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Arakawa I, Muramatsu I, Uwada J, Sada K, Matsukawa N, Masuoka T. Acetylcholine release from striatal cholinergic interneurons is controlled differently depending on the firing pattern. J Neurochem 2023; 167:38-51. [PMID: 37653723 DOI: 10.1111/jnc.15950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Revised: 07/31/2023] [Accepted: 08/11/2023] [Indexed: 09/02/2023]
Abstract
How is the quantal size in neurotransmitter release adjusted for various firing levels? We explored the possible mechanisms that regulate acetylcholine (ACh) release from cholinergic interneurons using an ultra-mini superfusion system. After preloading [3 H]ACh in rat striatal cholinergic interneurons, the release was elicited by electrical stimulation under a condition in which presynaptic cholinergic and dopaminergic feedback was inhibited. [3 H]ACh release was reproducible at intervals of more than 10 min; shorter intervals resulted in reduced levels of ACh release. Upon persistent stimulation for 10 min, ACh release transiently increased, before gradually decreasing. Vesamicol, an inhibitor of the vesicular ACh transporter (VAChT), had no effect on the release induced by the first single pulse, but it reduced the release caused by subsequent pulses. Vesamicol also reduced the [3 H]ACh release evoked by multiple pulses, and the inhibition was enhanced by repetitive stimulation. The decreasing phase of [3 H]ACh release during persistent stimulation was accelerated by vesamicol treatment. Thus, it is likely that releasable ACh was slowly compensated for via VAChT during and after stimulation, changing the vesicular ACh content. In addition, ACh release per pulse decreased under high-frequency stimulation. The present results suggest that ACh release from striatal cholinergic interneurons may be adjusted by changes in the quantal size due to slow replenishment via VAChT, and by a reduction in release probability upon high-frequency stimulation. These two distinct processes likely enable the fine tuning of neurotransmission and neuroprotection/limitation against excessive output and have important physiological roles in the brain.
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Affiliation(s)
- Itsumi Arakawa
- Department of Neurology, Nagoya City University Graduate School of Medicine, Nagoya, Japan
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, Uchinada, Japan
- Division of Genomic Science and Microbiology, School of Medicine, University of Fukui, Fukui, Japan
| | - Ikunobu Muramatsu
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, Uchinada, Japan
- Division of Genomic Science and Microbiology, School of Medicine, University of Fukui, Fukui, Japan
- Kimura Hospital, Fukui, Japan
| | - Junsuke Uwada
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, Uchinada, Japan
| | - Kiyonao Sada
- Division of Genomic Science and Microbiology, School of Medicine, University of Fukui, Fukui, Japan
| | - Noriyuki Matsukawa
- Department of Neurology, Nagoya City University Graduate School of Medicine, Nagoya, Japan
| | - Takayoshi Masuoka
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, Uchinada, Japan
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Acrylamide Neurotoxicity as a Possible Factor Responsible for Inflammation in the Cholinergic Nervous System. Int J Mol Sci 2022; 23:ijms23042030. [PMID: 35216144 PMCID: PMC8880090 DOI: 10.3390/ijms23042030] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 02/07/2022] [Accepted: 02/08/2022] [Indexed: 02/04/2023] Open
Abstract
Acrylamide (ACR) is a chemical compound that exhibits neurotoxic and genotoxic effects. It causes neurological symptoms such as tremors, general weakness, numbness, tingling in the limbs or ataxia. Numerous scientific studies show the effect of ACR on nerve endings and its close connection with the cholinergic system. The cholinergic system is part of the autonomic nervous system that regulates higher cortical functions related to memory, learning, concentration and attention. Within the cholinergic system, there are cholinergic neurons, anatomical cholinergic structures, the neurotransmitter acetylcholine (ACh) and cholinergic receptors. Some scientific reports suggest a negative effect of ACR on the cholinergic system and inflammatory reactions within the body. The aim of the study was to review the current state of knowledge on the influence of acrylamide on the cholinergic system and to evaluate its possible effect on inflammatory processes. The cholinergic anti-inflammatory pathway (CAP) is a neuroimmunomodulatory pathway that is located in the blood and mucous membranes. The role of CAP is to stop the inflammatory response in the appropriate moment. It prevents the synthesis and the release of pro-inflammatory cytokines and ultimately regulates the local and systemic immune response. The cellular molecular mechanism for inhibiting cytokine synthesis is attributed to acetylcholine (ACh), the major vagal neurotransmitter, and the α7 nicotinic receptor (α7nAChR) subunit is a key receptor for the cholinergic anti-inflammatory pathway. The combination of ACh with α7nAChR results in inhibition of the synthesis and release of pro-inflammatory cytokines. The blood AChE is able to terminate the stimulation of the cholinergic anti-inflammatory pathway due to splitting ACh. Accordingly, cytokine production is essential for pathogen protection and tissue repair, but over-release of cytokines can lead to systemic inflammation, organ failure, and death. Inflammatory responses are precisely regulated to effectively protect against harmful stimuli. The central nervous system dynamically interacts with the immune system, modulating inflammation through the humoral and nervous pathways. The stress-induced rise in acetylcholine (ACh) level acts to ease the inflammatory response and restore homeostasis. This signaling process ends when ACh is hydrolyzed by acetylcholinesterase (AChE). There are many scientific reports indicating the harmful effects of ACR on AChE. Most of them indicate that ACR reduces the concentration and activity of AChE. Due to the neurotoxic effect of acrylamide, which is related to the disturbance of the secretion of neurotransmitters, and its influence on the disturbance of acetylcholinesterase activity, it can be concluded that it disturbs the normal inflammatory response.
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Muramatsu I, Uwada J, Chihara K, Sada K, Wang MH, Yazawa T, Taniguchi T, Ishibashi T, Masuoka T. Evaluation of radiolabeled acetylcholine synthesis and release in rat striatum. J Neurochem 2021; 160:342-355. [PMID: 34878648 DOI: 10.1111/jnc.15556] [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: 03/26/2021] [Revised: 10/18/2021] [Accepted: 11/30/2021] [Indexed: 12/26/2022]
Abstract
Cholinergic transmission underlies higher brain functions such as cognition and movement. To elucidate the process whereby acetylcholine (ACh) release is maintained and regulated in the central nervous system, uptake of [3 H]choline and subsequent synthesis and release of [3 H]ACh were investigated in rat striatal segments. Incubation with [3 H]choline elicited efficient uptake via high-affinity choline transporter-1, resulting in accumulation of [3 H]choline and [3 H]ACh. However, following inhibition of ACh esterase (AChE), incubation with [3 H]choline led predominantly to the accumulation of [3 H]ACh. Electrical stimulation and KCl depolarization selectively released [3 H]ACh but not [3 H]choline. [3 H]ACh release gradually declined upon repetitive stimulation, whereas the release was reproducible under inhibition of AChE. [3 H]ACh release was abolished after treatment with vesamicol, an inhibitor of vesicular ACh transporter. These results suggest that releasable ACh is continually replenished from the cytosol to releasable pools of cholinergic vesicles to maintain cholinergic transmission. [3 H]ACh release evoked by electrical stimulation was abolished by tetrodotoxin, but that induced by KCl was largely resistant. ACh release was Ca2+ dependent and exhibited slightly different sensitivities to N- and P-type Ca2+ channel toxins (ω-conotoxin GVIA and ω-agatoxin IVA, respectively) between both stimuli. [3 H]ACh release was negatively regulated by M2 muscarinic and D2 dopaminergic receptors. The present results suggest that inhibition of AChE within cholinergic neurons and of presynaptic negative regulation of ACh release contributes to maintenance and facilitation of cholinergic transmission, providing a potentially useful clue for the development of therapies for cholinergic dysfunction-associated disorders, in addition to inhibition of synaptic cleft AChE.
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Affiliation(s)
- Ikunobu Muramatsu
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, Uchinada, Ishikawa, Japan.,Division of Genomic Science and Microbiology, School of Medicine, University of Fukui, Eiheiji, Fukui, Japan.,Kimura Hospital, Awara, Fukui, Japan
| | - Junsuke Uwada
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, Uchinada, Ishikawa, Japan.,Division of Cellular Signal Transduction, Department of Biochemistry, Asahikawa Medical University, Asahikawa, Hokkaido, Japan
| | - Kazuyasu Chihara
- Division of Genomic Science and Microbiology, School of Medicine, University of Fukui, Eiheiji, Fukui, Japan
| | - Kiyonao Sada
- Division of Genomic Science and Microbiology, School of Medicine, University of Fukui, Eiheiji, Fukui, Japan
| | - Mao-Hsien Wang
- Division of Genomic Science and Microbiology, School of Medicine, University of Fukui, Eiheiji, Fukui, Japan.,Department of Anesthesia, En Chu Kon Hospital, New Taipei City, Taiwan, ROC
| | - Takashi Yazawa
- Division of Cellular Signal Transduction, Department of Biochemistry, Asahikawa Medical University, Asahikawa, Hokkaido, Japan
| | - Takanobu Taniguchi
- Division of Cellular Signal Transduction, Department of Biochemistry, Asahikawa Medical University, Asahikawa, Hokkaido, Japan
| | - Takaharu Ishibashi
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, Uchinada, Ishikawa, Japan
| | - Takayoshi Masuoka
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, Uchinada, Ishikawa, Japan
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Acute benzo[a]pyrene exposure induced oxidative stress, neurotoxicity and epigenetic change in blood clam Tegillarca granosa. Sci Rep 2021; 11:18744. [PMID: 34548601 PMCID: PMC8455545 DOI: 10.1038/s41598-021-98354-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 04/22/2021] [Indexed: 12/16/2022] Open
Abstract
The blood clam (Tegillarca granosa) is being developed into a model bivalve mollusc for assessing and monitoring marine pollution on the offshore seabed. However, the information on the response of blood clam to PAHs, an organic pollutant usually deposited in submarine sediment, remains limited. Herein, we employed multiple biomarkers, including histological changes, oxidative stress, neurotoxicity and global DNA methylation, to investigate the effects of 10 and 100 μg/L Bap exposure on the blood clams under laboratory conditions, as well as the potential mechanisms. Acute Bap exposure can induce significant morphological abnormalities in gills as shown through hematoxylin–eosin (H.E) staining, providing an intuitive understanding on the effects of Bap on the structural organization of the blood clams. Meanwhile, the oxidative stress was significantly elevated as manifested by the increase of antioxidants activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione-s-transferase (GST), lipid peroxidation (LPO) level and 8-hydroxy-2′-deoxyguanosine (8-OHdG) content. The neurotoxicity was also strengthened by Bap toxicity manifested as inhibited acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) activities. In addition, the global DNA methylation level was investigated, and a significant DNA hypomethylation was observed in Bap exposed the blood clam. The correlation analysis showed that the global DNA methylation was negatively correlated with antioxidants (SOD, CAT and POD) activities, but positively correlated choline enzymes (AChE and ChAT) activities. These results collectively suggested that acute Bap exposure can cause damage in gills structures in the blood clam possibly by generating oxidative stress and neurotoxicity, and the global DNA methylation was inhibited to increase the transcriptional expression level of antioxidants genes and consequently elevate antioxidants activities against Bap toxicity. These results are hoped to shed some new light on the study of ecotoxicology effect of PAHs on marine bivalves.
