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Cropper EC, Perkins M, Jing J. Persistent modulatory actions and task switching in the feeding network of Aplysia. Curr Opin Neurobiol 2023; 82:102775. [PMID: 37625344 PMCID: PMC10530010 DOI: 10.1016/j.conb.2023.102775] [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] [Received: 06/18/2023] [Revised: 07/26/2023] [Accepted: 08/01/2023] [Indexed: 08/27/2023]
Abstract
The activity of multifunctional networks is configured by neuromodulators that exert persistent effects. This raises a question, does this impact the ability of a network to switch from one type of activity to another? We review studies that have addressed this question in the Aplysia feeding circuit. Task switching in this system occurs "asymmetrically." When there is a switch from egestion to ingestion neuromodulation impedes switching (creates a "negative bias"). When there is a switch from ingestion to egestion the biasing is "positive." Ingestion promotes subsequent egestion. We contrast mechanisms responsible for the two types of biasing and show that the observed asymmetry is a consequence of the fact that there is more than one set of egestive circuit parameters.
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Affiliation(s)
- Elizabeth C Cropper
- Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA.
| | - Matthew Perkins
- Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
| | - Jian Jing
- Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA; State Key Laboratory of Pharmaceutical Biotechnology, Institute for Brain Sciences, Chemistry and Biomedicine Innovation Center, Jiangsu Engineering Research Center for MicroRNA Biology and Biotechnology, Advanced Institute for Life Sciences, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China
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2
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Anton SE, Kayser C, Maiellaro I, Nemec K, Möller J, Koschinski A, Zaccolo M, Annibale P, Falcke M, Lohse MJ, Bock A. Receptor-associated independent cAMP nanodomains mediate spatiotemporal specificity of GPCR signaling. Cell 2022; 185:1130-1142.e11. [PMID: 35294858 DOI: 10.1016/j.cell.2022.02.011] [Citation(s) in RCA: 68] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 12/20/2021] [Accepted: 02/09/2022] [Indexed: 01/05/2023]
Abstract
G protein-coupled receptors (GPCRs) relay extracellular stimuli into specific cellular functions. Cells express many different GPCRs, but all these GPCRs signal to only a few second messengers such as cAMP. It is largely unknown how cells distinguish between signals triggered by different GPCRs to orchestrate their complex functions. Here, we demonstrate that individual GPCRs signal via receptor-associated independent cAMP nanodomains (RAINs) that constitute self-sufficient, independent cell signaling units. Low concentrations of glucagon-like peptide 1 (GLP-1) and isoproterenol exclusively generate highly localized cAMP pools around GLP-1- and β2-adrenergic receptors, respectively, which are protected from cAMP originating from other receptors and cell compartments. Mapping local cAMP concentrations with engineered GPCR nanorulers reveals gradients over only tens of nanometers that define the size of individual RAINs. The coexistence of many such RAINs allows a single cell to operate thousands of independent cellular signals simultaneously, rather than function as a simple "on/off" switch.
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Affiliation(s)
- Selma E Anton
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Strasse 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Charlotte Kayser
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Strasse 10, 13125 Berlin, Germany
| | - Isabella Maiellaro
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany; School of Life Sciences, Department of Neuroscience, University of Nottingham, Nottingham NG7 2UH, UK
| | - Katarina Nemec
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Strasse 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Jan Möller
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Strasse 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Andreas Koschinski
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | - Paolo Annibale
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Strasse 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany; School of Physics and Astronomy, University of St Andrews, North Haugh, St. Andrews KY16 9SS, UK
| | - Martin Falcke
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Strasse 10, 13125 Berlin, Germany; Department of Physics, Humboldt University, Newtonstr. 15, 12489 Berlin, Germany
| | - Martin J Lohse
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Strasse 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany; Institute for Chemistry and Biochemistry, Free University Berlin, Takustr. 3, 14195 Berlin, Germany; ISAR Bioscience Institute, Semmelweisstrasse 5, 82152 Planegg, Munich, Germany.
| | - Andreas Bock
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Strasse 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany; Rudolf Boehm Institute of Pharmacology and Toxicology, Medical Faculty, University of Leipzig, Härtelstr. 16-18, 04107 Leipzig, Germany.
