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Ferrer-Acosta Y, Rodriguez-Massó S, Pérez D, Eterovic VA, Ferchmin PA, Martins AH. Memantine has a nicotinic neuroprotective pathway in acute hippocampal slices after an NMDA insult. Toxicol In Vitro 2022; 84:105453. [PMID: 35944748 PMCID: PMC10026604 DOI: 10.1016/j.tiv.2022.105453] [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: 05/13/2022] [Revised: 07/14/2022] [Accepted: 08/03/2022] [Indexed: 10/15/2022]
Abstract
Memantine is a non-competitive antagonist with a moderate affinity to the N-methyl-d-Aspartate (NMDA) receptor. The present study assessed memantine's neuroprotective activity using electrophysiology of ex-vivo hippocampal slices. Interestingly, a nicotinic component was necessary for memantine's neuroprotection (NP). Memantine demonstrated a bell-shaped dose-response curve of NP against NMDA. Memantine was neuroprotective at concentrations below 3 μM, but the NP declined at higher concentrations (>3 μM) when memantine inhibits the NMDA receptor. Additional evidence that memantine NP is mediated by an alternate mechanism independent of the inhibition of the NMDA receptor is supported by its ability to protect neurons when applied before or after the NMDA insult and in the presence of D(-)-2-Amino-5-phosphonopentanoic acid (APV), the standard NMDA receptor inhibitor. We found several similarities between the memantine NP mechanism and the neuroprotective nicotinic drug, the 4R cembranoid. Memantine's NP requires the release of acetylcholine, the activation of α4β2, and is independent of MEK/MAPK signaling. Both 4R and memantine require the activation of PI3K/AKT for NP against NMDA-mediated excitotoxicity, although at different concentrations. In conclusion, our studies show memantine is neuroprotective through a nicotinic pathway, similar to the nicotinic drug 4R. This information leads to a better understanding of memantine's mechanisms of action and explains its dose-dependent effectiveness in Alzheimer's and other neurological disorders.
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Affiliation(s)
- Yancy Ferrer-Acosta
- Department of Neuroscience, Universidad Central del Caribe, Laurel Avenue 2U6, Lomas Verdes, Bayamón 00956, Puerto Rico.
| | - Sergio Rodriguez-Massó
- Department of Pharmacology and Toxicology, University of Puerto Rico, Medical Sciences Campus, Los Paseos Avenue, Guillermo Arbona Building, San Juan 00935, Puerto Rico.
| | - Dinely Pérez
- Department of Biochemistry, Universidad Central del Caribe Laurel Avenue, #100, Santa Juanita, Bayamón 00956, Puerto Rico
| | - Vesna A Eterovic
- Neuroprotection for Life, 480 E Village Dr., Carmel, IN 46032, USA
| | - P A Ferchmin
- Neuroprotection for Life, 480 E Village Dr., Carmel, IN 46032, USA
| | - Antonio Henrique Martins
- Department of Pharmacology and Toxicology, University of Puerto Rico, Medical Sciences Campus, Los Paseos Avenue, Guillermo Arbona Building, San Juan 00935, Puerto Rico.
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2
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In vitro characterization of [ 3H]VAT in cells, animal and human brain tissues for vesicular acetylcholine transporter. Eur J Pharmacol 2021; 911:174556. [PMID: 34627806 DOI: 10.1016/j.ejphar.2021.174556] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Revised: 09/02/2021] [Accepted: 09/03/2021] [Indexed: 11/23/2022]
Abstract
Vesicular acetylcholine transporter plays a crucial role in the cholinergic system, and its alterations is implicated in several neurodegenerative disorders. We recently developed a PET imaging tracer [18F]VAT to target VAChT in vivo with high affinity and selectivity. Here we report in vitro characterization of [3H]VAT, a tritiated counterpart of [18F]VAT. Using human VAChT-rich cell membrane extracts, a saturated binding curve was obtained for [3H]VAT with Kd = 6.5 nM and Bmax = 22.89 pmol/mg protein. In the [3H]VAT competition-binding assay with a panel of CNS ligands, binding inhibition of [3H]VAT was observed using VAChT ligands, the Ki values ranged from 5.41 to 33.3 nM. No inhibition was detected using a panel of other CNS ligands. In vitro [3H]VAT autoradiography of rat brain sections showed strong signals in the striatum, moderate to high signals in vermis, thalamus, cortex, and hippocampus, and weak signals in cerebellum. Strong [3H]VAT ARG signals were also observed from striatal sections of normal nonhuman primates and human brains. Competitive ARG study with human striatal sections demonstrated strong ARG signals of [3H]VAT in caudate and putamen were blocked significantly by either VAChT ligand TZ659 or (-)-vesamicol, but not by the σ1 receptor ligand Yun-122. ARG study also indicated that signal in the striatal sections from PSP human brains was lower than normal human brains. These data provide solid evidence supporting [18F]VAT as a suitable PET radiotracer for quantitative assessment of VAChT levels in vivo.
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Bradner JM, Kalia V, Lau FK, Sharma M, Bucher ML, Johnson M, Chen M, Walker DI, Jones DP, Miller GW. Genetic or Toxicant-Induced Disruption of Vesicular Monoamine Storage and Global Metabolic Profiling in Caenorhabditis elegans. Toxicol Sci 2021; 180:313-324. [PMID: 33538833 PMCID: PMC8041460 DOI: 10.1093/toxsci/kfab011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The proper storage and release of monoamines contributes to a wide range of neuronal activity. Here, we examine the effects of altered vesicular monoamine transport in the nematode Caenorhabditis elegans. The gene cat-1 is responsible for the encoding of the vesicular monoamine transporter (VMAT) in C. elegans and is analogous to the mammalian vesicular monoamine transporter 2 (VMAT2). Our laboratory has previously shown that reduced VMAT2 activity confers vulnerability on catecholamine neurons in mice. The purpose of this article was to determine whether this function is conserved and to determine the impact of reduced VMAT activity in C. elegans. Here we show that deletion of cat-1/VMAT increases sensitivity to the neurotoxicant 1-methyl-4-phenylpyridinium (MPP+) as measured by enhanced degeneration of dopamine neurons. Reduced cat-1/VMAT also induces changes in dopamine-mediated behaviors. High-resolution mass spectrometry-based metabolomics in the whole organism reveals changes in amino acid metabolism, including tyrosine metabolism in the cat-1/VMAT mutants. Treatment with MPP+ disrupted tryptophan metabolism. Both conditions altered glycerophospholipid metabolism, suggesting a convergent pathway of neuronal dysfunction. Our results demonstrate the evolutionarily conserved nature of monoamine function in C. elegans and further suggest that high-resolution mass spectrometry-based metabolomics can be used in this model to study environmental and genetic contributors to complex human disease.
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Affiliation(s)
- Joshua M Bradner
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York 10032, USA
| | - Vrinda Kalia
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York 10032, USA
| | - Fion K Lau
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York 10032, USA
| | - Monica Sharma
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York 10032, USA
| | - Meghan L Bucher
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York 10032, USA
| | - Michelle Johnson
- Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, Georgia 30322, USA
| | - Merry Chen
- Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, Georgia 30322, USA
| | - Douglas I Walker
- Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai, New York, New York 10029, USA
| | - Dean P Jones
- Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia 30303, USA
| | - Gary W Miller
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York 10032, USA
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4
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Chamorro‐Arenas D, Nolasco‐Hernández AA, Fuentes L, Quintero L, Sartillo‐Piscil F. Transition‐Metal‐Free Multiple Functionalization of Piperidines to 4‐Substituted and 3,4‐Disubstituted 2‐Piperidinones. Chemistry 2020; 26:4671-4676. [DOI: 10.1002/chem.201905262] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Indexed: 12/25/2022]
Affiliation(s)
- Delfino Chamorro‐Arenas
- Centro de Investigación de la Facultad de Ciencias QuímicasBenemérita Universidad Autónoma de Puebla (BUAP) 14 Sur Esq. San Claudio, Col. San Manuel 72570 Puebla México
| | - Alejandro A. Nolasco‐Hernández
- Centro de Investigación de la Facultad de Ciencias QuímicasBenemérita Universidad Autónoma de Puebla (BUAP) 14 Sur Esq. San Claudio, Col. San Manuel 72570 Puebla México
| | - Lilia Fuentes
- Centro de Investigación de la Facultad de Ciencias QuímicasBenemérita Universidad Autónoma de Puebla (BUAP) 14 Sur Esq. San Claudio, Col. San Manuel 72570 Puebla México
| | - Leticia Quintero
- Centro de Investigación de la Facultad de Ciencias QuímicasBenemérita Universidad Autónoma de Puebla (BUAP) 14 Sur Esq. San Claudio, Col. San Manuel 72570 Puebla México
| | - Fernando Sartillo‐Piscil
- Centro de Investigación de la Facultad de Ciencias QuímicasBenemérita Universidad Autónoma de Puebla (BUAP) 14 Sur Esq. San Claudio, Col. San Manuel 72570 Puebla México
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Do spiroindolines have the potential to replace vesamicol as lead compound for the development of radioligands targeting the vesicular acetylcholine transporter? Bioorg Med Chem 2017; 25:5107-5113. [PMID: 28347632 DOI: 10.1016/j.bmc.2017.03.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 03/13/2017] [Accepted: 03/15/2017] [Indexed: 11/24/2022]
Abstract
The vesicular acetylcholine transporter (VAChT) is an important target for in vivo imaging of neurodegenerative processes using positron emission tomography (PET). So far the development of VAChT PET radioligands is based on the single known lead compound vesamicol. In this study we investigated a recently published spiroindoline based compound class (Sluder et al., 2012), which was suggested to have potential in the development of VAChT ligands. Therefore, we synthesized a small series of N,N-substituted spiro[indoline-3,4'-piperidine] derivatives and determined their in vitro binding affinities toward the VAChT. In order to investigate the selectivity, the off-target binding toward σ1 and σ2 receptors was determined. The compounds possessed VAChT affinities with Ki values in the range of 39-376nM. Binding affinities toward the σ1 and σ2 receptors are in a similar range indicating that the strong structural difference between the spiroindolines and vesamicol did not improve the selectivity. The observed potential to additionally bind to σ receptors let us assume that the herein investigated spiroindolines are not suitable to replace vesamicol as lead compound for the development of VAChT ligands.