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Varga AG, Maletz SN, Bateman JT, Reid BT, Levitt ES. Neurochemistry of the Kölliker-Fuse nucleus from a respiratory perspective. J Neurochem 2020; 156:16-37. [PMID: 32396650 DOI: 10.1111/jnc.15041] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 04/27/2020] [Accepted: 05/04/2020] [Indexed: 12/11/2022]
Abstract
The Kölliker-Fuse nucleus (KF) is a functionally distinct component of the parabrachial complex, located in the dorsolateral pons of mammals. The KF has a major role in respiration and upper airway control. A comprehensive understanding of the KF and its contributions to respiratory function and dysfunction requires an appreciation for its neurochemical characteristics. The goal of this review is to summarize the diverse neurochemical composition of the KF, focusing on the neurotransmitters, neuromodulators, and neuropeptides present. We also include a description of the receptors expressed on KF neurons and transporters involved in each system, as well as their putative roles in respiratory physiology. Finally, we provide a short section reviewing the literature regarding neurochemical changes in the KF in the context of respiratory dysfunction observed in SIDS and Rett syndrome. By over-viewing the current literature on the neurochemical composition of the KF, this review will serve to aid a wide range of topics in the future research into the neural control of respiration in health and disease.
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Affiliation(s)
- Adrienn G Varga
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA.,Department of Physical Therapy, Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL, USA
| | - Sebastian N Maletz
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
| | - Jordan T Bateman
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA.,Department of Physical Therapy, Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL, USA
| | - Brandon T Reid
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
| | - Erica S Levitt
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA.,Department of Physical Therapy, Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL, USA
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Cansler HL, Wright KN, Stetzik LA, Wesson DW. Neurochemical organization of the ventral striatum's olfactory tubercle. J Neurochem 2020; 152:425-448. [PMID: 31755104 PMCID: PMC7042089 DOI: 10.1111/jnc.14919] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 11/08/2019] [Accepted: 11/17/2019] [Indexed: 12/11/2022]
Abstract
The ventral striatum is a collection of brain structures, including the nucleus accumbens, ventral pallidum and the olfactory tubercle (OT). While much attention has been devoted to the nucleus accumbens, a comprehensive understanding of the ventral striatum and its contributions to neurological diseases requires an appreciation for the complex neurochemical makeup of the ventral striatum's other components. This review summarizes the rich neurochemical composition of the OT, including the neurotransmitters, neuromodulators and hormones present. We also address the receptors and transporters involved in each system as well as their putative functional roles. Finally, we end with briefly reviewing select literature regarding neurochemical changes in the OT in the context of neurological disorders, specifically neurodegenerative disorders. By overviewing the vast literature on the neurochemical composition of the OT, this review will serve to aid future research into the neurobiology of the ventral striatum.
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Affiliation(s)
- Hillary L Cansler
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
- Center for Smell and Taste, University of Florida, Gainesville, FL, USA
| | - Katherine N Wright
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
- Center for Smell and Taste, University of Florida, Gainesville, FL, USA
- Center for Addiction Research and Education, University of Florida, Gainesville, FL, USA
| | - Lucas A Stetzik
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
- Center for Smell and Taste, University of Florida, Gainesville, FL, USA
| | - Daniel W Wesson
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
- Center for Smell and Taste, University of Florida, Gainesville, FL, USA
- Center for Addiction Research and Education, University of Florida, Gainesville, FL, USA
- Norman Fixel Institute for Neurological Diseases, University of Florida, Gainesville, FL, USA
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7
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Elkhatib SK, Case AJ. Autonomic regulation of T-lymphocytes: Implications in cardiovascular disease. Pharmacol Res 2019; 146:104293. [PMID: 31176794 DOI: 10.1016/j.phrs.2019.104293] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 04/22/2019] [Accepted: 05/31/2019] [Indexed: 12/20/2022]
Abstract
The nervous and immune systems both serve as essential assessors and regulators of physiological function. Recently, there has been a great interest in how the nervous and immune systems interact to modulate both physiological and pathological states. In particular, the autonomic nervous system has a direct line of communication with immune cells anatomically, and moreover, immune cells possess receptors for autonomic neurotransmitters. This circumstantial evidence is suggestive of a functional interplay between the two systems, and extensive research over the past few decades has demonstrated neurotransmitters such as the catecholamines (i.e. dopamine, norepinephrine, and epinephrine) and acetylcholine have potent immunomodulating properties. Furthermore, immune cells, particularly T-lymphocytes, have now been found to express the cellular machinery for both the synthesis and degradation of neurotransmitters, which suggests the ability for both autocrine and paracrine signaling from these cells independent of the nervous system. The details underlying the functional interplay of this complex network of neuroimmune communication are still unclear, but this crosstalk is suggestive of significant implications on the pathogenesis of a number of autonomic-dysregulated and inflammation-mediated diseases. In particular, it is widely accepted that numerous forms of cardiovascular diseases possess imbalanced autonomic tone as well as altered T-lymphocyte function, but a paucity of literature exists discussing the direct role of neurotransmitters in shaping the inflammatory microenvironment during the progression or therapeutic management of these diseases. This review seeks to provide a fundamental framework for this autonomic neuroimmune interaction within T-lymphocytes, as well as the implications this may have in cardiovascular diseases.
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Affiliation(s)
- Safwan K Elkhatib
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, United States
| | - Adam J Case
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, United States.
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Muramatsu I, Uwada J, Yoshiki H, Sada K, Lee K, Yazawa T, Taniguchi T, Nishio M, Ishibashi T, Masuoka T. Novel regulatory systems for acetylcholine release in rat striatum and anti‐Alzheimer's disease drugs. J Neurochem 2019; 149:605-623. [DOI: 10.1111/jnc.14701] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 02/20/2019] [Accepted: 03/27/2019] [Indexed: 10/27/2022]
Affiliation(s)
- Ikunobu Muramatsu
- Department of Pharmacology School of Medicine Kanazawa Medical University Uchinada, Ishikawa Japan
- Division of Genomic Science and Microbiology School of Medicine University of Fukui Eiheiji Fukui Japan
- Kimura Hospital Awara Fukui Japan
| | - Junsuke Uwada
- Division of Cellular Signal Transduction Department of Biochemistry Asahikawa Medical University Asahikawa Hokkaido Japan
| | - Hatsumi Yoshiki
- Division of Genomic Science and Microbiology School of Medicine University of Fukui Eiheiji Fukui Japan
| | - Kiyonao Sada
- Division of Genomic Science and Microbiology School of Medicine University of Fukui Eiheiji Fukui Japan
| | - Kung‐Shing Lee
- Division of Genomic Science and Microbiology School of Medicine University of Fukui Eiheiji Fukui Japan
- Department of Surgery Kaohsiung Medical University Kaohsiung Taiwan
| | - Takashi Yazawa
- Division of Cellular Signal Transduction Department of Biochemistry Asahikawa Medical University Asahikawa Hokkaido Japan
| | - Takanobu Taniguchi
- Division of Cellular Signal Transduction Department of Biochemistry Asahikawa Medical University Asahikawa Hokkaido Japan
| | - Matomo Nishio
- Department of Pharmacology School of Medicine Kanazawa Medical University Uchinada, Ishikawa Japan
| | - Takaharu Ishibashi
- Department of Pharmacology School of Medicine Kanazawa Medical University Uchinada, Ishikawa Japan
| | - Takayoshi Masuoka
- Department of Pharmacology School of Medicine Kanazawa Medical University Uchinada, Ishikawa Japan
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A Poly-Glutamine Region in the Drosophila VAChT Dictates Fill-Level of Cholinergic Synaptic Vesicles. eNeuro 2019; 6:eN-NWR-0477-18. [PMID: 30847389 PMCID: PMC6402538 DOI: 10.1523/eneuro.0477-18.2019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 01/03/2019] [Accepted: 01/07/2019] [Indexed: 01/08/2023] Open
Abstract
While the primary role of vesicular transporters is to load neurotransmitters into synaptic vesicles (SVs), accumulating evidence suggests that these proteins also contribute to additional aspects of synaptic function, including vesicle release. In this study, we extend the role of the VAChT to include regulating the transmitter content of SVs. We report that manipulation of a C-terminal poly-glutamine (polyQ) region in the Drosophila VAChT is sufficient to influence transmitter content, and release frequency, of cholinergic vesicles from the terminals of premotor interneurons. Specifically, we find that reduction of the polyQ region, by one glutamine residue (13Q to 12Q), results in a significant increase in both amplitude and frequency of spontaneous cholinergic miniature EPSCs (mEPSCs) recorded in the aCC and RP2 motoneurons. Moreover, this truncation also results in evoked synaptic currents that show increased duration: consistent with increased ACh release. By contrast, extension of the polyQ region by one glutamine (13Q to 14Q) is sufficient to reduce mEPSC amplitude and frequency and, moreover, prevents evoked SV release. Finally, a complete deletion of the polyQ region (13Q to 0Q) has no obvious effects to mEPSCs, but again evoked synaptic currents show increased duration. The mechanisms that ensure SVs are filled to physiologically-appropriate levels remain unknown. Our study identifies the polyQ region of the insect VAChT to be required for correct vesicle transmitter loading and, thus, provides opportunity to increase understanding of this critical aspect of neurotransmission.
