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Monteil A, Guérineau NC, Gil-Nagel A, Parra-Diaz P, Lory P, Senatore A. New insights into the physiology and pathophysiology of the atypical sodium leak channel NALCN. Physiol Rev 2024; 104:399-472. [PMID: 37615954 DOI: 10.1152/physrev.00014.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 07/13/2023] [Accepted: 08/15/2023] [Indexed: 08/25/2023] Open
Abstract
Cell excitability and its modulation by hormones and neurotransmitters involve the concerted action of a large repertoire of membrane proteins, especially ion channels. Unique complements of coexpressed ion channels are exquisitely balanced against each other in different excitable cell types, establishing distinct electrical properties that are tailored for diverse physiological contributions, and dysfunction of any component may induce a disease state. A crucial parameter controlling cell excitability is the resting membrane potential (RMP) set by extra- and intracellular concentrations of ions, mainly Na+, K+, and Cl-, and their passive permeation across the cell membrane through leak ion channels. Indeed, dysregulation of RMP causes significant effects on cellular excitability. This review describes the molecular and physiological properties of the Na+ leak channel NALCN, which associates with its accessory subunits UNC-79, UNC-80, and NLF-1/FAM155 to conduct depolarizing background Na+ currents in various excitable cell types, especially neurons. Studies of animal models clearly demonstrate that NALCN contributes to fundamental physiological processes in the nervous system including the control of respiratory rhythm, circadian rhythm, sleep, and locomotor behavior. Furthermore, dysfunction of NALCN and its subunits is associated with severe pathological states in humans. The critical involvement of NALCN in physiology is now well established, but its study has been hampered by the lack of specific drugs that can block or agonize NALCN currents in vitro and in vivo. Molecular tools and animal models are now available to accelerate our understanding of how NALCN contributes to key physiological functions and the development of novel therapies for NALCN channelopathies.
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Affiliation(s)
- Arnaud Monteil
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- LabEx "Ion Channel Science and Therapeutics," Montpellier, France
- Department of Physiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Nathalie C Guérineau
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- LabEx "Ion Channel Science and Therapeutics," Montpellier, France
| | - Antonio Gil-Nagel
- Department of Neurology, Epilepsy Program, Hospital Ruber Internacional, Madrid, Spain
| | - Paloma Parra-Diaz
- Department of Neurology, Epilepsy Program, Hospital Ruber Internacional, Madrid, Spain
| | - Philippe Lory
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
- LabEx "Ion Channel Science and Therapeutics," Montpellier, France
| | - Adriano Senatore
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
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2
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Nuñez KM, Catalano JL, Scaplen KM, Kaun KR. Ethanol Behavioral Responses in Drosophila. Cold Spring Harb Protoc 2023; 2023:719-24. [PMID: 37019606 PMCID: PMC10551053 DOI: 10.1101/pdb.top107887] [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: 04/07/2023]
Abstract
Drosophila melanogaster is a powerful genetic model for investigating the mechanisms underlying ethanol-induced behaviors, metabolism, and preference. Ethanol-induced locomotor activity is especially useful for understanding the mechanisms by which ethanol acutely affects the brain and behavior. Ethanol-induced locomotor activity is characterized by hyperlocomotion and subsequent sedation with increased exposure duration or concentration. Locomotor activity is an efficient, easy, robust, and reproducible behavioral screening tool for identifying underlying genes and neuronal circuits as well as investigating genetic and molecular pathways. We introduce a detailed protocol for performing experiments investigating how volatilized ethanol affects locomotor activity using the fly Group Activity Monitor (flyGrAM). We introduce installation, implementation, data collection, and subsequent data-analysis methods for investigating how volatilized stimuli affect activity. We also introduce a procedure for how to optogenetically probe neuronal activity to identify the neural mechanisms underlying locomotor activity.
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Affiliation(s)
- Kavin M Nuñez
- Molecular Pharmacology and Physiology Graduate Program, Brown University, Providence, Rhode Island 02912, USA
| | - Jamie L Catalano
- Molecular Pharmacology and Physiology Graduate Program, Brown University, Providence, Rhode Island 02912, USA
| | - Kristin M Scaplen
- Department of Psychology, Bryant University, Smithfield, Rhode Island 02917, USA
- Center for Health and Behavioral Sciences, Bryant University, Smithfield, Rhode Island 02917, USA
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912, USA
| | - Karla R Kaun
- Department of Neuroscience, Brown University, Providence, Rhode Island 02912, USA
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He J, Li B, Han S, Zhang Y, Liu K, Yi S, Liu Y, Xiu M. Drosophila as a Model to Study the Mechanism of Nociception. Front Physiol 2022; 13:854124. [PMID: 35418874 PMCID: PMC8996152 DOI: 10.3389/fphys.2022.854124] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 02/28/2022] [Indexed: 12/15/2022] Open
Abstract
Nociception refers to the process of encoding and processing noxious stimuli, which allow animals to detect and avoid potentially harmful stimuli. Several types of stimuli can trigger nociceptive sensory transduction, including thermal, noxious chemicals, and harsh mechanical stimulation that depend on the corresponding nociceptors. In view of the high evolutionary conservation of the mechanisms that govern nociception from Drosophila melanogaster to mammals, investigation in the fruit fly Drosophila help us understand how the sensory nervous system works and what happen in nociception. Here, we present an overview of currently identified conserved genetics of nociception, the nociceptive sensory neurons responsible for detecting noxious stimuli, and various assays for evaluating different nociception. Finally, we cover development of anti-pain drug using fly model. These comparisons illustrate the value of using Drosophila as model for uncovering nociception mechanisms, which are essential for identifying new treatment goals and developing novel analgesics that are applicable to human health.
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Affiliation(s)
- Jianzheng He
- Provincial-Level Key Laboratory for Molecular Medicine of Major Diseases and the Prevention and Treatment with Traditional Chinese Medicine Research in Gansu Colleges and University, Gansu University of Chinese Medicine, Lanzhou, China
- College of Basic Medicine, Gansu University of Chinese Medicine, Lanzhou, China
- Key Laboratory for Transfer of Dunhuang Medicine at the Provincial and Ministerial Level, Gansu University of Chinese Medicine, Lanzhou, China
| | - Botong Li
- Provincial-Level Key Laboratory for Molecular Medicine of Major Diseases and the Prevention and Treatment with Traditional Chinese Medicine Research in Gansu Colleges and University, Gansu University of Chinese Medicine, Lanzhou, China
- College of Basic Medicine, Gansu University of Chinese Medicine, Lanzhou, China
| | - Shuzhen Han
- Provincial-Level Key Laboratory for Molecular Medicine of Major Diseases and the Prevention and Treatment with Traditional Chinese Medicine Research in Gansu Colleges and University, Gansu University of Chinese Medicine, Lanzhou, China
- College of Basic Medicine, Gansu University of Chinese Medicine, Lanzhou, China
| | - Yuan Zhang
- Provincial-Level Key Laboratory for Molecular Medicine of Major Diseases and the Prevention and Treatment with Traditional Chinese Medicine Research in Gansu Colleges and University, Gansu University of Chinese Medicine, Lanzhou, China
- College of Basic Medicine, Gansu University of Chinese Medicine, Lanzhou, China
| | - Kai Liu
- College of Integrated Traditional Chinese and Western Medicine, Gansu University of Chinese Medicine, Lanzhou, China
| | - Simeng Yi
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing, China
| | - Yongqi Liu
- Provincial-Level Key Laboratory for Molecular Medicine of Major Diseases and the Prevention and Treatment with Traditional Chinese Medicine Research in Gansu Colleges and University, Gansu University of Chinese Medicine, Lanzhou, China
- Key Laboratory for Transfer of Dunhuang Medicine at the Provincial and Ministerial Level, Gansu University of Chinese Medicine, Lanzhou, China
- *Correspondence: Yongqi Liu,
| | - Minghui Xiu
- Provincial-Level Key Laboratory for Molecular Medicine of Major Diseases and the Prevention and Treatment with Traditional Chinese Medicine Research in Gansu Colleges and University, Gansu University of Chinese Medicine, Lanzhou, China
- Key Laboratory for Transfer of Dunhuang Medicine at the Provincial and Ministerial Level, Gansu University of Chinese Medicine, Lanzhou, China
- College of Public Health, Gansu University of Chinese Medicine, Lanzhou, China
- Minghui Xiu,
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Syntaxin1A Neomorphic Mutations Promote Rapid Recovery from Isoflurane Anesthesia in Drosophila melanogaster. Anesthesiology 2020; 131:555-568. [PMID: 31356232 DOI: 10.1097/aln.0000000000002850] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
BACKGROUND Mutations in the presynaptic protein syntaxin1A modulate general anesthetic effects in vitro and in vivo. Coexpression of a truncated syntaxin1A protein confers resistance to volatile and intravenous anesthetics, suggesting a target mechanism distinct from postsynaptic inhibitory receptor processes. Hypothesizing that recovery from anesthesia may involve a presynaptic component, the authors tested whether syntaxin1A mutations facilitated recovery from isoflurane anesthesia in Drosophila melanogaster. METHODS A truncated syntaxin1A construct was expressed in Drosophila neurons. The authors compared effects on isoflurane induction versus recovery in syntaxin1A mutant animals by probing behavioral responses to mechanical stimuli. The authors also measured synaptic responses from the larval neuromuscular junction using sharp intracellular recordings, and performed Western blots to determine whether the truncated syntaxin1A is associated with presynaptic core complexes. RESULTS Drosophila expressing a truncated syntaxin1A (syx, n = 40) were resistant to isoflurane induction for a behavioral responsiveness endpoint (ED50 0.30 ± 0.01% isoflurane, P < 0.001) compared with control (0.240 ± 0.002% isoflurane, n = 40). Recovery from isoflurane anesthesia was also faster, with syx-expressing flies showing greater levels of responsiveness earlier in recovery (reaction proportion 0.66 ± 0.48, P < 0.001, n = 68) than controls (0.22 ± 0.42, n = 68 and 0.33 ± 0.48, n = 66). Measuring excitatory junction potentials of larvae coexpressing the truncated syntaxin1A protein showed a greater recovery of synaptic function, compared with controls (17.39 ± 3.19 mV and 10.29 ± 4.88 mV, P = 0.014, n = 8 for both). The resistance-promoting truncated syntaxin1A was not associated with presynaptic core complexes, in the presence or absence of isoflurane anesthesia. CONCLUSIONS The same neomorphic syntaxin1A mutation that confers isoflurane resistance in cell culture and nematodes also produces isoflurane resistance in Drosophila. Resistance in Drosophila is, however, most evident at the level of recovery from anesthesia, suggesting that the syntaxin1A target affects anesthesia maintenance and recovery processes rather than induction. The absence of truncated syntaxin1A from the presynaptic complex suggests that the resistance-promoting effect of this molecule occurs before core complex formation.
