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Vafadari B, Tacke C, Harb A, Grützner AA, Hülsmann S. Increase of breathing rate mediated by unilateral optogenetic inactivation of inhibitory neurons in the preBötzinger Complex in vivo. Respir Physiol Neurobiol 2023; 311:104032. [PMID: 36758781 DOI: 10.1016/j.resp.2023.104032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/26/2023] [Accepted: 02/06/2023] [Indexed: 02/11/2023]
Abstract
Brainstem neural circuits located in the preBötzinger complex (preBötC) and Bötzinger complex (BötC) play a critical role in the control of breathing. In this study, glycinergic preBötC and BötC neurons were inactivated with optogenetics in vivo using mice with Cre inducible expression of eNpHR3.0-EYFP. Unilateral inhibition of glycinergic neurons in the preBötC, and to a lower extend also in the BötC, led to a higher respiratory rate. It can be concluded that functional inactivation of inhibitory neurons leads to a disinhibition of preBötC excitatory neurons and thus an increase in the respiratory drive of the network.
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Affiliation(s)
- Behnam Vafadari
- Department of Anesthesiology, University Medical Center, Georg-August University, Humboldtallee 23, D-37073 Göttingen, Germany.
| | - Charlotte Tacke
- Department of Anesthesiology, University Medical Center, Georg-August University, Humboldtallee 23, D-37073 Göttingen, Germany
| | - Ali Harb
- Department of Anesthesiology, University Medical Center, Georg-August University, Humboldtallee 23, D-37073 Göttingen, Germany
| | - Anja-Annett Grützner
- Department of Anesthesiology, University Medical Center, Georg-August University, Humboldtallee 23, D-37073 Göttingen, Germany
| | - Swen Hülsmann
- Department of Anesthesiology, University Medical Center, Georg-August University, Humboldtallee 23, D-37073 Göttingen, Germany.
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2
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Hülsmann S, Khan A, Hagos L, Hindermann M, Nägel T, Dullin C. Evaluation of a mechanical lung model to test small animal whole body plethysmography. Sci Rep 2021; 11:17099. [PMID: 34429449 PMCID: PMC8384843 DOI: 10.1038/s41598-021-96355-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 07/30/2021] [Indexed: 11/27/2022] Open
Abstract
Whole-body plethysmography (WBP) is an established method to determine physiological parameters and pathophysiological alteration of breathing in animals and animal models of a variety of diseases. Although frequently used, there is ongoing debate about what exactly is measured by whole-body-plethysmography and how reliable the data derived from this method are. Here, we designed an artificial lung model that enables a thorough evaluation of different predictions about and around whole-body plethysmography. Using our lung model, we confirmed that during WBP two components contribute to the pressure changes detected in the chamber: (1) the increase in the pressure due to heating and moistening of the air during inspiration, termed conditioning; (2) changes in the chamber pressure that depend on airway resistance. Both components overlap and contribute to the temporal pressure-profile measured in the chamber or across the wall of the chamber, respectively. Our data showed that a precise measurement of the breathing volume appears to be hindered by at least two factors: (1) the unknown relative contribution of each of these two components; (2) not only the air in the inspired volume is conditioned during inspiration, but also air within the residual volume and dead space that is recruited during inspiration. Moreover, our data suggest that the expiratory negative pressure peak that is used to determine the enhanced pause (Penh) parameter is not a measure for airway resistance as such but rather a consequence of the animal’s response to the airway resistance, using forced or active expiration to overcome the resistance by a higher thoracic pressure.