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Masuoka T, Uwada J, Kudo M, Yoshiki H, Yamashita Y, Taniguchi T, Nishio M, Ishibashi T, Muramatsu I. Augmentation of Endogenous Acetylcholine Uptake and Cholinergic Facilitation of Hippocampal Long-Term Potentiation by Acetylcholinesterase Inhibition. Neuroscience 2019; 404:39-47. [PMID: 30708046 DOI: 10.1016/j.neuroscience.2019.01.042] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 01/21/2019] [Accepted: 01/22/2019] [Indexed: 10/27/2022]
Abstract
Hippocampal cholinergic activity enhances long-term potentiation (LTP) of synaptic transmission in intrahippocampal circuits and regulates cognitive function. We recently demonstrated intracellular distribution of functional M1-muscarinic acetylcholine receptors (mAChRs) and neuronal uptake of acetylcholine (ACh) in the central nervous system. Here we examined whether endogenous ACh acts on intracellular M1-mAChRs following its uptake and causes cholinergic facilitation of hippocampal LTP. ACh esterase (AChE) activities and [3H]ACh uptake was measured in rat hippocampal segments. LTP of evoked field excitatory postsynaptic potentials at CA1 synapses was induced by high frequency stimulation in hippocampal slices. Pretreatment with diisopropylfluorophosphate (DFP) irreversibly inhibited AChE, augmented ACh uptake, and significantly enhanced the LTP. This cholinergic facilitation was inhibited by pirenzepine, a membrane-permeable M1 antagonist, while only the early stage of cholinergic facilitation was inhibited by a membrane-impermeable M1 antagonist, muscarinic toxin 7. Tetraethylammonium (TEA) inhibited ACh uptake in hippocampal segments and selectively suppressed late stage cholinergic facilitation without changing the early stage. In contrast, LTP in DFP-untreated slices was not affected by the muscarinic antagonists and TEA. Carbachol (CCh; an AChE-resistant muscarinic agonist) competed with ACh for its uptake and produced cholinergic facilitation of LTP in DFP-untreated slices. The late stage of CCh-induced facilitation was also selectively inhibited by TEA. Our results suggest that when AChE is inactivated by inhibitors, LTP in hippocampal slices is significantly enhanced by endogenous ACh and that cholinergic facilitation is caused by direct activation of cell-surface M1-mAChRs and subsequent activation of intracellular M1-mAChRs after ACh uptake.
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Affiliation(s)
- Takayoshi Masuoka
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa, 920-0293, Japan.
| | - Junsuke Uwada
- Division of Cellular Signal Transduction, Department of Biochemistry, Asahikawa Medical University, 2-1-1-1, Midorigaoka-Higashi, Asahikawa, Hokkaido, 078-8510, Japan
| | - Makiko Kudo
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa, 920-0293, Japan
| | - Hatsumi Yoshiki
- Division of Genomic Science and Microbiology, School of Medicine, University of Fukui, Eiheiji, Fukui 910-1193, Japan
| | - Yuka Yamashita
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa, 920-0293, Japan
| | - Takanobu Taniguchi
- Division of Cellular Signal Transduction, Department of Biochemistry, Asahikawa Medical University, 2-1-1-1, Midorigaoka-Higashi, Asahikawa, Hokkaido, 078-8510, Japan
| | - Matomo Nishio
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa, 920-0293, Japan
| | - Takaharu Ishibashi
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa, 920-0293, Japan
| | - Ikunobu Muramatsu
- Department of Pharmacology, School of Medicine, Kanazawa Medical University, 1-1 Daigaku, Uchinada, Ishikawa, 920-0293, Japan
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Saw EL, Kakinuma Y, Fronius M, Katare R. The non-neuronal cholinergic system in the heart: A comprehensive review. J Mol Cell Cardiol 2018; 125:129-139. [PMID: 30343172 DOI: 10.1016/j.yjmcc.2018.10.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 09/24/2018] [Accepted: 10/14/2018] [Indexed: 01/01/2023]
Abstract
The autonomic influences on the heart have a ying-yang nature, albeit oversimplified, the interplay between the sympathetic and parasympathetic system (known as the cholinergic system) is often complex and remain poorly understood. Recently, the heart has been recognized to consist of neuronal and non-neuronal cholinergic system (NNCS). The existence of cardiac NNCS has been confirmed by the presence of cholinergic markers in the cardiomyocytes, which are crucial for synthesis (choline acetyltransferase, ChAT), storage (vesicular acetylcholine transporter, VAChT), reuptake of choline for synthesis (high-affinity choline transporter, CHT1) and degradation (acetylcholinesterase, AChE) of acetylcholine (ACh). The non-neuronal ACh released from cardiomyocytes is believed to locally regulate some of the key physiological functions of the heart, such as regulation of heart rate, offsetting hypertrophic signals, maintenance of action potential propagation as well as modulation of cardiac energy metabolism via the muscarinic ACh receptor in an auto/paracrine manner. Apart from this, several studies have also provided evidence for the beneficial role of ACh released from cardiomyocytes against cardiovascular diseases such as sympathetic hyperactivity-induced cardiac remodeling and dysfunction as well as myocardial infarction, confirming the important role of NNCS in disease prevention. In this review, we aim to provide a fundamental overview of cardiac NNCS, and information about its physiological role, regulatory factors as well as its cardioprotective effects. Finally, we propose the different approaches to target cardiac NNCS as an adjunctive treatment to specifically address the withdrawal of neuronal cholinergic system in cardiovascular disease such as heart failure.
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Affiliation(s)
- Eng Leng Saw
- Department of Physiology-HeartOtago, School of Biomedical Sciences, University of Otago, New Zealand
| | - Yoshihiko Kakinuma
- Department of Physiology (Bioregulatory Science), Graduate School of Medicine, Nippon Medical School, Tokyo, Japan
| | - Martin Fronius
- Department of Physiology-HeartOtago, School of Biomedical Sciences, University of Otago, New Zealand.
| | - Rajesh Katare
- Department of Physiology-HeartOtago, School of Biomedical Sciences, University of Otago, New Zealand.
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Lohr KM, Masoud ST, Salahpour A, Miller GW. Membrane transporters as mediators of synaptic dopamine dynamics: implications for disease. Eur J Neurosci 2017; 45:20-33. [PMID: 27520881 PMCID: PMC5209277 DOI: 10.1111/ejn.13357] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Revised: 07/12/2016] [Accepted: 08/02/2016] [Indexed: 12/14/2022]
Abstract
Dopamine was first identified as a neurotransmitter localized to the midbrain over 50 years ago. The dopamine transporter (DAT; SLC6A3) and the vesicular monoamine transporter 2 (VMAT2; SLC18A2) are regulators of dopamine homeostasis in the presynaptic neuron. DAT transports dopamine from the extracellular space into the cytosol of the presynaptic terminal. VMAT2 then packages this cytosolic dopamine into vesicular compartments for subsequent release upon neurotransmission. Thus, DAT and VMAT2 act in concert to move the transmitter efficiently throughout the neuron. Accumulation of dopamine in the neuronal cytosol can trigger oxidative stress and neurotoxicity, suggesting that the proper compartmentalization of dopamine is critical for neuron function and risk of disease. For decades, studies have examined the effects of reduced transporter function in mice (e.g. DAT-KO, VMAT2-KO, VMAT2-deficient). However, we have only recently been able to assess the effects of elevated transporter expression using BAC transgenic methods (DAT-tg, VMAT2-HI mice). Complemented with in vitro work and neurochemical techniques to assess dopamine compartmentalization, a new focus on the importance of transporter proteins as both models of human disease and potential drug targets has emerged. Here, we review the importance of DAT and VMAT2 function in the delicate balance of neuronal dopamine.
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Affiliation(s)
- Kelly M Lohr
- Department of Environmental Health, Rollins School of Public Health, Emory University, 1518 Clifton Road, Atlanta, GA, 30322, USA
| | - Shababa T Masoud
- Department of Pharmacology and Toxicology, University of Toronto, ON, Canada
| | - Ali Salahpour
- Department of Pharmacology and Toxicology, University of Toronto, ON, Canada
| | - Gary W Miller
- Department of Environmental Health, Rollins School of Public Health, Emory University, 1518 Clifton Road, Atlanta, GA, 30322, USA
- Center for Neurodegenerative Diseases, Emory University, Atlanta, GA, USA
- Department of Pharmacology, Emory University, Atlanta, GA, USA
- Department of Neurology, Emory University, Atlanta, GA, USA
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Wehrwein EA, Orer HS, Barman SM. Overview of the Anatomy, Physiology, and Pharmacology of the Autonomic Nervous System. Compr Physiol 2016; 6:1239-78. [PMID: 27347892 DOI: 10.1002/cphy.c150037] [Citation(s) in RCA: 235] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Comprised of the sympathetic nervous system, parasympathetic nervous system, and enteric nervous system, the autonomic nervous system (ANS) provides the neural control of all parts of the body except for skeletal muscles. The ANS has the major responsibility to ensure that the physiological integrity of cells, tissues, and organs throughout the entire body is maintained (homeostasis) in the face of perturbations exerted by both the external and internal environments. Many commonly prescribed drugs, over-the-counter drugs, toxins, and toxicants function by altering transmission within the ANS. Autonomic dysfunction is a signature of many neurological diseases or disorders. Despite the physiological relevance of the ANS, most neuroscience textbooks offer very limited coverage of this portion of the nervous system. This review article provides both historical and current information about the anatomy, physiology, and pharmacology of the sympathetic and parasympathetic divisions of the ANS. The ultimate aim is for this article to be a valuable resource for those interested in learning the basics of these two components of the ANS and to appreciate its importance in both health and disease. Other resources should be consulted for a thorough understanding of the third division of the ANS, the enteric nervous system. © 2016 American Physiological Society. Compr Physiol 6:1239-1278, 2016.
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Affiliation(s)
- Erica A Wehrwein
- Department of Physiology, Michigan State University, East Lansing, Michigan, USA
| | - Hakan S Orer
- Department of Pharmacology, Koc University School of Medicine, Istanbul, Turkey
| | - Susan M Barman
- Department of Pharmacology &Toxicology, Michigan State University, East Lansing, Michigan, USA
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Iwamoto H, Calcutt MW, Blakely RD. Differential impact of genetically modulated choline transporter expression on the release of endogenous versus newly synthesized acetylcholine. Neurochem Int 2016; 98:138-45. [PMID: 27013347 DOI: 10.1016/j.neuint.2016.03.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2016] [Revised: 03/12/2016] [Accepted: 03/16/2016] [Indexed: 11/15/2022]
Abstract
The efficient import of choline into cholinergic nerve terminals by the presynaptic, high-affinity choline transporter (CHT, SLC5A7) dictates the capacity for acetylcholine (ACh) synthesis and release. Tissue levels of ACh are significantly reduced in mice heterozygous for a loss of function mutation in Slc5a7 (HET, CHT(+/-)), but significantly elevated in overexpressing, Slc5a7 BAC-transgenic mice (BAC). Since the readily-releasable pool of ACh is thought to constitute a small fraction of the total ACh pool, these genotype-dependent changes raised the question as to whether CHT expression or activity might preferentially influence the size of reserve pool ACh vesicles. In the current study, we approached this question by evaluating CHT genotype effects on the release of ACh from suprafused mouse forebrain slices. We treated slices from HET, BAC or wildtype (WT) controls with elevated K(+) and monitored release of both newly synthesized and storage pools of ACh. Newly synthesized ACh produced following uptake of [(3)H]choline was quantified by scintillation spectrometry whereas release of endogenous ACh storage pools was quantified by an HPLC-MS approach, from the same samples. Whereas endogenous ACh release scaled with CHT gene dosage, preloaded [(3)H]ACh release displayed no significant genotype dependence. Our findings suggest that CHT protein levels preferentially impact the capacity for ACh release afforded by mobilization of reserve pool vesicles.