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FUNATO H. Forward genetic approach for behavioral neuroscience using animal models. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2020; 96:10-31. [PMID: 31932526 PMCID: PMC6974404 DOI: 10.2183/pjab.96.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 10/18/2019] [Indexed: 06/10/2023]
Abstract
Forward genetics is a powerful approach to understand the molecular basis of animal behaviors. Fruit flies were the first animal to which this genetic approach was applied systematically and have provided major discoveries on behaviors including sexual, learning, circadian, and sleep-like behaviors. The development of different classes of model organism such as nematodes, zebrafish, and mice has enabled genetic research to be conducted using more-suitable organisms. The unprecedented success of forward genetic approaches was the identification of the transcription-translation negative feedback loop composed of clock genes as a fundamental and conserved mechanism of circadian rhythm. This approach has now expanded to sleep/wakefulness in mice. A conventional strategy such as dominant and recessive screenings can be modified with advances in DNA sequencing and genome editing technologies.
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Affiliation(s)
- Hiromasa FUNATO
- Department of Anatomy, Faculty of Medicine, Toho University, Tokyo, Japan
- International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Ibaraki, Japan
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Abstract
It is difficult to study the genetics and molecular mechanisms of anesthesia in humans. Fortunately, the genetic approaches in model organisms can, and have, led to profound insights as to the targets of anesthetics. In turn, the organization of these putative targets into meaningful pathways has begun to elucidate the mechanisms of action of these agents. However, it is important to first appreciate the strengths, and limitations, of genetic approaches to understand the anesthetic action. Here we compare the commonly used genetic model organisms, various anesthetic endpoints, and different modes of genetic screens. Coupled with the more specific data presented in subsequent chapters, this chapter places those results in a framework with which to analyze the discoveries across organisms and eventually extend the resulting models to humans.
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7
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Karunanithi S, Troup M, van Swinderen B. Using Drosophila to Understand General Anesthesia: From Synapses to Behavior. Methods Enzymol 2018; 602:153-176. [PMID: 29588027 DOI: 10.1016/bs.mie.2018.02.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Investigating mechanisms of general anesthesia requires access to multiple levels of neuronal function, from effects at individual synapses to responses in behaving animals. Drosophila melanogaster provides an excellent model to test different theories for general anesthesia because it offers robust methods for testing local as well as global target processes, in an animal that is similarly impacted by these diverse drugs as humans. Here, we outline methods to quantify two such endpoints, neurotransmission and behavioral responsiveness, focusing on the intravenous drug propofol.
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Affiliation(s)
- Shanker Karunanithi
- Queensland Brain Institute, The University of Queensland, St Lucia, QLD, Australia; School of Medical Science and Menzies Health Institute Queensland, Griffith University Gold Coast Campus, Gold Coast, QLD, Australia
| | - Michael Troup
- Queensland Brain Institute, The University of Queensland, St Lucia, QLD, Australia
| | - Bruno van Swinderen
- Queensland Brain Institute, The University of Queensland, St Lucia, QLD, Australia.
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8
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Olufs ZPG, Loewen CA, Ganetzky B, Wassarman DA, Perouansky M. Genetic variability affects absolute and relative potencies and kinetics of the anesthetics isoflurane and sevoflurane in Drosophila melanogaster. Sci Rep 2018; 8:2348. [PMID: 29402974 PMCID: PMC5799260 DOI: 10.1038/s41598-018-20720-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 01/24/2018] [Indexed: 01/12/2023] Open
Abstract
Genetic variability affects the response to numerous xenobiotics but its role in the clinically-observed irregular responses to general anesthetics remains uncertain. To investigate the pharmacogenetics of volatile general anesthetics (VGAs), we developed a Serial Anesthesia Array apparatus to expose multiple Drosophila melanogaster samples to VGAs and behavioral assays to determine pharmacokinetic and pharmacodynamic properties of VGAs. We studied the VGAs isoflurane and sevoflurane in four wild type strains from the Drosophila Genetic Reference Panel, two commonly used laboratory strains (Canton S and w 1118 ), and a mutant in Complex I of the mitochondrial electron transport chain (ND23 60114 ). In all seven strains, isoflurane was more potent than sevoflurane, as predicted by their relative lipid solubilities, and emergence from isoflurane was slower than from sevoflurane, reproducing cardinal pharmacokinetic and pharmacodynamic properties in mammals. In addition, ND23 60114 flies were more sensitive to both agents, as observed in worms, mice, and humans carrying Complex I mutations. Moreover, we found substantial variability among the fly strains both in absolute and in relative pharmacokinetic and pharmacodynamic profiles of isoflurane and sevoflurane. These data indicate that naturally occurring genetic variations measurably influence cardinal pharmacologic properties of VGAs and that flies can be used to identify relevant genetic variations.
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Affiliation(s)
- Zachariah P G Olufs
- Department of Anesthesiology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Carin A Loewen
- Department of Genetics, College of Agriculture and Life Sciences, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Barry Ganetzky
- Department of Genetics, College of Agriculture and Life Sciences, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - David A Wassarman
- Department of Medical Genetics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Misha Perouansky
- Department of Anesthesiology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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9
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Zalucki O, van Swinderen B. What is unconsciousness in a fly or a worm? A review of general anesthesia in different animal models. Conscious Cogn 2016; 44:72-88. [PMID: 27366985 DOI: 10.1016/j.concog.2016.06.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 05/31/2016] [Accepted: 06/20/2016] [Indexed: 12/14/2022]
Abstract
All animals are rendered unresponsive by general anesthetics. In humans, this is observed as a succession of endpoints from memory loss to unconsciousness to immobility. Across animals, anesthesia endpoints such as loss of responsiveness or immobility appear to require significantly different drug concentrations. A closer examination in key model organisms such as the mouse, fly, or the worm, uncovers a trend: more complex behaviors, either requiring several sub-behaviors, or multiple neural circuits working together, are more sensitive to volatile general anesthetics. This trend is also evident when measuring neural correlates of general anesthesia. Here, we review this complexity hypothesis in humans and model organisms, and attempt to reconcile these findings with the more recent view that general anesthetics potentiate endogenous sleep pathways in most animals. Finally, we propose a presynaptic mechanism, and thus an explanation for how these drugs might compromise a succession of brain functions of increasing complexity.
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Affiliation(s)
- Oressia Zalucki
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Bruno van Swinderen
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia.