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Gaydukov AE, Bogacheva PO, Balezina OP. Calcitonin gene-related peptide increases acetylcholine quantal size in neuromuscular junctions of mice. Neurosci Lett 2016; 628:17-23. [DOI: 10.1016/j.neulet.2016.06.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 06/01/2016] [Accepted: 06/06/2016] [Indexed: 11/29/2022]
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7
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Barthel C, Sorger D, Deuther-Conrad W, Scheunemann M, Schweiger S, Jäckel P, Roghani A, Steinbach J, Schüürmann G, Sabri O, Brust P, Wenzel B. New systematically modified vesamicol analogs and their affinity and selectivity for the vesicular acetylcholine transporter – A critical examination of the lead structure. Eur J Med Chem 2015; 100:50-67. [DOI: 10.1016/j.ejmech.2015.05.033] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 05/20/2015] [Accepted: 05/21/2015] [Indexed: 12/14/2022]
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8
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Zou Q, Leung SWS, Vanhoutte PM. Transient Receptor Potential Channel Opening Releases Endogenous Acetylcholine, which Contributes to Endothelium-Dependent Relaxation Induced by Mild Hypothermia in Spontaneously Hypertensive Rat but Not Wistar-Kyoto Rat Arteries. J Pharmacol Exp Ther 2015; 354:121-30. [DOI: 10.1124/jpet.115.223693] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 05/28/2015] [Indexed: 01/16/2023] Open
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Development of (18)F-labeled radiotracers for neuroreceptor imaging with positron emission tomography. Neurosci Bull 2014; 30:777-811. [PMID: 25172118 DOI: 10.1007/s12264-014-1460-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2014] [Accepted: 06/02/2014] [Indexed: 12/14/2022] Open
Abstract
Positron emission tomography (PET) is an in vivo molecular imaging tool which is widely used in nuclear medicine for early diagnosis and treatment follow-up of many brain diseases. PET uses biomolecules as probes which are labeled with radionuclides of short half-lives, synthesized prior to the imaging studies. These probes are called radiotracers. Fluorine-18 is a radionuclide routinely used in the radiolabeling of neuroreceptor ligands for PET because of its favorable half-life of 109.8 min. The delivery of such radiotracers into the brain provides images of transport, metabolic, and neurotransmission processes on the molecular level. After a short introduction into the principles of PET, this review mainly focuses on the strategy of radiotracer development bridging from basic science to biomedical application. Successful radiotracer design as described here provides molecular probes which not only are useful for imaging of human brain diseases, but also allow molecular neuroreceptor imaging studies in various small-animal models of disease, including genetically-engineered animals. Furthermore, they provide a powerful tool for in vivo pharmacology during the process of pre-clinical drug development to identify new drug targets, to investigate pathophysiology, to discover potential drug candidates, and to evaluate the pharmacokinetics and pharmacodynamics of drugs in vivo.
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Azim MAU, Kozaka T, Uno I, Miwa D, Kitamura Y, Ogawa K, Makino A, Kiyono Y, Shiba K. The potential ofo-bromo-trans-decalinvesamicol as a new PET ligand for vesicular acetylcholine transporter imaging. Synapse 2014; 68:445-53. [DOI: 10.1002/syn.21756] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 05/28/2014] [Accepted: 06/14/2014] [Indexed: 12/31/2022]
Affiliation(s)
- Mohammad Anwar-ul Azim
- Division of Tracer Kinetics; Advanced Science Research Center, Kanazawa University; 13-1 Takara-machi Kanazawa Ishikawa 920-8640 Japan
- Graduate School of Natural Science and Technology; Kanazawa University; Kakuma 920-1192 Japan
| | - Takashi Kozaka
- Division of Tracer Kinetics; Advanced Science Research Center, Kanazawa University; 13-1 Takara-machi Kanazawa Ishikawa 920-8640 Japan
- College of Medical; Pharmaceutical and Health Sciences, Kanazawa University; 13-1 Takara-machi Kanazawa Ishikawa 920-8640 Japan
| | - Izumi Uno
- Division of Tracer Kinetics; Advanced Science Research Center, Kanazawa University; 13-1 Takara-machi Kanazawa Ishikawa 920-8640 Japan
- College of Medical; Pharmaceutical and Health Sciences, Kanazawa University; 13-1 Takara-machi Kanazawa Ishikawa 920-8640 Japan
| | - Daisuke Miwa
- Division of Tracer Kinetics; Advanced Science Research Center, Kanazawa University; 13-1 Takara-machi Kanazawa Ishikawa 920-8640 Japan
- College of Medical; Pharmaceutical and Health Sciences, Kanazawa University; 13-1 Takara-machi Kanazawa Ishikawa 920-8640 Japan
| | - Yoji Kitamura
- Division of Tracer Kinetics; Advanced Science Research Center, Kanazawa University; 13-1 Takara-machi Kanazawa Ishikawa 920-8640 Japan
- Graduate School of Natural Science and Technology; Kanazawa University; Kakuma 920-1192 Japan
- College of Medical; Pharmaceutical and Health Sciences, Kanazawa University; 13-1 Takara-machi Kanazawa Ishikawa 920-8640 Japan
| | - Kazuma Ogawa
- College of Medical; Pharmaceutical and Health Sciences, Kanazawa University; 13-1 Takara-machi Kanazawa Ishikawa 920-8640 Japan
| | - Akira Makino
- Biomedical Imaging Research Center; University of Fukui, 23-3 Matsuokashimoaizuki, Eiheiji-cho, Yoshida-gun; Fukui Prefecture 910-1193 Japan
| | - Yasushi Kiyono
- Biomedical Imaging Research Center; University of Fukui, 23-3 Matsuokashimoaizuki, Eiheiji-cho, Yoshida-gun; Fukui Prefecture 910-1193 Japan
| | - Kazuhiro Shiba
- Division of Tracer Kinetics; Advanced Science Research Center, Kanazawa University; 13-1 Takara-machi Kanazawa Ishikawa 920-8640 Japan
- Graduate School of Natural Science and Technology; Kanazawa University; Kakuma 920-1192 Japan
- College of Medical; Pharmaceutical and Health Sciences, Kanazawa University; 13-1 Takara-machi Kanazawa Ishikawa 920-8640 Japan
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11
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Nishiyama S, Ohba H, Kobashi T, Nakamasu Y, Nakao H, Ogata T, Kitashoji T, Tsukada H. Development of novel PET probe [¹¹C](R,R)HAPT and its stereoisomer [¹¹C](S,S)HAPT for vesicular acetylcholine transporter imaging: a PET study in conscious monkey. Synapse 2014; 68:283-92. [PMID: 24687885 DOI: 10.1002/syn.21743] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 03/19/2014] [Accepted: 03/24/2014] [Indexed: 12/17/2022]
Abstract
Carbon-11-labeled (R,R)trans-8-methyl-2-hydroxy-3-[4-[2-aminophenyl]piperizinyl]-tetralin ([(11)C](R,R)HAPT) and its stereoisomer [(11)C](S,S)HAPT were developed for imaging vesicular acetylcholine transporters (VAChTs), exclusively located in presynaptic cholinergic neurons. Both positron emission tomography (PET) probes were evaluated in the brain of conscious monkey (Macaca mulatta) using high-resolution PET. Time-activity curves (TACs) of [(11)C](R,R)HAPT peaked within 5 min after the injection in all regions except the caudate and putamen, both of which showed peaks around 20 min postinjection. The regional distribution patterns of [(11)C](R,R)HAPT determined as total distribution volume (V(t)) were highest in the putamen, high in the caudate, intermediate in the amygdala, hippocampus, and thalamus, lower in the cingulate gyrus and frontal, temporal, and occipital cortices, and lowest in the cerebellum. In contrast, the distribution and TACs of [(11)C](S,S)HAPT were homogeneous in all regions. The uptake of [(11)C](R,R)HAPT was reduced by 1 mg/kg (-)-vesamicol, a specific VAChT antagonist, in all regions except the cerebellum, but not by 0.1 mg/kg SA4503, a specific sigma-1 receptor agonist. These results well reflect the in vitro affinity assessments using rat cerebral membranes. They also demonstrate that [(11)C](R,R)HAPT is a potential PET probe for noninvasive and quantitative imaging of VAChT in the living brain.
