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Akkol EK, Karatoprak GŞ, Carpar E, Hussain Y, Khan H, Aschner M. Effects of Natural Products on Neuromuscular Junction. Curr Neuropharmacol 2021; 20:594-610. [PMID: 34561984 DOI: 10.2174/1570159x19666210924092627] [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: 01/11/2021] [Revised: 05/05/2021] [Accepted: 06/01/2021] [Indexed: 11/22/2022] Open
Abstract
Neuromuscular junction (NMJ) disorders result from damage, malfunction or absence of one or more key proteins involved in neuromuscular transmission, comprising a wide range of disorders. The most common pathology is antibody-mediated or downregulation of ion channels or receptors, resulting in Lambert-Eaton myasthenic syndrome, myasthenia gravis, and acquired neuromyotonia (Isaac's syndrome), and rarely congenital myasthenic syndromes caused by mutations in NMJ proteins. A wide range of symptomatic treatments, immunomodulating therapies, or immunosuppressive drugs have been used to treat NMJ diseases. Future research must be directed at better understanding of the pathogenesis of these diseases, and developing novel disease-specific treatments. Numerous secondary metabolites, especially alkaloids isolated from plants have been used to treat NMJ diseases in traditional and clinical practices. An ethnopharmacological approach has provided leads for identifying new treatment for NMJ diseases. In this review, we performed a literature survey in Pubmed, Science Direct, and Google Scholar to gather information on drug discovery from plant sources for NMJ disease treatments. To date, most research has focused on the effect of herbal remedies on cholinesterase inhibitory and antioxidant activities. This review provides leads for identifying potential new drugs from plant sources for the treatment of NMJ diseases.
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Affiliation(s)
- Esra Küpeli Akkol
- Department of Pharmacognosy, Faculty of Pharmacy, Gazi University, 06330, Ankara. Turkey
| | - Gökçe Şeker Karatoprak
- Department of Pharmacognosy, Faculty of Pharmacy, Erciyes University, 38039, Kayseri. Turkey
| | - Elif Carpar
- Department of Psychiatry, Private French La Paix Hospital, 34360, Istanbul. Turkey
| | - Yaseen Hussain
- College of Pharmaceutical Sciences, Soochow University, Suzhou, Jiangsu, China
| | - Haroon Khan
- Department of Pharmacy, Abdul Wali Khan University Mardan, 23200, Mardan. Pakistan
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine Forchheimer 209 1300 Morris Park Avenue, Bronx, NY 10461, United States
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Bukharaeva E, Khuzakhmetova V, Dmitrieva S, Tsentsevitsky A. Adrenoceptors Modulate Cholinergic Synaptic Transmission at the Neuromuscular Junction. Int J Mol Sci 2021; 22:ijms22094611. [PMID: 33924758 PMCID: PMC8124642 DOI: 10.3390/ijms22094611] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 04/22/2021] [Accepted: 04/26/2021] [Indexed: 02/07/2023] Open
Abstract
Adrenoceptor activators and blockers are widely used clinically for the treatment of cardiovascular and pulmonary disorders. More recently, adrenergic agents have also been used to treat neurodegenerative diseases. Recent studies indicate a location of sympathetic varicosities in close proximity to neuromuscular junctions. The pressing question is whether there could be any effects of endo- or exogenous catecholamines on cholinergic neuromuscular transmission. It was shown that the pharmacological stimulation of adrenoceptors, as well as sympathectomy, can affect both acetylcholine release from motor nerve terminals and the functioning of postsynaptic acetylcholine receptors. In this review, we discuss the recent data regarding the effects of adrenergic drugs on neurotransmission at the neuromuscular junction. The elucidation of the molecular mechanisms by which the clinically relevant adrenomimetics and adrenoblockers regulate quantal acetylcholine release from the presynaptic nerve terminals and postsynaptic sensitivity may help in the design of highly effective and well-tolerated sympathomimetics for treating a number of neurodegenerative diseases accompanied by synaptic defects.
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3
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Nishiyama K, Kurokawa M, Torio M, Sakai Y, Arima M, Tsukamoto S, Obata S, Minamikawa S, Nozu K, Kaku N, Maehara Y, Sonoda KH, Taguchi T, Ohga S. Gastrointestinal symptoms as an extended clinical feature of Pierson syndrome: a case report and review of the literature. BMC MEDICAL GENETICS 2020; 21:80. [PMID: 32295525 PMCID: PMC7160948 DOI: 10.1186/s12881-020-01019-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2019] [Accepted: 04/01/2020] [Indexed: 11/17/2022]
Abstract
Background Pierson syndrome (PS) is a rare autosomal recessive disorder, characterized by congenital nephrotic syndrome and microcoria. Advances in renal replacement therapies have extended the lifespan of patients, whereas the full clinical spectrum of PS in infancy and beyond remains elusive. Case presentation We present the case of a 12-month-old boy with PS, manifesting as the bilateral microcoria and congenital nephrotic syndrome. He was born without asphyxia, and was neurologically intact from birth through the neonatal period. Generalized muscle weakness and hypotonia were recognized from 3 months of age. The infant showed recurrent vomiting at age 5 months of age, and was diagnosed with gastroesophageal reflux and intestinal malrotation. Despite the successful surgical treatment, vomiting persisted and led to severely impaired growth. Tulobuterol treatment was effective in reducing the frequency of vomiting. Targeted sequencing confirmed that he had a compound heterozygous mutation in LAMB2 (NM_002292.3: p.Arg550X and p.Glu1507X). A search of the relevant literature identified 19 patients with severe neuro-muscular phenotypes. Among these, only 8 survived the first 12 months of life, and one had feeding difficulty with similar gastrointestinal problems. Conclusions This report demonstrated that severe neurological deficits and gastrointestinal dysfunction may emerge in PS patients after the first few months of life.
