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Chang Z, Skach J, Kam K. Inhibitory Subpopulations in preBötzinger Complex Play Distinct Roles in Modulating Inspiratory Rhythm and Pattern. J Neurosci 2024; 44:e1928232024. [PMID: 38729762 PMCID: PMC11209648 DOI: 10.1523/jneurosci.1928-23.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 04/19/2024] [Accepted: 05/06/2024] [Indexed: 05/12/2024] Open
Abstract
Inhibitory neurons embedded within mammalian neural circuits shape breathing, walking, and other rhythmic motor behaviors. At the core of the neural circuit controlling breathing is the preBötzinger Complex (preBötC), where GABAergic (GAD1/2+) and glycinergic (GlyT2+) neurons are functionally and anatomically intercalated among glutamatergic Dbx1-derived (Dbx1+) neurons that generate rhythmic inspiratory drive. The roles of these preBötC inhibitory neurons in breathing remain unclear. We first characterized the spatial distribution of molecularly defined preBötC inhibitory subpopulations in male and female neonatal double reporter mice expressing either tdTomato or EGFP in GlyT2+, GAD1+, or GAD2+ neurons. We found that the majority of preBötC inhibitory neurons expressed both GlyT2 and GAD2 while a much smaller subpopulation also expressed GAD1. To determine the functional role of these subpopulations, we used holographic photostimulation, a patterned illumination technique, in rhythmically active medullary slices from neonatal Dbx1tdTomato;GlyT2EGFP and Dbx1tdTomato;GAD1EGFP double reporter mice of either sex. Stimulation of 4 or 8 preBötC GlyT2+ neurons during endogenous rhythm prolonged the interburst interval in a phase-dependent manner and increased the latency to burst initiation when bursts were evoked by stimulation of Dbx1+ neurons. In contrast, stimulation of 4 or 8 preBötC GAD1+ neurons did not affect interburst interval or latency to burst initiation. Instead, photoactivation of GAD1+ neurons during the inspiratory burst prolonged endogenous and evoked burst duration and decreased evoked burst amplitude. We conclude that GlyT2+/GAD2+ neurons modulate breathing rhythm by delaying burst initiation while a smaller GAD1+ subpopulation shapes inspiratory patterning by altering burst duration and amplitude.
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Affiliation(s)
- Zheng Chang
- Stanson Toshok Center for Brain Function and Repair, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064
| | - Jordan Skach
- Stanson Toshok Center for Brain Function and Repair, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064
| | - Kaiwen Kam
- Stanson Toshok Center for Brain Function and Repair, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064
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2
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Olmos-Pastoresa CA, Vázquez-Mendoza E, López-Meraz ML, Pérez-Estudillo CA, Beltran-Parrazal L, Morgado-Valle C. Transgenic rodents as dynamic models for the study of respiratory rhythm generation and modulation: a scoping review and a bibliometric analysis. Front Physiol 2023; 14:1295632. [PMID: 38179140 PMCID: PMC10764557 DOI: 10.3389/fphys.2023.1295632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 11/20/2023] [Indexed: 01/06/2024] Open
Abstract
The pre-Bötzinger complex, situated in the ventrolateral medulla, serves as the central generator for the inspiratory phase of the respiratory rhythm. Evidence strongly supports its pivotal role in generating, and, in conjunction with the post-inspiratory complex and the lateral parafacial nucleus, in shaping the respiratory rhythm. While there remains an ongoing debate concerning the mechanisms underlying these nuclei's ability to generate and modulate breathing, transgenic rodent models have significantly contributed to our understanding of these processes. However, there is a significant knowledge gap regarding the spectrum of transgenic rodent lines developed for studying respiratory rhythm, and the methodologies employed in these models. In this study, we conducted a scoping review to identify commonly used transgenic rodent lines and techniques for studying respiratory rhythm generation and modulation. Following PRISMA guidelines, we identified relevant papers in PubMed and EBSCO on 29 March 2023, and transgenic lines in Mouse Genome Informatics and the International Mouse Phenotyping Consortium. With strict inclusion and exclusion criteria, we identified 80 publications spanning 1997-2022 using 107 rodent lines. Our findings revealed 30 lines focusing on rhythm generation, 61 on modulation, and 16 on both. The primary in vivo method was whole-body plethysmography. The main in vitro method was hypoglossal/phrenic nerve recordings using the en bloc preparation. Additionally, we identified 119 transgenic lines with the potential for investigating the intricate mechanisms underlying respiratory rhythm. Through this review, we provide insights needed to design more effective experiments with transgenic animals to unravel the mechanisms governing respiratory rhythm. The identified transgenic rodent lines and methodological approaches compile current knowledge and guide future research towards filling knowledge gaps in respiratory rhythm generation and modulation.