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Affiliation(s)
- Shingo Nishiyama
- Central Research Laboratory, Hamamatsu Photonics K.K., Hamakita, Hamamatsu, Shizuoka, Japan
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Cholinergic Depletion in Alzheimer's Disease Shown by [ (18) F]FEOBV Autoradiography. INTERNATIONAL JOURNAL OF MOLECULAR IMAGING 2013; 2013:205045. [PMID: 24324884 PMCID: PMC3844185 DOI: 10.1155/2013/205045] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 09/21/2013] [Accepted: 09/23/2013] [Indexed: 12/03/2022]
Abstract
Rationale. Alzheimer's Disease (AD) is a neurodegenerative condition characterized in part by deficits in cholinergic basalocortical and septohippocampal pathways. [18F]Fluoroethoxybenzovesamicol ([18F]FEOBV), a Positron Emission Tomography ligand for the vesicular acetylcholine transporter (VAChT), is a potential molecular agent to investigate brain diseases associated with presynaptic cholinergic losses. Purpose. To demonstrate this potential, we carried out an [18F]FEOBV autoradiography study to compare postmortem brain tissues from AD patients to those of age-matched controls. Methods. [18F]FEOBV autoradiography binding, defined as the ratio between regional grey and white matter, was estimated in the hippocampus (13 controls, 8 AD) and prefrontal cortex (13 controls, 11 AD). Results. [18F]FEOBV binding was decreased by 33% in prefrontal cortex, 25% in CA3, and 20% in CA1. No changes were detected in the dentate gyrus of the hippocampus, possibly because of sprouting or upregulation toward the resilient glutamatergic neurons of the dentate gyrus. Conclusion. This is the first demonstration of [18F]FEOBV focal binding changes in cholinergic projections to the cortex and hippocampus in AD. Such cholinergic synaptic (and more specifically VAChT) alterations, in line with the selective basalocortical and septohippocampal cholinergic losses documented in AD, indicate that [18F]FEOBV is indeed a promising ligand to explore cholinergic abnormalities in vivo.
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Parent MJ, Cyr M, Aliaga A, Kostikov A, Schirrmacher E, Soucy JP, Mechawar N, Rosa-Neto P, Bedard MA. Concordance between in vivo and postmortem measurements of cholinergic denervation in rats using PET with [18F]FEOBV and choline acetyltransferase immunochemistry. EJNMMI Res 2013; 3:70. [PMID: 24103360 PMCID: PMC3852759 DOI: 10.1186/2191-219x-3-70] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 10/01/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Fluorine-18 fluoroethoxybenzovesamicol ([18F]FEOBV) is a radioligand for the selective imaging of the vesicular acetylcholine transporter with positron emission tomography (PET). The current study demonstrates that pathological cortical cholinergic deafferentation can be quantified in vivo with [18F]FEOBV PET, yielding analogous results to postmortem histological techniques. METHODS Fifteen male rats (3 months old) underwent a cerebral infusion of 192 IgG-saporin at the level of the nucleus basalis magnocellularis. They were scanned using [18F]FEOBV PET, then sacrificed, and their brain tissues collected for immunostaining and quantification of cholinergic denervation using optical density (OD). RESULTS For both PET binding and postmortem OD, the highest losses were found in the cortical areas, with the highest reductions in the orbitofrontal, sensorimotor, and cingulate cortices. In addition, OD quantification in the affected areas accurately predicts [18F]FEOBV uptake in the same regions when regressed linearly. CONCLUSIONS These findings support [18F]FEOBV as a reliable imaging agent for eventual use in human neurodegenerative conditions in which cholinergic losses are an important aspect.
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Affiliation(s)
- Maxime J Parent
- Douglas Mental Health University Institute, McGill University, Montreal, QC H4H 1R3, Canada
- Université du Québec à Montreal (UQAM), Montreal, QC H3C 3P8, Canada
| | - Marilyn Cyr
- Douglas Mental Health University Institute, McGill University, Montreal, QC H4H 1R3, Canada
- Université du Québec à Montreal (UQAM), Montreal, QC H3C 3P8, Canada
| | - Antonio Aliaga
- Montreal Neurological Institute (MNI), Montreal, QC H3A 2B4, Canada
| | - Alexey Kostikov
- Montreal Neurological Institute (MNI), Montreal, QC H3A 2B4, Canada
| | | | - Jean-Paul Soucy
- Montreal Neurological Institute (MNI), Montreal, QC H3A 2B4, Canada
| | - Naguib Mechawar
- Douglas Mental Health University Institute, McGill University, Montreal, QC H4H 1R3, Canada
| | - Pedro Rosa-Neto
- Douglas Mental Health University Institute, McGill University, Montreal, QC H4H 1R3, Canada
- Montreal Neurological Institute (MNI), Montreal, QC H3A 2B4, Canada
| | - Marc-Andre Bedard
- Université du Québec à Montreal (UQAM), Montreal, QC H3C 3P8, Canada
- Montreal Neurological Institute (MNI), Montreal, QC H3A 2B4, Canada
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14
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Abstract
Acetylcholine, the first chemical to be identified as a neurotransmitter, is packed in synaptic vesicles by the activity of VAChT (vesicular acetylcholine transporter). A decrease in VAChT expression has been reported in a number of diseases, and this has consequences for the amount of acetylcholine loaded in synaptic vesicles as well as for neurotransmitter release. Several genetically modified mice targeting the VAChT gene have been generated, providing novel models to understand how changes in VAChT affect transmitter release. A surprising finding is that most cholinergic neurons in the brain also can express a second type of vesicular neurotransmitter transporter that allows these neurons to secrete two distinct neurotransmitters. Thus a given neuron can use two neurotransmitters to regulate different physiological functions. In addition, recent data indicate that non-neuronal cells can also express the machinery used to synthesize and release acetylcholine. Some of these cells rely on VAChT to secrete acetylcholine with potential physiological consequences in the periphery. Hence novel functions for the oldest neurotransmitter known are emerging with the potential to provide new targets for the treatment of several pathological conditions.
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TGF-beta2 alters the characteristics of the neuromuscular junction by regulating presynaptic quantal size. Proc Natl Acad Sci U S A 2010; 107:13515-9. [PMID: 20624974 DOI: 10.1073/pnas.1001695107] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The amount of neurotransmitter released from a presynaptic terminal is the product of the quantal content (number of vesicles) and the presynaptic quantal size (QSpre, amount of transmitter per vesicle). QSpre varies with synaptic use, but its regulation is poorly understood. The motor nerve terminals at the neuromuscular junction (NMJ) contain TGF-beta receptors. We present evidence that TGF-beta2 regulates QSpre at the NMJ. Application of TGF-beta2 to the rat diaphragm NMJ increased the postsynaptic response to both spontaneous and evoked release of acetylcholine, whereas antibodies to TGF-beta2 or its receptor had the converse effect. L-vesamicol and bafilomycin blocked the actions of TGF-beta2, indicating that TGF-beta2 acts by altering the extent of vesicular filling. Recordings of the postsynaptic currents from the diaphragm were consistent with TGF-beta2 having this presynaptic action and a lesser postsynaptic effect on input resistance. TGF-beta2 also decreased quantal content by an atropine-sensitive pathway, indicating that this change is secondary to cholinergic feedback on vesicular release. Consequently, the net actions of TGF-beta2 at the NMJ were to amplify the postsynaptic effects of spontaneous transmission and to diminish the number of vesicles used per evoked stimulus, without diminishing the amount of acetylcholine released.