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Affiliation(s)
- Swen Hülsmann
- Clinic for Anesthesiology, University Medical Center, Göttingen, Germany.
| | - Amara Khan
- Department of Translational Molecular Imaging, Max-Plank-Institute of Experimental Medicine, Göttingen, Germany
| | - Liya Hagos
- Clinic for Anesthesiology, University Medical Center, Göttingen, Germany
| | - Martin Hindermann
- Department of Clinical Neuroscience, Max-Plank-Institute of Experimental Medicine, Göttingen, Germany
| | - Torsten Nägel
- Institute of Neuro- and Sensory Physiology, University Medical Center, Göttingen, Germany
| | - Christian Dullin
- Institute for Diagnostic and Interventional Radiology, University Medical Center, Göttingen, Germany.,Italian Synchrotron Light Source 'Elettra' Trieste, Trieste, Italy
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3
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Khan A, Markus A, Rittmann T, Albers J, Alves F, Hülsmann S, Dullin C. Simple low dose radiography allows precise lung volume assessment in mice. Sci Rep 2021; 11:4163. [PMID: 33602964 PMCID: PMC7893164 DOI: 10.1038/s41598-021-83319-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 01/08/2021] [Indexed: 02/07/2023] Open
Abstract
X-ray based lung function (XLF) as a planar method uses dramatically less X-ray dose than computed tomography (CT) but so far lacked the ability to relate its parameters to pulmonary air volume. The purpose of this study was to calibrate the functional constituents of XLF that are biomedically decipherable and directly comparable to that of micro-CT and whole-body plethysmography (WBP). Here, we developed a unique set-up for simultaneous assessment of lung function and volume using XLF, micro-CT and WBP on healthy mice. Our results reveal a strong correlation of lung volumes obtained from radiographic XLF and micro-CT and demonstrate that XLF is superior to WBP in sensitivity and precision to assess lung volumes. Importantly, XLF measurement uses only a fraction of the radiation dose and acquisition time required for CT. Therefore, the redefined XLF approach is a promising tool for preclinical longitudinal studies with a substantial potential of clinical translation.
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Affiliation(s)
- Amara Khan
- Translational Molecular Imaging, Max-Planck-Institute for Experimental Medicine, Hermann-Rein-Straße 3, 37075, Göttingen, Germany
| | - Andrea Markus
- Translational Molecular Imaging, Max-Planck-Institute for Experimental Medicine, Hermann-Rein-Straße 3, 37075, Göttingen, Germany
| | - Thomas Rittmann
- 4th Physical Institute - Solids and Nanostructures, University of Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
| | - Jonas Albers
- Translational Molecular Imaging, Max-Planck-Institute for Experimental Medicine, Hermann-Rein-Straße 3, 37075, Göttingen, Germany
- Institute for Diagnostic and Interventional Radiology, University Medical Center Göttingen, Robert-Koch-Straße 40, 37075, Göttingen, Germany
| | - Frauke Alves
- Translational Molecular Imaging, Max-Planck-Institute for Experimental Medicine, Hermann-Rein-Straße 3, 37075, Göttingen, Germany
- Institute for Diagnostic and Interventional Radiology, University Medical Center Göttingen, Robert-Koch-Straße 40, 37075, Göttingen, Germany
- Clinic for Hematology and Medical Oncology, University Medical Center Göttingen, Robert-Koch-Str. 40, 37075, Göttingen, Germany
| | - Swen Hülsmann
- Clinic for Anesthesiology, University Medical Center Göttingen, Humboldtallee 23, 37073, Göttingen, Germany
| | - Christian Dullin
- Translational Molecular Imaging, Max-Planck-Institute for Experimental Medicine, Hermann-Rein-Straße 3, 37075, Göttingen, Germany.
- Institute for Diagnostic and Interventional Radiology, University Medical Center Göttingen, Robert-Koch-Straße 40, 37075, Göttingen, Germany.