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3
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Bock A, Annibale P, Konrad C, Hannawacker A, Anton SE, Maiellaro I, Zabel U, Sivaramakrishnan S, Falcke M, Lohse MJ. Optical Mapping of cAMP Signaling at the Nanometer Scale. Cell 2020; 182:1519-1530.e17. [PMID: 32846156 DOI: 10.1016/j.cell.2020.07.035] [Citation(s) in RCA: 100] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 03/30/2020] [Accepted: 07/23/2020] [Indexed: 10/23/2022]
Abstract
Cells relay a plethora of extracellular signals to specific cellular responses by using only a few second messengers, such as cAMP. To explain signaling specificity, cAMP-degrading phosphodiesterases (PDEs) have been suggested to confine cAMP to distinct cellular compartments. However, measured rates of fast cAMP diffusion and slow PDE activity render cAMP compartmentalization essentially impossible. Using fluorescence spectroscopy, we show that, contrary to earlier data, cAMP at physiological concentrations is predominantly bound to cAMP binding sites and, thus, immobile. Binding and unbinding results in largely reduced cAMP dynamics, which we term "buffered diffusion." With a large fraction of cAMP being buffered, PDEs can create nanometer-size domains of low cAMP concentrations. Using FRET-cAMP nanorulers, we directly map cAMP gradients at the nanoscale around PDE molecules and the areas of resulting downstream activation of cAMP-dependent protein kinase (PKA). Our study reveals that spatiotemporal cAMP signaling is under precise control of nanometer-size domains shaped by PDEs that gate activation of downstream effectors.
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Affiliation(s)
- Andreas Bock
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany.
| | - Paolo Annibale
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Charlotte Konrad
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Annette Hannawacker
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Selma E Anton
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Isabella Maiellaro
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Ulrike Zabel
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany
| | - Sivaraj Sivaramakrishnan
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Martin Falcke
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany; Department of Physics, Humboldt University, Newtonstr. 15, 12489 Berlin, Germany
| | - Martin J Lohse
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Robert-Rössle-Str. 10, 13125 Berlin, Germany; Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078 Würzburg, Germany; Institute for Chemistry and Biochemistry, Free University, Takustr. 3, 14195 Berlin, Germany; ISAR Bioscience Institute, 82152 Munich/Planegg, Germany.
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4
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Perkins MH, Weiss KR, Cropper EC. Persistent effects of cyclic adenosine monophosphate are directly responsible for maintaining a neural network state. Sci Rep 2019; 9:9058. [PMID: 31227744 PMCID: PMC6588548 DOI: 10.1038/s41598-019-45241-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Accepted: 06/04/2019] [Indexed: 01/25/2023] Open
Abstract
Network states are often determined by modulators that alter the synaptic and cellular properties of the constituent neurons. Frequently neuromodulators act via second messengers, consequently their effects can persist. This persistence at the cellular/molecular level determines the maintenance of the state at the network level. Here we study a feeding network in Aplysia. In this network, persistent modulation supports the maintenance of an ingestive state, biasing the network to generate ingestive motor programs. Neuropeptides that exert cyclic adenosine monophosphate (cAMP) dependent effects play an important role in inducing the ingestive state. Most commonly, modulatory effects exerted through cAMP signaling are persistent as a consequence of PKA activation. This is not the case in the neurons we study. Instead maintenance of the network state depends on the persistence of cAMP itself. Data strongly suggest that this is a consequence of the direct activation of a cyclic nucleotide gated current.
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Affiliation(s)
- Matthew H Perkins
- Icahn School of Medicine at Mt. Sinai, Department of Neuroscience and Friedman Brain Institute, One Gustave L. Levy Place, Box 1065, New York, NY, 10029, USA.
| | - Klaudiusz R Weiss
- Icahn School of Medicine at Mt. Sinai, Department of Neuroscience and Friedman Brain Institute, One Gustave L. Levy Place, Box 1065, New York, NY, 10029, USA
| | - Elizabeth C Cropper
- Icahn School of Medicine at Mt. Sinai, Department of Neuroscience and Friedman Brain Institute, One Gustave L. Levy Place, Box 1065, New York, NY, 10029, USA
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5
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Green DJ, Huang RC, Sudlow L, Hatcher N, Potgieter K, McCrohan C, Lee C, Romanova EV, Sweedler JV, Gillette MLU, Gillette R. cAMP, Ca 2+, pH i, and NO Regulate H-like Cation Channels That Underlie Feeding and Locomotion in the Predatory Sea Slug Pleurobranchaea californica. ACS Chem Neurosci 2018; 9:1986-1993. [PMID: 30067017 PMCID: PMC6128535 DOI: 10.1021/acschemneuro.8b00187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A systems approach to regulation of neuronal excitation in the mollusc Pleurobranchaea has described novel interactions of cyclic AMP-gated cation current (INa,cAMP), Ca2+, pHi, and NO. INa,cAMP appears in many neurons of feeding and locomotor neuronal networks. It is likely one of the family of hyperpolarization-activated, cyclic-nucleotide-gated currents (h-current) of vertebrate and invertebrate pacemaker networks. There are two isoforms. Ca2+ regulates both voltage dependence and depolarization-sensitive inactivation in both isoforms. The Type 1 INa,cAMP of the feeding network is enhanced by intracellular acidification. A direct dependence of INa,cAMP on cAMP allows the current to be used as a reporter on cAMP concentrations in the cell, and from there to the intrinsic activities of the synthetic adenyl cyclase and the degradative phosphodiesterase. Type 2 INa,cAMP of the locomotor system is activated by serotonergic inputs, while Type 1 of the feeding network is thought to be regulated peptidergically. NO synthase activity is high in the CNS, where it differs from standard neuronal NO synthase in not being Ca2+ sensitive. NO acidifies pHi, potentiating Type 1, and may act to open proton channels. A cGMP pathway does not mediate NO effects as in other systems. Rather, nitrosylation likely mediates its actions. An integrated model of the action of cAMP, Ca2+, pHi, and NO in the feeding network postulates that NO regulates proton conductance to cause neuronal excitation in the cell body on the one hand, and relief of activity-induced hyperacidification in fine dendritic processes on the other.