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16
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Efange SMN, Khare AB, von Hohenberg K, Mach RH, Parsons SM, Tu Z. Synthesis and in vitro biological evaluation of carbonyl group-containing inhibitors of vesicular acetylcholine transporter. J Med Chem 2010; 53:2825-35. [PMID: 20218624 DOI: 10.1021/jm9017916] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
To identify selective high-affinity inhibitors of the vesicular acetylcholine transporter (VAChT), we have interposed a carbonyl group between the phenyl and piperidyl groups of the prototypical VAChT ligand vesamicol and its more potent analogues benzovesamicol and 5-aminobenzovesamicol. Of 33 compounds synthesized and tested, 6 display very high affinity for VAChT (K(i), 0.25-0.66 nM) and greater than 500-fold selectivity for VAChT over sigma(1) and sigma(2) receptors. Twelve compounds have high affinity (K(i), 1.0-10 nM) and good selectivity for VAChT. Furthermore, 3 halogenated compounds, namely, trans-3-[4-(4-fluorobenzoyl)piperidinyl]-2-hydroxy-1,2,3,4-tetrahydronaphthalene (28b) (K(i) = 2.7 nM, VAChT/sigma selectivity index = 70), trans-3-[4-(5-iodothienylcarbonyl)piperidinyl]-2-hydroxy-1,2,3,4-tetrahydronaphthalene (28h) (K(i) = 0.66 nM, VAChT/sigma selectivity index = 294), and 5-amino-3-[4-(p-fluorobenzoyl)piperidinyl]-2-hydroxy-1,2,3,4,-tetrahydronaphthalene (30b) (K(i) = 2.40 nM, VAChT/sigma selectivity index = 410) display moderate to high selectivity for VAChT. These three compounds can be synthesized with the corresponding radioisotopes so as to serve as PET/SPECT probes for imaging the VAChT in vivo.
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Affiliation(s)
- Simon M N Efange
- Departments of Radiology, Medicinal Chemistry and Neurosurgery, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Lima RDF, Prado VF, Prado MAM, Kushmerick C. Quantal release of acetylcholine in mice with reduced levels of the vesicular acetylcholine transporter. J Neurochem 2010; 113:943-51. [PMID: 20202084 DOI: 10.1111/j.1471-4159.2010.06657.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Mammalian motor nerve terminals contain hundreds of thousands of synaptic vesicles, but only a fraction of these vesicles is immediately available for release, the remainder forming a reserve pool. The supply of vesicles is replenished through endocytosis, and newly formed vesicles are refilled with acetylcholine through a process that depends on the vesicular acetylcholine transporter (VAChT). During expression of short-term plasticity, quantal release can be increased, but it is unknown whether this reflects enhanced recruitment of vesicles from the reserve pool or rapid recycling. We examined spontaneous and evoked release of acetylcholine at endplates from genetically modified VAChT KD(HOM) mice that express approximately 30% of the normal level of VAChT to determine steps rate-limited by synaptic vesicle filling. Quantal content and quantal size were reduced in VAChT KD(HOM) mice compared with wild-type controls. Although high-frequency stimulation did not reduce quantal size further, the post-tetanic increase in end-plate potential amplitude or MEPP frequency was significantly smaller in VAChT KD(HOM) mice. This was the case even when tetanic depression was eliminated using an extracellular solution containing reduced Ca(2+) and raised Mg(2+). These results reveal the dependence of short-term plasticity on the level of VAChT expression and efficient synaptic vesicle filling.
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Affiliation(s)
- Ricardo de Freitas Lima
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Minas Gerais, Brazil
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18
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Kim MJ, Lee SI, Lee JH, Lee SC. Neuromuscular Blocking Actions of Hexamethonium, Rocuronium and (-)Vesamicol. Korean J Anesthesiol 2007. [DOI: 10.4097/kjae.2007.52.6.681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Mi Jin Kim
- Department of Anesthesiology and Pain Medicine, Dong-A University Medical Center, College of Medicine, Dong-A University, Busan, Korea
| | - Soo Il Lee
- Department of Anesthesiology and Pain Medicine, Dong-A University Medical Center, College of Medicine, Dong-A University, Busan, Korea
| | - Jong Hwan Lee
- Department of Anesthesiology and Pain Medicine, Dong-A University Medical Center, College of Medicine, Dong-A University, Busan, Korea
| | - Seung Cheol Lee
- Department of Anesthesiology and Pain Medicine, Dong-A University Medical Center, College of Medicine, Dong-A University, Busan, Korea
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19
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Kallmünzer B, Sörensen B, Neuhuber WL, Wörl J. Heterogeneity of neuromuscular junctions in striated muscle of human esophagus demonstrated by triple staining for the vesicular acetylcholine transporter, α-bungarotoxin, and acetylcholinesterase. Cell Tissue Res 2006; 324:181-8. [PMID: 16437206 DOI: 10.1007/s00441-005-0154-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2005] [Accepted: 12/19/2005] [Indexed: 01/22/2023]
Abstract
During studies on enteric co-innervation in the human esophagus, we found that not all acetylcholinesterase (AChE)-positive motor endplates stained for alpha-bungarotoxin (alpha-BT) and the vesicular acetylcholine transporter (VAChT), respectively. Therefore, we probed for differences in neuromuscular junctions in human esophagus by using triple staining for VAChT, alpha-BT, and AChE followed by qualitative and quantitative analysis. To exclude that the results were caused by processing artifacts, we additionally examined the influence of a number of factors including post-mortem changes and the type and duration of fixation on the staining results. Four types of neuromuscular junction could be distinguished in human esophagus: type I with VAChT-positive and type II with VAChT-negative nerve terminals on a alpha-BT-positive and AChE-positive endplate area, type III with VAChT-positive nerve terminals on a alpha-BT-negative but AChE-positive endplate area, and type IV with VAChT-negative nerve terminals on a alpha-BT-negative but AChE-positive endplate area. On average, 32% of evaluated AChE-positive motor endplates were type I, 6% type II, 24% type III, and 38% type IV. Based on these results, we suggest that, in human esophagus, (1) the most reliable method for staining motor endplates is presently AChE histochemistry, (2) alpha-BT-sensitive and alpha-BT-resistant nicotinic acetylcholine receptors exist in neuromuscular junctions, and (3) different types of VAChT or transport mechanisms for acetylcholine probably exist in neuromuscular junctions.
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Affiliation(s)
- Bernd Kallmünzer
- Institute of Anatomy, University of Erlangen-Nuremberg, Krankenhausstrasse 9, 91054, Erlangen, Germany
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20
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Hefnawy MM, Aboul-Enein HY. A validated LC method for the determination of vesamicol enantiomers in human plasma using vancomycin chiral stationary phase and solid phase extraction. J Pharm Biomed Anal 2004; 35:535-43. [PMID: 15137978 DOI: 10.1016/j.jpba.2004.01.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2003] [Revised: 01/08/2004] [Accepted: 01/09/2004] [Indexed: 10/26/2022]
Abstract
An enantioseparation high performance liquid chromatographic (HPLC) method was developed and validated to determine D-(+)- and L-(-)-vesamicol in human plasma. The assay involved the use of a solid phase extraction for plasma sample clean up prior to HPLC analysis utilizing a C18 Bond-Elute column. Chromatographic resolution of the vesamicol enantiomers was performed on a vancomycin macrocyclic antibiotic chiral stationary phase (CSP) known as Chirobiotic V with a polar ionic mobile phase (PIM) consisting of methanol:glacial acetic acid:triethylamine (100:0.1:0.05 (v/v/v)) at a flow rate of 1.0 ml/min and UV detection set at 262 nm. All analyses were conducted at ambient temperature. The method was validated over the range of 1-20 microg/ml for each enantiomer concentration (R2>0.999). Recoveries for D-(+)- and L-(-)-vesamicol enantiomers were in the ranges of 96-105% at 3-16 microg/ml level. The method proved to be precise (within-run precision ranged from 1.3 to 2.7% and between-run precision ranged from 1.5 to 3.4%) and accurate (within-run accuracies ranged from 0.8 to 3.4% and between-run accuracies ranged from 1.7 to 5.0%). The limit of quantitation (LOQ) and limit of detection (LOD) for each enantiomer in human plasma were 1.0 and 0.5 microg/ml (S/N=3), respectively.
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Affiliation(s)
- Mohamed M Hefnawy
- Pharmaceutical Analysis Laboratory, Biological and Medical Research Department (MBC-03), King Faisal Specialist Hospital and Research Centre, P.O. Box 3354, Riyadh 1211 Saudi Arabia
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21
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Abstract
Presynaptic synthesis of acetylcholine (ACh) requires a steady supply of choline, acquired by a plasma membrane, hemicholinium-3-sensitive (HC-3) choline transporter (CHT). A significant fraction of synaptic choline is recovered from ACh hydrolyzed by acetylcholinesterase (AChE) after vesicular release. Although antecedent neuronal activity is known to dictate presynaptic CHT activity, the mechanisms supporting this regulation are unknown. We observe an exclusive localization of CHT to cholinergic neurons and demonstrate that the majority of CHTs reside on small vesicles within cholinergic presynaptic terminals in the rat and mouse brain. Furthermore, immunoisolation of presynaptic vesicles with multiple antibodies reveals that CHT-positive vesicles carry the vesicular acetylcholine transporter (VAChT) and synaptic vesicle markers such as synaptophysin and Rab3A and also contain acetylcholine. Depolarization of synaptosomes evokes a Ca2+-dependent botulinum neurotoxin C-sensitive increase in the Vmax for HC-3-sensitive choline uptake that is accompanied by an increase in the density of CHTs in the synaptic plasma membrane. Our study leads to the novel hypothesis that CHTs reside on a subpopulation of synaptic vesicles in cholinergic terminals that can transit to the plasma membrane in response to neuronal activity to couple levels of choline re-uptake to the rate of ACh release.