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Affiliation(s)
- Hideki Iwamoto
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - M Wade Calcutt
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA; Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Randy D Blakely
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Psychiatry, Vanderbilt University School of Medicine, Nashville, TN, USA.
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16
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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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Tamura Y, Ogita K, Ueda T. A new VGLUT-specific potent inhibitor: pharmacophore of Brilliant Yellow. Neurochem Res 2014; 39:117-28. [PMID: 24248859 PMCID: PMC4025951 DOI: 10.1007/s11064-013-1196-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Revised: 11/05/2013] [Accepted: 11/07/2013] [Indexed: 10/26/2022]
Abstract
The increased concentration of glutamate in synaptic vesicles, mediated by the vesicular glutamate transporter (VGLUT), is an initial vital step in glutamate synaptic transmission. Evidence indicates that aberrant overexpression of VGLUT is involved in certain pathophysiologies of the central nervous system. VGLUT is subject to inhibition by various types of agents. The most potent VGLUT-specific inhibitor currently known is Trypan Blue, which is highly charged, hence membrane-impermeable. We have sought a potent, VGLUT-specific agent amenable to easy modification to a membrane-permeable analog. We provide evidence that Brilliant Yellow exhibits potent, VGLUT-specific inhibition, with a Ki value of 12 nM. Based upon structure-activity relationship studies and molecular modeling, we have defined the potent inhibitory pharmacophore of Brilliant Yellow. This study provides new insight into development of a membrane-permeable agent to lead to specific blockade, with high potency, of accumulation of glutamate into synaptic vesicles in neurons.
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Affiliation(s)
- Yutaka Tamura
- Molecular and Behavioral Neuroscience Institute, Medical School, The University of Michigan, 109 Zina Pitcher Place, Ann Arbor, Michigan 48109-2200, USA
| | - Kiyokazu Ogita
- Molecular and Behavioral Neuroscience Institute, Medical School, The University of Michigan, 109 Zina Pitcher Place, Ann Arbor, Michigan 48109-2200, USA
| | - Tetsufumi Ueda
- Molecular and Behavioral Neuroscience Institute, Medical School, The University of Michigan, 109 Zina Pitcher Place, Ann Arbor, Michigan 48109-2200, USA
- Department of Pharmacology, Medical School, The University of Michigan, Ann Arbor, Michigan 48109, USA
- Department of Psychiatry, Medical School, The University of Michigan, Ann Arbor, Michigan 48109, USA
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18
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Organic cation transporter 2 (SLC22A2), a low-affinity and high-capacity choline transporter, is preferentially enriched on synaptic vesicles in cholinergic neurons. Neuroscience 2013; 252:212-21. [DOI: 10.1016/j.neuroscience.2013.08.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 08/07/2013] [Accepted: 08/07/2013] [Indexed: 01/11/2023]
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Park JJ, Gondré-Lewis MC, Eiden LE, Loh YP. A distinct trans-Golgi network subcompartment for sorting of synaptic and granule proteins in neurons and neuroendocrine cells. J Cell Sci 2011; 124:735-44. [PMID: 21321327 DOI: 10.1242/jcs.076372] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Golgi-to-plasma-membrane trafficking of synaptic-like microvesicle (SLMV) proteins, vesicular acetylcholine transporter (VAChT) and synaptophysin (SYN), and a large dense-core vesicle (LDCV) protein, chromogranin A (CgA), was investigated in undifferentiated neuroendocrine PC12 cells. Live cell imaging and 20°C block-release experiments showed that VAChT-GFP, SYN-GFP and CgA-RFP specifically and transiently cohabitated in a distinct sorting compartment during cold block and then separated into synaptic protein transport vesicles (SPTVs) and LDCVs, after release from temperature block. We found that in this trans-Golgi subcompartment there was colocalization of SPTV and LDCV proteins, most significantly with VAMP4 and Golgin97, and to some degree with TGN46, but not at all with TGN38. Moreover, some SNAP25 and VAMP2, two subunits of the exocytic machinery, were also recruited onto this compartment. Thus, in neuroendocrine cells, synaptic vesicle and LDCV proteins converge briefly in a distinct trans-Golgi network subcompartment before sorting into SPTVs and LDCVs, ultimately for delivery to the plasma membrane. This specialized sorting compartment from which SPTVs and LDCVs bud might facilitate the acquisition of common exocytic machinery needed on the membranes of these vesicles.
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Affiliation(s)
- Joshua J Park
- Section on Cellular Neurobiology, Program in Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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20
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Kalogiannis M, Grupke SL, Potter PE, Edwards JG, Chemelli RM, Kisanuki YY, Yanagisawa M, Leonard CS. Narcoleptic orexin receptor knockout mice express enhanced cholinergic properties in laterodorsal tegmental neurons. Eur J Neurosci 2010; 32:130-42. [PMID: 20576035 DOI: 10.1111/j.1460-9568.2010.07259.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Pharmacological studies of narcoleptic canines indicate that exaggerated pontine cholinergic transmission promotes cataplexy. As disruption of orexin (hypocretin) signaling is a primary defect in narcolepsy with cataplexy, we investigated whether markers of cholinergic synaptic transmission might be altered in mice constitutively lacking orexin receptors (double receptor knockout; DKO). mRNA for Choline acetyltransferase (ChAT), vesicular acetylcholine transporter (VAChT) and the high-affinity choline transporter (CHT1) but not acetylcholinesterase (AChE) was significantly higher in samples from DKO than wild-type (WT) mice. This was region-specific; levels were elevated in samples from the laterodorsal tegmental nucleus (LDT) and the fifth motor nucleus (Mo5) but not in whole brainstem samples. Consistent with region-specific changes, we were unable to detect significant differences in Western blots for ChAT and CHT1 in isolates from brainstem, thalamus and cortex or in ChAT enzymatic activity in the pons. However, using ChAT immunocytochemistry, we found that while the number of cholinergic neurons in the LDT and Mo5 were not different, the intensity of somatic ChAT immunostaining was significantly greater in the LDT, but not Mo5, from DKO than from WT mice. We also found that ChAT activity was significantly reduced in cortical samples from DKO compared with WT mice. Collectively, these findings suggest that the orexins can regulate neurotransmitter expression and that the constitutive absence of orexin signaling results in an up-regulation of the machinery necessary for cholinergic neurotransmission in a mesopontine population of neurons that have been associated with both normal rapid eye movement sleep and cataplexy.
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Affiliation(s)
- M Kalogiannis
- Department of Physiology, New York Medical College, Valhalla, NY 10595, USA
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21
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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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Khare P, White AR, Parsons SM. Multiple protonation states of vesicular acetylcholine transporter detected by binding of [3H]vesamicol. Biochemistry 2009; 48:8965-75. [PMID: 19685929 DOI: 10.1021/bi900759v] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Vesicular acetylcholine transporter (VAChT) is inhibited by (-)-vesamicol [(-)-trans-2-(4-phenylpiperidino)cyclohexanol], which binds tightly to an allosteric site. The tertiary alkylamine center in (-)-vesamicol is protonated and positively charged at acidic and neutral pH and unprotonated and uncharged at alkaline pH. Deprotonation of the amine has been taken to explain loss of (-)-vesamicol binding at alkaline pH. However, binding data deviate from a stereotypical bell shape, and more binding occurs than expected at alkaline pH. The current study characterizes the binding of (-)-vesamicol from pH 5 to pH 10 using filter assays, (-)-[3H]vesamicol (hereafter called [3H]vesamicol), and human VAChT expressed in PC12(A123.7) cells. At acidic pH, protons and [3H]vesamicol compete for binding to VAChT. Preexposure or long-term exposure of VAChT to high pH does not affect binding, thus eliminating potential denaturation of VAChT and failure of the filter assay. The dissociation constant for the complex between protonated [3H]vesamicol and VAChT decreases from 12 nM at neutral pH to 2.1 nM at pH 10. The simplest model of VAChT that explains the behavior requires a proton at site 1 to dissociate with pK1 = 6.5 +/- 0.1, a proton at site A to dissociate with pKA = 7.6 +/- 0.2, and a proton at site B to dissociate with pKB = 10.0 +/- 0.1. Deprotonation of the site 1 proton is obligatory for [3H]vesamicol binding. Deprotonation of site A decreases affinity (2.2 +/- 0.5)-fold, and deprotonation of site B increases affinity (18 +/- 4)-fold. Time-dependent dissociation of bound [3H]vesamicol is biphasic, but equilibrium saturation curves are not. The contrasting phasicity suggests that the pathway to and from the [3H]vesamicol binding site exists in open and at least partially closed states. The potential significance of the findings to development of PET and SPECT ligands based on (-)-vesamicol for human diagnostics also is discussed.
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Affiliation(s)
- Parul Khare
- Department of Chemistry and Biochemistry, Neuroscience Research Institute, University of California, Santa Barbara, California 93106, USA
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Molgó J, Colasante C, Benoit E, Poulain B. [A reminder of the structure and function of the skeletal neuromuscular junction]. Ann Dermatol Venereol 2009; 136 Suppl 4:S55-60. [PMID: 19576486 DOI: 10.1016/s0151-9638(09)74528-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The skeletal neuromuscular junction has been considered as a model of chemical synapses due to its relatively simple organization. It is made up of three cellular partners including the motoneuron nerve terminals, the peri-synaptic Schwann cells and a specialized region of skeletal muscle fibers. It has been extensively studied revealing its ultrastructural complexity involving many molecular actors. The neuromuscular junction is a highly specialized structure, optimized for the rapid transmission of information from the presynaptic nerve terminal to the post-synaptic muscle fiber. This rapid transmission requires a very close apposition of plasmic membranes of pre- and post-synaptic partners, and a strict structural and molecular arrangement on both sides of the narrow synaptic cleft separating nerve terminal and muscle membranes. In this short review, we summarize the knowledge regarding pre- and post-synaptic ultrastructural specializations and give an overview of some functional aspects of neuromuscular transmission, including the quantal acetylcholine release process, which will help to better understand the pharmacological actions of botulinum toxins in esthetic and corrective dermatology.