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Affiliation(s)
- Kei Nishiyama
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
| | - Mari Kurokawa
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
| | - Michiko Torio
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
| | - Yasunari Sakai
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
| | - Mitsuru Arima
- Department of Ophthalmology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Shoko Tsukamoto
- Department of Ophthalmology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Satoshi Obata
- Department of Pediatric Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Shogo Minamikawa
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Kandai Nozu
- Department of Pediatrics, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Noriyuki Kaku
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.,Emergency and Critical Care Center, Kyushu University Hospital, Fukuoka, Japan
| | - Yoshihiko Maehara
- Emergency and Critical Care Center, Kyushu University Hospital, Fukuoka, Japan
| | - Koh-Hei Sonoda
- Department of Ophthalmology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Tomoaki Taguchi
- Department of Pediatric Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.,Emergency and Critical Care Center, Kyushu University Hospital, Fukuoka, Japan
| | - Shouichi Ohga
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
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4
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McMacken GM, Spendiff S, Whittaker RG, O’Connor E, Howarth RM, Boczonadi V, Horvath R, Slater CR, Lochmüller H. Salbutamol modifies the neuromuscular junction in a mouse model of ColQ myasthenic syndrome. Hum Mol Genet 2019; 28:2339-2351. [PMID: 31220253 PMCID: PMC6606850 DOI: 10.1093/hmg/ddz059] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Revised: 03/14/2019] [Accepted: 03/15/2019] [Indexed: 12/23/2022] Open
Abstract
The β-adrenergic agonists salbutamol and ephedrine have proven to be effective as therapies for human disorders of the neuromuscular junction, in particular many subsets of congenital myasthenic syndromes. However, the mechanisms underlying this clinical benefit are unknown and improved understanding of the effect of adrenergic signalling on the neuromuscular junction is essential to facilitate the development of more targeted therapies. Here, we investigated the effect of salbutamol treatment on the neuromuscular junction in the ColQ deficient mouse, a model of end-plate acetylcholinesterase deficiency. ColQ-/- mice received 7 weeks of daily salbutamol injection, and the effect on muscle strength and neuromuscular junction morphology was analysed. We show that salbutamol leads to a gradual improvement in muscle strength in ColQ-/- mice. In addition, the neuromuscular junctions of salbutamol treated mice showed significant improvements in several postsynaptic morphological defects, including increased synaptic area, acetylcholine receptor area and density, and extent of postjunctional folds. These changes occurred without alterations in skeletal muscle fibre size or type. These findings suggest that β-adrenergic agonists lead to functional benefit in the ColQ-/- mouse and to long-term structural changes at the neuromuscular junction. These effects are primarily at the postsynaptic membrane and may lead to enhanced neuromuscular transmission.
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Affiliation(s)
- Grace M McMacken
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne, UK
| | - Sally Spendiff
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne, UK
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Canada
| | - Roger G Whittaker
- Institute of Neuroscience, Newcastle University, Newcastle Upon Tyne, UK
| | - Emily O’Connor
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne, UK
| | - Rachel M Howarth
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle Upon Tyne, UK
| | - Veronika Boczonadi
- Institute of Neuroscience, Newcastle University, Newcastle Upon Tyne, UK
| | - Rita Horvath
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Clarke R Slater
- Institute of Neuroscience, Newcastle University, Newcastle Upon Tyne, UK
| | - Hanns Lochmüller
- Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Canada
- Department of Neuropediatrics and Muscle Disorders, Medical Center – University of Freiburg, Faculty of Medicine, Freiburg, Germany
- Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), Barcelona, Catalonia, Spain
- Division of Neurology, Department of Medicine, The Ottawa Hospital, Ottawa, Canada
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5
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Nicole S, Azuma Y, Bauché S, Eymard B, Lochmüller H, Slater C. Congenital Myasthenic Syndromes or Inherited Disorders of Neuromuscular Transmission: Recent Discoveries and Open Questions. J Neuromuscul Dis 2019; 4:269-284. [PMID: 29125502 PMCID: PMC5701762 DOI: 10.3233/jnd-170257] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Congenital myasthenic syndromes (CMS) form a heterogeneous group of rare diseases characterized by fatigable muscle weakness. They are genetically-inherited and caused by defective synaptic transmission at the cholinergic neuromuscular junction (NMJ). The number of genes known to cause CMS when mutated is currently 30, and the relationship between fatigable muscle weakness and defective functions is quite well-understood for many of them. However, some of the most recent discoveries in individuals with CMS challenge our knowledge of the NMJ, where the basis of the pathology has mostly been investigated in animal models. Frontier forms between CMS and congenital myopathy, which have been genetically and clinically identified, underline the poorly understood interplay between the synaptic and extrasynaptic molecules in the neuromuscular system. In addition, precise electrophysiological and histopathological investigations of individuals with CMS suggest an important role of NMJ plasticity in the response to CMS pathogenesis. While efficient drug-based treatments are already available to improve neuromuscular transmission for most forms of CMS, others, as well as neurological and muscular comorbidities, remain resistant. Taken together, the available pathological data point to physiological issues which remain to be understood in order to achieve precision medicine with efficient therapeutics for all individuals suffering from CMS.