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10
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Are Some Fungal Volatile Organic Compounds (VOCs) Mycotoxins? Toxins (Basel) 2015; 7:3785-804. [PMID: 26402705 PMCID: PMC4591661 DOI: 10.3390/toxins7093785] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2015] [Revised: 08/28/2015] [Accepted: 08/31/2015] [Indexed: 01/07/2023] Open
Abstract
Volatile organic compounds (VOCs) are carbon-compounds that easily evaporate at room temperature. Toxins are biologically produced poisons; mycotoxins are those toxins produced by microscopic fungi. All fungi emit blends of VOCs; the qualitative and quantitative composition of these volatile blends varies with the species of fungus and the environmental situation in which the fungus is grown. These fungal VOCs, produced as mixtures of alcohols, aldehydes, acids, ethers, esters, ketones, terpenes, thiols and their derivatives, are responsible for the characteristic moldy odors associated with damp indoor spaces. There is increasing experimental evidence that some of these VOCs have toxic properties. Laboratory tests in mammalian tissue culture and Drosophila melanogaster have shown that many single VOCs, as well as mixtures of VOCs emitted by growing fungi, have toxic effects. This paper describes the pros and cons of categorizing toxigenic fungal VOCs as mycotoxins, uses genomic data to expand on the definition of mycotoxin, and summarizes some of the linguistic and other conventions that can create barriers to communication between the scientists who study VOCs and those who study toxins. We propose that "volatoxin" might be a useful term to describe biogenic volatile compounds with toxigenic properties.
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Zalucki O, Day R, Kottler B, Karunanithi S, van Swinderen B. Behavioral and electrophysiological analysis of general anesthesia in 3 background strains of Drosophila melanogaster. Fly (Austin) 2015; 9:7-15. [PMID: 26267354 DOI: 10.1080/19336934.2015.1072663] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
General anesthetics achieve behavioral unresponsiveness via a mechanism that is incompletely understood. The study of genetic model systems such as the fruit fly Drosophila melanogaster is crucial to advancing our understanding of how anesthetic drugs render animals unresponsive. Previous studies have shown that wild-type control strains differ significantly in their sensitivity to general anesthetics, which potentially introduces confounding factors for comparing genetic mutations placed on these wild-type backgrounds. Here, we examined a variety of behavioral and electrophysiological endpoints in Drosophila, in both adult and larval animals. We characterized these endpoints in 3 commonly used fly strains: wild-type Canton Special (CS), and 2 commonly used white-eyed strains, isoCJ1 and w(1118). We found that CS and isoCJ1 show remarkably similar sensitivity to isoflurane across a variety of behavioral and electrophysiological endpoints. In contrast, w(1118) is resistant to isoflurane compared to the other 2 strains at both the adult and larval stages. This resistance is however not reflected at the level of neurotransmitter release at the larval neuromuscular junction (NMJ). This suggests that the w(1118) strain harbors another mutation that produces isoflurane resistance, by acting on an arousal pathway that is most likely preserved between larval and adult brains. This mutation probably also affects sleep, as marked differences between isoCJ1 and w(1118) have also recently been found for behavioral responsiveness and sleep intensity measures.
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Affiliation(s)
- Oressia Zalucki
- a Queensland Brain Institute; The University of Queensland ; Brisbane , Queensland , Australia
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12
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Abstract
We show that the general anesthetics xenon, sulfur hexafluoride, nitrous oxide, and chloroform cause rapid increases of different magnitude and time course in the electron spin content of Drosophila. With the exception of CHCl3, these changes are reversible. Anesthetic-resistant mutant strains of Drosophila exhibit a different pattern of spin responses to anesthetic. In two such mutants, the spin response to CHCl3 is absent. We propose that these spin changes are caused by perturbation of the electronic structure of proteins by general anesthetics. Using density functional theory, we show that general anesthetics perturb and extend the highest occupied molecular orbital of a nine-residue α-helix. The calculated perturbations are qualitatively in accord with the Meyer-Overton relationship and some of its exceptions. We conclude that there may be a connection between spin, electron currents in cells, and the functioning of the nervous system.
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13
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Cochet-Bissuel M, Lory P, Monteil A. The sodium leak channel, NALCN, in health and disease. Front Cell Neurosci 2014; 8:132. [PMID: 24904279 PMCID: PMC4033012 DOI: 10.3389/fncel.2014.00132] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 04/28/2014] [Indexed: 12/12/2022] Open
Abstract
Ion channels are crucial components of cellular excitability and are involved in many neurological diseases. This review focuses on the sodium leak, G protein-coupled receptors (GPCRs)-activated NALCN channel that is predominantly expressed in neurons where it regulates the resting membrane potential and neuronal excitability. NALCN is part of a complex that includes not only GPCRs, but also UNC-79, UNC-80, NLF-1 and src family of Tyrosine kinases (SFKs). There is growing evidence that the NALCN channelosome critically regulates its ion conduction. Both in mammals and invertebrates, animal models revealed an involvement in many processes such as locomotor behaviors, sensitivity to volatile anesthetics, and respiratory rhythms. There is also evidence that alteration in this NALCN channelosome can cause a wide variety of diseases. Indeed, mutations in the NALCN gene were identified in Infantile Neuroaxonal Dystrophy (INAD) patients, as well as in patients with an Autosomal Recessive Syndrome with severe hypotonia, speech impairment, and cognitive delay. Deletions in NALCN gene were also reported in diseases such as 13q syndrome. In addition, genes encoding NALCN, NLF- 1, UNC-79, and UNC-80 proteins may be susceptibility loci for several diseases including bipolar disorder, schizophrenia, Alzheimer's disease, autism, epilepsy, alcoholism, cardiac diseases and cancer. Although the physiological role of the NALCN channelosome is poorly understood, its involvement in human diseases should foster interest for drug development in the near future. Toward this goal, we review here the current knowledge on the NALCN channelosome in physiology and diseases.
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Affiliation(s)
- Maud Cochet-Bissuel
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, Universités Montpellier 1&2 Montpellier, France ; INSERM, U 661 Montpellier, France ; LabEx 'Ion Channel Science and Therapeutics' Montpellier, France
| | - Philippe Lory
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, Universités Montpellier 1&2 Montpellier, France ; INSERM, U 661 Montpellier, France ; LabEx 'Ion Channel Science and Therapeutics' Montpellier, France
| | - Arnaud Monteil
- Institut de Génomique Fonctionnelle, CNRS UMR 5203, Universités Montpellier 1&2 Montpellier, France ; INSERM, U 661 Montpellier, France ; LabEx 'Ion Channel Science and Therapeutics' Montpellier, France
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14
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van Swinderen B, Kottler B. Explaining general anesthesia: a two-step hypothesis linking sleep circuits and the synaptic release machinery. Bioessays 2014; 36:372-81. [PMID: 24449137 DOI: 10.1002/bies.201300154] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Several general anesthetics produce their sedative effect by activating endogenous sleep pathways. We propose that general anesthesia is a two-step process targeting sleep circuits at low doses, and synaptic release mechanisms across the entire brain at the higher doses required for surgery. Our hypothesis synthesizes data from a variety of model systems, some which require sleep (e.g. rodents and adult flies) and others that probably do not sleep (e.g. adult nematodes and cultured cell lines). Non-sleeping systems can be made insensitive (or hypersensitive) to some anesthetics by modifying a single pre-synaptic protein, syntaxin1A. This suggests that the synaptic release machinery, centered on the highly conserved SNARE complex, is an important target of general anesthetics in all animals. A careful consideration of SNARE architecture uncovers a potential mechanism for general anesthesia, which may be the primary target in animals that do not sleep, but a secondary target in animals that sleep.
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Affiliation(s)
- Bruno van Swinderen
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
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15
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Dawson AG, Heidari P, Gadagkar SR, Murray MJ, Call GB. An airtight approach to the inebriometer: from construction to application with volatile anesthetics. Fly (Austin) 2013; 7:112-7. [PMID: 23579237 DOI: 10.4161/fly.24142] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The mechanism by which inhaled anesthetics work is not fully understood, although they have been extensively used. Much research has been done showing the likelihood that there is more than one pathway or mechanism of action. A long-term goal of our laboratory is to decipher these mechanisms using Drosophila melanogaster, an excellent model organism for this purpose. In order to do this, we have modified and constructed an apparatus called the inebriometer to quantitatively analyze the response of flies to inhaled anesthetics. While the inebriometer is not new to the fly community, our updated design provides a relatively low-labor, high-throughput means for performing screens in search of genes involved in the anesthetic mechanism. Here we describe our construction of an airtight inebriometer that we have designed for this purpose. We also provide data that validates this apparatus and establishes a procedure for its use.