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22
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Van der Kloot W. Loading and recycling of synaptic vesicles in the Torpedo electric organ and the vertebrate neuromuscular junction. Prog Neurobiol 2003; 71:269-303. [PMID: 14698765 DOI: 10.1016/j.pneurobio.2003.10.003] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In vertebrate motor nerve terminals and in the electromotor nerve terminals of Torpedo there are two major pools of synaptic vesicles: readily releasable and reserve. The electromotor terminals differ in that the reserve vesicles are twice the diameter of the readily releasable vesicles. The vesicles contain high concentrations of ACh and ATP. Part of the ACh is brought into the vesicle by the vesicular ACh transporter, VAChT, which exchanges two protons for each ACh, but a fraction of the ACh seems to be accumulated by different, unexplored mechanisms. Most of the vesicles in the terminals do not exchange ACh or ATP with the axoplasm, although ACh and ATP are free in the vesicle interior. The VAChT is controlled by a multifaceted regulatory complex, which includes the proteoglycans that characterize the cholinergic vesicles. The drug (-)-vesamicol binds to a site on the complex and blocks ACh exchange. Only 10-20% of the vesicles are in the readily releasable pool, which therefore is turned over fairly rapidly by spontaneous quantal release. The turnover can be followed by the incorporation of false transmitters into the recycling vesicles, and by the rate of uptake of FM dyes, which have some selectivity for the two recycling pathways. The amount of ACh loaded into recycling vesicles in the readily releasable pool decreases during stimulation. The ACh content of the vesicles can be varied over eight-fold range without changing vesicle size.
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Affiliation(s)
- William Van der Kloot
- Department of Physiology and Biophysics, SUNY at Stony Brook, 8661 SUNT, Stony Brook, NY 11794-8661, USA.
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23
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Characterization of the circuits that generate spontaneous episodes of activity in the early embryonic mouse spinal cord. J Neurosci 2003. [PMID: 12533619 DOI: 10.1523/jneurosci.23-02-00587.2003] [Citation(s) in RCA: 183] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In the developing nervous system, patterned spontaneous activity affects a variety of developmental processes. Thus, it is important to identify the earliest time that such activity occurs and to characterize the underlying circuitry. In isolated mouse spinal cord-limb preparations, highly rhythmic spontaneous activity occurred as early as embryonic day 11 (E11)-E12, when many lumbosacral motoneurons were still migrating and extending their peripheral projections. This activity required both electrical and chemical transmission, and acetylcholine, rather than glutamate, provided the main excitatory drive. Our data are consistent with motoneurons themselves playing a critical role in generating such activity by making excitatory connections on each other and on GABAergic interneurons via dihydro-beta-erythroidine hydrobromide (DHbetaE)-insensitive nicotinic receptors. This resulted in the generation of local bursts. Consistent with these observations, E12-E12.5 mouse motoneurons retrogradely labeled by HRP were observed to have extensive axon collaterals that projected locally within the lateral motor column and to interneuron-containing regions dorsal and medial of the lateral motor column. Cholinergic axons, presumably from motoneurons, were also observed in the ventral and lateral funiculi. However, for local bursts to propagate throughout the cord, a second DHbetaE-sensitive cholinergic pathway that also involved glycinergic interneurons was required. This circuit characterization should facilitate the use of genetic mutations that alter specific subpopulations of interneurons or cholinergic transmission to determine how modifying different aspects of this early activity affects subsequent development of the spinal motor circuit.
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24
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Zhou M, Stewart JT. Enantioseparation of vesamicol in human serum by capillary electrophoresis with solid phase extraction and sulfated-beta-cyclodextrin. J Pharm Biomed Anal 2002; 30:443-9. [PMID: 12367668 DOI: 10.1016/s0731-7085(02)00219-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
An enantioseparation of racemic vesamicol in human serum by capillary electrophoresis with solid phase extraction and sulfated B-cyclodextrin (S-B-CD) is presented The separation was achieved on an uncoated 72 cm x 50 microm id fused silica capillary maintained at 30 degrees C and + 15 kV applied voltage using a run buffer of 128 micro-B-CD in 50 mM phosphate buffer at pH 5. The detection wavelength was 260 nm. Bond Elut C18 solid phase extraction cartridges were used in the sample preparation of the vesamicol samples from serum. Among the CDs studied, the migration order of the enantiomers was reversed in CM-B-CD compared to S-B-CD. Increases in migration time and differences in time between enantiomers was observed with increasing concentrations of S-B-CD. Baseline separation was achieved in the 2-20 microg/ml range of enantiomer concentration (r > .996). A sample stacking technique was used to improve peak shape and LOD. LODs were 0.5 microg/ml for each enantiomer. Studies of various factors and CE conditions showed the effect of CD type, CD concentration, buffer type, buffer concentration and pH on stability and resolution.
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Affiliation(s)
- Meng Zhou
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, Athens, GA 30602, USA
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25
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Zhou FM, Liang Y, Dani JA. Endogenous nicotinic cholinergic activity regulates dopamine release in the striatum. Nat Neurosci 2001; 4:1224-9. [PMID: 11713470 DOI: 10.1038/nn769] [Citation(s) in RCA: 410] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dopamine is vital for coordinated motion and for association learning linked to behavioral reinforcement. Here we show that the precise overlap of striatal dopaminergic and cholinergic fibers underlies potent control of dopamine release by ongoing nicotinic receptor activity. In mouse striatal slices, nicotinic antagonists or depletion of endogenous acetylcholine decreased evoked dopamine release by 90%. Nicotine at the concentration experienced by smokers also regulated dopamine release. In mutant mice lacking the beta2 nicotinic subunit, evoked dopamine release was dramatically suppressed, and those mice did not show cholinergic regulation of dopamine release. The results offer new perspectives when considering nicotine addiction and the high prevalence of smoking in schizophrenics.
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Affiliation(s)
- F M Zhou
- Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030-3498, USA
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26
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Naves LA, Van der Kloot W. Repetitive nerve stimulation decreases the acetylcholine content of quanta at the frog neuromuscular junction. J Physiol 2001; 532:637-47. [PMID: 11313435 PMCID: PMC2278574 DOI: 10.1111/j.1469-7793.2001.0637e.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
We investigated how elevated quantal release produced by motor nerve stimulation affects the size of the quanta. The motor nerve was stimulated at 10 Hz in preparations in which excitation-contraction coupling was disrupted. Two hundred stimuli reduced the size of the time integrals of the miniature endplate currents ([integral]MEPCs), measured at the same junction immediately after stimulation, by 16 %. Three thousand stimuli reduced size by 23 %. When the solution contained 10 microM neostigmine (NEO) 3000 stimuli reduced [integral]MEPCs by 60 %, because with acetylcholinesterase (AChE) inhibited, [integral]MEPC size is more sensitive to changes in acetylcholine (ACh) content. Similar decreases in miniature endplate potential size ([integral]MEPP) followed repetitive stimulation of contracting preparations. The depolarization produced by iontophoretic pulses of ACh was scarcely changed by 3000 nerve stimuli at 10 Hz, suggesting that the decreases in miniature sizes are largely due to less ACh released per quantum. Following 3000 stimuli at 10 Hz the sizes of the [integral]MEPCs increased back to pre-stimulus values with a half-time of 8-10 min. Recovery was blocked by (-)-vesamicol (VES), by hemicholinium-3 (HC3) and by nicotinic cholinergic agonists - all of which inhibit ACh loading into synaptic vesicles. The number of quanta in the total store was estimated by releasing them with carbonyl cyanide m-chlorophenylhydrazone (CCCP). CCCP releases fewer quanta after stimulation than from unstimulated controls. After resting for hours following stimulation, the releasable number increased, even when ACh loading inhibitors were present. We conclude that the inhibitors do not block a significant fraction of the ACh loading into reformed reserve vesicles and propose that ACh can be loaded in a series of steps.
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Affiliation(s)
- L A Naves
- Department of Physiology, State University of New York at Stony Brook, Stony Brook, NY 11794-8661, USA.
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27
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Efange SM, Khare AB, Tu Z, Mach RH, Parsons SM. Synthesis and biological characterization of stable and radioiodinated (+/-)-trans-2-hydroxy-3-P[4-(3-iodophenyl)piperidyl]-1,2,3,4-tetrahydronaphthalene (3'-IBVM). Nucl Med Biol 2000; 27:749-55. [PMID: 11150707 DOI: 10.1016/s0969-8051(00)00157-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The vesamicol analogue (+/-)-trans-2-Hydroxy-3-[4-(3-iodophenyl)piperidyl]-1,2,3,4-tetrahydronaphthalene (3'-IBVM), a potent ligand for the vesicular acetylcholine transporter (VAChT), was evaluated as a potential radiotracer for studying VAChT density in vivo. In radioligand binding experiments, 3'-IBVM displays subnanomolar affinity for VAChT and 100-fold selectivity for VAChT over sigma1 and sigma2 receptors. Consistent with this profile, radioiodinated (+/-)-3'-IBVM distributed heterogenously in the rat brain following a bolus IV injection, displaying high concentrations in the striatum and moderate to low concentrations in the cortex and cerebellum, respectively. However, co-injection of the radiotracer with the sigma ligand haloperidol resulted in significant reductions of radiotracer levels in all brain regions examined. Therefore, radioiodinated (+/-)-IBVM appears to bind to both VAChT and sigma receptors in vivo.