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Affiliation(s)
- Sophie Nicole
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, 75013 Paris, France
| | - Yoshiteru Azuma
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK
| | - Stéphanie Bauché
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, 75013 Paris, France
| | - Bruno Eymard
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, 75013 Paris, France.,AP-HP, Hôpital Pitié-Salpétrière, 75013 Paris, France
| | - Hanns Lochmüller
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK
| | - Clarke Slater
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
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6
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Lipka AF, Vrinten C, van Zwet EW, Schimmel KJ, Cornel MC, Kuijpers MR, Hekster YA, Weinreich SS, Verschuuren JJ. Ephedrine treatment for autoimmune myasthenia gravis. Neuromuscul Disord 2017; 27:259-265. [DOI: 10.1016/j.nmd.2016.11.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 11/09/2016] [Accepted: 11/14/2016] [Indexed: 11/27/2022]
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7
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Adrenoceptors at the Frog Neuromuscular Junction: an Immunohistochemical Study. BIONANOSCIENCE 2017. [DOI: 10.1007/s12668-016-0319-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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8
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Vrinten C, Lipka AF, van Zwet EW, Schimmel KJM, Cornel MC, Kuijpers MR, Hekster YA, Weinreich SS, Verschuuren JJGM. Ephedrine as add-on therapy for patients with myasthenia gravis: protocol for a series of randomised, placebo-controlled n-of-1 trials. BMJ Open 2015; 5:e007863. [PMID: 26185179 PMCID: PMC4513481 DOI: 10.1136/bmjopen-2015-007863] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
INTRODUCTION Myasthenia gravis (MG), a rare neuromuscular disease, is often initially treated using acetylcholinesterase inhibitors. Patients who do not respond adequately depend on the use of corticosteroids or other immunosuppressive medication, but these may have serious side effects. Clinical observations suggest that ephedrine can diminish, postpone or even prevent the need for immunosuppressive therapy when added to acetylcholinesterase inhibitors or low-dose prednisone. In the Netherlands, ephedrine is not licensed for MG nor is reimbursement guaranteed. MG is a rare condition, and ephedrine might be indicated only in a subset of patients. Thus, randomised controlled trials comparing large groups are difficult to conduct. We, therefore, aim to aggregate data from a small series of n-of-1 trials (also known as single patient trials) to assess the effect of ephedrine as add-on treatment for MG. METHODS AND ANALYSIS Single-centre, placebo-controlled, double-blind, randomised, multiple crossover n-of-1 studies in 4 adult patients with generalised MG who show inadequate improvement on pyridostigmine and/or immunosuppressive drugs. Each n-of-1 trial has 3 cycles of two 5-day intervention periods. TREATMENT 25 mg ephedrine or placebo, twice daily. MAIN OUTCOME MEASURE Quantitative Myasthenia Gravis (QMG) test. STATISTICAL ANALYSIS fixed effects linear model for QMG for all patients combined. SECONDARY OUTCOME MEASURES Clinical: effects on MG-Composite and MG-Activities of Daily Living (MG-ADL) scales; QMG at individual level; adverse events. Acceptability of trial design: number of patients eligible and enrolled; number of treatment cycles completed; patients' and caregivers' experiences. ETHICS AND DISSEMINATION This study was approved by the Medical Ethics Committee of Leiden University Medical Center, No. P14.108. Results of the trial will be reported in a peer-reviewed publication. Regulatory stakeholders will comment on the suitability of the trial for market authorisation and reimbursement purposes. TRIAL REGISTRATION NUMBER This study is registered under EudraCT number 2014-001355-23, protocol no. 40960, V.1.0, registration date 27 March 2014.
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Affiliation(s)
- Charlotte Vrinten
- Department of Epidemiology and Public Health, University College London, London, UK
- Department of Clinical Genetics, EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands
| | - Alexander F Lipka
- Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
| | - Erik W van Zwet
- Department of Medical Statistics and Bioinformatics, Leiden University Medical Center, Leiden, The Netherlands
| | - Kirsten J M Schimmel
- Department of Clinical Pharmacy and Toxicology, Leiden University Medical Center, Leiden, The Netherlands
| | - Martina C Cornel
- Department of Clinical Genetics, EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands
| | - Marja R Kuijpers
- Department of Care, Section Pharmaceutical Care, National Health Care Institute, Diemen, The Netherlands
| | - Yechiel A Hekster
- Department of Pharmacy, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Stephanie S Weinreich
- Department of Clinical Genetics, EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands
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Vrinten C, van der Zwaag AM, Weinreich SS, Scholten RJPM, Verschuuren JJGM. Ephedrine for myasthenia gravis, neonatal myasthenia and the congenital myasthenic syndromes. Cochrane Database Syst Rev 2014; 2014:CD010028. [PMID: 25515947 PMCID: PMC7387729 DOI: 10.1002/14651858.cd010028.pub2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Myasthenia is a condition in which neuromuscular transmission is affected by antibodies against neuromuscular junction components (autoimmune myasthenia gravis, MG; and neonatal myasthenia gravis, NMG) or by defects in genes for neuromuscular junction proteins (congenital myasthenic syndromes, CMSs). Clinically, some individuals seem to benefit from treatment with ephedrine, but its effects and adverse effects have not been systematically evaluated. OBJECTIVES To assess the effects and adverse effects of ephedrine in people with autoimmune MG, transient neonatal MG, and the congenital myasthenic syndromes. SEARCH METHODS On 17 November 2014, we searched the Cochrane Neuromuscular Disease Group Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE. We also searched reference lists of articles, conference proceedings of relevant conferences, and prospective trial registers. In addition, we contacted manufacturers and researchers in the field. SELECTION CRITERIA We considered randomised controlled trials (RCTs) and quasi-RCTs comparing ephedrine as a single or add-on treatment with any other active treatment, placebo, or no treatment in adults or children with autoimmune MG, NMG, or CMSs. DATA COLLECTION AND ANALYSIS Two review authors independently assessed study design and quality, and extracted data. We contacted study authors for additional information. We collected information on adverse effects from included articles, and contacted authors. MAIN RESULTS We found no RCTs or quasi-RCTs, and therefore could not establish the effect of ephedrine on MG, NMG and CMSs. We describe the results of 53 non-randomised studies narratively in the Discussion section, including observations of endurance, muscle strength and quality of life. Effects may differ depending on the type of myasthenia. Thirty-seven studies were in participants with CMS, five in participants with MG, and in 11 the precise form of myasthenia was unknown. We found no studies for NMG. Reported adverse effects included tachycardia, sleep disturbances, nervousness, and withdrawal symptoms. AUTHORS' CONCLUSIONS There was no evidence available from RCTs or quasi-RCTs, but some observations from non-randomised studies are available. There is a need for more evidence from suitable forms of prospective RCTs, such as series of n-of-one RCTs, that use appropriate and validated outcome measures.
