processing areas of the spinal cord (dorsal horn), whereas the motor areas in the ventral horn more strongly express the excitatory D1 receptor subtype. D3 and D1 receptors can form functional heteromeric ensembles that influence each other. In the spinal cord, long-term treatment with D3 receptor agonists is associated with the upregulation of the D1 receptor subtype and block of D1 receptor function at this stage can restore the D3 receptor effect. Alternate scenarios for a role of dopamine involve a role for the D5 receptor in regulating motor excitability and for the D4 receptor subtype in controlling D3-like effects. A model emerges that proposes that the behavioral changes in RLS, while responsive to D3 receptor agonists, may be ultimately be the result of unmasked increased D1-like receptor activities.
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Jiménez-Jiménez FJ, Alonso-Navarro H, García-Martín E, Agúndez JA. Neurochemical features of idiopathic restless legs syndrome. Sleep Med Rev 2019; 45:70-87. [DOI: 10.1016/j.smrv.2019.03.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Revised: 03/08/2019] [Accepted: 03/15/2019] [Indexed: 11/26/2022]
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Wanner V, Garcia Malo C, Romero S, Cano-Pumarega I, García-Borreguero D. Non-dopaminergic vs. dopaminergic treatment options in restless legs syndrome. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2019; 84:187-205. [PMID: 31229171 DOI: 10.1016/bs.apha.2019.02.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Two types of drugs have been extensively investigated for the treatment of restless legs syndrome (RLS)/Willis-Ekbom disease (WED): dopamine agonists and α2δ ligands to the α2δ subunit of calcium channels. Comparative studies show that both classes of drugs are similarly effective in treating RLS symptoms over the short- and long-term. While dopamine agonists are more effective in treating periodic limb movements (PLMs), α2δ ligands are more effective in consolidating sleep. However, given the fact that dopamine agonists cause high rates of augmentation of symptoms, recent international guidelines recommend that whenever possible the initial treatment of choice should be an α2δ ligand. In fact, the most effective preventive strategy involves not using dopaminergic agents unless absolutely necessary. Indeed, should dopaminergic treatment be needed to handle the symptoms effectively, then it is recommended that the dopaminergic load be reduced by using the lowest effective dose for the shortest possible period of time. However, it must be taken into account that the only α2δ ligand approved for RLS/WED is gabapentin enacarbil, which is not yet available in Europe. Furthermore, recent studies have also reported on the efficacy of opioids as a second-line treatment of RLS/WED, following treatment failure with dopamine agonists. Recent guidelines have taken these new data into account and highlight that a low dose of an opioid (prolonged-release oxycodone or methadone) may be considered in patients with very severe augmentation of symptoms. Alternative non-dopaminergic treatment concepts based on glutamatergic and adenosinergic mechanisms are currently in development, and are likely to provide encouraging therapeutic alternatives.
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Affiliation(s)
- Sergi Ferré
- Editor in Chief of the Journal of Caffeine and Adenosine Research
- Integrative Neurobiology Section, National Institute on Drug Abuse, IRP, NIH, DHHS, Baltimore, Maryland
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Cortés A, Casadó-Anguera V, Moreno E, Casadó V. The heterotetrameric structure of the adenosine A 1-dopamine D 1 receptor complex: Pharmacological implication for restless legs syndrome. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2019; 84:37-78. [PMID: 31229177 DOI: 10.1016/bs.apha.2019.01.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Dopaminergic and purinergic signaling play a pivotal role in neurological diseases associated with motor symptoms, including Parkinson's disease (PD), multiple sclerosis, amyotrophic lateral sclerosis, Huntington disease, Restless Legs Syndrome (RLS), spinal cord injury (SCI), and ataxias. Extracellular dopamine and adenosine exert their functions interacting with specific dopamine (DR) or adenosine (AR) receptors, respectively, expressed on the surface of target cells. These receptors are members of the family A of G protein-coupled receptors (GPCRs), which is the largest protein superfamily in mammalian genomes. GPCRs are target of about 40% of all current marketed drugs, highlighting their importance in clinical medicine. The striatum receives the densest dopamine innervations and contains the highest density of dopamine receptors. The modulatory role of adenosine on dopaminergic transmission depends largely on the existence of antagonistic interactions mediated by specific subtypes of DRs and ARs, the so-called A2AR-D2R and A1R-D1R interactions. Due to the dopamine/adenosine antagonism in the CNS, it was proposed that ARs and DRs could form heteromers in the neuronal cell surface. Therefore, adenosine can affect dopaminergic signaling through receptor-receptor interactions and by modulations in their shared intracellular pathways in the striatum and spinal cord. In this work we describe the allosteric modulations between GPCR protomers, focusing in those of adenosine and dopamine within the A1R-D1R heteromeric complex, which is involved in RLS. We also propose that the knowledge about the intricate allosteric interactions within the A1R-D1R heterotetramer, may facilitate the treatment of motor alterations, not only when the dopamine pathway is hyperactivated (RLS, chorea, etc.) but also when motor function is decreased (SCI, aging, PD, etc.).