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Affiliation(s)
- J Molgó
- CNRS, Institut de Neurobiologie Alfred Fessard - FRC2118, Laboratoire de Neurobiologie Cellulaire et Moléculaire - UPR9040, F-91198 Gif-sur-Yvette cedex, France.
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Positron emission tomography imaging of (2R,3R)-5-[(18)F]fluoroethoxybenzovesamicol in rat and monkey brain: a radioligand for the vesicular acetylcholine transporter. Nucl Med Biol 2009; 36:489-93. [PMID: 19520289 DOI: 10.1016/j.nucmedbio.2009.02.007] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Revised: 02/12/2009] [Accepted: 02/17/2009] [Indexed: 11/22/2022]
Abstract
INTRODUCTION The regional brain distribution of (2R,3R)-5-[(18)F]fluoroethoxy-benzovesamicol ((-)-[(18)F]FEOBV), a radioligand for the vesicular acetylcholine transporter (VAChT), was examined in vivo in mice, rats and rhesus monkeys. METHODS Regional brain distributions of (-)-[(18)F]FEOBV in mice were determined using ex vivo dissection. MicroPET imaging was used to determine the regional brain pharmacokinetics of the radioligand in rat and rhesus monkey brains. RESULTS In all three species, clear heterogeneous regional brain distributions were obtained, with the rank order of brain tissues (striatum>thalamus>cortex>cerebellum) consistent with the distribution of cholinergic nerve terminals containing the VAChT. CONCLUSIONS (-)-[(18)F]FEOBV remains a viable candidate for further development as an in vivo imaging agent for positron emission tomography (PET) studies of the VAChT in the human brain.
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Borycz J, Borycz JA, Kubów A, Lloyd V, Meinertzhagen IA. Drosophila ABC transporter mutants white, brown and scarlet have altered contents and distribution of biogenic amines in the brain. J Exp Biol 2008; 211:3454-66. [DOI: 10.1242/jeb.021162] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Monoamines such as dopamine, histamine and serotonin (5-HT) are widely distributed throughout the brain of the fruit fly Drosophila melanogaster, where many of their actions have been investigated. For example, histamine is released from photoreceptor synapses in the lamina neuropile of the visual system. Mutations of the genes white, an important eye pigmentation marker in fly genetics that encodes an ABC transporter, and its binding partner brown, cause neural phenotypes not readily reconciled solely with actions in eye pigmentation. We find that flies mutant for these genes, and another binding partner, scarlet, have about half the wild-type amount of histamine in the head, as well as reduced 5-HT and dopamine. These differences parallel reductions in immunoreactivity to the corresponding biogenic amines. They also correlate with the amine content of fractions after differential centrifugation of head homogenates. Thus, most of the amine is found in the vesicle-rich fraction of wild-type head homogenates, whereas it is found in the supernatant fractions from white, brown and scarlet flies. White co-expresses in lamina epithelial glia with Ebony, which conjugates histamine to β-alanine. Histamine is then released when the conjugate is hydrolyzed in photoreceptors, by Tan. Mutant white ameliorates the effects of tan on head histamine whereas it exacerbates the effects of ebony. Our results are consistent with the proposal that histamine uptake by the epithelial glia may be white dependent. Behavioral abnormalities in white, brown and scarlet mutants could arise because aminergic neurons in the Drosophila brain have reduced amine for release.
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Affiliation(s)
- J. Borycz
- Department of Psychology, Life Sciences Centre, Dalhousie University, Halifax,NS, Canada B3H 4J1
| | - J. A. Borycz
- Department of Psychology, Life Sciences Centre, Dalhousie University, Halifax,NS, Canada B3H 4J1
| | - A. Kubów
- Department of Psychology, Life Sciences Centre, Dalhousie University, Halifax,NS, Canada B3H 4J1
| | - V. Lloyd
- Department of Biology, Life Sciences Centre, Dalhousie University, Halifax,NS, Canada B3H 4J1
| | - I. A. Meinertzhagen
- Department of Psychology, Life Sciences Centre, Dalhousie University, Halifax,NS, Canada B3H 4J1
- Department of Biology, Life Sciences Centre, Dalhousie University, Halifax,NS, Canada B3H 4J1
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Chaudhry FA, Edwards RH, Fonnum F. Vesicular neurotransmitter transporters as targets for endogenous and exogenous toxic substances. Annu Rev Pharmacol Toxicol 2008; 48:277-301. [PMID: 17883368 DOI: 10.1146/annurev.pharmtox.46.120604.141146] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Exocytotic release of neurotransmitters requires their accumulation inside preformed secretory vesicles. Distinct vesicular transport activities translocate classical transmitters into synaptic vesicles energized by a H+ electrochemical gradient (Delta(mu(H+))), with subtle but important differences in dependence on the electrical and chemical components. The vesicular transporters also interact with toxic compounds and drugs. They mediate neuroprotection by sequestering toxic compounds as well as neurotransmitters into vesicles, reducing their concentration in the cytosol where they may have detrimental effects. Both therapeutic agents and psychostimulants interfering with vesicular transport have yielded insight into the pathogenesis of psychiatric as well as neurodegenerative diseases. Thus, specific inhibitors have helped to characterize both the physiological role and mechanism of vesicular neurotransmitter transport.
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Affiliation(s)
- Farrukh A Chaudhry
- Centre for Molecular Biology and Neuroscience, The Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway.
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27
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Chaudhry FA, Boulland JL, Jenstad M, Bredahl MKL, Edwards RH. Pharmacology of neurotransmitter transport into secretory vesicles. Handb Exp Pharmacol 2008:77-106. [PMID: 18064412 DOI: 10.1007/978-3-540-74805-2_4] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Many neuropsychiatric disorders appear to involve a disturbance of chemical neurotransmission, and the mechanism of available therapeutic agents supports this impression. Postsynaptic receptors have received considerable attention as drug targets, but some of the most successful agents influence presynaptic processes, in particular neurotransmitter reuptake. The pharmacological potential of many other presynaptic elements, and in particular the machinery responsible for loading transmitter into vesicles, has received only limited attention. The similarity of vesicular transporters to bacterial drug resistance proteins and the increasing evidence for regulation of vesicle filling and recycling suggest that the pharmacological potential of vesicular transporters has been underestimated. In this review, we discuss the pharmacological effects of psychostimulants and therapeutic agents on transmitter release.
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Affiliation(s)
- Farrukh A Chaudhry
- The Biotechnology Centre of Oslo, University of Oslo, 1125, Blindern, Oslo, 0317, Norway.
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Gaydukov AE, Balezina OP. Potentiating effect of allatostatin on transmitter quantal secretion in the mouse nerve-muscle synapse. J EVOL BIOCHEM PHYS+ 2006. [DOI: 10.1134/s0022093006060068] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Iwamoto H, Blakely RD, De Felice LJ. Na+, Cl-, and pH dependence of the human choline transporter (hCHT) in Xenopus oocytes: the proton inactivation hypothesis of hCHT in synaptic vesicles. J Neurosci 2006; 26:9851-9. [PMID: 17005849 PMCID: PMC6674471 DOI: 10.1523/jneurosci.1862-06.2006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The recent cloning of the human choline transporter (hCHT) has allowed its expression in Xenopus laevis oocytes and the simultaneous measurement of choline transport and choline-induced current under voltage clamp. hCHT currents and choline transport are evident in cRNA-injected oocytes and significantly enhanced by the hCHT trafficking mutant L530A/V531A. The charge/choline ratio of hCHT varies from 10e/choline at -80 mV to 3e/choline at -20 mV, in contrast with the reported fixed stoichiometry of the Na+-coupled glucose transporter in the same gene family. Ion substitution shows that the choline uptake and choline-induced current are Na+ and Cl- dependent; however, the reversal potential of the induced current suggests a Na+-selective mechanism, consigning Cl- to a regulatory role rather than a coupled, cotransported-ion role. The hCHT-specific inhibitor hemicholinium-3 (HC-3) blocks choline uptake and choline-induced current; in addition, HC-3 alone reveals a constitutive, depolarizing leak current through hCHT. We show that external protons reduce hCHT current, transport, and binding with a similar pKa of 7.4, suggesting proton titration of residue(s) that support choline binding and transport. Given the localization of the choline transporter to synaptic vesicles, we propose that proton inactivation of hCHT prevents acetylcholine and proton leakage from the acidic interior of cholinergic synaptic vesicles. This mechanism would allow cholinergic, activity-triggered delivery of silent choline transporters to the plasma membrane, in which normal pH would reactivate the transporters for choline uptake and subsequent acetylcholine synthesis.
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Affiliation(s)
- Hideki Iwamoto
- Department of Pharmacology and Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville Tennessee 37232-8548
| | - Randy D. Blakely
- Department of Pharmacology and Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville Tennessee 37232-8548
| | - Louis J. De Felice
- Department of Pharmacology and Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville Tennessee 37232-8548
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Prado VF, Martins-Silva C, de Castro BM, Lima RF, Barros DM, Amaral E, Ramsey AJ, Sotnikova TD, Ramirez MR, Kim HG, Rossato JI, Koenen J, Quan H, Cota VR, Moraes MFD, Gomez MV, Guatimosim C, Wetsel WC, Kushmerick C, Pereira GS, Gainetdinov RR, Izquierdo I, Caron MG, Prado MAM. Mice Deficient for the Vesicular Acetylcholine Transporter Are Myasthenic and Have Deficits in Object and Social Recognition. Neuron 2006; 51:601-12. [PMID: 16950158 DOI: 10.1016/j.neuron.2006.08.005] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2006] [Revised: 06/27/2006] [Accepted: 08/03/2006] [Indexed: 01/19/2023]
Abstract
An important step for cholinergic transmission involves the vesicular storage of acetylcholine (ACh), a process mediated by the vesicular acetylcholine transporter (VAChT). In order to understand the physiological roles of the VAChT, we developed a genetically altered strain of mice with reduced expression of this transporter. Heterozygous and homozygous VAChT knockdown mice have a 45% and 65% decrease in VAChT protein expression, respectively. VAChT deficiency alters synaptic vesicle filling and affects ACh release. Whereas VAChT homozygous mutant mice demonstrate major neuromuscular deficits, VAChT heterozygous mice appear normal in that respect and could be used for analysis of central cholinergic function. Behavioral analyses revealed that aversive learning and memory are not altered in mutant mice; however, performance in cognitive tasks involving object and social recognition is severely impaired. These observations suggest a critical role of VAChT in the regulation of ACh release and physiological functions in the peripheral and central nervous system.