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Affiliation(s)
| | | | | | | | - Luis Beltran-Parrazal
- Laboratorio de Neurofisiología, Instituto de Investigaciones Cerebrales, Universidad Veracruzana, Xalapa, Veracruz, Mexico
| | - Consuelo Morgado-Valle
- Laboratorio de Neurofisiología, Instituto de Investigaciones Cerebrales, Universidad Veracruzana, Xalapa, Veracruz, Mexico
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3
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Chang Z, Skach J, Kam K. Inhibitory subpopulations in preBötzinger Complex play distinct roles in modulating inspiratory rhythm and pattern. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.07.552303. [PMID: 37609332 PMCID: PMC10441369 DOI: 10.1101/2023.08.07.552303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Inhibitory neurons embedded within mammalian neural circuits shape breathing, walking, chewing, and other rhythmic motor behaviors. At the core of the neural circuit controlling breathing is the preBötzinger Complex (preBötC), a nucleus in the ventrolateral medulla necessary for generation of inspiratory rhythm. In the preBötC, a recurrently connected network of glutamatergic Dbx1-derived (Dbx1 + ) neurons generates rhythmic inspiratory drive. Functionally and anatomically intercalated among Dbx1 + preBötC neurons are GABAergic (GAD1/2 + ) and glycinergic (GlyT2 + ) neurons, whose roles in breathing remain unclear. To elucidate the inhibitory microcircuits within preBötC, we first characterized the spatial distribution of molecularly-defined inhibitory preBötC subpopulations in double reporter mice expressing either the red fluorescent protein tdTomato or EGFP in GlyT2 + , GAD1 + , or GAD2 + neurons. We found that, in postnatal mice, the majority of inhibitory preBötC neurons expressed a combination of GlyT2 and GAD2 while a much smaller subpopulation also expressed GAD1. To determine the functional role of these subpopulations, we used holographic photostimulation, a patterned illumination technique with high spatiotemporal resolution, in rhythmically active medullary slices from neonatal Dbx1 tdTomato ;GlyT2 EGFP and Dbx1 tdTomato ;GAD1 EGFP double reporter mice. Stimulation of 4 or 8 preBötC GlyT2 + neurons during endogenous rhythm prolonged the interburst interval in a phase-dependent manner and increased the latency to burst initiation when bursts were evoked by stimulation of Dbx1 + neurons. In contrast, stimulation of 4 or 8 preBötC GAD1 + neurons did not affect interburst interval or latency to burst initiation. Instead, photoactivation of GAD1 + neurons during the inspiratory burst prolonged endogenous and evoked burst duration and decreased evoked burst amplitude. We conclude that the majority of preBötC inhibitory neurons express both GlyT2 and GAD2 and modulate breathing rhythm by delaying burst initiation while a smaller GAD1 + subpopulation shapes inspiratory patterning by altering burst duration and amplitude.