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Affiliation(s)
- Adam G Dawson
- Arizona College of Osteopathic Medicine, Midwestern University, Glendale, AZ, USA
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16
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Burg ED, Langan ST, Nash HA. Drosophila social clustering is disrupted by anesthetics and in narrow abdomen ion channel mutants. GENES BRAIN AND BEHAVIOR 2013; 12:338-47. [PMID: 23398613 DOI: 10.1111/gbb.12025] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 12/06/2012] [Accepted: 02/05/2013] [Indexed: 12/11/2022]
Abstract
Members of many species tend to congregate, a behavioral strategy known as local enhancement. Selective advantages of local enhancement range from efficient use of resources to defense from predators. While previous studies have examined many types of social behavior in fruit flies, few have specifically investigated local enhancement. Resource-independent local enhancement (RILE) has recently been described in the fruit fly using a measure called social space index (SSI), although the neural mechanisms remain unknown. Here, we analyze RILE of Drosophila under conditions that allow us to elucidate its neural mechanisms. We have investigated the effects of general volatile anesthetics, compounds that compromise higher order functioning of the type typically required for responding to social cues. We exposed Canton-S flies to non-immobilizing concentrations of halothane and found that flies had a significantly decreased SSI compared with flies tested in air. Narrow abdomen (na) mutants, which display altered responses to anesthetics in numerous behavioral assays, also have a significantly reduced SSI, an effect that was fully reversed by restoring expression of na by driving a UAS-NA rescue construct with NA-GAL4. We found that na expression in cholinergic neurons fully rescued the behavioral defect, whereas expression of na in glutamatergic neurons did so only partially. Our results also suggest a role for na expression in the mushroom bodies (MBs), as suppressing na expression in the MBs of NA-GAL4 rescue flies diminishes SSI. Our data indicate that RILE, a simple behavioral strategy, requires complex neural processing.
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Affiliation(s)
- E D Burg
- Section on Neural Function, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA.
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Senatore A, Monteil A, van Minnen J, Smit AB, Spafford JD. NALCN ion channels have alternative selectivity filters resembling calcium channels or sodium channels. PLoS One 2013; 8:e55088. [PMID: 23383067 PMCID: PMC3557258 DOI: 10.1371/journal.pone.0055088] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 12/19/2012] [Indexed: 11/17/2022] Open
Abstract
NALCN is a member of the family of ion channels with four homologous, repeat domains that include voltage-gated calcium and sodium channels. NALCN is a highly conserved gene from simple, extant multicellular organisms without nervous systems such as sponges and placozoans and mostly remains a single gene compared to the calcium and sodium channels which diversified into twenty genes in humans. The single NALCN gene has alternatively-spliced exons at exons 15 or exon 31 that splices in novel selectivity filter residues that resemble calcium channels (EEEE) or sodium channels (EKEE or EEKE). NALCN channels with alternative calcium, (EEEE) and sodium, (EKEE or EEKE) -selective pores are conserved in simple bilaterally symmetrical animals like flatworms to non-chordate deuterostomes. The single NALCN gene is limited as a sodium channel with a lysine (K)-containing pore in vertebrates, but originally NALCN was a calcium-like channel, and evolved to operate as both a calcium channel and sodium channel for different roles in many invertebrates. Expression patterns of NALCN-EKEE in pond snail, Lymnaea stagnalis suggest roles for NALCN in secretion, with an abundant expression in brain, and an up-regulation in secretory organs of sexually-mature adults such as albumen gland and prostate. NALCN-EEEE is equally abundant as NALCN-EKEE in snails, but is greater expressed in heart and other muscle tissue, and 50% less expressed in the brain than NALCN-EKEE. Transfected snail NALCN-EEEE and NALCN-EKEE channel isoforms express in HEK-293T cells. We were not able to distinguish potential NALCN currents from background, non-selective leak conductances in HEK293T cells. Native leak currents without expressing NALCN genes in HEK-293T cells are NMDG(+) impermeant and blockable with 10 µM Gd(3+) ions and are indistinguishable from the hallmark currents ascribed to mammalian NALCN currents expressed in vitro by Lu et al. in Cell. 2007 Apr 20;129(2):371-83.
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Anesthetic action of volatile anesthetics by using Paramecium as a model. ACTA ACUST UNITED AC 2012; 32:410-414. [PMID: 22684567 DOI: 10.1007/s11596-012-0071-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Indexed: 11/27/2022]
Abstract
Although empirically well understood in their clinical administration, volatile anesthetics are not yet well comprehended in their mechanism studies. A major conundrum emerging from these studies is that there is no validated model to assess the presumed candidate sites of the anesthetics. We undertook this study to test the hypothesis that the single-celled Paramecium could be anesthetized and served as a model organism in the study of anesthetics. We assessed the motion of Paramecium cells with Expert Vision system and the chemoresponse of Paramecium cells with T-maze assays in the presence of four different volatile anesthetics, including isoflurane, sevoflurane, enflurane and ether. Each of those volatiles was dissolved in buffers to give drug concentrations equal to 0.8, 1.0, and 1.2 EC50, respectively, in clinical practice. We could see that after application of volatile anesthetics, the swimming of the Paramecium cells was accelerated and then suppressed, or even stopped eventually, and the index of the chemoresponse of the Paramecium cells (denoted as I ( che )) was decreased. All of the above impacts were found in a concentration-dependent fashion. The biphasic effects of the clinical concentrations of volatile anesthetics on Paramecium simulated the situation of high species in anesthesia, and the inhibition of the chemoresponse also indicated anesthetized. In conclusion, the findings in our studies suggested that the single-celled Paramecium could be anesthetized with clinical concentrations of volatile anesthetics and therefore be utilized as a model organism to study the mechanisms of volatile anesthetics.
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Campbell JL, Gu Q, Guo D, Nash HA. Genetic effects in Drosophila on the potency of diverse general anesthetics: a distinctive pattern of altered sensitivity. J Neurogenet 2012; 23:412-21. [PMID: 19863272 DOI: 10.3109/01677060903177800] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mutations that influence the sensitivity of an organism to a volatile general anesthetic can be divided into two classes. In one, sensitivity to all other volatile agents is affected to a similar degree. Although this class may contain mutations of interest for understanding anesthesia, it is also likely to contain mutations that merely alter general health. In the second class, mutations confer non-uniform effects on potency (NEP), i.e., larger effects for some volatile anesthetics than for others. Members of this class are of special interest for studies of arousal and its pharmacological suppression because they not only avoid the pitfall of effects on global health, but also imply the existence of drug targets that are preferentially affected by particular agents. In this work, we provide the first systematic investigation of the relative frequency and diversity of NEP mutations in Drosophila. As a first step, we isolated and characterized a set of P element insertion mutations that confer altered sensitivity of the fruit fly to the clinical anesthetic halothane. Then we tested the members of this collection for their effect on the sensitivity of flies to five other volatile agents. Not only do we find that most of the mutations show non-uniform effects, they also share a characteristic arrangement of altered potencies (halothane > >desflurane >or= enflurane approximately isoflurane approximately methoxyflurane > sevoflurane). From this result, although we do not know how direct or indirect are the effects of the mutations, we infer the existence of a biologically relevant target for anesthetic action that has a distinct preference for halothane over other agents. Intriguingly, P element insertions that co-map with several NEP loci have been shown to alter the fly's response to cocaine and ethanol, suggesting that common genetic elements are involved in the response to all three drugs.
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Affiliation(s)
- Joseph L Campbell
- Laboratory of Molecular Biology, National Institute of Mental Health, Bethesda, MD 20892-3736, USA
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Singaram VK, Somerlot BH, Falk SA, Falk MJ, Sedensky MM, Morgan PG. Optical reversal of halothane-induced immobility in C. elegans. Curr Biol 2011; 21:2070-6. [PMID: 22137475 DOI: 10.1016/j.cub.2011.10.042] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 10/04/2011] [Accepted: 10/26/2011] [Indexed: 01/29/2023]
Abstract
Volatile anesthetics (VAs) cause profound neurological effects, including reversible loss of consciousness and immobility. Despite their widespread use, the mechanism of action of VAs remains one of the unsolved puzzles of neuroscience [1, 2]. Genetic studies in Caenorhabditis elegans [3, 4], Drosophila [3, 5], and mice [6-9] indicate that ion channels controlling the neuronal resting membrane potential (RMP) also control anesthetic sensitivity. Leak channels selective for K(+) [10-13] or permeable to Na(+) [14] are critical for establishing RMP. We hypothesized that halothane, a VA, caused immobility by altering the neuronal RMP. In C. elegans, halothane-induced immobility is acutely and completely reversed by channelrhodopsin-2 based depolarization of the RMP when expressed specifically in cholinergic neurons. Furthermore, hyperpolarizing cholinergic neurons via halorhodopsin activation increases sensitivity to halothane. The sensitivity of C. elegans to halothane can be altered by 25-fold by either manipulation of membrane conductance with optogenetic methods or generation of mutations in leak channels that set the RMP. Immobility induced by another VA, isoflurane, is not affected by these treatments, thereby excluding the possibility of nonspecific hyperactivity. The sum of our data indicates that leak channels and the RMP are important determinants of halothane-induced general anesthesia.