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Affiliation(s)
- Vania F Prado
- Departamento de Bioquímica-Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Avenida Antônio Carlos 6627, Belo Horizonte, MG 31270-901, Brazil
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31
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Shackman HM, Shou M, Cellar NA, Watson CJ, Kennedy RT. Microdialysis coupled on-line to capillary liquid chromatography with tandem mass spectrometry for monitoring acetylcholine in vivo. J Neurosci Methods 2006; 159:86-92. [PMID: 16876256 DOI: 10.1016/j.jneumeth.2006.06.020] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2006] [Revised: 06/23/2006] [Accepted: 06/26/2006] [Indexed: 12/01/2022]
Abstract
Capillary liquid chromatography-mass spectrometry (cLC-MS) was coupled on-line to microdialysis sampling to monitor endogenous acetylcholine (ACh) from the rodent brain. In vivo microdialysate sampled at 0.6 microL/min from the striatum of ketamine or chloral hydrate anesthetized rats was loaded onto a sample loop and then injected onto a approximately 5 cm long strong cation exchange (SCX) capillary column. A step gradient was used to separate the analyte from ionization suppressing salts contained in dialysate in 2.4 min. Sampling coupled on-line with cLC-MS allowed for high temporal resolution (data points at 2.4 min intervals), good reproducibility (10-15% relative standard deviation, R.S.D.), and sensitive limits of detection (0.04 nM or 8 amol injected). The method successfully monitored basal and stimulated levels (induced by increased K+ concentrations) of ACh from the anesthetized rat without necessitating perfusion of an acetylcholinesterase (AChE) inhibitor. Absolute and percent basal levels of ACh from rats receiving different anesthetics were also compared.
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Affiliation(s)
- Holly M Shackman
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
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Elwary SMA, Chavan B, Schallreuter KU. The vesicular acetylcholine transporter is present in melanocytes and keratinocytes in the human epidermis. J Invest Dermatol 2006; 126:1879-84. [PMID: 16763548 DOI: 10.1038/sj.jid.5700268] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The human epidermis holds the full machinery for cholinergic signal transduction. However, the presence of the vesicular transporter (vesicular acetylcholine (ACh) transporter (VAChT)) for both choline and ACh has never been shown in this compartment. The results of this study confirm the presence of VAChT in cutaneous nerves and in both epidermal melanocytes and keratinocytes as well as in their nuclei using immunofluorescence labelling in situ and in vitro, Western blot analysis of cellular and nuclear extracts and reverse transcription-PCR. These results underline that ACh/choline transport in the non-neuronal epidermis is no different from the neuronal pathway. However, the function of VAChT in the nucleus remains to be shown.
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Affiliation(s)
- Souna M A Elwary
- Clinical and Experimental Dermatology/Department of Biomedical Sciences, University of Bradford, Bradford, UK
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Serra CSM, Oliveira AC. Cisatracurium: myographical and electrophysiological studies in the isolated rat muscle. Fundam Clin Pharmacol 2006; 20:291-8. [PMID: 16671964 DOI: 10.1111/j.1472-8206.2006.00395.x] [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] [Indexed: 11/28/2022]
Abstract
Myographical and electrophysiological studies of cisatracurium were performed, in vitro, in the isolated sciatic nerve-extensor digitorum longus muscle preparation of the rat. Indirect twitches were generated at 0.1 Hz and tetanic contractions at 50 Hz. endplate potentials (epps) were generated in trains of 50 Hz. The electrophysiological variables used in the analysis of the epps were: amplitude of the first epp in the train, average amplitude of the 30 degrees to the 59 degrees epp in the train (epps-plateau), tetanic rundown (percent loss in amplitude of epps-plateau relative to the first epp in the train), quantal size and quantal content. The myographical results showed that the inhibitory concentration 50% (IC(50)) of cisatracurium for the blockade of twitches (0.48 microm) is 12 times its IC(50) for the induction of tetanic fade (0.04 microm). The electrophysiological results showed a concentration dependent decrease in the amplitudes of first epps in the trains and of epps-plateau in the two used concentrations (0.13 microm and 0.38 microm). The tetanic rundown was intensified only in the presence of the higher (0.38 microm) concentration of cisatracurium. In cisatracurium 0.13 microm (a concentration which affects only tetanic contractions, inducing their fade, while leaving the twitch unaffected) there was a decrease in the quantal content of the first epp and of epps-plateau in the train. In cisatracurium (0.38 microm), a concentration, which affects the twitch, there was a decrease of the quantal size and of quantal content of epps-plateau, but not of the quantal content of the first epp in the train. The results indicate that the fade of the tetanic contraction induced by cisatracurium at the concentration of 0.13 microm is entirely because of a pre-synaptic blocking effect while the decrease in the twitch induced by cisatracurium at the concentration of 0.38 microm is due to a post-synaptic blocking effect.
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Affiliation(s)
- C S M Serra
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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34
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Sharifzadeh M, Tavasoli M, Soodi M, Mohammadi-Eraghi S, Ghahremani MH, Roghani A. A time course analysis of cyclooxygenase-2 suggests a role in spatial memory retrieval in rats. Neurosci Res 2006; 54:171-9. [PMID: 16364481 DOI: 10.1016/j.neures.2005.11.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Revised: 10/22/2005] [Accepted: 11/10/2005] [Indexed: 11/21/2022]
Abstract
We previously showed a role for COX-2 in spatial memory retention. In that study we investigated the effects of post-training intrahippocampal infusion of celecoxib as a COX-2-specific inhibitor on spatial memory retention. Those infusions impaired spatial memory retention in the Morris water maze. In the present study a time course analysis of role of COX-2 in spatial memory was conducted. Here stereotaxic surgery was employed for the bilateral implantation of guide cannulas into the CA1 region of the hippocampus. Training trials were started after recovery of the animals. Immediately after last trial of training on third day, the celecoxib (0.1M) was infused bilaterally and testing trials, were performed 1, 2, 3, and 7 days after celecoxib infusions. Significant alterations were observed in escape latency and traveled distance 2 and 3 days after celecoxib infusions. The maximum impairment was obtained 72 h after the infusions. The data suggests that the effect of celecoxib is transient and that its effect on performance is likely caused by a problem in memory retrieval. Quantification analyses of the immunostaining of COX-2-containing neurons in the dorsal hippocampus show that celecoxib infusions significantly reduced (P<0.05) COX-2 immunoreactivity for the animals that were tested 3 days after the drug infusion. Results from the behavioral study along with the findings from immunohistochemical analyses suggest that COX-2 has significant role in spatial memory retrieval. Moreover, the memory deficits induced by the infusions continuously persists for 3 days.
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Affiliation(s)
- Mohammad Sharifzadeh
- Department of Toxicology and Pharmacology, Faculty of Pharmacy, Pharmaceutical Sciences and Medicinal Plants Research Centers, Tehran University of Medical Sciences, Tehran, Iran.
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Vasudevan M, Parle M. Pharmacological Evidence for the Potential of Daucus carota in the Management of Cognitive Dysfunctions. Biol Pharm Bull 2006; 29:1154-61. [PMID: 16755009 DOI: 10.1248/bpb.29.1154] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study was aimed at investigating the effects of Daucus carota seeds on cognitive functions, total serum cholesterol levels and brain cholinesterase activity in mice. The ethanolic extract of Daucus carota seeds (DCE) was administered orally in three doses (100, 200, 400 mg/kg) for seven successive days to different groups of young and aged mice. Elevated plus maze and passive avoidance apparatus served as the exteroceptive behavioral models for testing memory. Diazepam-, scopolamine- and ageing-induced amnesia served as the interoceptive behavioral models. DCE (200, 400 mg/kg, p.o.) showed significant improvement in memory scores of young and aged mice. The extent of memory improvement evoked by DCE was 23% at the dose of 200 mg/kg and 35% at the dose of 400 mg/kg in young mice using elevated plus maze. Similarly, significant improvements in memory scores were observed using passive avoidance apparatus and aged mice. Furthermore, DCE reversed the amnesia induced by scopolamine (0.4 mg/kg, i.p.) and diazepam (1 mg/kg, i.p.). Daucus carota extract (200, 400 mg/kg, p.o.) reduced significantly the brain acetylcholinesterase activity and cholesterol levels in young and aged mice. The extent of inhibition of brain cholinesterase activity evoked by DCE at the dose of 400 mg/kg was 22% in young and 19% in aged mice. There was a remarkable reduction in total cholesterol level as well, to the extent of 23% in young and 21% in aged animals with this dose of DCE. Therefore, DCE may prove to be a useful remedy for the management of cognitive dysfunctions on account of its multifarious beneficial effects such as, memory improving property, cholesterol lowering property and anticholinesterase activity.
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Affiliation(s)
- Mani Vasudevan
- Pharmacology Division, Department of Pharmaceutical Sciences, Guru Jambheshwar University (State Technical University), Hisar, Haryana, India
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36
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37
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Wenzel B, Sorger D, Heinitz K, Scheunemann M, Schliebs R, Steinbach J, Sabri O. Structural changes of benzylether derivatives of vesamicol and their influence on the binding selectivity to the vesicular acetylcholine transporter. Eur J Med Chem 2005; 40:1197-205. [PMID: 16095762 DOI: 10.1016/j.ejmech.2005.06.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2005] [Accepted: 06/20/2005] [Indexed: 11/29/2022]
Abstract
18F labelled vesamicol analogues, which bind to the vesicular acetylcholine transporter (VAChT) in central cholinergic nerve terminals, are expected to be potential radioligands for the visualisation of cholinergic transmission deficits via positron emission tomography (PET). In this report the regioselective synthesis of five novel vesamicol analogues as well as their in vitro binding properties to the VAChT are described. Beside having the 4-fluorobenzylether-substitution at the cyclohexyl ring as an unique structural feature, the new compounds are additionally modified at the phenyl and piperidine moiety of the vesamicol skeleton. The affinity and selectivity to the VAChT were analysed by competitive binding studies using tritium labelled radioligands. The VAChT affinities (Ki-values) of the novel compounds were estimated ranging between 7.8+/-3.5 nM and 161.6+/-17.3 nM, thus some of them are binding with higher affinity to the transporter than vesamicol. However, the compounds tested demonstrated also affinities to the sigma receptors sigma1 and sigma2 ranging between 4.1+/-1.5 nM and 327.5+/-75.9 nM. Nevertheless, these data provide the basis for future structure-binding-studies and further underline the potential and usefulness of vesamicol analogues for imaging of the VAChT.