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Affiliation(s)
- Antoni Cortés
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain; Institute of Biomedicine of the University of Barcelona (IBUB), Barcelona, Spain; Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, University of Barcelona, Barcelona, Spain
| | - Verònica Casadó-Anguera
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain; Institute of Biomedicine of the University of Barcelona (IBUB), Barcelona, Spain; Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, University of Barcelona, Barcelona, Spain
| | - Estefanía Moreno
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain; Institute of Biomedicine of the University of Barcelona (IBUB), Barcelona, Spain; Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, University of Barcelona, Barcelona, Spain
| | - Vicent Casadó
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain; Institute of Biomedicine of the University of Barcelona (IBUB), Barcelona, Spain; Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, University of Barcelona, Barcelona, Spain.
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Ferré S, Quiroz C, Rea W, Guitart X, García-Borreguero D. Adenosine mechanisms and hypersensitive corticostriatal terminals in restless legs syndrome. Rationale for the use of inhibitors of adenosine transport. PHARMACOLOGY OF RESTLESS LEGS SYNDROME (RLS) 2019; 84:3-19. [DOI: 10.1016/bs.apha.2018.12.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Lanza G, Ferri R. The neurophysiology of hyperarousal in restless legs syndrome: Hints for a role of glutamate/GABA. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2019; 84:101-119. [PMID: 31229167 DOI: 10.1016/bs.apha.2018.12.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Restless legs syndrome (RLS) is a common sensory-motor circadian disorder, whose basic components include urge to move the legs, unpleasant sensory experience, and periodic leg movements during sleep, all associated with an enhancement of the individual's arousal state. Brain iron deficiency (BID) is considered to be a key initial pathobiological factor, based on alterations of iron acquisition by the brain, also moderated by genetic factors. In addition to the well-known dopaminergic involvement in RLS, previous studies pointed out that BID brings also a hyperglutamatergic state that influences a dysfunctional cortico-striatal-thalamic-cortical circuit in genetically vulnerable individuals. However, the enhancement of arousal mechanisms in RLS may also be explained by functional changes of the ascending arousal systems and by deficitary GABA-mediated inhibitory control. Very recently, it was also suggested that BID induces a hypoadenosinergic state in RLS, thus possibly providing a link for a putative unified pathophysiological mechanism accounting for both hyperarousal and sensory-motor signs. Consequently, RLS might be viewed as a multitransmitter neurochemical disorder, globally resulting in enhanced excitability and decreased inhibition. In this framework, understanding the complex interaction of different neuronal circuits in generating the symptoms of RLS is mandatory both for a better diagnostic refinement and for an innovative therapeutic support. Notably, multiple neurotransmission dysfunction, either primary or triggered by BID, may also bridge the gap between RLS and other chronic pain disorders. This chapter summarizes the current experimental and clinical findings into a heuristic model of the electrophysiology and neurochemistry underlying RLS.
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Franco B, Daubian-Nosé P, De-Mello MT, Esteves AM. Exercise as a favorable non-pharmacologic treatment to Sleep-Related Movement Disorders: a review. ACTA ACUST UNITED AC 2019; 12:116-121. [PMID: 31879545 PMCID: PMC6922544 DOI: 10.5935/1984-0063.20190064] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Non-pharmacologic treatments of Sleep-Related Movement Disorders (SRMD) are already well described in the literature. The physical activity has been presented as a factor to improve quality of life and in several aspects related to sleep disorders. Thus, the purpose of this review was to analyze the benefits of physical exercise and your indication to improve to SRMD. In the research, 19 studies were found that evaluate the efficacy of physical exercise on SRMD in both human and animal models. The results demonstrate that both acute and chronic physical exercises are effective in reducing symptoms of SRMD. However, most studies were performed with aerobic exercise. Three studies evaluated the efficacy of combined exercise, and no studies have investigated the relationship of resistance exercise. Regarding the mechanisms involved, a study discusses the relationship between the release of beta-endorphin and the exercise practice, and two studies with animal models show the changes of the dopaminergic system after physical exercise. From this evidences, we suggested that physical exercise is a favorable non-pharmacological treatment for SRMD. However, more studies should be available for a better understanding of the molecular mechanisms involved, as well of the type, duration and better time of the day to practice.