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Affiliation(s)
- Daniel J Green
- Neuroscience Program , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Rong-Chi Huang
- Department of Molecular & Integrative Physiology , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Leland Sudlow
- Department of Molecular & Integrative Physiology , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Nathan Hatcher
- Department of Molecular & Integrative Physiology , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Kurt Potgieter
- Department of Molecular & Integrative Physiology , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Catherine McCrohan
- School of Biological Sciences , University of Manchester , Manchester M13 9PT , United Kingdom
| | - Colin Lee
- Neuroscience Program , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Elena V Romanova
- Beckman Institute for Advanced Science and Technology and Department of Chemistry , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Jonathan V Sweedler
- Beckman Institute for Advanced Science and Technology and Department of Chemistry , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Martha L U Gillette
- Department of Cell & Developmental Biology , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Rhanor Gillette
- Department of Molecular & Integrative Physiology , University of Illinois at Urbana-Champaign , Urbana , Illinois 61801 , United States
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6
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Potgieter K, Hatcher NG, Gillette R, McCrohan CR. Nitric oxide potentiates cAMP-gated cation current by intracellular acidification in feeding neurons of pleurobranchaea. J Neurophysiol 2010; 104:742-5. [PMID: 20484526 DOI: 10.1152/jn.00021.2010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A pH-sensitive cAMP-gated cation current (I(Na,cAMP)) is widely distributed in neurons of the feeding motor networks of gastropods. In the sea slug Pleurobranchaea this current is potentiated by nitric oxide (NO), which itself is produced by many feeding neurons. The action of NO is not dependent on either cGMP or cAMP signaling pathways. However, we found that NO potentiation of I(Na,cAMP) in the serotonergic metacerebral cells could be blocked by intracellular injection of MOPS buffer (pH 7.2). In neurons injected with the pH indicator BCECF, NO induced rapid intracellular acidification to several tenths of a pH unit. Intracellular pH has not previously been identified as a specific target of NO, but in this system NO modulation of I(Na,cAMP) via pH(i) may be an important regulator of the excitability of the feeding motor network.
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Affiliation(s)
- Kurt Potgieter
- Department of Molecular and Integrative Physiology, University of Illinois, Urbana, Illinois 61801, USA
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7
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Abstract
A key challenge for neuroinformatics is to devise methods for representing, accessing, and integrating vast amounts of diverse and complex data. A useful approach to represent and integrate complex data sets is to develop mathematical models [Arbib (The Handbook of Brain Theory and Neural Networks, pp. 741-745, 2003); Arbib and Grethe (Computing the Brain: A Guide to Neuroinformatics, 2001); Ascoli (Computational Neuroanatomy: Principles and Methods, 2002); Bower and Bolouri (Computational Modeling of Genetic and Biochemical Networks, 2001); Hines et al. (J. Comput. Neurosci. 17, 7-11, 2004); Shepherd et al. (Trends Neurosci. 21, 460-468, 1998); Sivakumaran et al. (Bioinformatics 19, 408-415, 2003); Smolen et al. (Neuron 26, 567-580, 2000); Vadigepalli et al. (OMICS 7, 235-252, 2003)]. Models of neural systems provide quantitative and modifiable frameworks for representing data and analyzing neural function. These models can be developed and solved using neurosimulators. One such neurosimulator is simulator for neural networks and action potentials (SNNAP) [Ziv (J. Neurophysiol. 71, 294-308, 1994)]. SNNAP is a versatile and user-friendly tool for developing and simulating models of neurons and neural networks. SNNAP simulates many features of neuronal function, including ionic currents and their modulation by intracellular ions and/or second messengers, and synaptic transmission and synaptic plasticity. SNNAP is written in Java and runs on most computers. Moreover, SNNAP provides a graphical user interface (GUI) and does not require programming skills. This chapter describes several capabilities of SNNAP and illustrates methods for simulating neurons and neural networks. SNNAP is available at http://snnap.uth.tmc.edu .