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Affiliation(s)
- Charlotte Vrinten
- VU University Medical CenterCommunity Genetics Section, Clinical GeneticsBS7, D450PO Box 7057AmsterdamNetherlands1007 MB
| | - Angeli M van der Zwaag
- VU University Medical CenterCommunity Genetics Section, Clinical GeneticsBS7, D450PO Box 7057AmsterdamNetherlands1007 MB
| | - Stephanie S Weinreich
- VU University Medical CenterCommunity Genetics Section, Clinical GeneticsBS7, D450PO Box 7057AmsterdamNetherlands1007 MB
| | - Rob JPM Scholten
- Julius Center for Health Sciences and Primary Care / University Medical Center UtrechtDutch Cochrane CentreRoom Str. 6.126P.O. Box 85500UtrechtNetherlands3508 GA
| | - Jan JGM Verschuuren
- Leiden University Medical CenterDepartment of NeurologyPO Box 9600LeidenNetherlands2300 RC
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10
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Webster RG, Cossins J, Lashley D, Maxwell S, Liu WW, Wickens JR, Martinez-Martinez P, de Baets M, Beeson D. A mouse model of the slow channel myasthenic syndrome: Neuromuscular physiology and effects of ephedrine treatment. Exp Neurol 2013; 248:286-98. [PMID: 23797154 DOI: 10.1016/j.expneurol.2013.06.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 05/10/2013] [Accepted: 06/14/2013] [Indexed: 02/04/2023]
Abstract
In the slow channel congenital myasthenic syndrome mutations in genes encoding the muscle acetylcholine receptor give rise to prolonged ion channel activations. The resulting cation overload in the postsynaptic region leads to damage of synaptic structures, impaired neuromuscular transmission and fatigable muscle weakness. Previously we identified and characterised in detail the properties of the slow channel syndrome mutation εL221F. Here, using this mutation, we generate a transgenic mouse model for the slow channel syndrome that expresses mutant human ε-subunits harbouring an EGFP tag within the M3-M4 cytoplasmic region, driven by a ~1500 bp region of the CHRNB promoter. Fluorescent mutant acetylcholine receptors are assembled, cluster at the motor endplates and give rise to a disease model that mirrors the human condition. Mice demonstrate mild fatigable muscle weakness, prolonged endplate and miniature endplate potentials, and variable degeneration of the postsynaptic membrane. We use our model to investigate ephedrine as a potential treatment. Mice were assessed before and after six weeks on oral ephedrine (serum ephedrine concentration 89 ± 3 ng/ml) using an inverted screen test and in vivo electromyography. Treated mice demonstrated modest benefit for screen hang time, and in measures of compound muscle action potentials and mean jitter that did not reach statistical significance. Ephedrine and salbutamol show clear benefit when used in the treatment of DOK7 or COLQ congenital myasthenic syndromes. Our results highlight only a modest potential benefit of these β2-adrenergic receptor agonists for the treatment of the slow channel syndrome.
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Affiliation(s)
- R G Webster
- Neurosciences Group, Nuffield Dept. of Clinical Neurosciences, University of Oxford, Oxford, UK
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11
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Liewluck T, Selcen D, Engel AG. Beneficial effects of albuterol in congenital endplate acetylcholinesterase deficiency and Dok-7 myasthenia. Muscle Nerve 2011; 44:789-94. [PMID: 21952943 DOI: 10.1002/mus.22176] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/18/2011] [Indexed: 12/20/2022]
Abstract
INTRODUCTION Congenital myasthenic syndromes (CMS) are disabling but treatable disorders. Anticholinesterase therapy is effective in most of them, but is contraindicated in endplate (EP) acetylcholinesterase (AChE) deficiency, the slow-channel syndrome, Dok-7 myasthenia, and β(2) -laminin deficiency, and is not useful in CMS due to defects in muscle-specific kinase (MuSK), agrin, and plectin. EP AChE, Dok-7, and β(2)-laminin deficiencies respond favorably to ephedrine, but ephedrine can no longer be prescribed in the USA. METHODS We used albuterol, another sympathomimetic agent, to treat 3 patients with EP AChE deficiency and 15 with Dok-7 myasthenia. Response to therapy was evaluated by a 9-point questionnaire pertaining to activities of daily life. RESULTS Comparison of the pre- and posttreatment responses indicated a beneficial response to albuterol (P < 0.001) in both patient groups. The adverse effects of therapy were like those of ephedrine. CONCLUSION Our observations should spur controlled, prospective clinical trials of albuterol in these as well as other CMS.