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4
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Inspiratory Off-Switch Mediated by Optogenetic Activation of Inhibitory Neurons in the preBötzinger Complex In Vivo. Int J Mol Sci 2021; 22:ijms22042019. [PMID: 33670653 PMCID: PMC7922779 DOI: 10.3390/ijms22042019] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 02/14/2021] [Accepted: 02/16/2021] [Indexed: 01/02/2023] Open
Abstract
The role of inhibitory neurons in the respiratory network is a matter of ongoing debate. Conflicting and contradicting results are manifold and the question whether inhibitory neurons are essential for the generation of the respiratory rhythm as such is controversial. Inhibitory neurons are required in pulmonary reflexes for adapting the activity of the central respiratory network to the status of the lung and it is hypothesized that glycinergic neurons mediate the inspiratory off-switch. Over the years, optogenetic tools have been developed that allow for cell-specific activation of subsets of neurons in vitro and in vivo. In this study, we aimed to identify the effect of activation of inhibitory neurons in vivo. Here, we used a conditional transgenic mouse line that expresses Channelrhodopsin 2 in inhibitory neurons. A 200 µm multimode optical fiber ferrule was implanted in adult mice using stereotaxic surgery, allowing us to stimulate inhibitory, respiratory neurons within the core excitatory network in the preBötzinger complex of the ventrolateral medulla. We show that, in anesthetized mice, activation of inhibitory neurons by blue light (470 nm) continuously or with stimulation frequencies above 10 Hz results in a significant reduction of the respiratory rate, in some cases leading to complete cessation of breathing. However, a lower stimulation frequency (4–5 Hz) could induce a significant increase in the respiratory rate. This phenomenon can be explained by the resetting of the respiratory cycle, since stimulation during inspiration shortened the associated breath and thereby increased the respiratory rate, while stimulation during the expiratory interval reduced the respiratory rate. Taken together, these results support the concept that activation of inhibitory neurons mediates phase-switching by inhibiting excitatory rhythmogenic neurons in the preBötzinger complex.
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5
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Xing H, Cui N, Johnson CM, Faisthalab Z, Jiang C. Dual synaptic inhibitions of brainstem neurons by GABA and glycine with impact on Rett syndrome. J Cell Physiol 2020; 236:3615-3628. [PMID: 33169374 DOI: 10.1002/jcp.30098] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 09/20/2020] [Accepted: 09/24/2020] [Indexed: 12/29/2022]
Abstract
Rett syndrome (RTT) is a neurodevelopmental disease caused mostly by mutations in the MECP2 gene. People with RTT show breathing dysfunction attributable to the high rate of sudden death. Previous studies have shown that insufficient GABA synaptic inhibition contributes to the breathing abnormalities in mouse models of RTT, while it remains elusive how the glycine system is affected. We found that optogenetic stimulation of GAD-expressing neurons in mice produced GABAergic and glycinergic postsynaptic inhibitions of neurons in the hypoglossal nucleus (XII) and the dorsal motor nucleus of vagus (DMNV). By sequential applications of bicuculline and strychnine, such inhibition appeared approximately 44% GABAA ergic and 52% glycinergic in XII neurons, and approximately 49% GABAA ergic and 46% glycinergic in DMNV neurons. Miniature inhibitory postsynaptic potentials (mIPSCs) in these neurons were approximately 47% GABAA ergic and 49% glycinergic in XII neurons, and approximately 48% versus 50% in DMNV neurons, respectively. Consistent with the data, our single-cell polymerase chain reaction studies indicated that transcripts of GABAA receptor γ2 subunit (GABAA Rγ2) and glycine receptor β subunit (GlyRβ) were simultaneously expressed in these cells. In MeCP2R168X mice, proportions of GABAA ergic and glycinergic mIPSCs became approximately 28% versus 69% in XII neurons, and approximately 31% versus 66% in DMNV cells. In comparison with control mice, the GABAA ergic and glycinergic mIPSCs decreased significantly in the XII and DMNV neurons from the MeCP2R168X mice, so did the transcripts of GABAA Rγ2 and GlyRβ. These results suggest that XII and DMNV neurons adopt dual GABAA ergic and glycinergic synaptic inhibitions, and with Mecp2 disruption these neurons rely more on glycinergic synaptic inhibition.