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Affiliation(s)
- Barbara Wenzel
- Institut für Interdisziplinäre Isotopenforschung, Permoserstr. 15, 04318 Leipzig, Germany.
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38
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Sharifzadeh M, Tavasoli M, Naghdi N, Ghanbari A, Amini M, Roghani A. Post-training intrahippocampal infusion of nicotine prevents spatial memory retention deficits induced by the cyclo-oxygenase-2-specific inhibitor celecoxib in rats. J Neurochem 2005; 95:1078-90. [PMID: 16150053 DOI: 10.1111/j.1471-4159.2005.03454.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recently, we demonstrated that intrahippocampal infusion of the cyclo-oxygenase (COX)-2-specific inhibitor celecoxib impaired spatial memory retention in the Morris water maze. In the present work, we investigated the effects of nicotine, infused in the rat dorsal hippocampus several minutes after infusion of celecoxib, on memory retention in the Morris water maze. Rats were trained for 3 days; each day included two blocks, and each block contained four trials. Test trials were conducted 48 h after surgery. As expected, bilateral intrahippocampal infusion of celecoxib (19 microg/side; 0.1 m) increased escape latency and travel distance in rats, indicating significant impairment of spatial memory retention. We also examined the effects of bilateral infusion of nicotine (0.5, 1.0 and 2.0 microg/side) on memory retention. Infusion of 1 microg nicotine significantly decreased escape latency and travel distance but not swimming speed, compared with controls, suggesting memory retention enhancement by nicotine at this concentration. In separate experiments, bilateral infusion of nicotine, infused 5 min after 0.1 m (19 microg/side) celecoxib infusion, was associated with escape latency, travel distance and swimming speed profiles very similar to those in control animals. Brain tissue sections from several of these animals were subjected to immunohistochemical staining analysis with anti-COX-2 antibodies. Quantification analysis by optical density measurements showed that the celecoxib infusion reduced the immunoreactivity of COX-2-containing neurons in the CA1 area of the hippocampus compared with controls, although this reduction was not significant. However, infusion of a combination of celecoxib and nicotine significantly increased this immunoreactivity compared with levels in control and celecoxib-infused groups. These results suggest that nicotine prevented or reversed the adverse effects of celecoxib on spatial memory retention and protected or restored the immunostaining pattern of COX-2 neurons in the rat dorsal hippocampus.
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Affiliation(s)
- Mohammad Sharifzadeh
- Department of Toxicology and Pharmacology, School of Pharmacy, Pharmaceutical Sciences and Medicinal Plant Research Centers, University of Medical Sciences, Tehran, Iran.
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Hernandez CM, Terry AV. Repeated nicotine exposure in rats: effects on memory function, cholinergic markers and nerve growth factor. Neuroscience 2005; 130:997-1012. [PMID: 15652996 DOI: 10.1016/j.neuroscience.2004.10.006] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/04/2004] [Indexed: 11/17/2022]
Abstract
A decrease in the number of nicotinic-acetylcholine receptors (nAChRs) in the brain is thought to contribute to the cognitive dysfunction associated with diseases as diverse as Alzheimer's disease and schizophrenia. Interestingly, nicotine and similar compounds have been shown to enhance memory function and increase the expression of nAChRs and therefore, could have a therapeutic role in the aforementioned diseases. Nicotine has also been shown to exert positive effects on certain neurotrophins such as nerve growth factor (NGF), and therefore could play a role beyond mere symptomatic therapy. However, to date, comprehensive studies of nicotine's effects on the expression of specific acetylcholine (ACh) receptor subtypes, key cholinergic proteins (that are regulated by NGF) such as choline acetyltransferase (ChAT) and the vesicular ACh transporter (VAChT) are lacking. Studies to further investigate the effects of nicotine on NGF especially its high- and low-affinity receptors are also needed. In the present study, male Wistar rats exposed a relatively low dosage of nicotine (0.35 mg/kg every 12 h) for 14 days demonstrated improved memory performance (assessed in two separate water maze testing methods) when compared with controls. Autoradiographic experiments indicated that nicotine increased [3H]-epibatidine, [125I]-alpha-bungarotoxin and [3H]-AFDX384, but not [3H]-pirenzepine binding sites in several learning- and memory-related brain areas. The expression of ChAT, VAChT, as well as tropomyosin-receptor kinase A (TrkA) NGF receptors and phospho-TrK receptors was increased by nicotine in the hippocampus. No changes were observed in the levels of the NGF peptide or low affinity p75 neurotrophin receptors (p75NTR), however. These results suggest that repeated exposure to nicotine results in positive effects on central cholinergic markers and memory function, which may be mediated via effects on high-affinity NGF receptors.
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Affiliation(s)
- C M Hernandez
- Program in Clinical and Experimental Therapeutics, University of Georgia, College of Pharmacy, Department of Pharmacology and Toxicology, 1120 15th Street (CJ-1020), Medical College of Georgia, Augusta, GA 30912-2450, USA
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Borycz JA, Borycz J, Kubów A, Kostyleva R, Meinertzhagen IA. Histamine compartments of the Drosophila brain with an estimate of the quantum content at the photoreceptor synapse. J Neurophysiol 2005; 93:1611-9. [PMID: 15738275 DOI: 10.1152/jn.00894.2004] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Reliable estimates of the quantum size in histaminergic neurons are not available. We have exploited two unusual opportunities in the fly's (Drosophila melanogaster) visual system to make such determinations for histaminergic photoreceptor synapses: 1) the possibility to microdissect successively from whole fly heads freeze-dried in acetone: the compound eyes; the first optic neuropils, or lamina; and the rest of the brain; and 2) the uniform sheaves of lamina synaptic terminals of photoreceptors R1-R6. We used this organization to count scrupulously the numbers of 30-nm synaptic vesicles from electron micrographs of R1-R6 profiles, and from microdissections we determined the regional contents of histamine in the compound eye, lamina, and central brain. Total head histamine averages 1.98 ng of which 9% was lost after freeze-drying in acetone and a further 28% after the brain was microdissected. Of the remainder, 71% was in the eye and lamina. Assuming that histamine loss from the tissue occurred mostly by diffusion evenly distributed among all regions, the overall lamina content of the head would be 0.1935 ng before dissection. From published values for the volumes of the brain's compartments, the computed regional concentrations of histamine are highest in the lamina (4.35 mM) because of the terminals of R1-R6. The concentration in the retina is approximately 13% that in the lamina, suggesting that most histamine is vesicular. There are approximately 43,500 +/- 7,400 (SD) synaptic vesicles per terminal and, if all histamine is allocated equally and exclusively among these, the vesicle contents would be 858 +/- 304 x 10(-21) moles or approximately 5,000 +/- 1,800 (SD) molecules at an approximate concentration of 670 mM. These values are compared with the vesicle contents at synapses using acetylcholine and catecholamines.
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Affiliation(s)
- J A Borycz
- Life Sciences Centre, Dalhousie University, 1355 Oxford St., Halifax, Nova Scotia, Canada B3H 4J1
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Tinkler GP, Voytko ML. Estrogen modulates cognitive and cholinergic processes in surgically menopausal monkeys. Prog Neuropsychopharmacol Biol Psychiatry 2005; 29:423-31. [PMID: 15795051 DOI: 10.1016/j.pnpbp.2004.12.016] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/13/2004] [Indexed: 11/22/2022]
Abstract
Estrogen deficiency in postmenopausal women is associated with changes in physiological processes. The extent to which estrogen loss is associated with cognitive changes noted by postmenopausal women has been more difficult to determine for a variety of reasons. Primate models of menopause are now being used to determine the effects of estrogen loss and replacement on cognitive abilities and to investigate the neural mechanisms by which estrogen may influence cognitive function. The present report presents data from cognitive and neurobiological studies in surgically menopausal monkeys that have examined how estrogen loss and replacement may be affecting cognitive abilities and the cholinergic system; a neural system that is known to influence memory and attention function. These studies are indicating that visuospatial attention function is especially sensitive to estrogen states in young monkeys, but that multiple cognitive domains are sensitive to estrogen states in middle-aged monkeys. In addition, anatomical and functional imaging studies indicate that the primate cholinergic system is modulated by estrogen, and pharmacological studies demonstrate that estrogen uses cholinergic muscarinic receptors to influence visuospatial attention. These studies demonstrate that estrogen influences cognitive abilities in monkey models of menopause and the cholinergic system may be one of the mechanisms by which estrogen modulates cognitive function. Given the current unknowns and concerns regarding the use of hormone replacement therapy in postmenopausal women, continued studies in monkey models of menopause are especially needed to further elucidate the effects of estrogen on cognitive and neurobiological processes, with particular emphasis on studies in middle-aged monkeys, determining the optimal aspects of ERT regimens, and identifying the relationships between estrogen effects on cognitive and neurobiological function.
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Affiliation(s)
- Gregory Paul Tinkler
- Interdisciplinary Neuroscience Program, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
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42
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Sharifzadeh M, Sharifzadeh K, Naghdi N, Ghahremani MH, Roghani A. Posttraining intrahippocampal infusion of a protein kinase AII inhibitor impairs spatial memory retention in rats. J Neurosci Res 2005; 79:392-400. [PMID: 15622518 DOI: 10.1002/jnr.20358] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The role of protein kinase AII (PKA II) in spatial memory retention in male rats and its regulation of cholinergic gene expression were explored through the effects of intrahippocampal infusion of H-89, a selective PKA II inhibitor. Alterations in escape latency, travel distance, and swimming speed in a Morris water maze were measured. Animals were trained for 3 days; each day included two blocks, and each block contained four trials. Stereotaxic surgery was employed for the infusions after the last trial on the third day of training, and the animals were tested 48 hr after surgery. Bilateral intrahippocampal infusion of H-89 (2.5 or 5 microM) into the CA1 region generated significant alterations in escape latency and traveled distance but not swimming speed. The response was fairly dose dependent, and the maximal effect was obtained with 5 microM H-89. After behavioral testing, several of the infused animals were transcardially perfused and their brains removed. Brain tissue sections from these rats were subjected to immunohistochemical staining analysis with anticholine acetyltransferase (ChAT) antibodies. These analyses indicated that 5 microM H-89 infusions qualitatively reduced the density of ChAT-containing cholinergic nerve terminals in the dorsal hippocampus. The intrahippocampal infusions with 5 microM H-89 also caused an apparent reduction in the number of ChAT-containing neurons in the medial septum. Our results suggest that PKA II is involved in regulation of cholinergic gene expression and plays an important role in spatial memory retention in rats.