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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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5
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Tacke C, Bischoff AM, Harb A, Vafadari B, Hülsmann S. Angiotensin II increases respiratory rhythmic activity in the preBötzinger complex without inducing astroglial calcium signaling. Front Cell Neurosci 2023; 17:1111263. [PMID: 36816850 PMCID: PMC9932970 DOI: 10.3389/fncel.2023.1111263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 01/17/2023] [Indexed: 02/05/2023] Open
Abstract
Angiotensin II (Ang II) is the primary modulator of the renin-angiotensin system and has been widely studied for its effect on the cardiovascular system. While a few studies have also indicated an involvement of Ang II in the regulation of breathing, very little is known in this regard and its effect on brainstem respiratory regions such as the preBötzinger complex (preBötC), the kernel for inspiratory rhythm generation, has not been investigated yet. This study reports that Ang II temporarily increases phrenic nerve activity in the working heart-brainstem preparation, indicating higher central respiratory drive. Previous studies have shown that the carotid body is involved in mediating this effect and we revealed that the preBötC also plays a part, using acute slices of the brainstem. It appears that Ang II is increasing the respiratory drive in an AT1R-dependent manner by optimizing the interaction of inhibitory and excitatory neurons of the preBötC. Thus, Ang II-mediated effects on the preBötC are potentially involved in dysregulating breathing in patients with acute lung injury.
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Oke Y, Miwakeichi F, Oku Y, Hirrlinger J, Hülsmann S. Cell types and synchronous-activity patterns of inspiratory neurons in the preBötzinger complex of mouse medullary slices during early postnatal development. Sci Rep 2023; 13:586. [PMID: 36631589 PMCID: PMC9834223 DOI: 10.1038/s41598-023-27893-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 01/10/2023] [Indexed: 01/13/2023] Open
Abstract
To examine whether and how the inspiratory neuronal network in the preBötzinger complex (preBötC) develops during the early postnatal period, we quantified the composition of the population of inspiratory neurons between postnatal day 1 (p1) and p10 by applying calcium imaging to medullary transverse slices in double-transgenic mice expressing fluorescent marker proteins. We found that putative excitatory and glycinergic neurons formed a majority of the population of inspiratory neurons, and the composition rates of these two inspiratory neurons inverted at p5-6. We also found that the activity patterns of these two types of inspiratory neurons became significantly well-synchronized with the inspiratory rhythmic bursting pattern in the preBötC within the first postnatal week. GABAergic and GABA-glycine cotransmitting inspiratory neurons formed only a small population just after birth, which almost disappeared until p10. In conclusion, the inspiratory neuronal network in the preBötC matures at the level of both neuronal population and neuronal activities during early postnatal development.
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Affiliation(s)
- Yoshihiko Oke
- Division of Physiome, Department of Physiology, Hyogo Medical University, 1-1 Mukogawa-cho, Nishinomiya, 663-8501, Japan.
| | - Fumikazu Miwakeichi
- grid.507381.80000 0001 1945 4756Department of Statistical Modeling, The Institute of Statistical Mathematics, 10-3, Midori-cho, Tachikawa, 190-0014 Japan ,grid.275033.00000 0004 1763 208XDepartment of Statistical Science, School of Multidisciplinary Sciences, The Graduate University for Advanced Studies, Shounan-Kokusai-Mura, Hayama-cho, Miura, 240-0193 Japan
| | - Yoshitaka Oku
- grid.272264.70000 0000 9142 153XDivision of Physiome, Department of Physiology, Hyogo Medical University, 1-1 Mukogawa-cho, Nishinomiya, 663-8501 Japan
| | - Johannes Hirrlinger
- grid.9647.c0000 0004 7669 9786Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Liebigstraße 27, 04103 Leipzig, Germany ,grid.516369.eDepartment of Neurogenetics, Max Planck Institute for Multidisciplinary Science, Hermann-Rein-Straße 3, 37075 Göttingen, Germany
| | - Swen Hülsmann
- grid.411984.10000 0001 0482 5331Department of Anesthesiology, University Medical Center, Humboldtallee 23, 37073 Göttingen, Germany
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Hirrlinger J, Nimmerjahn A. A perspective on astrocyte regulation of neural circuit function and animal behavior. Glia 2022; 70:1554-1580. [PMID: 35297525 PMCID: PMC9291267 DOI: 10.1002/glia.24168] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 01/19/2022] [Accepted: 02/27/2022] [Indexed: 12/16/2022]
Abstract
Studies over the past two decades have demonstrated that astrocytes are
tightly associated with neurons and play pivotal roles in neural circuit
development, operation, and adaptation in health and disease. Nevertheless,
precisely how astrocytes integrate diverse neuronal signals, modulate neural
circuit structure and function at multiple temporal and spatial scales, and
influence animal behavior or disease through aberrant excitation and molecular
output remains unclear. This Perspective discusses how new and state-of-the-art
approaches, including fluorescence indicators, opto- and chemogenetic actuators,
genetic targeting tools, quantitative behavioral assays, and computational
methods, might help resolve these longstanding questions. It also addresses
complicating factors in interpreting astrocytes’ role in neural circuit
regulation and animal behavior, such as their heterogeneity, metabolism, and
inter-glial communication. Research on these questions should provide a deeper
mechanistic understanding of astrocyte-neuron assemblies’ role in neural
circuit function, complex behaviors, and disease.