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Affiliation(s)
- Beatriz Franco
- Universidade Estadual de Campinas, Faculdade de Educação Física - Campinas - São Paulo - Brazil
| | - Paulo Daubian-Nosé
- Universidade Estadual de Campinas, Faculdade de Ciências Aplicadas - Limeira - São Paulo - Brazil
| | - Marco Túlio De-Mello
- Universidade Federal de Minas Gerais, Professor Associado II do Departamento de Esportes, da Escola de Educação Física, Fisioterapia e Terapia Ocupacional - Belo Horizonte - Minas Gerais - Brazil
| | - Andrea Maculano Esteves
- Universidade Estadual de Campinas, Faculdade de Ciências Aplicadas - Limeira - São Paulo - Brazil
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Sánchez-Soto M, Yano H, Cai NS, Casadó-Anguera V, Moreno E, Casadó V, Ferré S. Revisiting the Functional Role of Dopamine D 4 Receptor Gene Polymorphisms: Heteromerization-Dependent Gain of Function of the D 4.7 Receptor Variant. Mol Neurobiol 2018; 56:4778-4785. [PMID: 30387076 DOI: 10.1007/s12035-018-1413-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 10/24/2018] [Indexed: 12/28/2022]
Abstract
The two most common polymorphisms of the human DRD4 gene encode a dopamine D4 receptor (D4R) with four or seven repeats of a proline-rich sequence of 16 amino acids (D4.4R or D4.7R). Although the seven-repeat polymorphism has been repeatedly associated with attention-deficit hyperactivity disorder and substance use disorders, the differential functional properties between D4.4R and D4.7R remained enigmatic until recent electrophysiological and optogenetic-microdialysis experiments indicated a gain of function of D4.7R. Since no clear differences in the biochemical properties of individual D4.4R and D4.7R have been reported, it was previously suggested that those differences emerge upon heteromerization with dopamine D2 receptor (D2R), which co-localizes with D4R in the brain. However, contrary to a gain of function, experiments in mammalian transfected cells suggested that heteromerization with D2R results in lower MAPK signaling by D4.7R as compared to D4.4R. In the present study, we readdressed the question of functional differences of D4.4R and D4.7R forming homomers or heteromers with the short isoform of D2R (D2SR), using a functional bioluminescence resonance energy transfer (BRET) assay that allows the measurement of ligand-induced changes in the interaction between G protein-coupled receptors (GPCRs) forming homomers or heteromers with their cognate G protein. Significant functional and pharmacological differences between D4.4R and D4.7R were only evident upon heteromerization with the short isoform of D2R (D2SR). The most dramatic finding was a significant increase and decrease in the constitutive activity of D2S upon heteromerization with D4.7R and D4.4R, respectively, providing the first clear mechanism for a functional difference between both products of polymorphic variants and for a gain of function of the D4.7R.
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Affiliation(s)
- Marta Sánchez-Soto
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Hideaki Yano
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Ning-Sheng Cai
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA
| | - Verònica Casadó-Anguera
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine of the University of Barcelona, University of Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08028, Barcelona, Spain
| | - Estefanía Moreno
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine of the University of Barcelona, University of Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08028, Barcelona, Spain
| | - Vicent Casadó
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine of the University of Barcelona, University of Barcelona, and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), 08028, Barcelona, Spain
| | - Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, 21224, USA.