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Affiliation(s)
- Vinod K Singaram
- Department of Genetics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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Inamdar AA, Masurekar P, Bennett JW. Neurotoxicity of fungal volatile organic compounds in Drosophila melanogaster. Toxicol Sci 2010; 117:418-26. [PMID: 20643751 DOI: 10.1093/toxsci/kfq222] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Many volatile organic compounds (VOCs) are found in indoor environment as products of microbial metabolism. In damp indoor environments, fungi are associated with poor air quality. Some epidemiological studies have suggested that microbial VOCs have a negative impact on human health. Our study was designed to provide a reductionist approach toward studying fungal VOC-mediated toxicity using the inexpensive model organism, Drosophila melanogaster, and pure chemical standards of several important fungal VOCs. Low concentrations of the following known fungal VOCs, 0.1% of 1-octen-3-ol and 0.5% of 2-octanone; 2,5 dimethylfuran; 3-octanol; and trans-2-octenal, caused locomotory defects and changes in green fluorescent protein (GFP)- and antigen-labeled dopaminergic neurons in adult D. melanogaster. Locomotory defects could be partially rescued with L-DOPA. Ingestion of the antioxidant, vitamin E, improved the survival span and delayed the VOC-mediated changes in dopaminergic neurons, indicating that the VOC-mediated toxicity was due, in part, to generation of reactive oxygen species.
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Affiliation(s)
- Arati A Inamdar
- Department of Plant Biology and Pathology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901, USA.
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Anaesthetic mechanisms: update on the challenge of unravelling the mystery of anaesthesia. Eur J Anaesthesiol 2009; 26:807-20. [PMID: 19494779 DOI: 10.1097/eja.0b013e32832d6b0f] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
General anaesthesia is administered each day to thousands of patients worldwide. Although more than 160 years have passed since the first successful public demonstration of anaesthesia, a detailed understanding of the anaesthetic mechanism of action of these drugs is still lacking. An important early observation was the Meyer-Overton correlation, which associated the potency of an anaesthetic with its lipid solubility. This work focuses attention on the lipid membrane as a likely location for anaesthetic action. With the advent of cellular electrophysiology and molecular biology techniques, tools to dissect the components of the lipid membrane have led, in recent years, to the widespread acceptance of proteins, namely receptors and ion channels, as more likely targets for the anaesthetic effect. Yet these accumulated data have not produced a comprehensive explanation for how these drugs produce central nervous system depression. In this review, we follow the story of anaesthesia mechanisms research from its historical roots to the intensely neurophysiological research regarding it today. We will also describe recent findings that identify specific neuroanatomical locations mediating the actions of some anaesthetic agents.
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Faust K, Gehrke S, Yang Y, Yang L, Beal MF, Lu B. Neuroprotective effects of compounds with antioxidant and anti-inflammatory properties in a Drosophila model of Parkinson's disease. BMC Neurosci 2009; 10:109. [PMID: 19723328 PMCID: PMC3152779 DOI: 10.1186/1471-2202-10-109] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Accepted: 09/01/2009] [Indexed: 12/21/2022] Open
Abstract
Background Parkinson's disease (PD) is the most common movement disorder. Extrapyramidal motor symptoms stem from the degeneration of the dopaminergic pathways in patient brain. Current treatments for PD are symptomatic, alleviating disease symptoms without reversing or retarding disease progression. Although the cause of PD remains unknown, several pathogenic factors have been identified, which cause dopaminergic neuron (DN) death in the substantia nigra (SN). These include oxidative stress, mitochondrial dysfunction, inflammation and excitotoxicity. Manipulation of these factors may allow the development of disease-modifying treatment strategies to slow neuronal death. Inhibition of DJ-1A, the Drosophila homologue of the familial PD gene DJ-1, leads to oxidative stress, mitochondrial dysfunction, and DN loss, making fly DJ-1A model an excellent in vivo system to test for compounds with therapeutic potential. Results In the present study, a Drosophila DJ-1A model of PD was used to test potential neuroprotective drugs. The drugs applied are the Chinese herb celastrol, the antibiotic minocycline, the bioenergetic amine coenzyme Q10 (coQ10), and the glutamate antagonist 2,3-dihydroxy-6-nitro-7-sulphamoylbenzo[f]-quinoxaline (NBQX). All of these drugs target pathogenic processes implicated in PD, thus constitute mechanism-based treatment strategies. We show that celastrol and minocycline, both having antioxidant and anti-inflammatory properties, confer potent dopaminergic neuroprotection in Drosophila DJ-1A model, while coQ10 shows no protective effect. NBQX exerts differential effects on cell survival and brain dopamine content: it protects against DN loss but fails to restore brain dopamine level. Conclusion The present study further validates Drosophila as a valuable model for preclinical testing of drugs with therapeutic potential for neurodegenerative diseases. The lower cost and amenability to high throughput testing make Drosophila PD models effective in vivo tools for screening novel therapeutic compounds. If our findings can be further validated in mammalian PD models, they would implicate drugs combining antioxidant and anti-inflammatory properties as strong therapeutic candidates for mechanism-based PD treatment.
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Affiliation(s)
- Katharina Faust
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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Abstract
BACKGROUND Chromosomal deletions and duplications, which result in halving or doubling of copy number in a block of genes, are an important source of variation between individuals. Phenotypic effects of copy number variation are commonly observed, but effects on sensitivity to volatile anesthetics have not been assessed in any organism. METHODS The potency with which halothane depresses the righting reflex of fruit flies was measured in congenic Drosophila strains, each of which was heterozygous for a deletion of average size 400 kb. Over 200 strains were examined, thereby scanning approximately half of the fly genome. RESULTS Although the vast majority of deletion heterozygotes were indistinguishable from the control, eight had significantly altered sensitivity to halothane. Genetic tests supported the hypothesis that the change in anesthetic sensitivity was the result of reduction in copy number and not adventitious mutations in the strains. Among the eight outliers, the difference in halothane potency ranged from a 25% increase to a 15% decrease. Changes of similar magnitude but distinctive patterns were found when these lines were tested with enflurane, isoflurane, and sevoflurane. CONCLUSIONS Variation in gene copy number has a significant impact on anesthetic sensitivity in Drosophila melanogaster. The level of transcription of a few genes must thus be limiting for a normal response to volatiles. Coupling between gene copy and gene expression is universal, and the components of the fly's nervous system are highly conserved; therefore, this work provides a rationale for investigating the clinical impact of copy number variation.
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Milutinovic PS, Yang L, Cantor RS, Eger EI, Sonner JM. Anesthetic-like modulation of a gamma-aminobutyric acid type A, strychnine-sensitive glycine, and N-methyl-d-aspartate receptors by coreleased neurotransmitters. Anesth Analg 2007; 105:386-92. [PMID: 17646495 DOI: 10.1213/01.ane.0000267258.17197.7d] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
INTRODUCTION A mechanism of anesthesia has recently been proposed which predicts that coreleased neurotransmitters may modulate neurotransmitter receptors for which they are not the native agonist in a manner similar to anesthetics. METHODS We tested this prediction by applying acetylcholine to a NR1/NR2A N-methyl-d-aspartate receptor, glycine to a wild-type alpha(1)beta(2) and anesthetic-resistant alpha(1)(S270I)beta(2) gamma-amino-butyric acid (GABA) type A receptor, and GABA to a homomeric alpha(1) wild type and anesthetic-resistant alpha(1) S267I glycine receptor. Receptors were expressed in Xenopus laevis oocytes and studied using two-electrode voltage clamping. RESULTS We found inhibition of N-methyl-d-aspartate receptor function by acetylcholine, enhancement of glycine receptor function by GABA, and enhancement of GABA type A receptor function by glycine. As expected of compounds with anesthetic activity, GABA showed far less potentiation (enhancement) of the function of the anesthetic-resistant S267I glycine receptor than that of the wild-type receptor. Glycine potentiated the function of wild-type GABA type A receptors but inhibited the function of the anesthetic-resistant S270I GABA type A receptor. CONCLUSIONS These results show that neurotransmitters that are coreleased onto anesthetic-sensitive receptors may modulate the function of receptors for which they are not the native agonist via an anesthetic-like mechanism. These findings lend support to a recent theory of anesthetic action.
