1
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Naffaa MM. Neurogenesis dynamics in the olfactory bulb: deciphering circuitry organization, function, and adaptive plasticity. Neural Regen Res 2025; 20:1565-1581. [PMID: 38934393 DOI: 10.4103/nrr.nrr-d-24-00312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 05/31/2024] [Indexed: 06/28/2024] Open
Abstract
Adult neurogenesis persists after birth in the subventricular zone, with new neurons migrating to the granule cell layer and glomerular layers of the olfactory bulb, where they integrate into existing circuitry as inhibitory interneurons. The generation of these new neurons in the olfactory bulb supports both structural and functional plasticity, aiding in circuit remodeling triggered by memory and learning processes. However, the presence of these neurons, coupled with the cellular diversity within the olfactory bulb, presents an ongoing challenge in understanding its network organization and function. Moreover, the continuous integration of new neurons in the olfactory bulb plays a pivotal role in regulating olfactory information processing. This adaptive process responds to changes in epithelial composition and contributes to the formation of olfactory memories by modulating cellular connectivity within the olfactory bulb and interacting intricately with higher-order brain regions. The role of adult neurogenesis in olfactory bulb functions remains a topic of debate. Nevertheless, the functionality of the olfactory bulb is intricately linked to the organization of granule cells around mitral and tufted cells. This organizational pattern significantly impacts output, network behavior, and synaptic plasticity, which are crucial for olfactory perception and memory. Additionally, this organization is further shaped by axon terminals originating from cortical and subcortical regions. Despite the crucial role of olfactory bulb in brain functions and behaviors related to olfaction, these complex and highly interconnected processes have not been comprehensively studied as a whole. Therefore, this manuscript aims to discuss our current understanding and explore how neural plasticity and olfactory neurogenesis contribute to enhancing the adaptability of the olfactory system. These mechanisms are thought to support olfactory learning and memory, potentially through increased complexity and restructuring of neural network structures, as well as the addition of new granule granule cells that aid in olfactory adaptation. Additionally, the manuscript underscores the importance of employing precise methodologies to elucidate the specific roles of adult neurogenesis amidst conflicting data and varying experimental paradigms. Understanding these processes is essential for gaining insights into the complexities of olfactory function and behavior.
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Affiliation(s)
- Moawiah M Naffaa
- Department of Psychology and Neuroscience, Duke University, Durham, NC, USA
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, USA
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2
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Suyama H, Bianchini G, Lukas M. Vasopressin differentially modulates the excitability of rat olfactory bulb neuron subtypes. Front Neural Circuits 2024; 18:1448592. [PMID: 39268350 PMCID: PMC11390533 DOI: 10.3389/fncir.2024.1448592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Accepted: 08/13/2024] [Indexed: 09/15/2024] Open
Abstract
Vasopressin (VP) plays a crucial role in social memory even at the level of the olfactory bulb (OB), where OB VP cells are activated during social interactions. However, it remains unclear how VP modulates olfactory processing to enable enhanced discrimination of very similar odors, e.g., rat body odors. Thus far, it has been shown that VP reduces firing rates in mitral cells (MCs) during odor presentation in vivo and decreases the amplitudes of olfactory nerve-evoked excitatory postsynaptic potentials (ON-evoked EPSPs) in external tufted cells in vitro. We performed whole-cell patch-clamp recordings and population Ca2+ imaging on acute rat OB slices. We recorded ON-evoked EPSPs as well as spontaneous inhibitory postsynaptic currents (IPSCs) from two types of projection neurons: middle tufted cells (mTCs) and MCs. VP bath application reduced the amplitudes of ON-evoked EPSPs and the frequencies of spontaneous IPSCs in mTCs but did not change those in MCs. Therefore, we analyzed ON-evoked EPSPs in inhibitory interneurons, i.e., periglomerular cells (PGCs) and granule cells (GCs), to search for the origin of increased inhibition in mTCs. However, VP did not increase the amplitudes of evoked EPSPs in either type of interneurons. We next performed two-photon population Ca2+ imaging in the glomerular layer and the superficial GC layer of responses to stronger ON stimulation than during patch-clamp experiments that should evoke action potentials in the measured cells. We observed that VP application increased ON-evoked Ca2+ influx in juxtaglomerular cells and GC somata. Thus, our findings indicate inhibition by VP on projection neurons via strong ON input-mediated inhibitory interneuron activity. This neural modulation could improve representation of odors, hence, better discriminability of similar odors, e.g., conspecific body odors.