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Suzuki K, Suzuki S, Haruyama Y, Kobashi G, Shiina T, Hirata K. Restless legs syndrome is associated with headache-related disabilities in patients with migraine: a prospective 7-year follow-up study. Eur J Neurol 2018; 26:238-245. [PMID: 30169898 DOI: 10.1111/ene.13796] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 08/28/2018] [Indexed: 11/29/2022]
Abstract
BACKGROUND AND PURPOSE No prospective study has evaluated the impact of restless legs syndrome (RLS) on clinical factors in patients with migraine. We planned a prospective study to assess the impact of RLS comorbid status on clinical factors in patients with migraine. METHODS A total of 101 patients with migraine who were evaluated for RLS twice at 7-year intervals in a university hospital setting were included in this study. The RLS group was defined as positive for RLS at either baseline or follow-up and the non-RLS group was defined as negative for RLS at both baseline and follow-up. The Migraine Disability Assessment (MIDAS) questionnaire, Beck Depression Inventory-II (BDI-II), Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale were administered to all patients. RESULTS The RLS prevalence was 16.8% at baseline and 20.8% at follow-up. Compared with the non-RLS group (n = 27), the RLS group (n = 74) showed a significantly higher rate of smoking and higher MIDAS and BDI-II scores at 7-year follow-up. A significant reduction in MIDAS and BDI-II scores at 7-year follow-up compared with those at baseline was observed in the non-RLS group, but not in the RLS group. The non-RLS group showed a significantly lower MIDAS score at 7-year follow-up than the RLS group after adjusting for confounding variables such as age, gender, smoking status, Epworth Sleepiness Scale and PSQI scores using analysis of covariance. The persistent RLS group (n = 11) (positive for RLS at both baseline and follow-up) showed a significantly higher rate of smoking and increased MIDAS, BDI-II and PSQI scores compared with the non-RLS group (n = 74) at 7-year follow-up. CONCLUSION Our prospective study showed that RLS had a significant impact on headache-related disability in patients with migraine.
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Affiliation(s)
- K Suzuki
- Department of Neurology, Dokkyo Medical University, Tochigi, Japan
| | - S Suzuki
- Department of Neurology, Dokkyo Medical University, Tochigi, Japan
| | - Y Haruyama
- Department of Public Health School of Medicine, Dokkyo Medical University, Tochigi, Japan
| | - G Kobashi
- Department of Public Health School of Medicine, Dokkyo Medical University, Tochigi, Japan
| | - T Shiina
- Department of Neurology, Dokkyo Medical University, Tochigi, Japan
| | - K Hirata
- Department of Neurology, Dokkyo Medical University, Tochigi, Japan
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Ferré S, García-Borreguero D, Allen RP, Earley CJ. New Insights into the Neurobiology of Restless Legs Syndrome. Neuroscientist 2018; 25:113-125. [PMID: 30047288 DOI: 10.1177/1073858418791763] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Restless legs syndrome (RLS) is a common sensorimotor disorder, whose basic components include a sensory experience, akathisia, and a sleep-related motor sign, periodic leg movements during sleep (PLMS), both associated with an enhancement of the individual's arousal state. The present review attempts to integrate the major clinical and experimental neurobiological findings into a heuristic pathogenetic model. The model also integrates the recent findings on RLS genetics indicating that RLS has aspects of a genetically moderated neurodevelopmental disorder involving mainly the cortico-striatal-thalamic-cortical circuits. Brain iron deficiency (BID) remains the key initial pathobiological factor and relates to alterations of iron acquisition by the brain, also moderated by genetic factors. Experimental evidence indicates that BID leads to a hyperdopaminergic and hyperglutamatergic states that determine the dysfunction of cortico-striatal-thalamic-cortical circuits in genetically vulnerable individuals. However, the enhanced arousal mechanisms critical to RLS are better explained by functional changes of the ascending arousal systems. Recent experimental and clinical studies suggest that a BID-induced hypoadenosinergic state provides the link for a putative unified pathophysiological mechanism for sensorimotor signs of RLS and the enhanced arousal state.
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Affiliation(s)
- Sergi Ferré
- 1 National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, USA
| | | | - Richard P Allen
- 3 Department of Neurology, Johns Hopkins University, Baltimore, MD, USA
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Bollu PC, Yelam A, Thakkar MM. Sleep Medicine: Restless Legs Syndrome. MISSOURI MEDICINE 2018; 115:380-387. [PMID: 30228773 PMCID: PMC6140269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Restless Legs Syndrome is a highly prevalent sensorimotor disorder characterized by urge to move the legs due to discomfort that primarily happens in the evening or at nights. Although the exact pathophysiology remains unclear, brain iron deficiency and altered dopaminergic function appears to play an important role in the pathogenesis of this condition. This disorder affects women more frequently and is associated with significant morbidity.