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Affiliation(s)
- Teerin Liewluck
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, Minnesota 55905, USA
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12
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Sadeh M, Shen XM, Engel AG. Beneficial effect of albuterol in congenital myasthenic syndrome with epsilon-subunit mutations. Muscle Nerve 2011; 44:289-91. [PMID: 21721016 DOI: 10.1002/mus.22153] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/25/2011] [Indexed: 11/06/2022]
Abstract
Mutations in the epsilon subunit of the acetylcholine receptor (AChR) are a common cause of congenital myasthenic syndrome (CMS). Patients are usually treated with acetylcholinesterase inhibitors and 3,4-diaminopyridine with modest clinical benefit. We report 2 patients with CMS due to mutations in the AChR epsilon subunit. The first patient carries two heterozygous frameshift mutations, ε127ins5 and ε1293insG. The second patient is homozygous for the εC142Y mutation that curtails AChR expression to 22% of wild-type in HEK cells. Treatment with pyridostigmine and 3,4-diaminopyridine had a limited beneficial effect in the first patient, and the second patient became wheelchair-bound during therapy. The additional use of albuterol produced dramatic improvement in strength and in activities of daily living in both patients. The efficacy and safety of albuterol in patients who harbor identified low-expressor or null mutations in the epsilon or other subunits of AChR merits a well-designed clinical trial.
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Affiliation(s)
- Menachem Sadeh
- Department of Neurology, Wolfson Medical Center, Holon and Tel Aviv University, Halochamin Street, Holon 58100, Israel.
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13
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Lashley D, Palace J, Jayawant S, Robb S, Beeson D. Ephedrine treatment in congenital myasthenic syndrome due to mutations in DOK7. Neurology 2010; 74:1517-23. [PMID: 20458068 DOI: 10.1212/wnl.0b013e3181dd43bf] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Mutations in the postsynaptic adaptor protein Dok-7 underlie congenital myasthenic syndrome (CMS) with a characteristic limb girdle pattern of muscle weakness. Patients usually do not respond to or worsen with the standard CMS treatments: cholinesterase inhibitors and 3,4-diaminopyridine. However, anecdotal reports suggest they may improve with ephedrine. METHODS This was an open prospective follow-up study to determine muscle strength in response to ephedrine in Dok-7 CMS. Patients were first evaluated as inpatients for suitability for a trial of treatment with ephedrine. The response was assessed at 2 and 6 to 8 months follow-up clinic visits using a quantitative myasthenia gravis (severity) score (QMG) and mobility measures. RESULTS Ten out of 12 of the cohort with DOK7 mutations tolerated ephedrine. We noted a progressive response to treatment over the 6 to 8 months assessment period with a significant improvement at the final QMG score (p = 0.009). Mobility scores also improved (p = 0.0006). Improvements in the subcomponents of the QMG score that measured proximal muscle function (those muscle groups most severely affected) were most marked, and in some cases were dramatic. All patients reported enhanced activities of daily living at 6-8 months. CONCLUSION Ephedrine appears to be an effective treatment for Dok-7 CMS. It is well-tolerated by most patients and improvement in strength can be profound. Determining the long-term response and the most effective dosing regimen will require further research. CLASSIFICATION OF EVIDENCE This study provides Class IV evidence that ephedrine given at doses between 15 and 90 mg/day improves muscle strength in patients with documented mutations in DOK7.
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Affiliation(s)
- D Lashley
- Weatherall Institute of Molecular Medicine, The John Radcliffe, Oxford OX3 9DS, UK
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Skeie GO, Apostolski S, Evoli A, Gilhus NE, Illa I, Harms L, Hilton-Jones D, Melms A, Verschuuren J, Horge HW. Guidelines for treatment of autoimmune neuromuscular transmission disorders. Eur J Neurol 2010; 17:893-902. [PMID: 20402760 DOI: 10.1111/j.1468-1331.2010.03019.x] [Citation(s) in RCA: 235] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Important progress has been made in our understanding of the autoimmune neuromuscular transmission (NMT) disorders; myasthenia gravis (MG), Lambert-Eaton myasthenic syndrome (LEMS) and neuromyotonia (Isaacs' syndrome). METHODS To prepare consensus guidelines for the treatment of the autoimmune NMT disorders, references retrieved from MEDLINE, EMBASE and the Cochrane Library were considered and statements prepared and agreed on by disease experts. CONCLUSIONS Anticholinesterase drugs should be given first in the management of MG, but with some caution in patients with MuSK antibodies (good practice point). Plasma exchange is recommended in severe cases to induce remission and in preparation for surgery (recommendation level B). IvIg and plasma exchange are effective for the treatment of MG exacerbations (recommendation level A). For patients with non-thymomatous MG, thymectomy is recommended as an option to increase the probability of remission or improvement (recommendation level B). Once thymoma is diagnosed, thymectomy is indicated irrespective of MG severity (recommendation level A). Oral corticosteroids are first choice drugs when immunosuppressive drugs are necessary (good practice point). When long-term immunosuppression is necessary, azathioprine is recommended to allow tapering the steroids to the lowest possible dose whilst maintaining azathioprine (recommendation level A). 3,4-Diaminopyridine is recommended as symptomatic treatment and IvIG has a positive short-term effect in LEMS (good practice point). Neuromyotonia patients should be treated with an antiepileptic drug that reduces peripheral nerve hyperexcitability (good practice point). For paraneoplastic LEMS and neuromyotonia optimal treatment of the underlying tumour is essential (good practice point). Immunosuppressive treatment of LEMS and neuromyotonia should be similar to MG (good practice point).
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Affiliation(s)
- G O Skeie
- Department of Neurology, University of Bergen, Norway.