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Affiliation(s)
- Mohammad Sharifzadeh
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
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Sha D, Jin H, Kopke RD, Wu JY. Choline acetyltransferase: regulation and coupling with protein kinase and vesicular acetylcholine transporter on synaptic vesicles. Neurochem Res 2004; 29:199-207. [PMID: 14992279 DOI: 10.1023/b:nere.0000010449.05927.f9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Both the membrane-bound choline acetyltransferase (MChAT) and soluble ChAT (SChAT) were found to be activated by ATP-mediated protein phosphorylation. ATP activation of MChAT but not SChAT was found to depend on the integrity of proton gradient of synaptic vesicles because conditions disrupting the proton gradient also abolished the activation of MChAT by ATP. Among the kinases studied, Ca2+/calmodulin kinase II is most effective in activation of MChAT. Transport of ACh into synaptic vesicles by vesicular acetylcholine transporter (VAChT) is also proton gradient-dependent; therefore we proposed that there is a functional coupling between ACh synthesis and its packaging into synaptic vesicles. This notion is supported by the following findings: first, the newly synthesized [3H]-ACh from [3H]-choline was taken up much more efficiently than the pre-existing ACh; second, ATP-activation of MChAT was abolished when VAChT was inhibited by the specific inhibitor vesamicol; third, the activity of ChAT was found to be markedly increased when neurons are under depolarizing conditions.
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Affiliation(s)
- Di Sha
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, USA
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Nascimento DC, Serra CSM, Oliveira AC. Cellular mechanisms of atracurium-induced tetanic fade in the isolated rat muscle. Basic Clin Pharmacol Toxicol 2004; 95:9-14. [PMID: 15245570 DOI: 10.1111/j.1742-7843.2004.pto950103.x] [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: 11/30/2022]
Abstract
Although atracurium is a widely used neuromuscular blocker, we still lack knowledge regarding some of its cellular mechanisms of action. Thus, similar to other clinically used blockers atracurium induces, both in vivo and in vitro, fade of the tetanic contraction. However, the cellular mechanisms underlying this tetanic fade have never been systematically studied. In the present work these mechanisms were investigated in vitro. A sciatic nerve extensor digitorum longus muscle preparation of the rat was used. A combination of myographical and electrophysiological techniques was employed. Indirect twitches were evoked at 0.1 Hz and tetanic contractions at 50 Hz. Trains of end-plate potentials were evoked at a frequency of 50 Hz. The electrophysiological variables used in the analysis of the trains of end-plate potentials were: peak amplitude of the first end-plate potential in the train, peak amplitude of plateau end-plate potentials in the train, tetanic run-down of the end-plate potentials' train, quantal content of first and plateau end-plate potentials in the train, quantal size. In the myographical study atracurium, at a concentration of 2.4 microM, induced a complete fade of the tetanic contraction while only slightly affected the twitch. In the electrophysiological study atracurium, at the same 2.4 microM concentration, significantly decreased the amplitude of both first end-plate potentials in the train (control: 14.4 mV; atracurium: 3.2 mV) and plateau end-plate potentials (control: 10.8 mV; atracurium: 2.4 mV) and reinforced the tetanic run-down of the train of end-plate potentials, evaluated as the percent loss in amplitude of plateau end-plate potentials compared to first end-plate potentials in the trains (control: 25.2%; atracurium: 33.2%). Atracurium also significantly decreased the quantal content of first end-plate potentials in the train (control: 231; atracurium: 68), the quantal content of plateau end-plate potentials (control: 159; atracurium: 42) and the quantal size (control: 0.119 mV; atracurium: 0.075 mV). In relative terms the decrease in quantal content was about twice as large as the decrease in quantal size. This indicates that the fade of the tetanic contraction induced by atracurium (2.4 microM) is due to both pre- and postsynaptic blocking effects, the presynaptic one being stronger.
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Affiliation(s)
- Dejair C Nascimento
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo, Brazil
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Faundez V, Hartzell HC. Intracellular Chloride Channels: Determinants of Function in the Endosomal Pathway. Sci Signal 2004; 2004:re8. [PMID: 15150424 DOI: 10.1126/stke.2332004re8] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Endosomes, and related subcellular compartments, contain various Cl- channels in the ClC family. In this review, we describe the known roles of intracellular Cl- channels and also explore some of the functional implications of transmembrane Cl- flux in these organelles. Cl- influx acts to control intralumenal pH, both by shunting the effects of the proton pump on membrane potential and, possibly, through direct effects of Cl- on the proton pump. Changes in intralumenal pH likely help regulate membrane trafficking. We propose that changes in intralumenal Cl- concentration ([Cl-]) could theoretically play a direct role in regulating membrane trafficking and organellar function through effects on chloride-sensitive proteins in the vesicular membrane, which could transduce information about intralumenal [Cl-] to the outside of the vesicle and thereby recruit various signaling molecules. We present a model in which regulation of cytosolic [Cl-] and vesicular Cl- conductance could help control the amount or type of neurotransmitter stored in a particular population of synaptic vesicles.
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Affiliation(s)
- Victor Faundez
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
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Abstract
Over the last 15 years, a number of transporters that translocate organic cations were characterized functionally and also identified on the molecular level. Organic cations include endogenous compounds such as monoamine neurotransmitters, choline, and coenzymes, but also numerous drugs and xenobiotics. Some of the cloned organic cation transporters accept one main substrate or structurally similar compounds (oligospecific transporters), while others translocate a variety of structurally diverse organic cations (polyspecific transporters). This review provides a survey of cloned organic cation transporters and tentative models that illustrate how different types of organic cation transporters, expressed at specific subcellular sites in hepatocytes and renal proximal tubular cells, are assembled into an integrated functional framework. We briefly describe oligospecific Na(+)- and Cl(-)-dependent monoamine neurotransmitter transporters ( SLC6-family), high-affinity choline transporters ( SLC5-family), and high-affinity thiamine transporters ( SLC19-family), as well as polyspecific transporters that translocate some organic cations next to their preferred, noncationic substrates. The polyspecific cation transporters of the SLC22 family including the subtypes OCT1-3 and OCTN1-2 are presented in detail, covering the current knowledge about distribution, substrate specificity, and recent data on their electrical properties and regulation. Moreover, we discuss artificial and spontaneous mutations of transporters of the SLC22 family that provide novel insight as to the function of specific protein domains. Finally, we discuss the clinical potential of the increasing knowledge about polymorphisms and mutations in polyspecific organic cation transporters.
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Affiliation(s)
- H Koepsell
- Institut für Anatomie und Zellbiologie, Bayerischen Julius-Maximilians-Universität, Koellikerstr. 6, 97070 Würzburg, Germany.
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Eiden LE, Schäfer MKH, Weihe E, Schütz B. The vesicular amine transporter family (SLC18): amine/proton antiporters required for vesicular accumulation and regulated exocytotic secretion of monoamines and acetylcholine. Pflugers Arch 2004; 447:636-40. [PMID: 12827358 DOI: 10.1007/s00424-003-1100-5] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2003] [Revised: 04/28/2003] [Accepted: 04/28/2003] [Indexed: 12/25/2022]
Abstract
The vesicular amine transporters (VATs) are expressed as integral proteins of the lipid bilayer membrane of secretory vesicles in neuronal and endocrine cells. Their function is to allow the transport of acetylcholine (by the vesicular acetylcholine transporter VAChT; SLC18A3) and biogenic amines (by the vesicular monoamine transporters VMAT1 and VMAT2; SLC18A1 and SLC18A2) into secretory vesicles, which then discharge them into the extracellular space by exocytosis. Transport of positively charged amines by members of the SLC18 family in all cases utilizes an electrochemical gradient across the vesicular membrane established by proton pumping into the vesicle via a vacuolar ATPase; the amine is accumulated in the vesicle at the expense of the proton gradient, at a ratio of one translocated amine per two translocated protons. The members of the SLC18 family have become important histochemical markers for chemical coding in neuroendocrine tissues and cells. The structural basis of their remarkable ability to transport positively charged amines against a very large concentration gradient, as well as potential disease association with impaired transporter function and expression, are under intense investigation.
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Affiliation(s)
- Lee E Eiden
- Section on Molecular Neuroscience, Laboratory of Cellular and Molecular Regulation, National Institute of Mental Health, Building 36, Room 2A-11, 9000 Rockville Pike, Bethesda, MD 20892, USA.
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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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Kim MH, Lu M, Rogers G, Parsons S, Hersh LB. Specificity of the rat vesicular acetylcholine transporter. Neurochem Res 2003; 28:473-6. [PMID: 12675133 DOI: 10.1023/a:1022804903088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The protein kinase A-deficient PC12 cell line PC12A123.7 lacks both choline acetyltransferase and the vesicular acetylcholine transporter. This cell line has been used to establish a stably transfected cell line expressing recombinant rat vesicular acetylcholine transporter that is appropriately trafficked to small synaptic vesicles. Acetylcholine is transported by the rat vesicular acetylcholine transporter at a maximal rate of 1.45 nmol acetylcholine/min/mg protein and exhibits a Km for transport of 2.5 mM. The transporter binds vesamicol with a Kd of 7.5 nM. The ability of structural analogs of acetylcholine to inhibit both acetylcholine uptake and vesamicol binding was measured. The results demonstrate that like Torpedo vesicular acetylcholine transporter, the mammalian transporter can bind a diverse group of acetylcholine analogs.
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Affiliation(s)
- Myung-Hee Kim
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536-0084, USA
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Van der Kloot W. A chloride channel blocker reduces acetylcholine uptake into synaptic vesicles at the frog neuromuscular junction. Brain Res 2003; 961:287-9. [PMID: 12531496 DOI: 10.1016/s0006-8993(02)03954-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A key mechanism for loading acetylcholine (ACh(+)) into synaptic vesicles uses energy to transport H(+) into the vesicle interior and then exchanges H(+) for ACh(+). This mechanism requires anions to follow the H(+) into the vesicles to prevent the building up of an overwhelming electrical gradient across the vesicle membrane. Frog nerve-muscle preparations were treated with hypertonic solution in which sodium gluconate was the major constituent, which substantially increases the sizes of the quanta by increasing their ACh(+) content. The Cl(-) channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) antagonized the increases in quantal size, so it seems likely that Cl(-) follows H(+) to prevent the buildup of a potential gradient across the vesicular membrane.
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