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Affiliation(s)
- Pradeep C Bollu
- Pradeep C. Bollu, MD, Anudeep Yelam, MD and Mahesh Thakkar, PhD are in the Department of Neurology, University of Missouri-Columbia
| | - Anudeep Yelam
- Pradeep C. Bollu, MD, Anudeep Yelam, MD and Mahesh Thakkar, PhD are in the Department of Neurology, University of Missouri-Columbia
| | - Mahesh M Thakkar
- Pradeep C. Bollu, MD, Anudeep Yelam, MD and Mahesh Thakkar, PhD are in the Department of Neurology, University of Missouri-Columbia
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Garcia-Borreguero D, Guitart X, Garcia Malo C, Cano-Pumarega I, Granizo JJ, Ferré S. Treatment of restless legs syndrome/Willis-Ekbom disease with the non-selective ENT1/ENT2 inhibitor dipyridamole: testing the adenosine hypothesis. Sleep Med 2018; 45:94-97. [DOI: 10.1016/j.sleep.2018.02.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 12/15/2017] [Accepted: 02/14/2018] [Indexed: 01/20/2023]
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Ferré S, Quiroz C, Guitart X, Rea W, Seyedian A, Moreno E, Casadó-Anguera V, Díaz-Ríos M, Casadó V, Clemens S, Allen RP, Earley CJ, García-Borreguero D. Pivotal Role of Adenosine Neurotransmission in Restless Legs Syndrome. Front Neurosci 2018; 11:722. [PMID: 29358902 PMCID: PMC5766678 DOI: 10.3389/fnins.2017.00722] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 12/11/2017] [Indexed: 11/13/2022] Open
Abstract
The symptomatology of Restless Legs Syndrome (RLS) includes periodic leg movements during sleep (PLMS), dysesthesias, and hyperarousal. Alterations in the dopaminergic system, a presynaptic hyperdopaminergic state, seem to be involved in PLMS, while alterations in glutamatergic neurotransmission, a presynaptic hyperglutamatergic state, seem to be involved in hyperarousal and also PLMS. Brain iron deficiency (BID) is well-recognized as a main initial pathophysiological mechanism of RLS. BID in rodents have provided a pathogenetic model of RLS that recapitulates the biochemical alterations of the dopaminergic system of RLS, although without PLMS-like motor abnormalities. On the other hand, BID in rodents reproduces the circadian sleep architecture of RLS, indicating the model could provide clues for the hyperglutamatergic state in RLS. We recently showed that BID in rodents is associated with changes in adenosinergic transmission, with downregulation of adenosine A1 receptors (A1R) as the most sensitive biochemical finding. It was hypothesized that A1R downregulation leads to hypersensitive striatal glutamatergic terminals and facilitation of striatal dopamine release. Hypersensitivity of striatal glutamatergic terminals was demonstrated by an optogenetic-microdialysis approach in the rodent with BID, indicating that it could represent a main pathogenetic factor that leads to PLMS in RLS. In fact, the dopaminergic agonists pramipexole and ropinirole and the α2δ ligand gabapentin, used in the initial symptomatic treatment of RLS, completely counteracted optogenetically-induced glutamate release from both normal and BID-induced hypersensitive corticostriatal glutamatergic terminals. It is a main tenet of this essay that, in RLS, a single alteration in the adenosinergic system, downregulation of A1R, disrupts the adenosine-dopamine-glutamate balance uniquely controlled by adenosine and dopamine receptor heteromers in the striatum and also the A1R-mediated inhibitory control of glutamatergic neurotransmission in the cortex and other non-striatal brain areas, which altogether determine both PLMS and hyperarousal. Since A1R agonists would be associated with severe cardiovascular effects, it was hypothesized that inhibitors of nucleoside equilibrative transporters, such as dipyridamole, by increasing the tonic A1R activation mediated by endogenous adenosine, could represent a new alternative therapeutic strategy for RLS. In fact, preliminary clinical data indicate that dipyridamole can significantly improve the symptomatology of RLS.
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Affiliation(s)
- Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - César Quiroz
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Xavier Guitart
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - William Rea
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Arta Seyedian
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Estefanía Moreno
- Center for Biomedical Research in Neurodegenerative Diseases Network and Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine of the University of Barcelona, University of Barcelona, Barcelona, Spain
| | - Verònica Casadó-Anguera
- Center for Biomedical Research in Neurodegenerative Diseases Network and Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine of the University of Barcelona, University of Barcelona, Barcelona, Spain
| | - Manuel Díaz-Ríos
- Department of Anatomy and Neurobiology and Institute of Neurobiology, University of Puerto Rico, San Juan, PR, United States
| | - Vicent Casadó
- Center for Biomedical Research in Neurodegenerative Diseases Network and Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine of the University of Barcelona, University of Barcelona, Barcelona, Spain
| | - Stefan Clemens
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, NC, United States
| | - Richard P Allen
- Center for Restless Legs Study, Department of Neurology, Johns Hopkins University, Baltimore, MD, United States
| | - Christopher J Earley
- Center for Restless Legs Study, Department of Neurology, Johns Hopkins University, Baltimore, MD, United States
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