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Schara U, Barisic N, Deschauer M, Lindberg C, Straub V, Strigl-Pill N, Wendt M, Abicht A, Müller J, Lochmüller H. Ephedrine therapy in eight patients with congenital myasthenic syndrome due to DOK7 mutations. Neuromuscul Disord 2009; 19:828-32. [DOI: 10.1016/j.nmd.2009.09.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Accepted: 09/21/2009] [Indexed: 10/20/2022]
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Soliven B, Rezania K, Gundogdu B, Harding-Clay B, Oger J, Arnason BG. Terbutaline in myasthenia gravis: A pilot study. J Neurol Sci 2009; 277:150-4. [DOI: 10.1016/j.jns.2008.09.033] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Revised: 09/18/2008] [Accepted: 09/23/2008] [Indexed: 10/21/2022]
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Abstract
Congenital myasthenic syndromes (CMS) are classified in terms of the located defect: presynaptic, postsynaptic, and synaptic. They are inherited disorders caused by various genetic defects, all but the slow-channel CMS by recessive inheritance. To date, 10 different CMS are known and further CMS subtypes and their genetic cause may be disclosed by future investigations. Prognosis in CMS is variable and largely depends on the pathophysiological and genetic defect. Subtypes showing progression and life-threatening crises with apneas are generally less favorable than others. Therapeutic agents used in CMS depend on the underlying defect and include acetylcholinesterase inhibitor, 3,4-diaminopyridine, quinidine sulfate, fluoxetine, acetazolamide, and ephedrine. Although there are no double-blind, placebo-controlled clinical trials for CMS, several drugs have shown convincingly positive clinical effects. It is therefore necessary to start a rational therapy regime as early as possible. In most CMS, however, mild and severe clinical courses are reported, which makes assessment on an individual basis necessary. This review emphasizes therapeutic strategies in CMS.
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Affiliation(s)
- Ulrike Schara
- Department of Pediatric Neurology, University of Essen, Essen, Germany.
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18
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The rush to adrenaline: drugs in sport acting on the beta-adrenergic system. Br J Pharmacol 2008; 154:584-97. [PMID: 18500380 DOI: 10.1038/bjp.2008.164] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Athletes attempt to improve performance with drugs that act on the beta-adrenergic system directly or indirectly. Of three beta-adrenoceptor (AR) subtypes, the beta(2)-AR is the main target in sport; they have bronchodilator and anabolic actions and enhance anti-inflammatory actions of corticosteroids. Although demonstrable in animal experiments and humans, there is little evidence that these properties can significantly improve performance in trained athletes. Their actions may also be compromised by receptor desensitization and by common, naturally occurring receptor mutations (polymorphisms) that can influence receptor signalling and desensitization properties in individuals. Indirectly acting agents affect release and reuptake of noradrenaline and adrenaline, thereby influencing all AR subtypes including the three beta-ARs. These agents can have potent psychostimulant effects that provide an illusion of better performance that does not usually translate into improvement in practice. Amphetamines and cocaine also have considerable potential for cardiac damage. beta-AR antagonists (beta-blockers) are used in sports that require steadiness and accuracy, such as archery and shooting, where their ability to reduce heart rate and muscle tremor may improve performance. They have a deleterious effect in endurance sports because they reduce physical performance and maximum exercise load. Recent studies have identified that many beta-AR antagonists not only block the actions of agonists but also activate other (mitogen-activated PK) signalling pathways influencing cell growth and fate. The concept that many compounds previously regarded as 'blockers' may express their own spectrum of pharmacological properties has potentially far-reaching consequences for the use of drugs both therapeutically and illicitly.
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Cereda C, Kuntzer T. The potential use of ephedrine in Lambert-Eaton myasthenic syndrome : clinical and electrophysiological evaluation. J Neurol 2008; 255:1259-60. [PMID: 18535871 DOI: 10.1007/s00415-008-0856-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2007] [Revised: 12/12/2007] [Accepted: 12/18/2007] [Indexed: 11/30/2022]
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Reliability of neuromuscular transmission and how it is maintained. HANDBOOK OF CLINICAL NEUROLOGY 2008; 91:27-101. [PMID: 18631840 DOI: 10.1016/s0072-9752(07)01502-3] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Skeie GO, Apostolski S, Evoli A, Gilhus NE, Hart IK, Harms L, Hilton-Jones D, Melms A, Verschuuren J, Horge HW. Guidelines for the treatment of autoimmune neuromuscular transmission disorders. Eur J Neurol 2006; 13:691-9. [PMID: 16834699 DOI: 10.1111/j.1468-1331.2006.01476.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Important progress has been made in our understanding of the cellular and molecular processes underlying the autoimmune neuromuscular transmission (NMT) disorders; myasthenia gravis (MG), Lambert-Eaton myasthenic syndrome (LEMS) and neuromyotonia (peripheral nerve hyperexcitability; Isaacs syndrome). To prepare consensus guidelines for the treatment of the autoimmune NMT disorders. References retrieved from MEDLINE, EMBASE and the Cochrane Library were considered and statements prepared and agreed on by disease experts and a patient representative. The proposed practical treatment guidelines are agreed upon by the Task Force: (i) Anticholinesterase drugs should be the first drug to be given in the management of MG (good practice point). (ii) Plasma exchange is recommended as a short-term treatment in MG, especially in severe cases to induce remission and in preparation for surgery (level B recommendation). (iii) Intravenous immunoglobulin (IvIg) and plasma exchange are equally effective for the treatment of MG exacerbations (level A Recommendation). (iv) For patients with non-thymomatous autoimmune MG, thymectomy (TE) is recommended as an option to increase the probability of remission or improvement (level B recommendation). (v) Once thymoma is diagnosed TE is indicated irrespective of the severity of MG (level A recommendation). (vi) Oral corticosteroids is a first choice drug when immunosuppressive drugs are necessary in MG (good practice point). (vii) In patients where long-term immunosuppression is necessary, azathioprine is recommended together with steroids to allow tapering the steroids to the lowest possible dose whilst maintaining azathioprine (level A recommendation). (viii) 3,4-diaminopyridine is recommended as symptomatic treatment and IvIg has a positive short-term effect in LEMS (good practice point). (ix) All neuromyotonia patients should be treated symptomatically with an anti-epileptic drug that reduces peripheral nerve hyperexcitability (good practice point). (x) Definitive management of paraneoplastic neuromyotonia and LEMS is treatment of the underlying tumour (good practice point). (xi) For immunosuppressive treatment of LEMS and NMT it is reasonable to adopt treatment procedures by analogy with MG (good practice point).