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Affiliation(s)
- Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany.,Department of Neurogenetics, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Axel Nimmerjahn
- Waitt Advanced Biophotonics Center, The Salk Institute for Biological Studies, La Jolla, California
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8
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Developmental changes in GABAergic and glycinergic synaptic transmission to rat motoneurons innervating jaw-closing and jaw-opening muscles. Brain Res 2021; 1777:147753. [PMID: 34914930 DOI: 10.1016/j.brainres.2021.147753] [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: 08/05/2021] [Revised: 11/03/2021] [Accepted: 12/09/2021] [Indexed: 11/21/2022]
Abstract
Trigeminal motoneurons (MNs) innervating the jaw-closing and jaw-opening muscles receive numerous inhibitory synaptic inputs from GABAergic and glycinergic neurons, which are essential for oromotor functions, such as the orofacial reflex, suckling, and mastication. The properties of the GABAergic and glycinergic inputs of these MNs undergo developmental alterations during the period in which their feeding behavior proceeds from suckling to mastication; however, the detailed characteristics of the developmental patterns of GABAergic and glycinergic transmission in these neurons remain to be elucidated. This study was conducted to investigate developmental changes in miniature inhibitory postsynaptic currents (mIPSCs) in masseter (jaw-closing) and digastric (jaw-opening) MNs using brainstem slice preparations obtained from Wistar rats on postnatal day (P)2-5, P9-12, and P14-17. The frequency and amplitude of glycinergic mIPSCs substantially increased with age in both the masseter and digastric MNs. The rise time and decay time of glycinergic mIPSCs in both MNs decreased during development. In contrast, the frequency of GABAergic components in masseter MNs was higher at P2-5 than at P14-17, whereas that in the digastric MNs remained unchanged throughout the postnatal period. The proportion of currents mediated by GABA-glycine co-transmission was higher at P2-5, and then it decreased with age in both MNs. These results suggest that characteristics related to the development of inhibitory synaptic inputs differ between jaw-closing and jaw-opening MNs and between GABAergic and glycinergic currents. These distinct developmental characteristics may contribute to the development of feeding behaviors.
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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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GABAergic Inhibition of Presynaptic Ca 2+ Transients in Respiratory PreBötzinger Neurons in Organotypic Slice Cultures. eNeuro 2021; 8:ENEURO.0154-21.2021. [PMID: 34380658 PMCID: PMC8387147 DOI: 10.1523/eneuro.0154-21.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 08/02/2021] [Accepted: 08/08/2021] [Indexed: 11/21/2022] Open
Abstract
GABAergic somatodendritic inhibition in the preBötzinger complex (preBötC), a medullary site for the generation of inspiratory rhythm, is involved in respiratory rhythmogenesis and patterning. Nevertheless, whether GABA acts distally on presynaptic terminals, evoking presynaptic inhibition is unknown. Here, we begin to address this problem by measuring presynaptic Ca2+ transients in preBötC neurons, under rhythmic and non-rhythmic conditions, with two variants of genetically encoded Ca2+ indicators (GECIs). Organotypic slice cultures from newborn mice, containing the preBötC, were drop-transduced with jGCaMP7s, or injected with jGCaMP7f-labeling commissural preBötC neurons. Then, Ca2+ imaging combined with whole-cell patch-clamp or field stimulation was obtained from inspiratory preBötC neurons. We found that rhythmically active neurons expressed synchronized Ca2+ transients in soma, proximal and distal dendritic regions, and punctate synapse-like structures. Expansion microscopy revealed morphologic characteristics of bona fide synaptic boutons of the en passant and terminal type. Under non-rhythmic conditions, we found that bath application of the GABAA receptor agonist muscimol, and local microiontophoresis of GABA, reduced action potential (AP)-evoked and field stimulus-evoked Ca2+ transients in presynaptic terminals in inspiratory neurons and commissural neurons projecting to the contralateral preBötC. In addition, under rhythmic conditions, network rhythmic activity was suppressed by muscimol, while the GABAA receptor antagonist bicuculline completely re-activated spontaneous activity. These observations demonstrate that the preBötC includes neurons that show GABAergic inhibition of presynaptic Ca2+ transients, and presynaptic inhibition may play a role in the network activity that underlies breathing.