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Affiliation(s)
- S M Efange
- Department of Radiology, University of Minnesota, Minneapolis, Minnesota, USA.
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28
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Zhou Q, Petersen CC, Nicoll RA. Effects of reduced vesicular filling on synaptic transmission in rat hippocampal neurones. J Physiol 2000; 525 Pt 1:195-206. [PMID: 10811737 PMCID: PMC2269926 DOI: 10.1111/j.1469-7793.2000.t01-1-00195.x] [Citation(s) in RCA: 180] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/1999] [Accepted: 02/21/2000] [Indexed: 11/28/2022] Open
Abstract
The consequence of reduced uptake of neurotransmitters into synaptic vesicles on synaptic transmission was examined in rat hippocampal slices and culture using bafilomycin A1 (Baf), a potent and specific blocker of the vacuolar-type (V-type) ATPase, which eliminates the driving force for the uptake of both glutamate and GABA into synaptic vesicles. After incubation with Baf, both the amplitude and frequency of GABAergic miniature inhibitory postsynaptic currents (mIPSCs) were reduced in the slice preparation. Similar effects were seen with glutamatergic miniature excitatory postsynaptic currents (mEPSCs) and GABAergic mIPSCs from cultured neurons. This result indicates that vesicular content is reduced by Baf. The dramatic reduction in the frequency of mPSCs could result either from the exocytosis of empty vesicles or from a mechanism which prevents the exocytosis of depleted vesicles. Vesicle cycling was directly examined using confocal imaging with FM 1-43. In the presence of Baf, vesicles could still be endocytosed and they were released at the same probability as from control untreated synapses. Prolonged high-frequency electrical stimulation of synapses in culture failed to alter the amplitude of mEPSCs, suggesting that the filling of vesicles is rapid compared to the rate of vesicle recycling during repetitive synaptic stimulation. Profound release of glutamate with alpha-latrotoxin did cause a small, but reproducible, reduction in quantal size. These results indicate that decreasing the amount of glutamate and GABA in synaptic vesicles reduces quantal size. Furthermore, the probability of vesicle exocytosis appears to be entirely independent of the state of filling of the vesicle. However, even during high-frequency action potential-evoked release of glutamate, quantal size remained unchanged.
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Affiliation(s)
- Q Zhou
- Departments of Cellular & Molecular Pharmacology and Physiology, University of California, San Francisco, San Francisco, CA 94143-0450, USA
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29
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Khare AB, Langason RB, Parsons SM, Mach RH, Efange SM. N-(3-Iodophenyl)trozamicol (IPHT) and related inhibitors of vesicular acetylcholine transport: synthesis and preliminary biological characterization. Nucl Med Biol 1999; 26:609-17. [PMID: 10587098 DOI: 10.1016/s0969-8051(99)00013-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Four isomeric N-(halophenyl)trozamicol analogues (6a-d) were synthesized and evaluated as potential vesicular acetylcholine transporter (VAChT) ligands. Of the four compounds, N-(3-bromophenyl) trozamicol (6b) and N-(3-iodophenyl)trozamicol (6d) displayed the highest affinity for the VAChT in vitro, whereas the para-substituted compound 6c showed the lowest affinity for this transporter. Tissue distribution studies of N-(3-[125I]iodophenyl)trozamicol ([125I]6d, [125I)IPHT) suggest that the central distribution of the latter is consistent with cholinergic innervation. However, only moderate target-to-background ratios were obtained, suggesting little improvement over the N-(halobenzyl)trozamicols described previously.
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Affiliation(s)
- A B Khare
- Department of Radiology, University of Minnesota, Minneapolis 55455, USA
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30
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Efange SM, Khare AB, Mach RH, Parsons SM. Hydroxylated decahydroquinolines as ligands for the vesicular acetylcholine transporter: synthesis and biological evaluation. J Med Chem 1999; 42:2862-9. [PMID: 10425095 DOI: 10.1021/jm980560x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Analogues of the potent anticholinergic 2-(4-phenylpiperidino)cyclohexanol (vesamicol, 1) in which the cyclohexyl fragment was replaced with an N-acyl or N-alkyl trans-decahydroquinolyl moiety were synthesized and evaluated as potential ligands for the vesicular acetylcholine transporter (VAChT). The binding of compounds, such as 18, 20, and 21, was both stereospecific and of comparable magnitude to that of the closely related vesamicol analogue 2,3-trans-4a, 8a-trans-3-hydroxy-2-(4-phenylpiperidino)-1,2,3,4,5,6,7, 8-decahydronaphthalene (6) which displays subnanomolar affinity for this transporter. However, these compounds also demonstrated high affinities for sigma(1) and sigma(2) receptors and thus failed to show significantly improved selectivity over previously reported vesamicol analogues.
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Affiliation(s)
- S M Efange
- University of Minnesota, Minneapolis, Minnesota 55455, Wake Forest University School of Medicine, Winston Salem, North Carolina 27157, USA.
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31
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Efange SM, Nader MA, Ehrenkaufer RL, Khare AB, Smith CR, Morton TE, Mach RH. (+)-p-([18F]fluorobenzyl)spirotrozamicol [(+)-[18F]spiro-FBT]: synthesis and biological evaluation of a high-affinity ligand for the vesicular acetylcholine transporter (VAChT). Nucl Med Biol 1999; 26:189-92. [PMID: 10100218 DOI: 10.1016/s0969-8051(98)00090-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
(+)-1'-[4-Hydroxy-1-(4-fluorobenzyl)piperidin-3-yl]spiro[1H- indene-1,4'- piperidine] {(+)-Spiro-FBT}, a high-affinity vesicular acetylcholine transporter ligand, was labeled with fluorine-18, and evaluated in the rat and monkey. In the rat brain, (+)-[18F]Spiro-FBT accumulated preferentially in the striatum, hippocampus, and cortex, brains regions containing high-to-moderate densities of cholinergic terminals. However, due to rapid metabolism, no preferential accumulation of the radiotracer was observed in corresponding regions of the monkey brain. Consequently, rapid metabolism renders (+)-[18F]Spiro-FBT unsuitable for studying cholinergic function with positron emission tomography.
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Affiliation(s)
- S M Efange
- Department of Radiology, University of Minnesota, Minneapolis 55455, USA
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32
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Van der Kloot W, Benjamin WB, Balezina OP. Calcitonin gene-related peptide acts presynaptically to increase quantal size and output at frog neuromuscular junctions. J Physiol 1998; 507 ( Pt 3):689-95. [PMID: 9508830 PMCID: PMC2230837 DOI: 10.1111/j.1469-7793.1998.689bs.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
1. Calcitonin gene-related peptide (CGRP) is found in dense-cored vesicles in the motor nerve terminal. 2. Exogenous CGRP increased the size of the quanta. The increase in size reached a maximum after about 40 min. The lowest effective concentration of human CGRP (hCGRP) was 0.8 nM. The action of hCGRP was antagonized by (-)-vesamicol, a drug that blocks active acetylcholine (ACh) uptake into synaptic vesicles, so it appears that hCGRP increases size by adding more ACh to the quanta. The action of hCGRP was antagonized by drugs that block the activation of protein kinase A (PKA). (In other preparations CGRP also activates PKA.) 3. The hCGRP effect was not blocked by fragment 8-37, an antagonist of one class of CGRP receptor. 4. hCGRP increases evoked quantal output and miniature endplate potential (MEPP) frequency, again by activating PKA. 5. CGRP release was measured by radioimmunoassay. Release was increased by depolarization with elevated K+, but the amounts released appear to be below those needed to affect quantal size or output. Moreover, although elevated K+ can increase quantal size it acts by a pathway that does not involve PKA. We suggest that the most likely target of endogenously released CGRP is the regulation of circulation of the muscle.
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Affiliation(s)
- W Van der Kloot
- Department of Physiology and Biophysics, Health Sciences Center, State University of New York at Stony Brook, NY 11794-8661, USA.