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Affiliation(s)
- G O Skeie
- Department of Neurology, University of Bergen, Bergen, Norway.
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23
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Ezri T, Szmuk P, Warters RD, Gebhard RE, Pivalizza EG, Katz J. Changes in onset time of rocuronium in patients pretreated with ephedrine and esmolol--the role of cardiac output. Acta Anaesthesiol Scand 2003; 47:1067-72. [PMID: 12969097 DOI: 10.1034/j.1399-6576.2003.00218.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND We investigated the hypothesis that manipulation of cardiac output (CO) with esmolol (Es) or ephedrine (E) affects the onset time of rocuronium. METHODS Following anesthesia induction, 33 patients received E (70 micro g kg-1), Es (500 micro g kg-1) or placebo (P) 30 s before rocuronium (0.6 mg kg-1) administration. Cardiac output was measured non-invasively after intubation every 3 min. The interval from the end of rocuronium administration to the disappearance of all twitches was considered to be the onset time. RESULTS Onset time was shorter after E (52.2 +/- 16.5 s) and longer after Es (114.3 +/- 11.1 s) compared with P (87.4 +/- 7.3 s) (P < 0.0001). Cardiac output increased (P < 0.05) in group E for 15 min after rocuronium. In group Es, CO decreased (P < 0.05) at 3 and 6 min. Cardiac output was higher in group E vs. group Es, 3-6 min post administration of rocuronium (P=0.015). CONCLUSION Pretreatment with E or Es appears to affect the onset time of rocuronium by altering CO as measured with the NICO (Non-Invasive Cardiac Output) monitor (Novametrix Medical Systems Inc., Willingford, CO).
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Affiliation(s)
- T Ezri
- Department of Anesthesia Wolfson Medical Center, Holon, affiliated to the Sackler School of Medicine, Tel Aviv, Israel
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Richman DP, Agius MA. Treatment Principles in the Management of Autoimmune Myasthenia Gravis. Ann N Y Acad Sci 2003; 998:457-72. [PMID: 14592915 DOI: 10.1196/annals.1254.060] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The pathogenesis of myasthenia gravis (MG) involves a T cell-directed antibody-mediated autoimmune attack on the nicotinic acetylcholine receptor (AChR) or, occasionally, on other postsynaptic antigens. The antibodies induce their effects through complement-mediated destruction of the postsynaptic endplate membrane with resultant reduction in endplate AChR, and to a lesser degree by increased turnover of endplate AChR or blockade of AChR function. Considerable progress in the treatment of MG has accrued from so-called symptomatic treatments, including improved critical care of seriously ill patients and medications (e.g., cholinesterase inhibitors) increasing the concentration of acetylcholine at the remaining endplate AChRs. Information from other autoimmune diseases and from the response of the normal immune system to invading pathogens supports the view that the course of MG is characterized by exacerbations and remissions. Therefore, the goal in MG treatment is to induce and maintain a remission. This usually involves combinations of short-term and long-term immunosuppressive agents. Selection of the particular combinations of agents in a given patient is guided by the goal of minimizing the cost/benefit ratio of the regimen in an individual patient. In general, the plan involves an initial forceful attack followed by a slow and measured withdrawal.
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Affiliation(s)
- David P Richman
- Department of Neurology, University of California, Davis, Davis, California 95616, USA.
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25
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Abstract
Reliable transmission of activity from nerve to muscle is necessary for the normal function of the body. The term 'safety factor' refers to the ability of neuromuscular transmission to remain effective under various physiological conditions and stresses. This is a result of the amount of transmitter released per nerve impulse being greater than that required to trigger an action potential in the muscle fibre. The safety factor is a measure of this excess of released transmitter. In this review we discuss the practical difficulties involved in estimating the safety factor in vitro. We then consider the factors that influence the safety factor in vivo. While presynaptic transmitter release may be modulated on a moment to moment basis, the postsynaptic features that determine the effect of released transmitter are not so readily altered to meet changing demands. Different strategies are used by different species to ensure reliable neuromuscular transmission. Some, like frogs, rely on releasing a large amount of transmitter while others, like man, rely on elaborate postsynaptic specialisations to enhance the response to transmitter. In normal adult mammals, the safety factor is generally 3-5. Both pre- and postsynaptic components change during development and may show plasticity in response to injury or disease. Thus, both acquired autoimmune and inherited congenital diseases of the neuromuscular junction (NMJ) can significantly reduce, or even transiently increase, safety factor.
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Affiliation(s)
- S J Wood
- Department of Physiology, School of Medical Sciences, University of Bristol, University Walk, BS8 1TD, Bristol, UK.