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Cleary CM, Milla BM, Kuo FS, James S, Flynn WF, Robson P, Mulkey DK. Somatostatin-expressing parafacial neurons are CO 2/H + sensitive and regulate baseline breathing. eLife 2021; 10:e60317. [PMID: 34013884 PMCID: PMC8169115 DOI: 10.7554/elife.60317] [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: 06/23/2020] [Accepted: 05/19/2021] [Indexed: 01/16/2023] Open
Abstract
Glutamatergic neurons in the retrotrapezoid nucleus (RTN) function as respiratory chemoreceptors by regulating breathing in response to tissue CO2/H+. The RTN and greater parafacial region may also function as a chemosensing network composed of CO2/H+-sensitive excitatory and inhibitory synaptic interactions. In the context of disease, we showed that loss of inhibitory neural activity in a mouse model of Dravet syndrome disinhibited RTN chemoreceptors and destabilized breathing (Kuo et al., 2019). Despite this, contributions of parafacial inhibitory neurons to control of breathing are unknown, and synaptic properties of RTN neurons have not been characterized. Here, we show the parafacial region contains a limited diversity of inhibitory neurons including somatostatin (Sst)-, parvalbumin (Pvalb)-, and cholecystokinin (Cck)-expressing neurons. Of these, Sst-expressing interneurons appear uniquely inhibited by CO2/H+. We also show RTN chemoreceptors receive inhibitory input that is withdrawn in a CO2/H+-dependent manner, and chemogenetic suppression of Sst+ parafacial neurons, but not Pvalb+ or Cck+ neurons, increases baseline breathing. These results suggest Sst-expressing parafacial neurons contribute to RTN chemoreception and respiratory activity.
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Affiliation(s)
- Colin M Cleary
- Department of Physiology and Neurobiology, University of ConnecticutStorrsUnited States
| | - Brenda M Milla
- Department of Physiology and Neurobiology, University of ConnecticutStorrsUnited States
| | - Fu-Shan Kuo
- Department of Physiology and Neurobiology, University of ConnecticutStorrsUnited States
| | - Shaun James
- Department of Physiology and Neurobiology, University of ConnecticutStorrsUnited States
| | - William F Flynn
- The Jackson Laboratory for Genomic MedicineFarmingtonUnited States
| | - Paul Robson
- The Jackson Laboratory for Genomic MedicineFarmingtonUnited States
- Institute for Systems Genomics, University of ConnecticutFarmingtonUnited States
| | - Daniel K Mulkey
- Department of Physiology and Neurobiology, University of ConnecticutStorrsUnited States
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Schmeichel AM, Coon EA, Parisi JE, Singer W, Low PA, Benarroch EE. Loss of putative GABAergic neurons in the ventrolateral medulla in multiple system atrophy. Sleep 2021; 44:6182442. [PMID: 33755181 DOI: 10.1093/sleep/zsab074] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 03/17/2021] [Indexed: 11/12/2022] Open
Abstract
STUDY OBJECTIVES Multiple system atrophy (MSA) is associated with disturbances in cardiovascular, sleep and respiratory control. The lateral paragigantocellular nucleus (LPGi) in the ventrolateral medulla (VLM) contains GABAergic neurons that participate in control of rapid eye movement (REM) sleep and cardiovagal responses. We sought to determine whether there was loss of putative GABAergic neurons in the LPGi and adjacent regions in MSA. METHODS Sections of the medulla were processed for GAD65/67 immunoreactivity in eight subjects with clinical and neuropathological diagnosis of MSA and in six control subjects. These putative GABAergic LPGi neurons were mapped based on their relationship to adjacent monoaminergic VLM groups. RESULTS There were markedly decreased numbers of GAD-immunoreactive neurons in the LPGi and adjacent VLM regions in MSA. CONCLUSIONS There is loss of GABAergic neurons in the VLM, including the LPGi in patients with MSA. Whereas these findings provide a possible mechanistic substrate, given the few cases included, further studies are necessary to determine whether they contribute to REM sleep-related cardiovagal and possibly respiratory dysregulation in MSA.