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Efange SM, Kamath AP, Khare AB, Kung MP, Mach RH, Parsons SM. N-hydroxyalkyl derivatives of 3 beta-phenyltropane and 1-methylspiro[1H-indoline-3,4'-piperidine]: vesamicol analogues with affinity for monoamine transporters. J Med Chem 1997; 40:3905-14. [PMID: 9397171 DOI: 10.1021/jm970326r] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
As part of our ongoing structure-activity studies of the vesicular acetylcholine transporter ligand 2-(4-phenylpiperidino)cyclohexanol (vesamicol, 1), 22 N-hydroxy(phenyl)alkyl derivatives of 3 beta-phenyltropane, 6, and 1-methylspiro[1H-indoline-3,4'-piperidine], 7, were synthesized and tested for binding in vitro. Although a few compounds displayed moderately high affinity for the vesicular acetylcholine transporter, no compound was more potent than the prototypical vesicular acetylcholine transporter ligand vesamicol. However, a few derivatives of 6 displayed higher affinity for the dopamine transporter than cocaine. We conclude that modification of the piperidyl fragment of 1 will not lead to more potent vesicular acetylcholine transporter ligands.
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Affiliation(s)
- S M Efange
- Department of Radiology, University of Minnesota, Minneapolis 55455, USA.
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Song H, Ming G, Fon E, Bellocchio E, Edwards RH, Poo M. Expression of a putative vesicular acetylcholine transporter facilitates quantal transmitter packaging. Neuron 1997; 18:815-26. [PMID: 9182805 DOI: 10.1016/s0896-6273(00)80320-7] [Citation(s) in RCA: 148] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A putative vesicular acetylcholine transporter (VAChT) was overexpressed in developing Xenopus spinal neurons by injection of rat VAChT cDNA or synthetic mRNA into Xenopus embryos. This resulted in a marked increase in the amplitude and frequency of miniature excitatory postsynaptic currents at neuromuscular synapses, reflecting an over 10-fold increase in the vesicular packaging of acetylcholine (ACh). The effect appeared in developing neurons even before synaptogenesis and was blocked by L-vesamicol, a specific blocker of ACh uptake into synaptic vesicles. Mutational studies showed that two highly conserved aspartate residues within putative transmembrane domains 4 and 10 are essential for the transport activity. These results provide direct evidence for the physiological function of a putative VAChT and demonstrate that quantal size can be regulated by changes in vesicular transporter activity.
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Affiliation(s)
- H Song
- Department of Biology, University of California at San Diego, La Jolla 92093, USA
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35
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Abstract
The vesamicol-like compound (+/-)-4-aminobenzovesamicol (ABV) non-competitively inhibits vesicular packaging of acetylcholine (ACh) in presynaptic terminals. This study tested the hypothesis that microinjection of ABV into the medial pontine reticular formation (mPRF) of intact, unanesthetized cats would inhibit rapid eye movement (REM) sleep. Microinjection of ABV alone or before administration of the acetylcholinesterase inhibitor neostigmine was used to evaluate the effects of ABV on natural REM sleep and on the neostigmine-induced REM sleep-like state. ABV decreased (24.8%) REM sleep and significantly reduced (33.6%) the neostigmine-induced REM sleep-like state. The results show for the first time that REM sleep generation can be disrupted by blocking a synaptic vesicle protein that modulates ACh transport in localized regions of the mPRF.
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Affiliation(s)
- M L Capece
- Department of Anesthesia, Pennsylvania State University, College of Medicine, Hershey 17033, USA
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Kobayashi H, Watanabe T, Yasufuku T, Suzuki T, Saitoh S, Takeno K. Effects of systemic administration of 2-(4-phenyl-piperidino)-cyclohexanol (vesamicol) and an organophosphate DDVP on the cholinergic system in brain regions of rats. Brain Res Bull 1997; 43:17-23. [PMID: 9205789 DOI: 10.1016/s0361-9230(96)00343-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Vesamicol is known to inhibit the transport of acetylcholine (ACh) into synaptic vesicles in vitro, but much less is known about its effects in the brain in vivo. To assess the effect of vesamicol in vivo, we examined cholinergic parameters, such as the subcellular distribution of ACh, activities of enzymes, uptake of choline, and muscarinic receptor binding in the striatum, hippocampus, and cerebral cortex of rats 30 and 60 min after intraperitoneal injection of vesamicol (3 mg/kg) or of vesamicol in combination with DDVP (5 mg/kg), which was administered 10 min before vasamicol. The levels of cytosolic ACh increased in all regions of the brain after injection of vesamicol, while those of vesicular ACh decreased in all regions except for the striatum. The increase in the levels of extracellular ACh and cytosolic ACh in the striatum induced by DDVP was generally enhanced after injection of vesamicol, Vesamicol did not reduce the level of vesicular ACh when DDVP had been injected previously. Vesamicol did not induce any significant changes in the activities of enzymes, choline uptake, or binding of [6H]quinuclidinyl benzilate to the muscarinic ACh receptors in the three regions. Changes in the cholinergic parameters caused by DDVP were not reversed by the combined administration of DDVP with vesamicol. The present results indicate that vesamicol can inhibit the transport of ACh into synaptic vesicles in the brain tissue in vivo, although it cannot reverse the effects of DDVP that has been injected prior to vesamicol.
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Affiliation(s)
- H Kobayashi
- Department of Veterinary Pharmacology, Faculty of Agriculture, Iwate University, Morioka, Japan
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37
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Naves LA, Balezina OP, Van der Kloot W. Monoethylcholine as a false transmitter precursor at the frog and mouse neuromuscular junctions. Brain Res 1996; 730:58-66. [PMID: 8883889 DOI: 10.1016/0006-8993(96)00431-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Monoethylcholine (MECH) enters motor nerve terminals where it is made into acetylmonoethylcholine (AMECH). AMECH opens endplate channels for about half of the average duration observed where they are opened by acetylcholine (ACH). Therefore when AMECH is present in a quantum the endplate currents decay more rapidly. MECH has been used to measure quantal turnover in motor nerve terminals. We find that the incorporation of AMECH into quanta is blocked by vesamicol, an inhibitor of ACH transport into synaptic vesicles. AMECH is incorporated more rapidly when acetylcholinesterase is inhibited, when the choline uptake inhibitor, hemicholinium-3, is present or when extracellular Na+ (required for active CH uptake) is replaced with methylamine. This suggests that in the absence of these inhibitors CH obtained from released ACH is recycled. Therefore, experiments on the rate of incorporation of MECH are misleading unless CH recycling is prevented. Previous work also suggested that MECH is incorporated at a faster rate into those quanta which are released by stimulation than into those released spontaneously. We conclude that quanta released spontaneously and following nerve stimulation probably come from the same pool. The distribution of t1/2's during the incorporation of MECH can be accounted for in the framework of recent studies of the recycling of synaptic vesicles. We conclude that false transmitter is a valuable tool for studying the loading of quanta, but that there are several complications to be considered when trying to use it to measure the turnover of the population of quanta.
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Affiliation(s)
- L A Naves
- Department of Physiology, Health Sciences Center, SUNY, Stony Brook 11794-8661, USA
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Van der Kloot W, Naves LA. Accounting for the shapes and size distributions of miniature endplate currents. Biophys J 1996; 70:2175-84. [PMID: 9172741 PMCID: PMC1225192 DOI: 10.1016/s0006-3495(96)79783-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The current model does not account adequately for the characteristics of miniature endplate currents (MEPCs). We do not understand their relatively slow rise, the shape of their rise, their variable and sometimes prolonged decay, and the correlation between amplitude and decay time. If we assume that ACh is released from the vesicle through a pore and that the vesicle enlarges as it takes on additional transmitter, the predictions are more like MEPCs. However, previous measurements showed that after quantal size was increased the vesicles in the terminal were not enlarged. This need not be a problem, because some of the ACh is added to vesicles positioned at the active zones, a process known as second-stage loading. By using the false transmitter precursor monoethylcholine we provide additional evidence for second-stage loading. The distribution of quantal sizes at the junction usually does not follow a normal probability distribution; it is skewed to the right. The skew can be accounted for by a model incorporating second-stage loading in which the vesicles are released randomly, without regard to their ACh content. If the vesicles increase in size when they contain more transmitter, only vesicles at the active zone need swell.
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Affiliation(s)
- W Van der Kloot
- Department of Physiology and Biophysics, Health Sciences Center, State University at Stony Brook, New York 11794-8661, USA.
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Prior C, Tian L, Dempster J, Marshall IG. Prejunctional actions of muscle relaxants: synaptic vesicles and transmitter mobilization as sites of action. GENERAL PHARMACOLOGY 1995; 26:659-66. [PMID: 7635241 DOI: 10.1016/0306-3623(94)00246-j] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
1. Nicotinic antagonists such as tubocurarine affect acetylcholine release from motor nerve terminals at the neuromuscular junction. 2. Electrophysiological studies comparing the prejunctional actions of tubocurarine to those of vesamicol and vecuronium have been used to provide an insight into the mechanisms involved in the prejunctional effects of tubocurarine-like compounds. 3. The observed prejunctional actions of tubocurarine can be accounted for by a model in which the compound has two separately identifiable effects on the nerve terminal. At low frequencies of nerve stimulation tubocurarine augments acetylcholine release while at high frequencies of nerve stimulation tubocurarine depresses acetylcholine release. 4. Both of the effects of tubocurarine on acetylcholine release are a consequence of a change in the number of quanta within the nerve terminal immediately available for release upon nerve stimulation. 5. On the basis of our experimental observations, we suggest that the two prejunctional effects of tubocurarine are mediated through two pharmacologically distinct prejunctional nAChRs.