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Gill ND, Shield A, Blazevich AJ, Zhou S, Weatherby RP. Muscular and cardiorespiratory effects of pseudoephedrine in human athletes. Br J Clin Pharmacol 2000; 50:205-13. [PMID: 10971304 PMCID: PMC2014984 DOI: 10.1046/j.1365-2125.2000.00252.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS Pseudoephedrine (PSE) is a readily available over-the-counter nasal decongestant which is structurally similar to amphetamine and is included on the International Olympic Committee's list of banned substances. However to date, little research has supported its putative ergogenic effect. This study investigated whether a 180 mg dose of PSE ingested 45 min prior to exercise enhanced short-term maximal exercise performance and/or altered related physiological variables. METHODS A randomised, double-blind, crossover study in 22 healthy male athletes. RESULTS Maximum torque (mean +/- s.d., n = 22) produced in an isometric knee extension exercise was 321.1+/-62.0 Nm (PSE) and 295.7+/-72.4 Nm (placebo), and peak power obtained on the 'all-out' 30 s cycle test was 1262.5+/-48.5 W (PSE) and 1228.4+/-47.1 W (placebo) (P<0.01, P<0.03, respectively). Subjects were estimated to be producing 96.9+/-2.4% of their maximal possible isometric leg extension force after PSE ingestion, but only 95.3+/-2.4% when PSE was not ingested. Bench press tasks and total work during the cycle test were not affected by the ingestion of PSE. Lung function was altered following ingestion of PSE (P<0.05) with FEV1 and FVC significantly increased (P<0.02, P<0.01, respectively) although the FEV1/FVC ratio was not altered. Heart rate was significantly elevated by the ingestion of PSE immediately following the 30 s cycle sprint (P<0.01) however, lactate concentration was not altered by the ingestion of PSE. CONCLUSIONS The administration of a 180 mg dose of PSE increased maximum torque, produced in an isometric knee extension and produced an improvement in peak power during maximal cycle performance, as well as improving lung function.
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Affiliation(s)
- N D Gill
- Centre for Sport and Exercise Science, The Waikato Polytechnic, Private Bag HN 3036, Hamilton, New Zealand
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Abstract
A combination of transient expression of wild-type and a mutant muscle nicotinic receptor (AChR) found in a patient suffering from a congenital myasthenic syndrome and single-channel recordings was used to characterize the action of ephedrine on the AChR. In the presence of ephedrine, both types of AChR channel showed a flickering behaviour and a dose-dependent reduction in the mean open time. The duration of the blocking events was dependent on the membrane potential. The forward rate constant for the blocking process was of the order of 10(7) M-1 s-1 in both types of AChR. The results are consistent with ephedrine acting as a channel blocker in wild-type AChR as well as in long-lived AChR channels present in patients with the slow-channel syndrome.
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Affiliation(s)
- C Bouzat
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Argentina
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Milone M, Engel AG. Block of the endplate acetylcholine receptor channel by the sympathomimetic agents ephedrine, pseudoephedrine, and albuterol. Brain Res 1996; 740:346-52. [PMID: 8973833 DOI: 10.1016/s0006-8993(96)00894-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Recent observations suggest that some patients with congenital myasthenic syndromes respond favorably to ephedrine, pseudoephedrine, or albuterol. Conventional microelectrode studies, however, provide no clear explanation for a beneficial effect of ephedrine in endplate diseases. To gain further insight into how these drugs affect neuromuscular transmission, we investigated their effects on the kinetic properties of the acetylcholine (ACh) receptor. Single channel currents were recorded from rat lumbrical muscles endplates using low concentrations of ACh and 2.5-100 microM of drugs. Between 10-100 microM, each drug progressively increased the rate of channel closure in a concentration dependent manner, consistent with an open-channel block. Albuterol acted as a sequential fast-acting channel blocker, increasing the mean burst duration in a concentration dependent manner without altering the total open time per burst or the duration of intraburst blockages. Increasing concentrations of ephedrine and pseudoephedrine also increased the number of intraburst closures but decreased the total open time per burst. None of the drugs altered single channel conductance. The channel blocking effects of ephedrine and pseudoephedrine might reduce the synaptic overactivity that occurs in the slow-channel myasthenic syndromes or in endplate ACh esterase deficiency, but these effects occur at concentrations not attainable in clinical practice.
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Affiliation(s)
- M Milone
- Department of Neurology and Neuromuscular Research Laboratory, Mayo Clinic, Rochester, MN 55905, USA
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Hwang GI, Chung JH, Lee WK. Efficient Synthesis of Ephedra Alkaloid Analogues Using an Enantiomerically Pure N-[(R)-(+)-alpha-Methylbenzyl]aziridine-2-carboxaldehyde. J Org Chem 1996; 61:6183-6188. [PMID: 11667453 DOI: 10.1021/jo9603183] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Efficient preparation of enantiomerically pure (2S)-aziridine-2-carboxaldehyde 9 and its 2(R) isomer and highly diastereoselective addition of organolithium reagents to the aldehyde 9 are described. The diastereoselectivity in additions of the lithium reagents seems to come from "chelation-controlled" carbon-carbon bond formation and is influenced by the source of the organometallic compound, solvent, and the presence of a Li salt. The C(3)-N bond of the aziridine ring of the addition products was regioselectively reduced by catalytic hydrogenation in the presence of Pearlman's catalyst to provide enantiomerically pure 1,2-amino alcohols. The absolute stereochemistries of the amino alcohol 13a were assigned as (1S,2S) when the C-1 substituent was phenyl by comparison with those of commercially available norpseudoephedrine.
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Affiliation(s)
- Gwon-Il Hwang
- Department of Chemistry, Sogang University, Seoul 121-742, Korea
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Lefaucheur JP, Sebille A. Features of dystrophy in smooth and skeletal muscles of mdx mice. Muscle Nerve 1996; 19:793-4. [PMID: 8609936 DOI: 10.1002/mus.880190602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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