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Affiliation(s)
- Hao Xing
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | - Ningren Cui
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | | | - Zaakir Faisthalab
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
| | - Chun Jiang
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
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6
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Eichel MA, Gargareta VI, D'Este E, Fledrich R, Kungl T, Buscham TJ, Lüders KA, Miracle C, Jung RB, Distler U, Kusch K, Möbius W, Hülsmann S, Tenzer S, Nave KA, Werner HB. CMTM6 expressed on the adaxonal Schwann cell surface restricts axonal diameters in peripheral nerves. Nat Commun 2020; 11:4514. [PMID: 32908139 PMCID: PMC7481192 DOI: 10.1038/s41467-020-18172-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 08/07/2020] [Indexed: 01/25/2023] Open
Abstract
The velocity of nerve conduction is moderately enhanced by larger axonal diameters and potently sped up by myelination of axons. Myelination thus allows rapid impulse propagation with reduced axonal diameters; however, no myelin-dependent mechanism has been reported that restricts radial growth of axons. By label-free proteomics, STED-microscopy and cryo-immuno electron-microscopy we here identify CMTM6 (chemokine-like factor-like MARVEL-transmembrane domain-containing family member-6) as a myelin protein specifically localized to the Schwann cell membrane exposed to the axon. We find that disruption of Cmtm6-expression in Schwann cells causes a substantial increase of axonal diameters but does not impair myelin biogenesis, radial sorting or integrity of axons. Increased axonal diameters correlate with accelerated sensory nerve conduction and sensory responses and perturbed motor performance. These data show that Schwann cells utilize CMTM6 to restrict the radial growth of axons, which optimizes nerve function.
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Affiliation(s)
- Maria A Eichel
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Vasiliki-Ilya Gargareta
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Elisa D'Este
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany
- Optical Microscopy Facility, Max Planck Institute for Medical Research, 69120, Heidelberg, Germany
| | - Robert Fledrich
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
- Institute of Anatomy, University of Leipzig, 04103, Leipzig, Germany
| | - Theresa Kungl
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
- Institute of Anatomy, University of Leipzig, 04103, Leipzig, Germany
| | - Tobias J Buscham
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Katja A Lüders
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Cristina Miracle
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Ramona B Jung
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Ute Distler
- Institute of Immunology, University Medical Center, Johannes Gutenberg University, 55131, Mainz, Germany
- Focus Program Translational Neuroscience, University Medical Center, Johannes Gutenberg University, 55131, Mainz, Germany
| | - Kathrin Kusch
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Wiebke Möbius
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
- Electron Microscopy Core Unit, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Swen Hülsmann
- Clinic for Anesthesiology, University Medical Center, 37073, Göttingen, Germany
| | - Stefan Tenzer
- Institute of Immunology, University Medical Center, Johannes Gutenberg University, 55131, Mainz, Germany
| | - Klaus-Armin Nave
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany
| | - Hauke B Werner
- Department of Neurogenetics, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany.
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7
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Hirrlinger J, Marx G, Besser S, Sicker M, Köhler S, Hirrlinger PG, Wojcik SM, Eulenburg V, Winkler U, Hülsmann S. GABA-Glycine Cotransmitting Neurons in the Ventrolateral Medulla: Development and Functional Relevance for Breathing. Front Cell Neurosci 2019; 13:517. [PMID: 31803026 PMCID: PMC6877658 DOI: 10.3389/fncel.2019.00517] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 11/04/2019] [Indexed: 11/13/2022] Open
Abstract
Inhibitory neurons crucially contribute to shaping the breathing rhythm in the brain stem. These neurons use GABA or glycine as neurotransmitter; or co-release GABA and glycine. However, the developmental relationship between GABAergic, glycinergic and cotransmitting neurons, and the functional relevance of cotransmitting neurons has remained enigmatic. Transgenic mice expressing fluorescent markers or the split-Cre system in inhibitory neurons were developed to track the three different interneuron phenotypes. During late embryonic development, the majority of inhibitory neurons in the ventrolateral medulla are cotransmitting cells, most of which differentiate into GABAergic and glycinergic neurons around birth and around postnatal day 4, respectively. Functional inactivation of cotransmitting neurons revealed an increase of the number of respiratory pauses, the cycle-by-cycle variability, and the overall variability of breathing. In summary, the majority of cotransmitting neurons differentiate into GABAergic or glycinergic neurons within the first 2 weeks after birth and these neurons contribute to fine-tuning of the breathing pattern.