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Affiliation(s)
| | | | - Joseph E Parisi
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | | | - Phillip A Low
- Department of Neurology, Mayo Clinic, Rochester, MN, USA
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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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A Discrete Glycinergic Neuronal Population in the Ventromedial Medulla That Induces Muscle Atonia during REM Sleep and Cataplexy in Mice. J Neurosci 2021; 41:1582-1596. [PMID: 33372061 DOI: 10.1523/jneurosci.0688-20.2020] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 12/13/2020] [Accepted: 12/15/2020] [Indexed: 12/20/2022] Open
Abstract
During rapid eye movement (REM) sleep, anti-gravity muscle tone and bodily movements are mostly absent, because somatic motoneurons are inhibited by descending inhibitory pathways. Recent studies showed that glycine/GABA neurons in the ventromedial medulla (VMM; GlyVMM neurons) play an important role in generating muscle atonia during REM sleep (REM-atonia). However, how these REM-atonia-inducing neurons interconnect with other neuronal populations has been unknown. In the present study, we first identified a specific subpopulation of GlyVMM neurons that play an important role in induction of REM-atonia by virus vector-mediated tracing in male mice in which glycinergic neurons expressed Cre recombinase. We found these neurons receive direct synaptic input from neurons in several brain stem regions, including glutamatergic neurons in the sublaterodorsal tegmental nucleus (SLD; GluSLD neurons). Silencing this circuit by specifically expressing tetanus toxin light chain (TeTNLC) resulted in REM sleep without atonia. This manipulation also caused a marked decrease in time spent in cataplexy-like episodes (CLEs) when applied to narcoleptic orexin-ataxin-3 mice. We also showed that GlyVMM neurons play an important role in maintenance of sleep. This present study identified a population of glycinergic neurons in the VMM that are commonly involved in REM-atonia and cataplexy.SIGNIFICANCE STATEMENT We identified a population of glycinergic neurons in the ventral medulla that plays an important role in inducing muscle atonia during rapid eye movement (REM) sleep. It sends axonal projections almost exclusively to motoneurons in the spinal cord and brain stem except to those that innervate extraocular muscles, while other glycinergic neurons in the same region also send projections to other regions including monoaminergic nuclei. Furthermore, these neurons receive direct inputs from several brainstem regions including glutamatergic neurons in the sublaterodorsal tegmental nucleus (SLD). Genetic silencing of this pathway resulted in REM sleep without atonia and a decrease of cataplexy when applied to narcoleptic mice. This work identified a neural population involved in generating muscle atonia during REM sleep and cataplexy.