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Affiliation(s)
- Douglas A Baxter
- Department of Neurobiology and Anatomy, The University of Texas Medical School at Houston, Houston, TX, USA
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8
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Clemens S, Katz PS. G protein signaling in a neuronal network is necessary for rhythmic motor pattern production. J Neurophysiol 2003; 89:762-72. [PMID: 12574454 DOI: 10.1152/jn.00765.2002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G protein-coupled receptors are widely recognized as playing important roles in mediating the actions of extrinsic neuromodulatory inputs to motor networks. However, the potential for their direct involvement in rhythmic motor pattern generation has received considerably less attention. Results from this study indicate that G protein signaling appears to be integral to the operation of the central pattern generator (CPG) underlying the escape swim of the mollusk Tritonia diomedea. Blocking G protein signaling in a single CPG neuron, cerebral neuron C2, with intracellular iontophoresis of the guanine nucleotide analogue guanosine 5'-O-(2-thiodiphosphate) (GDP-beta-S), prevented the production of the swim motor program. Moreover, tonic activation of G protein signaling in this neuron by iontophoresis of the GTP analogues guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S) and 5'-guanylyl-imidodiphosphate also inhibited motor pattern production. The possible sites of action of these guanine nucleotide analogues were examined to assess potential mechanisms by which they interfered with motor pattern production. Intracellular iontophoresis of GDP-beta-S into C2 did not affect C2 basal synaptic strength. However, it did reduce heterosynaptic facilitation of C2 synapses caused by the dorsal swim interneurons (DSIs), a set of serotonergic swim CPG neurons. In contrast, GTP-gamma-S directly enhanced C2 synaptic strength onto DFN, mimicking the neuromodulatory effect of the DSIs. GDP-beta-S, but not the GTP analogues, decreased C2 excitability, whereas both GTP analogues, but not GDP-beta-S, blocked the ability of DSI stimulation to increase C2 excitability. The decrease in C2 excitability caused by GDP-beta-S is not likely to be responsible for the inhibition of the swim motor pattern because decreasing C2 firing rate, by injecting hyperpolarizing current, did not prevent the production of the rhythmic motor pattern. Taken together, these data suggest that G protein signaling is a necessary and integral component of the escape swim CPG in Tritonia and that G protein signaling mediates DSI heterosynaptic facilitation of C2 but may not mediate the DSI-evoked enhancement of C2 excitability.
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Affiliation(s)
- Stefan Clemens
- Department of Biology, SE Unit 8, Georgia State University, Atlanta, Georgia 30303-3088, USA.
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9
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Gola M, Delmas P, Chagneux H. Encoding properties induced by a persistent voltage-gated muscarinic sodium current in rabbit sympathetic neurones. J Physiol 1998; 510 ( Pt 2):387-99. [PMID: 9705991 PMCID: PMC2231040 DOI: 10.1111/j.1469-7793.1998.387bk.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
1. A time- and voltage-dependent Na(+)-selective current termed INa,M is activated by muscarinic agonists or splanchnic nerve stimulation in sympathetic neurones of rabbit coeliac and superior mesenteric ganglia. The firing patterns induced by INa,M were investigated in patch-clamped neurones within intact ganglia, and compared with those generated by a neuronal model including INa,M. 2. INa,M was characterized by voltage-dependent low threshold activation and high-threshold inactivation functions. The overlapping functions produced a persistent U-shaped current between -100 and -20 mV, which peaked at the cell resting potential. The activation and inactivation kinetics were fitted to single exponentials with time constants of approximately 100 and 400 ms, respectively. 3. Activating INa,M with muscarinic agonists or nerve stimulation depolarized and fired the neurones. The depolarization was paralleled by an apparent increase in input membrane resistance. The model showed that this paradox resulted from the turning off of INa,M during resistance tests, which also accounted for the all-or-none slow hyperpolarizing responses to current pulses. 4. INa,M gave the neurones an N-shaped I-V relationship capable of producing complex firing patterns. Under given conditions, carbachol-treated neurones could either fire regularly or remain silent at approximately -80 mV, i.e. they displayed bistability. Transitions from one state to the other were triggered with short current pulses. The transitions resulted from the turning on and off of INa,M. 5. Firing reduced INa,M, an effect abolished by blocking Ca2+ channels or adding BAPTA (40 mM) to the pipette. The Ca(2+)-related negative regulation of INa,M may have mediated endogenous bursting activity. Burst firing was generated by the model upon introducing Ca2+ regulation of INa,M. 6. The results demonstrate that INa,M gives prevertebral sympathetic neurones a wide repertoire of firing patterns: pacemaker-like properties, bistability and burst firing capability. They suggest that the INa,M-related encoding properties may provide sympathetic neurotransmission with new potentialities.