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Humphrey JA, Hamming KS, Thacker CM, Scott RL, Sedensky MM, Snutch TP, Morgan PG, Nash HA. A putative cation channel and its novel regulator: cross-species conservation of effects on general anesthesia. Curr Biol 2007; 17:624-9. [PMID: 17350263 DOI: 10.1016/j.cub.2007.02.037] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Revised: 01/31/2007] [Accepted: 02/02/2007] [Indexed: 11/18/2022]
Abstract
Volatile anesthetics like halothane and enflurane are of interest to clinicians and neuroscientists because of their ability to preferentially disrupt higher functions that make up the conscious state. All volatiles were once thought to act identically; if so, they should be affected equally by genetic variants. However, mutations in two distinct genes, one in Caenorhabditis and one in Drosophila, have been reported to produce much larger effects on the response to halothane than enflurane [1, 2]. To see whether this anesthesia signature is adventitious or fundamental, we have identified orthologs of each gene and determined the mutant phenotype within each species. The fly gene, narrow abdomen (na), encodes a putative ion channel whose sequence places it in a unique family; the nematode gene, unc-79, is identified here as encoding a large cytosolic protein that lacks obvious motifs. In Caenorhabditis, mutations that inactivate both of the na orthologs produce an Unc-79 phenotype; in Drosophila, mutations that inactivate the unc-79 ortholog produce an na phenotype. In each organism, studies of double mutants place the genes in the same pathway, and biochemical studies show that proteins of the UNC-79 family control NA protein levels by a posttranscriptional mechanism. Thus, the anesthetic signature reflects an evolutionarily conserved role for the na orthologs, implying its intimate involvement in drug action.
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Affiliation(s)
- John A Humphrey
- Department of Genetics, Case Medical Center, Cleveland, OH 44106, USA
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Abstract
General anesthetics abolish behavioral responsiveness in all animals, and in humans this is accompanied by loss of consciousness. Whether similar target mechanisms and behavioral endpoints exist across species remains controversial, although model organisms have been successfully used to study mechanisms of anesthesia. In Drosophila, a number of key mutants have been characterized as hypersensitive or resistant to general anesthetics by behavioral assays. In order to investigate general anesthesia in the Drosophila brain, local field potential (LFP) recordings were made during incremental exposures to isoflurane in wild-type and mutant flies. As in higher animals, general anesthesia in flies was found to involve a succession of distinct endpoints. At low doses, isoflurane uncoupled brain activity from ongoing movement, followed by a sudden attenuation in neural correlates of perception. Average LFP activity in the brain was more gradually attenuated with higher doses, followed by loss of movement behavior. Among mutants, a strong correspondence was found between behavioral and LFP sensitivities, thereby suggesting that LFP phenotypes are proximal to the anesthetic's mechanism of action. Finally, genetic and pharmacological analysis revealed that anesthetic sensitivities in the fly brain are, like other arousal states, influenced by dopaminergic activity. These results suggest that volatile anesthetics such as isoflurane may target the same processes that sustain wakefulness and attention in the brain. LFP correlates of general anesthesia in Drosophila provide a powerful new approach to uncovering the nature of these processes.
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Rajaram S, Scott RL, Nash HA. Retrograde signaling from the brain to the retina modulates the termination of the light response in Drosophila. Proc Natl Acad Sci U S A 2005; 102:17840-5. [PMID: 16314566 PMCID: PMC1308915 DOI: 10.1073/pnas.0508858102] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A critical factor in visual function is the speed with which photoreceptors (PRs) return to the resting state when light intensity dims. Several elements subserve this process, many of which promote the termination of the phototransduction cascade. Although the known elements are intrinsic to PRs, we have found that prompt restoration to the resting state of the Drosophila electroretinogram can require effective communication between the retina and the underlying brain. The requirement is seen more dramatically with long than with short light pulses, distinguishing the phenomenon from gross disruption of the termination machinery. The speed of recovery is affected by mutations (in the Hdc and ort genes) that prevent PRs from transmitting visual information to the brain. It is also affected by manipulation (using either drugs like neostigmine or genetic tools to inactivate neurotransmitter release) of cholinergic signals that arise in the brain. Intracellular recordings support the hypothesis that PRs are the target of this communication. We infer that signaling from the retina to the optic lobe prompts a feedback signal to retinal PRs. Although the mechanism of this retrograde signaling remains to be discerned, the phenomenon establishes a previously unappreciated mode of control of the temporal responsiveness of a primary sensory neuron.
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Affiliation(s)
- Shantadurga Rajaram
- Laboratory of Molecular Biology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892-3736, USA
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Abstract
A mechanistic study of consciousness need not be confined to human complexity. Other animals also display key behaviors and responses that have long been intimately tied to the measure of consciousness in humans. Among them are some very well-defined and measurable endpoints: selective attention, sleep and general anesthesia. That these three variables associated with changes in consciousness might exist even in a fruit-fly does not necessarily imply that a fly is "conscious", but it does suggest that some of the problems central to the field of consciousness studies could be investigated in a model organism such as Drosophila melanogaster. Demonstrating suppression of unattended stimuli, which is central to attention studies in humans, is now possible in Drosophila by measuring neural correlates of visual selection. By combining such studies with an eventual understanding of suppression in other arousal states in the fly, such as sleep and general anesthesia, we might be unraveling mechanisms relevant to consciousness as well.
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Affiliation(s)
- Bruno van Swinderen
- The Neurosciences Institute, 10640 John Jay Hopkins Dr, San Diego, CA 92121, USA.
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Manev H, Dimitrijevic N. Fruit flies for anti-pain drug discovery. Life Sci 2005; 76:2403-7. [PMID: 15763072 DOI: 10.1016/j.lfs.2004.12.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2004] [Accepted: 12/21/2004] [Indexed: 11/20/2022]
Abstract
Recent work has indicated that fruit flies (Drosophila melanogaster) can be used in nociception research. Genetic screening identified a gene, painless, that is required for thermal and mechanical nociception in Drosophila larvae. On the other hand, pharmacological techniques and noxious heat were used to assay antinocieceptive behavior in intact adult Drosophila. In general, animal models for pain research are bound by ethical concerns. Since no serious ethical controversies have been raised regarding experiments in insects, Drosophila may be, for the time being an ethically acceptable animal model for combined genetic and pharmacological analgesia research.
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Affiliation(s)
- Hari Manev
- Department of Psychiatry, The Psychiatric Institute, University of Illinois at Chicago, 1601 West Taylor Street, MC912, Chicago, IL 60612, USA.
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Rajaram S, Nash HA. A specific alteration in the electroretinogram of Drosophila melanogaster is induced by halothane and other volatile general anesthetics. Anesth Analg 2004; 98:1705-1711. [PMID: 15155332 DOI: 10.1213/01.ane.0000113548.27457.a3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
UNLABELLED In higher organisms, physiological investigations have provided a valuable complement to assays of anesthetic effects on whole-animal behavior. However, although complex motor programs of Drosophila melanogaster have been used to identify genes that influence anesthesia, electrophysiological studies of anesthetic effects in this invertebrate have been limited. Here we show that the electroretinogram (ERG), the extracellular recording of light-evoked mass potentials from the surface of the eye, reveals a distinct effect of halothane, enflurane, isoflurane, and desflurane. Behaviorally relevant concentrations of these volatile anesthetics severely reduced the transient component of the ERG at lights-off. Other prominent ERG components, such as the photoreceptor potential and the lights-on transient, were not consistently affected by these drugs. Surprisingly, for most anesthetics, a diminished off-transient was obtained only with short light pulses. An identical effect was observed in the absence of anesthetic by depressing the function of Shaker potassium channels. The possibility that halothane acts in the visual circuit by closing potassium channels was examined with a simple genetic test; the results were consistent with the hypothesis but fell short of providing definitive support. Nevertheless, our studies establish the ERG as a useful tool both for examining the influence of volatile anesthetics on a simple circuit and for identifying genes that contribute to anesthetic sensitivity. IMPLICATIONS Electroretinography (ERG) provides a useful monitor of anesthetic effects on the fruit fly. The effects of volatile anesthetics on the ERG are recapitulated by inactivation of potassium channels.
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Affiliation(s)
- Shantadurga Rajaram
- Laboratory of Molecular Biology, National Institute of Mental Health, Bethesda, Maryland
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Sandstrom DJ. Isoflurane depresses glutamate release by reducing neuronal excitability at the Drosophila neuromuscular junction. J Physiol 2004; 558:489-502. [PMID: 15169847 PMCID: PMC1664974 DOI: 10.1113/jphysiol.2004.065748] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The mechanisms through which volatile general anaesthetics exert their behavioural effects remain unclear. The accessibility of the Drosophila larval neuromuscular junction to genetic and neurophysiological analysis has made it an attractive model system for identification of anaesthetic targets. This study provides a mechanistic basis for the genetic analysis of anaesthetic action, by analysing the neurophysiological effects of the volatile anaesthetic isoflurane on axonal and synaptic function in the Drosophila larva. The most robust effect of isoflurane was a reversible decrease in the amplitude and area of glutamatergic excitatory junctional currents (EJCs) evoked at the neuromuscular junction. Isoflurane did not affect postsynaptic glutamate receptor function detectably, in that the amplitudes, areas and decay times of spontaneous miniature EJCs were unchanged at any concentration. Therefore, decreased EJC amplitude resulted from reduction of neurotransmitter release. Reduced neurotransmitter release was associated with decreased presynaptic excitability, measured as increased delay to EJC onset and reduced axonal conduction velocity. EJC amplitude was rescued to control levels by direct electrotonic stimulation of the synapse in the presence of tetrodotoxin, indicating that isoflurane inhibits neurotransmitter release by reducing presynaptic excitability. In addition, isoflurane reduced release probability, measured as increased paired-pulse facilitation. The EC(50) for suppression of larval locomotion was similar to that for reduction of transmitter release, indicating that the axonal and synaptic effects were occurring in a behaviourally relevant range. These results provide a cellular context for ongoing genetic and neurophysiological analyses of volatile anaesthetic action in Drosophila, and suggest candidate anaesthetic target molecules.