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Affiliation(s)
- Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany.,Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
| | - Grit Marx
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Stefanie Besser
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Marit Sicker
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Susanne Köhler
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Petra G Hirrlinger
- Medizinisch-Experimentelles Zentrum, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
| | - Volker Eulenburg
- Department for Anesthesiology and Intensive Care Therapy, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Ulrike Winkler
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Swen Hülsmann
- Department of Anaesthesiology, University Medical Center, Georg-August University, Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
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8
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Hülsmann S, Oke Y, Mesuret G, Latal AT, Fortuna MG, Niebert M, Hirrlinger J, Fischer J, Hammerschmidt K. The postnatal development of ultrasonic vocalization-associated breathing is altered in glycine transporter 2-deficient mice. J Physiol 2018; 597:173-191. [PMID: 30296333 DOI: 10.1113/jp276976] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 10/01/2018] [Indexed: 01/03/2023] Open
Abstract
KEY POINTS Newborn mice produce ultrasonic vocalization to communicate with their mother. The neuronal glycine transporter (GlyT2) is required for efficient loading of synaptic vesicles in glycinergic neurons. Mice lacking GlyT2 develop a phenotype that resembles human hyperekplexia and the mice die in the second postnatal week. In the present study, we show that GlyT2-knockout mice do not acquire adult ultrasonic vocalization-associated breathing patterns. Despite the strong impairment of glycinergic inhibition, they can produce sufficient expiratory airflow to produce ultrasonic vocalization. Because mouse ultrasonic vocalization is a valuable read-out in translational research, these data are highly relevant for a broad range of research fields. ABSTRACT Mouse models are instrumental with respect to determining the genetic basis and neural foundations of breathing regulation. To test the hypothesis that glycinergic synaptic inhibition is required for normal breathing and proper post-inspiratory activity, we analysed breathing and ultrasonic vocalization (USV) patterns in neonatal mice lacking the neuronal glycine transporter (GlyT2). GlyT2-knockout (KO) mice have a profound reduction of glycinergic synaptic currents already at birth, develop a severe motor phenotype and survive only until the second postnatal week. At this stage, GlyT2-KO mice are smaller, have a reduced respiratory rate and still display a neonatal breathing pattern with active expiration for the production of USV. By contrast, wild-type mice acquire different USV-associated breathing patterns that depend on post-inspiratory control of air flow. Nonetheless, USVs per se remain largely indistinguishable between both genotypes. We conclude that GlyT2-KO mice, despite the strong impairment of glycinergic inhibition, can produce sufficient expiratory airflow to produce ultrasonic vocalization.
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Affiliation(s)
- Swen Hülsmann
- Clinic for Anesthesiology, University Medical Center, Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany
| | - Yoshihiko Oke
- Division of Physiome, Department of Physiology, Hyogo College of Medicine, Nishinomiya, Japan
| | - Guillaume Mesuret
- Clinic for Anesthesiology, University Medical Center, Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany
| | - A Tobias Latal
- Clinic for Anesthesiology, University Medical Center, Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany
| | - Michal G Fortuna
- Clinic for Anesthesiology, University Medical Center, Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany
| | - Marcus Niebert
- Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Göttingen, Germany
| | - Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany.,Max Planck Institute of Experimental Medicine, Department of Neurogenetics, Göttingen, Germany
| | - Julia Fischer
- German Primate Center - Leibniz Institute for Primate Research, Cognitive Ethology Laboratory, Göttingen, Germany
| | - Kurt Hammerschmidt
- German Primate Center - Leibniz Institute for Primate Research, Cognitive Ethology Laboratory, Göttingen, Germany
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9
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Probing the function of glycinergic neurons in the mouse respiratory network using optogenetics. Respir Physiol Neurobiol 2018; 265:141-152. [PMID: 30395936 DOI: 10.1016/j.resp.2018.10.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 10/23/2018] [Accepted: 10/31/2018] [Indexed: 12/15/2022]
Abstract
Glycine is a primary inhibitory transmitter in the ventral medullary respiratory network, but the functional role of glycinergic neurons for breathing remains a matter of debate. We applied optogenetics to selectively modulate glycinergic neuron activity within regions of the rostral ventral respiratory column (VRC). Responses of the phrenic nerve activity to the light-driven stimulation were studied in the working heart-brainstem preparation from adult glycine transporter 2 Cre mice (GlyT2-Cre), which received a unilateral injection of a Cre-dependent AAV virus into Bötzinger and preBötzinger Complex. Sustained light stimulation from the ventral medullary surface resulted in a substantial depression of the phrenic nerve (PN) frequency, which in most cases was compensated by an increase in PN amplitude. Periodic, burst stimulation with variable intervals could alter and reset respiratory rhythm. We conclude that unilateral activation of the rostral VRC glycinergic neurons can significantly affect respiratory pattern by lengthening the expiratory interval and modulating phase transition.