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15
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Turecek J, Regehr WG. Cerebellar and vestibular nuclear synapses in the inferior olive have distinct release kinetics and neurotransmitters. eLife 2020; 9:e61672. [PMID: 33259288 PMCID: PMC7707816 DOI: 10.7554/elife.61672] [Citation(s) in RCA: 2] [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] [Received: 07/31/2020] [Accepted: 11/12/2020] [Indexed: 01/16/2023] Open
Abstract
The inferior olive (IO) is composed of electrically-coupled neurons that make climbing fiber synapses onto Purkinje cells. Neurons in different IO subnuclei are inhibited by synapses with wide ranging release kinetics. Inhibition can be exclusively synchronous, asynchronous, or a mixture of both. Whether the same boutons, neurons or sources provide these kinetically distinct types of inhibition was not known. We find that in mice the deep cerebellar nuclei (DCN) and vestibular nuclei (VN) are two major sources of inhibition to the IO that are specialized to provide inhibitory input with distinct kinetics. DCN to IO synapses lack fast synaptotagmin isoforms, release neurotransmitter asynchronously, and are exclusively GABAergic. VN to IO synapses contain fast synaptotagmin isoforms, release neurotransmitter synchronously, and are mediated by combined GABAergic and glycinergic transmission. These findings indicate that VN and DCN inhibitory inputs to the IO are suited to control different aspects of IO activity.
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Affiliation(s)
- Josef Turecek
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
| | - Wade G Regehr
- Department of Neurobiology, Harvard Medical SchoolBostonUnited States
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16
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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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Novel biomarkers and age-related metabolite correlations in plasma and dried blood spots from patients with succinic semialdehyde dehydrogenase deficiency. Orphanet J Rare Dis 2020; 15:261. [PMID: 32967698 PMCID: PMC7510106 DOI: 10.1186/s13023-020-01522-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 08/24/2020] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Previous work has identified age-related negative correlations for γ-hydroxybutyric acid (GHB) and γ-aminobutyric acid (GABA) in plasma of patients with succinic semialdehyde dehydrogenase deficiency (SSADHD). Using plasma and dried blood spots (DBS) collected in an ongoing natural history study, we tested the hypothesis that other biomarkers would follow a similar age-related negative correlation as seen for GHB/GABA. Samples (mixed sex) included: patients (n = 21 unique samples, 1-39.5 yrs) and parallel controls (n = 9 unique samples, 8.4-34.8 yrs). Archival control data (DBS only; n = 171, 0.5-39.9 yrs) was also included. RESULTS Metabolites assessed included amino acids (plasma, DBS) and acylcarnitines, creatine, creatinine, and guanidinoacetate (DBS only). Age-related negative correlations for glycine (plasma, DBS) and sarcosine (N-methylglycine, plasma) were detected, accompanied by elevated proline and decreased levels of succinylacetone, argininosuccinate, formaminoglutamate, and creatinine. Significantly low acylcarnitines were detected in patients across all chain lengths (short-, medium- and long-chain). Significant age-dependent positive correlations for selected acylcarnitines (C6-, C12DC(dicarboxylic)-, C16-, C16:1-, C18:1-, C18:2OH-carnitines) were detected in patients and absent in controls. Receiver operating characteristic (ROC) curves for all binary comparisons revealed argininosuccinate and succinylacetone to be the most discriminating biomarkers (area > 0.92). CONCLUSIONS Age-dependent acylcarnitine correlations may represent metabolic compensation responsive to age-related changes in GHB and GABA. Our study highlights novel biomarkers in SSADHD and expands the metabolic pathophysiology of this rare disorder of GABA metabolism.
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Yamakawa M, Santosa SM, Chawla N, Ivakhnitskaia E, Del Pino M, Giakas S, Nadel A, Bontu S, Tambe A, Guo K, Han KY, Cortina MS, Yu C, Rosenblatt MI, Chang JH, Azar DT. Transgenic models for investigating the nervous system: Currently available neurofluorescent reporters and potential neuronal markers. Biochim Biophys Acta Gen Subj 2020; 1864:129595. [PMID: 32173376 DOI: 10.1016/j.bbagen.2020.129595] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 02/24/2020] [Accepted: 03/03/2020] [Indexed: 02/06/2023]
Abstract
Recombinant DNA technologies have enabled the development of transgenic animal models for use in studying a myriad of diseases and biological states. By placing fluorescent reporters under the direct regulation of the promoter region of specific marker proteins, these models can localize and characterize very specific cell types. One important application of transgenic species is the study of the cytoarchitecture of the nervous system. Neurofluorescent reporters can be used to study the structural patterns of nerves in the central or peripheral nervous system in vivo, as well as phenomena involving embryologic or adult neurogenesis, injury, degeneration, and recovery. Furthermore, crucial molecular factors can also be screened via the transgenic approach, which may eventually play a major role in the development of therapeutic strategies against diseases like Alzheimer's or Parkinson's. This review describes currently available reporters and their uses in the literature as well as potential neural markers that can be leveraged to create additional, robust transgenic models for future studies.