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Affiliation(s)
- David J Sandstrom
- Laboratory of Molecular Biology, National Institute of Mental Health, National Institutes of Health MSC 4034, Bethesda, MD 20892, USA.
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Zheng XS, Chan TF, Zhou HH. Genetic and Genomic Approaches to Identify and Study the Targets of Bioactive Small Molecules. ACTA ACUST UNITED AC 2004; 11:609-18. [PMID: 15157872 DOI: 10.1016/j.chembiol.2003.08.011] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Natural and synthetic bioactive small molecules form the backbone of modern therapeutics. These drugs primarily exert their effect by targeting cellular host or foreign proteins that are critical for the progression of disease. Therefore, a crucial step in the process of recognizing valuable new drug leads is identification of their protein targets; this is often a time consuming and difficult task. This report is intended to provide a comprehensive review of recent developments in genetic and genomic approaches to overcome the hurdle of discovering the protein targets of bioactive small molecules.
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Affiliation(s)
- Xiaofeng S Zheng
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110 USA.
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34
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Abstract
Arousal can be described as an endogenously generated or exogenously induced change in behavioral responsiveness. Changes in levels of arousal, such as occur during sleep or attention, most likely accomplish adaptive functions common to most animals. Recent evidence demonstrating changing arousal states in Drosophila melanogaster complements other behavioral research in this model organism. Herein we review the methodology related to the study of circadian rhythms, sleep and anesthesia where arousal, or lack of it, plays an essential role. We end this review by discussing a new method that allows for the first time to correlate changes in brain electrophysiology to changes in behavioral arousal in the fruit fly.
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Affiliation(s)
- Bruno van Swinderen
- The Neurosciences Institute, 10640 John Jay Hopkins Dr., 92121, San Diego, CA, USA
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35
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Affiliation(s)
- Jason A Campagna
- Department of Anesthesia and Critical Care, Massachusetts General Hospital, Boston, MA 02114, USA
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36
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Sonner JM. Issues in the Design and Interpretation of Minimum Alveolar Anesthetic Concentration (MAC) Studies. Anesth Analg 2002. [DOI: 10.1213/00000539-200209000-00021] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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37
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Sonner JM. Issues in the design and interpretation of minimum alveolar anesthetic concentration (MAC) studies. Anesth Analg 2002; 95:609-14, table of contents. [PMID: 12198046 DOI: 10.1097/00000539-200209000-00021] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
IMPLICATIONS The two experimental designs (quantal and bracketing) used for population minimum alveolar anesthetic concentration studies give equivalent results. An expression relating variability in terms of Hill coefficients and SD is presented. Evolutionary implications of low population variability in anesthetic phenotypes is discussed.
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Affiliation(s)
- James M Sonner
- Department of Anesthesia and Perioperative Care, Room S-455i, Box 0464, University of California, San Francisco, CA 94143-0464, USA.
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38
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Affiliation(s)
- H A Nash
- Laboratory of Molecular Biology, National Institute of Mental Health, Building 36/Room 1B08, 9000 Rockville Pike, Bethesda, MD 20892-4034, USA
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39
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Eckenhoff MF, Chan K, Eckenhoff RG. Multiple specific binding targets for inhaled anesthetics in the mammalian brain. J Pharmacol Exp Ther 2002; 300:172-9. [PMID: 11752113 DOI: 10.1124/jpet.300.1.172] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous work showed widespread saturable binding of halothane in rat brain. To determine whether this represents selective binding to a few widespread proteins or less selective binding to many different proteins, we used [(14)C]halothane photolabeling and quantitative electrophoresis/autoradiography in rat cerebellar homogenates. Many proteins incorporate label. Stoichiometry values ranged from 0 to 4 at 0.2 mM [(14)C]halothane in a group of 24 randomly selected protein bands. Apparent IC(50) values from unlabeled halothane competition experiments ranged from 0.2 to 2.0 mM, with soluble protein having significantly lower values (higher affinity) than membrane protein. Chloroform inhibited halothane labeling similar to unlabeled halothane but with higher apparent IC(50) values, whereas isoflurane and an anesthetic, cyclobutane (1-chloro-1,2,2-trifluorocyclobutane), inhibited halothane labeling to a smaller degree. A nonanesthetic, cyclobutane (1,2-dichlorohexafluorocyclobutane), inhibited halothane labeling the least. We conclude that halothane binding motifs are sufficiently degenerate to be found in many proteins, both soluble and membrane-bound.
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40
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Campbell JL, Nash HA. Volatile general anesthetics reveal a neurobiological role for the white and brown genes of Drosophila melanogaster. JOURNAL OF NEUROBIOLOGY 2001; 49:339-49. [PMID: 11745669 DOI: 10.1002/neu.10009] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Molecular and cellular evidence argues that a heterodimer between two ABC transporters, the White protein and the Brown protein, is responsible for pumping guanine into pigment-synthesizing cells of the fruit fly, Drosophila melanogaster. Previous studies have not detected White or Brown outside pigment-synthesizing cells nor have behavioral effects of null mutants been reported, other than those that are visually dependent. Nevertheless, we show here that exposure to the volatile general anesthetic (VGA) enflurane reveals a difference in neuromuscular performance between wild-type flies and those that carry a null allele in either the white or brown gene. Specifically, in a test of climbing ability, w1118 or bw1 flies are much less affected by enflurane than are congenic controls. Altered anesthetic sensitivity is still observed when visual cues are reduced or eliminated, arguing that white and brown contribute to neural function outside the eye. This hypothesis is supported by the detection of white message in heads of flies that are genetically altered so as to lack pigment-producing cells. The w1118 or bw1 mutations also alter the response to a second VGA, halothane, albeit somewhat differently. Under some conditions, the combination of w1118 with another mutation that affects anesthesia leads to a drastically altered phenotype. We consider several ways by which diminished transport of guanine could influence neural function and anesthetic sensitivity.
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Affiliation(s)
- J L Campbell
- Laboratory of Molecular Biology, National Institute of Mental Health, Bethesda, Maryland 20892-4034, USA
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41
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Sonner JM, Gong D, Eger EI. Naturally occurring variability in anesthetic potency among inbred mouse strains. Anesth Analg 2000; 91:720-6. [PMID: 10960407 DOI: 10.1097/00000539-200009000-00042] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
UNLABELLED We measured the naturally occurring variability in anesthetic potency, defined by the minimum alveolar anesthetic concentrations (MACs) of inhaled anesthetics required to produce immobility in response to noxious stimuli, in seven widely used laboratory mouse strains. To these data, we added similar data for eight other mouse strains. The average MAC values for each anesthetic for the 15 strains were normally distributed, with a coefficient of variation (ratio of SD to mean) of 0.1. The range of MAC values was 39% for desflurane, 44% for isoflurane, and 55% for halothane. MAC values were highly reliable, with approximately 1% of the variance in MAC measurements for the strains being explained by measurement error. One hundred forty-six statistically significant differences among the 15 strains were found for the three inhaled anesthetics (isoflurane, desflurane, and halothane). Our results suggest that multiple genes underlie the observed variability in anesthetic potency. IMPLICATIONS Laboratory mouse strains differ significantly in susceptibility to anesthetics. These phenotypic differences may be exploited to help determine the genetic basis of anesthetic-induced immobility.
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Affiliation(s)
- J M Sonner
- Department of Anesthesia and Perioperative Care, University of California, San Francisco 94143-0464, USA.
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42
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Sonner JM, Gong D, Eger EI. Naturally Occurring Variability in Anesthetic Potency Among Inbred Mouse Strains. Anesth Analg 2000. [DOI: 10.1213/00000539-200009000-00042] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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43
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Guan Z, Scott RL, Nash HA. A new assay for the genetic study of general anesthesia in Drosophila melanogaster: use in analysis of mutations in the X-chromosomal 12E region. J Neurogenet 2000; 14:25-42. [PMID: 10938546 DOI: 10.3109/01677060009083475] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We describe a new measure of the influence of general anesthetics on Drosophila that uses the robust tendency of fruit flies to briskly walk upwards after being tapped down. We expose flies to a fixed concentration of anesthetic gas in a 50 ml tube for a period of up to 1 h and then test the distribution of flies in the tube shortly after tapping them to its bottom. By measuring the effect of a series of anesthetic concentrations on the fraction of flies that fail to climb, we derive quantitative descriptors of the potency of the drug. This "distribution test" is superior to previous assays of anesthetic potency in terms of ease and reliability. We have used the assay to further the genetic analysis of several mutations that cluster on the X chromosome and are known to influence both neural function and anesthesia sensitivity. The results establish complementation patterns between the mutations, refine their genetic map positions, and open the way for the molecular identification of the relevant gene(s).