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10
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Vogelgesang S, Niebert M, Bischoff AM, Hülsmann S, Manzke T. Persistent Expression of Serotonin Receptor 5b Alters Breathing Behavior in Male MeCP2 Knockout Mice. Front Mol Neurosci 2018. [PMID: 29515365 PMCID: PMC5826236 DOI: 10.3389/fnmol.2018.00028] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Mutations in the transcription factor methyl-CpG-binding protein 2 (MeCP2) cause the neurodevelopmental disorder Rett syndrome (RTT). Besides many other neurological problems, RTT patients show irregular breathing with recurrent apneas or breath-holdings. MeCP2-deficient mice, which recapitulate this breathing phenotype, show a dysregulated, persistent expression of G-protein-coupled serotonin receptor 5-ht5b (Htr5b) in the brainstem. To investigate whether the persistence of 5-ht5b expression is contributing to the respiratory phenotype, we crossbred MeCP2-deficient mice with 5-ht5b-deficient mice to generate double knockout mice (Mecp2−/y;Htr5b−/−). To compare respiration between wild type (WT), Mecp2−/y and Mecp2−/y;Htr5b−/− mice, we used unrestrained whole-body plethysmography. While the breathing of MeCP2-deficient male mice (Mecp2−/y) at postnatal day 40 is characterized by a slow breathing rate and the occurrence of prolonged respiratory pauses, we found that in MeCP2-deficient mice, which also lacked the 5-ht5b receptor, the breathing rate and the number of pauses were indistinguishable from WT mice. To test for a potential mechanism, we also analyzed if the known coupling of 5-ht5b receptors to Gi proteins is altering second messenger signaling. Tissue cAMP levels in the medulla of Mecp2−/y mice were decreased as compared to WT mice. In contrast, cAMP levels in Mecp2−/y;Htr5b−/− mice were indistinguishable from WT mice. Taken together, our data points towards a role of 5-ht5b receptors within the complex breathing phenotype of MeCP2-deficient mice.
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Affiliation(s)
- Steffen Vogelgesang
- DFG-Research Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University of Göttingen, Göttingen, Germany.,Institute of Neuro- and Sensory Physiology, University of Göttingen, Göttingen, Germany
| | - Marcus Niebert
- DFG-Research Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University of Göttingen, Göttingen, Germany.,Institute of Neuro- and Sensory Physiology, University of Göttingen, Göttingen, Germany
| | - Anne M Bischoff
- DFG-Research Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University of Göttingen, Göttingen, Germany.,Clinic for Anesthesiology, University Medical Göttingen, Göttingen, Germany
| | - Swen Hülsmann
- DFG-Research Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University of Göttingen, Göttingen, Germany.,Clinic for Anesthesiology, University Medical Göttingen, Göttingen, Germany
| | - Till Manzke
- DFG-Research Center Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University of Göttingen, Göttingen, Germany.,Institute of Neuro- and Sensory Physiology, University of Göttingen, Göttingen, Germany
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11
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Mesuret G, Dannenberg J, Arnoldt M, Grützner AA, Niebert M, Hülsmann S. Breathing disturbances in a model of Rett syndrome: A potential involvement of the glycine receptor α3 subunit? Respir Physiol Neurobiol 2018; 248:43-47. [DOI: 10.1016/j.resp.2017.11.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 11/30/2017] [Accepted: 11/30/2017] [Indexed: 11/30/2022]
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