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Affiliation(s)
- M Gola
- Laboratoire de Neurobiologie, CNRS, Marseille, France.
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10
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Sudlow LC, Jing J, Moroz LL, Gillette R. Serotonin immunoreactivity in the central nervous system of the marine molluscs
Pleurobranchaea californica
and
Tritonia diomedea. J Comp Neurol 1998. [DOI: 10.1002/(sici)1096-9861(19980615)395:4<466::aid-cne4>3.0.co;2-#] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Leland C. Sudlow
- Department of Molecular and Integrative Physiology and the Neuroscience Program, University of Illinois, Urbana‐Champaign, Urbana, Illinois 61801
| | - Jian Jing
- Department of Molecular and Integrative Physiology and the Neuroscience Program, University of Illinois, Urbana‐Champaign, Urbana, Illinois 61801
| | - Leonid L. Moroz
- Department of Molecular and Integrative Physiology and the Neuroscience Program, University of Illinois, Urbana‐Champaign, Urbana, Illinois 61801
| | - Rhanor Gillette
- Department of Molecular and Integrative Physiology and the Neuroscience Program, University of Illinois, Urbana‐Champaign, Urbana, Illinois 61801
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11
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Delmas P, Raggenbass M, Gola M. Low-threshold Na+ currents: a new family of receptor-operated inward currents in mammalian nerve cells. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1997; 25:246-54. [PMID: 9403140 DOI: 10.1016/s0165-0173(97)00022-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In the mammalian nervous system, various neurotransmitters can modulate cell excitability by inducing slow membrane potential changes. In the last decade, inhibition of potassium currents has been characterized as the primary mechanism by which neurones can undergo sustained depolarization. More recently (1990s), a new class of inward currents, which are voltage-dependent and mainly carried by sodium ions, has been found to be activated by various neurotransmitter receptors in mammalian central and peripheral neurones. Because the channels involved pass depolarizing current, are open at more negative membrane potentials than the resting potential, and are voltage-gated and persistent, these currents are capable of producing regenerative and maintained depolarizations and play an important role in neuronal signalling.
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Affiliation(s)
- P Delmas
- Laboratoire de Neurobiologie, CNRS, Marseille, France.
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12
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Sudlow LC, Gillette R. Cyclic AMP levels, adenylyl cyclase activity, and their stimulation by serotonin quantified in intact neurons. J Gen Physiol 1997; 110:243-55. [PMID: 9276752 PMCID: PMC2229365 DOI: 10.1085/jgp.110.3.243] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In molluscan central neurons that express cAMP-gated Na+ current (INa,cAMP), estimates of the cAMP binding affinity of the channels have suggested that effective native intracellular cAMP concentrations should be much higher than characteristic of most cells. Using neurons of the marine opisthobranch snail Pleurobranchaea californica, we applied theory and conventional voltage clamp techniques to use INa,cAMP to report basal levels of endogenous cAMP and adenylyl cyclase, and their stimulation by serotonin. Measurements were calibrated to iontophoretic cAMP injection currents to enable expression of the data in molar terms. In 30 neurons, serotonin stimulated on average a 23-fold increase in submembrane [cAMP], effected largely by an 18-fold increase in adenylyl cyclase activity. Serotonin stimulation of adenylyl cyclase and [cAMP] was inversely proportional to cells' resting adenylyl cyclase activity. Average cAMP concentration at the membrane rose from 3.6 to 27.6 microM, levels consistent with the expected cAMP dissociation constants of the INa,cAMP channels. These measures confirm the functional character of INa,cAMP in the context of high levels of native cAMP. Methods similar to those employed here might be used to establish critical characters of cyclic nucleotide metabolism in the many cells of invertebrates and vertebrates that are being found to express ion currents gated by direct binding of cyclic nucleotides.
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Affiliation(s)
- L C Sudlow
- Department of Molecular and Integrative Physiology and the Neuroscience Program, University of Illinois, Urbana-Champaign, Urbana, Illinois 61801, USA
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