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Affiliation(s)
- Michael Yamakawa
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Samuel M Santosa
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Neeraj Chawla
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Evguenia Ivakhnitskaia
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Matthew Del Pino
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Sebastian Giakas
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Arnold Nadel
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Sneha Bontu
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Arjun Tambe
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Kai Guo
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Kyu-Yeon Han
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Maria Soledad Cortina
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Charles Yu
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Mark I Rosenblatt
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America
| | - Jin-Hong Chang
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America.
| | - Dimitri T Azar
- Department of Ophthalmology and Visual Sciences, Illinois Eye and Ear Infirmary, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States of America.
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Zheng F, Nixdorf-Bergweiler BE, Edelmann E, van Brederode JFM, Alzheimer C. Muscarinic Modulation of Morphologically Identified Glycinergic Neurons in the Mouse PreBötzinger Complex. Front Cell Neurosci 2020; 13:562. [PMID: 31998077 PMCID: PMC6962194 DOI: 10.3389/fncel.2019.00562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Accepted: 12/05/2019] [Indexed: 11/13/2022] Open
Abstract
The cholinergic system plays an essential role in central respiratory control, but the underlying mechanisms remain elusive. We used whole-cell recordings in brainstem slices from juvenile mice expressing enhanced green fluorescent protein (EGFP) under the control of the glycine transporter type 2 (GlyT2) promoter, to examine muscarinic modulation of morphologically identified glycinergic neurons in the preBötzinger complex (preBötC), an area critical for central inspiratory rhythm generation. Biocytin-filled reconstruction of glycinergic neurons revealed that the majority of them had few primary dendrites and had axons arborized within their own dendritic field. Few glycinergic neurons had axon collaterals extended towards the premotor/motor areas or ran towards the contralateral preBötC, and had more primary dendrites and more compact dendritic trees. Spontaneously active glycinergic neurons fired regular spikes, or less frequently in a "burst-like" pattern at physiological potassium concentration. Muscarine suppressed firing in the majority of regular spiking neurons via M2 receptor activation while enhancing the remaining neurons through M1 receptors. Interestingly, rhythmic bursting was augmented by muscarine in a small group of glycinergic neurons. In contrast to its heterogeneous modulation of glycinergic neuronal excitability, muscarine generally depressed inhibitory and excitatory synaptic inputs onto both glycinergic and non-glycinergic preBötC neurons, with a stronger effect on inhibitory input. Notably, presynaptic muscarinic attenuation of excitatory synaptic input was dependent on M1 receptors in glycinergic neurons and on M2 receptors in non-glycinergic neurons. Additional field potential recordings of excitatory synaptic potentials in the M2 receptor knockout mice indicate that glycinergic and non-glycinergic neurons contribute equally to the general suppression by muscarine of excitatory activity in preBötC circuits. In conclusion, our data show that preBötC glycinergic neurons are morphologically heterogeneous, and differ in the properties of synaptic transmission and muscarinic modulation in comparison to non-glycinergic neurons. The dominant and cell-type-specific muscarinic inhibition of synaptic neurotransmission and spiking may contribute to central respiratory disturbances in high cholinergic states.
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Affiliation(s)
- Fang Zheng
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Barbara E Nixdorf-Bergweiler
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Elke Edelmann
- Institut für Physiologie, Otto-von-Guericke-Universität, Magdeburg, Germany
| | - Johannes F M van Brederode
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.,Department of Physiology and Biophysics, University of Washington, Seattle, WA, United States
| | - Christian Alzheimer
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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