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Affiliation(s)
- C Prior
- Department of Physiology and Pharmacology, University of Strathclyde, Royal College, Glasgow, Scotland
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Efange SM, Khare AB, Langason RB. Comparative tissue distribution of conformationally restricted radioiodinated vesamicol receptor ligands. Nucl Med Biol 1995; 22:437-44. [PMID: 7550019 DOI: 10.1016/0969-8051(94)00135-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Three conformationally restricted analogs of vesamicol, 1'-[1-(3-iodobenzyl)-4-hydroxypiperidin-3-yl]-spirol[1H-i nde ne-1,4'- piperidine] (5), 1'-[1-(3-iodobenzyl)-4-hydroxypiperidin-3-yl]-3,4- dihydrospiro[indene-1,4'-piperidine] (6) and 1'-[1-(3-iodobenzyl)-4-hydroxypiperidin-3-yl)-3,4- dihydrospiro[naphthalene-1(2H),4'-piperidine] (7), were labelled with iodine-125 and evaluated as potential radioligands for mapping vesamicol receptor (VR) density and cholinergic function in vivo. All compounds showed similar kinetics in most tissues. However, differences were observed in the brain. Although comparable levels of each corresponding enantiomeric pair were obtained initially in the brain, the levels of the dextrorotatory enantiomers (+)-5, (+)-6 and (+)-7 were found to decrease by 72-82% over a period of 3 h. In contrast, the brain levels of the corresponding levorotatory isomers were maintained throughout the duration of the experiment. Among the dextrorotatory isomers, (+)-6 showed the highest brain extraction, while (+)-7 showed the lowest. In tissue dissection experiments, the levels of (+)-5, (+)-6 and (+)-7 were highest in the striatum and moderate to low in the cortex and cerebellum. Co-administration of haloperidol with (+)-6 decreased the levels of the latter in the striatum by 27%, while the levels in the cortex and cerebellum were each reduced by 60%. In addition, haloperidol failed to affect the regional distribution of (+)-7 in the brain. However, both haloperidol and spiperone increased the striatal levels of (+)-5 by 67 and 76%, respectively, suggesting that the binding of this radioligand is related to cholinergic function.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- S M Efange
- Department of Radiology, University of Minnesota, Minneapolis 55455, USA
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41
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Maziere M. Cholinergic neurotransmission studied in vivo using positron emission tomography or single photon emission computerized tomography. Pharmacol Ther 1995; 66:83-101. [PMID: 7630931 DOI: 10.1016/0163-7258(95)00003-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
During the past decade, considerable efforts have been made in the development of radiopharmaceuticals for the in vivo study of the cholinergic neurotransmission using positron emission tomography or single photon emission computerized tomography. The main cholinergic radioligands, labelled with positron- or gamma-photon-emitting radionuclides, are reviewed with respect to use as in vivo markers of either acetylcholinesterase, vesicular acetylcholine transporter, brain and heart muscarinic receptors, or cholinergic nicotinic receptors. The main results obtained in the in vivo study of the physiology, pharmacology or pathology of the different steps of the cholinergic neurotransmission using single photon emission computerized tomography and positron emission tomography are discussed.
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Affiliation(s)
- M Maziere
- CNRS URA 1285, Service Hospitalier Frédéric Joliot, DRIPP, CEA, Orsay, France
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Efange SM, Mach RH, Smith CR, Khare AB, Foulon C, Akella SK, Childers SR, Parsons SM. Vesamicol analogues as sigma ligands. Molecular determinants of selectivity at the vesamicol receptor. Biochem Pharmacol 1995; 49:791-7. [PMID: 7702637 DOI: 10.1016/0006-2952(94)00541-s] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The present study compares the affinities of 2-(4-phenylpiperidino)cyclohexanol (vesamicol, 1) and selected analogues of the latter at the vesamicol receptor (VR) with the corresponding affinities at sigma 1 and sigma 2 binding sites. For this study, the parent structure 1 was divided into three fragments: A (cyclohexyl), B (piperidyl) and C (phenyl). Vesamicol analogues were then selected to reflect structural modifications in these fragments. Consistent with earlier reports, vesamicol was found to exhibit nanomolar affinities at the VR and sigma 1 and sigma 2 sites, resulting in poor selectivity for the VR over the sigma sites. Vesamicol analogues characterized by an acyclic A-fragment showed moderate to low affinities at the VR and moderate to high affinities at sigma 1 and sigma 2 sites. As a result, many of these analogues showed poor selectivity for the VR. Replacement of the C4 carbon of 1 with a halobenzyl amine resulted in higher affinities at the VR coupled with moderate to low affinities at sigma 1 and sigma 2 sites. The introduction of a benzofused substituent at the C4 and C5 positions of 1 (compound 2) resulted in a 200-fold increase in affinity at the VR accompanied by a 5- to 6-fold decrease in affinity at sigma 1 and sigma 2 sites relative to the parent structure. Consequently, compound 2 showed 12,000-fold higher affinity at the VR than at sigma sites. Restricting the rotation of fragment C relative to B (by means of alkyl and alkenyl bridges) generally yielded analogues with subnanomolar affinities at the VR. The corresponding affinities of these spirofused conformationally restricted analogues were moderate to poor at sigma 1 and sigma 2 sites when fragment A was preserved. In contrast, the affinities at sigma 1 and sigma 2 sites were decreased 3- to 11-fold when fragment A was modified at position C4 and decreased up to 100-fold with benzofusion at the C4 and C5 positions of fragment A. Consequently, the spirofused analogues 15-19 were among the most selective VR ligands examined. Thus, the effect of conformational restriction in fragments A and B-C is to increase affinity at the VR while decreasing affinity at sigma 1 and sigma 2 sites, and thereby increasing selectivity for the VR over the sigma sites.
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Affiliation(s)
- S M Efange
- Department of Radiology, University of Minnesota, Minneapolis 55455
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43
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Aglan MY, Pollard BJ. Molecular mechanisms of neuromuscular blocking agents: is the increased understanding of importance to the practising anaesthetist? Pharmacol Ther 1995; 68:365-83. [PMID: 8788563 DOI: 10.1016/0163-7258(95)02012-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A neuromuscular blocking agent is an essential component of many general anaesthetics. Although a great deal is known about the neuromuscular junction, the site of action of these agents, their precise mode of action remains unclear. This article reviews our present knowledge of the anatomy and physiology of neuromuscular transmission and the ways in which clinically useful drugs may modify this system. The decisions involved in clinical choice of which agent to use are described with particular respect to basic physiology and pharmacology and also to potential interactions with other drugs.
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Affiliation(s)
- M Y Aglan
- University Department of Anaesthesia, Manchester Royal Infirmary, UK
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Van der Kloot W, Balezina OP, Molgó J, Naves LA. The timing of channel opening during miniature endplate currents at the frog and mouse neuromuscular junctions: effects of fasciculin-2, other anti-cholinesterases and vesamicol. Pflugers Arch 1994; 428:114-26. [PMID: 7971167 DOI: 10.1007/bf00374848] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Fluctuation analysis was used to estimate the mean single-channel conductance and the mean channel duration of opening. Miniature endplate currents (MEPCs) were measured with the voltage-clamp technique. The timing of endplate channel opening during the generation of the MEPC was estimated by a deconvolution method. Often all of the channels opened during the rise of the MEPC, but in about half of the examples some 10% of the channels opened after the peak. We studied the effects of acetylcholinesterase (AChE) inhibition with neostigmine, diisopropyl fluorophosphate (DFP) and fasciculin-2. With AChE largely inhibited, the number of channels opening increased as much as fourfold, largely by channels opening in the "tail" that follows the peak of the MEPC. The results were compared to models of MEPC generation. Models did not account well for the pattern of channel opening, particularly after AChE inhibition. In the presence of fasciculin-2, the addition of 2 microM (-)-vesamicol reduced the number of channels opening and shortened the period over which channels were open. One interpretation is that quantal ACh release is not almost instantaneous, but that some of the ACh is released over a period of a millisecond or more and that some of the release is blocked by (-)-vesamicol.
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Affiliation(s)
- W Van der Kloot
- Department of Physiology and Biophysics, HSC, SUNY 11794-8661
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Cunnane TC, Searl TJ. Neurotransmitter release mechanisms in autonomic nerve terminals. ADVANCES IN SECOND MESSENGER AND PHOSPHOPROTEIN RESEARCH 1994; 29:425-59. [PMID: 7848725 DOI: 10.1016/s1040-7952(06)80029-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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46
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Chapter 26. In Vivo Diagnostics for Alzheimer's Disease Based on the Acetylcholine Transporter. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 1993. [DOI: 10.1016/s0065-7743(08)60896-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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