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Affiliation(s)
- Z Guan
- Laboratory of Molecular Biology, National Institute of Mental Health, Building 36, Room 1B08, Bethesda, MD 20892-4034, USA
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44
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Sonner JM, Gong D, Li J, Eger EI, Laster MJ. Mouse Strain Modestly Influences Minimum Alveolar Anesthetic Concentration and Convulsivity of Inhaled Compounds. Anesth Analg 1999. [DOI: 10.1213/00000539-199910000-00039] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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45
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van Swinderen B, Galifianakis A, Crowder CM. A quantitative genetic approach towards volatile anesthetic mechanisms in C. elegans. Toxicol Lett 1998; 100-101:309-17. [PMID: 10049158 DOI: 10.1016/s0378-4274(98)00200-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Quantitative genetics is the study of the heritability of continuous traits such as height or IQ. Quantitative trait loci (QTLs) represent the genes that are responsible for these quantitative traits. Sensitivity to the volatile anesthetic halothane is a genetically controlled quantitative trait in the nematode C. elegans. The QTLs that are responsible for the 12-fold range in halothane EC50 in these strains map to a few places with at least one major effect locus on chromosome V. Congenic strains for chromosome V confirmed these loci and offer the means to finely map them for positional cloning.
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Affiliation(s)
- B van Swinderen
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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46
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Campbell JL, Nash HA. The visually-induced jump response of Drosophila melanogaster is sensitive to volatile anesthetics. J Neurogenet 1998; 12:241-51. [PMID: 10656111 DOI: 10.3109/01677069809108561] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Fruit flies jump when startled by a sudden decrease in light intensity. We show that this visually-induced jump response in Drosophila melanogaster is sensitive to three general anesthetic agents: halothane, enflurane, and methoxyflurane. The concentration of anesthetic required to inhibit this response is similar to that needed for the inhibition of other assays in flies and other organisms. We believe the simplicity of this assay coupled with the insight gained from the more complex electrophysiological monitoring of the same neural pathway will be of value in the genetic identification of the molecular target of volatile anesthetics.
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Affiliation(s)
- J L Campbell
- Laboratory of Molecular Biology, National Institute of Mental Health, Bethesda, MD 20892-4034, USA.
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47
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Rajaram S, Sedensky MM, Morgan PG. Unc-1: a stomatin homologue controls sensitivity to volatile anesthetics in Caenorhabditis elegans. Proc Natl Acad Sci U S A 1998; 95:8761-6. [PMID: 9671752 PMCID: PMC21150 DOI: 10.1073/pnas.95.15.8761] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
To identify sites of action of volatile anesthetics, we are studying genes in a functional pathway that controls sensitivity to volatile anesthetics in the nematode Caenorhabditis elegans. The unc-1 gene occupies a central position in this pathway. Different alleles of unc-1 have unique effects on sensitivity to the different volatile anesthetics. UNC-1 shows extensive homology to human stomatin, an integral membrane protein thought to regulate an associated ion channel. We postulate that UNC-1 has a direct effect on anesthetic sensitivity in C. elegans and may represent a molecular target for volatile anesthetics.
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Affiliation(s)
- S Rajaram
- Departments of Anesthesiology and Genetics, University Hospitals, Case Western Reserve University, Cleveland, OH 44106, USA
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48
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Mir B, Iyer S, Ramaswami M, Krishnan KS. A genetic and mosaic analysis of a locus involved in the anesthesia response of Drosophila melanogaster. Genetics 1997; 147:701-12. [PMID: 9335606 PMCID: PMC1208191 DOI: 10.1093/genetics/147.2.701] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We describe a genetic and behavioral analysis of several alleles of har38, a mutant with altered sensitivity to the general anesthetic halothane. We obtained a P-element-induced allele of har38 and generated several excision alleles by remobilizing the P element. The mutants narrow abdomen (na) and har85 are confirmed to be allelic to har 38. Besides a decreased sensitivity to halothane, all mutant alleles of this locus cause a characteristic walking behavior in the absence of anesthetics. We have quantified this behavior using a geotaxis apparatus. Responses of the mutant alleles to different inhalational anesthetics were tested. The results strongly favor a multipathway model for the onset of anesthesia. Mosaic flies were tested for their response to halothane and checked for their abnormal walking behavior. The analysis suggests that both the behaviors are exhibited only by such mosaics as have the entire head of mutant origin. It is likely that this focus represents an element of a common pathway in the anesthetic response to several inhalational anesthetics but not all. This result is the first demonstration of regional specificity in the CNS of any animal for general anesthetic action.
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Affiliation(s)
- B Mir
- Molecular Biology Unit, Tata Institute of Fundamental Research, Bombay, India
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49
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van Swinderen B, Shook DR, Ebert RH, Cherkasova VA, Johnson TE, Shmookler Reis RJ, Crowder CM. Quantitative trait loci controlling halothane sensitivity in Caenorhabditis elegans. Proc Natl Acad Sci U S A 1997; 94:8232-7. [PMID: 9223344 PMCID: PMC21586 DOI: 10.1073/pnas.94.15.8232] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/1996] [Accepted: 03/13/1997] [Indexed: 02/04/2023] Open
Abstract
Genetic analysis is an essential tool for defining the molecular mechanisms whereby volatile anesthetics (VA) disrupt nervous system function. However, the degree of natural variation of the genetic determinants of VA sensitivity has not been determined nor have mutagenesis approaches been very successful at isolating significantly resistant mutant strains. Thus, a quantitative genetic approach was taken toward these goals. Recombinant-inbred strains derived from two evolutionarily distinct lineages of the nematode Caenorhabditis elegans were tested for sensitivity to clinically relevant concentrations (0.3-0.5 mM) of the VA halothane. The halothane sensitivities of coordinated movement and male mating behavior were highly variant among the recombinant-inbred strains with a range of EC50 values of 13- and 4-fold, respectively. Both traits were highly heritable (H2 = 0.82, 0.87, respectively). Several strains were found to be significantly resistant to halothane when compared with the wild-type strain N2. A major locus or loci mapping to the middle of chromosome V accounted for more than 40% of the phenotypic variance for both traits. Five weaker loci, four of which interact, explained most of the remaining variance. None of the halothane-sensitivity quantitative trait loci significantly affected behavior in the absence of halothane or halothane's potency for C. elegans immobilization, which requires 5-fold higher drug concentrations. Thus, the quantitative trait loci are unlikely to result from differences in halothane-independent (native) behavior or differences in halothane metabolism or permeability. Rather, these loci may code for targets and/or downstream effectors of halothane in the C. elegans nervous system or for modifiers of such gene products.
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Affiliation(s)
- B van Swinderen
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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50
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Lin M, Nash HA. Influence of general anesthetics on a specific neural pathway in Drosophila melanogaster. Proc Natl Acad Sci U S A 1996; 93:10446-51. [PMID: 8816820 PMCID: PMC38404 DOI: 10.1073/pnas.93.19.10446] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The neural pathway that governs an escape response of Drosophila to sudden changes in light intensity can be artificially induced by electrical stimulation of the brain and monitored by electrical recording from the effector muscles. We have refined previous work in this system to permit reliable ascertainment of two kinds of response: (i) a short-latency response that follows from direct excitation of a giant fiber neuron in the interior of the fly brain and (ii) a long-latency response in which electrical stimulation triggers neurons in the optic ganglia that ultimately impinge on the giant fiber neuron. The general anesthetic halothane is reported here to have very different potencies in inhibiting these two responses. The long-latency response is obliterated at concentrations similar to those that cause gross behavioral effects in adult flies, whereas the short-latency response is only partially inhibited at doses that are 10-fold higher. Three other volatile anesthetic agents show a similar pattern. Thus, as in higher organisms, the Drosophila nervous system is differentiated into components of high and low sensitivity to general anesthetics. Moreover, this work shows that one of the sensitive components of the nervous system lies in the optic lobe and is readily assayed by its effect on downstream systems; it should provide a focus for exploring the effects of genetic alteration of anesthetic sensitivity.
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Affiliation(s)
- M Lin
- Laboratory of Molecular Biology, National Institute of Mental Health, Bethesda MD 20892-4034, USA
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