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Affiliation(s)
- Hajime Suyama
- Institute of Zoology, Neurophysiology, University of Regensburg, Regensburg, Germany
| | - Gaia Bianchini
- Neural Circuits and Behavior Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Michael Lukas
- Institute of Zoology, Neurophysiology, University of Regensburg, Regensburg, Germany
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3
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Burton SD, Malyshko CM, Urban NN. Fast-spiking interneuron detonation drives high-fidelity inhibition in the olfactory bulb. PLoS Biol 2024; 22:e3002660. [PMID: 39186804 PMCID: PMC11379389 DOI: 10.1371/journal.pbio.3002660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 09/06/2024] [Accepted: 07/26/2024] [Indexed: 08/28/2024] Open
Abstract
Inhibitory circuits in the mammalian olfactory bulb (OB) dynamically reformat olfactory information as it propagates from peripheral receptors to downstream cortex. To gain mechanistic insight into how specific OB interneuron types support this sensory processing, we examine unitary synaptic interactions between excitatory mitral and tufted cells (MTCs), the OB projection neurons, and a conserved population of anaxonic external plexiform layer interneurons (EPL-INs) using pair and quartet whole-cell recordings in acute mouse brain slices. Physiological, morphological, neurochemical, and synaptic analyses divide EPL-INs into distinct subtypes and reveal that parvalbumin-expressing fast-spiking EPL-INs (FSIs) perisomatically innervate MTCs with release-competent dendrites and synaptically detonate to mediate fast, short-latency recurrent and lateral inhibition. Sparse MTC synchronization supralinearly increases this high-fidelity inhibition, while sensory afferent activation combined with single-cell silencing reveals that individual FSIs account for a substantial fraction of total network-driven MTC lateral inhibition. OB output is thus powerfully shaped by detonation-driven high-fidelity perisomatic inhibition.
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Affiliation(s)
- Shawn D Burton
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
| | - Christina M Malyshko
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
| | - Nathaniel N Urban
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, United States of America
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4
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Fulton KA, Zimmerman D, Samuel A, Vogt K, Datta SR. Common principles for odour coding across vertebrates and invertebrates. Nat Rev Neurosci 2024; 25:453-472. [PMID: 38806946 DOI: 10.1038/s41583-024-00822-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/30/2024] [Indexed: 05/30/2024]
Abstract
The olfactory system is an ideal and tractable system for exploring how the brain transforms sensory inputs into behaviour. The basic tasks of any olfactory system include odour detection, discrimination and categorization. The challenge for the olfactory system is to transform the high-dimensional space of olfactory stimuli into the much smaller space of perceived objects and valence that endows odours with meaning. Our current understanding of how neural circuits address this challenge has come primarily from observations of the mechanisms of the brain for processing other sensory modalities, such as vision and hearing, in which optimized deep hierarchical circuits are used to extract sensory features that vary along continuous physical dimensions. The olfactory system, by contrast, contends with an ill-defined, high-dimensional stimulus space and discrete stimuli using a circuit architecture that is shallow and parallelized. Here, we present recent observations in vertebrate and invertebrate systems that relate the statistical structure and state-dependent modulation of olfactory codes to mechanisms of perception and odour-guided behaviour.
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Affiliation(s)
- Kara A Fulton
- Department of Neuroscience, Harvard Medical School, Boston, MA, USA
| | - David Zimmerman
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Aravi Samuel
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Katrin Vogt
- Department of Physics, Harvard University, Cambridge, MA, USA.
- Department of Biology, University of Konstanz, Konstanz, Germany.
- Centre for the Advanced Study of Collective Behaviour, University of Konstanz, Konstanz, Germany.
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5
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Tsuboi A. A specific olfactory bulb interneuron subtype Tpbg/5T4 generated at embryonic and neonatal stages. Front Neural Circuits 2024; 18:1427378. [PMID: 38933598 PMCID: PMC11203798 DOI: 10.3389/fncir.2024.1427378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2024] [Accepted: 05/24/2024] [Indexed: 06/28/2024] Open
Abstract
Various mammals have shown that sensory stimulation plays a crucial role in regulating the development of diverse structures, such as the olfactory bulb (OB), cerebral cortex, hippocampus, and retina. In the OB, the dendritic development of excitatory projection neurons like mitral/tufted cells is influenced by olfactory experiences. Odor stimulation is also essential for the dendritic development of inhibitory OB interneurons, such as granule and periglomerular cells, which are continuously produced in the ventricular-subventricular zone throughout life. Based on the morphological and molecular features, OB interneurons are classified into several subtypes. The role for each interneuron subtype in the control of olfactory behavior remains poorly understood due to lack of each specific marker. Among the several OB interneuron subtypes, a specific granule cell subtype, which expresses the oncofetal trophoblast glycoprotein (Tpbg or 5T4) gene, has been reported to be required for odor detection and discrimination behavior. This review will primarily focus on elucidating the contribution of different granule cell subtypes, including the Tpbg/5T4 subtype, to olfactory processing and behavior during the embryonic and adult stages.
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Affiliation(s)
- Akio Tsuboi
- Graduate School of Pharmaceutical Sciences, Osaka University, Toyonaka, Japan
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6
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Burton SD, Malyshko CM, Urban NN. Fast-spiking interneuron detonation drives high-fidelity inhibition in the olfactory bulb. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.07.592874. [PMID: 38766161 PMCID: PMC11100763 DOI: 10.1101/2024.05.07.592874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Inhibitory circuits in the mammalian olfactory bulb (OB) dynamically reformat olfactory information as it propagates from peripheral receptors to downstream cortex. To gain mechanistic insight into how specific OB interneuron types support this sensory processing, we examine unitary synaptic interactions between excitatory mitral and tufted cells (MTCs), the OB projection cells, and a conserved population of anaxonic external plexiform layer interneurons (EPL-INs) using pair and quartet whole-cell recordings in acute mouse brain slices. Physiological, morphological, neurochemical, and synaptic analyses divide EPL-INs into distinct subtypes and reveal that parvalbumin-expressing fast-spiking EPL-INs (FSIs) perisomatically innervate MTCs with release-competent dendrites and synaptically detonate to mediate fast, short-latency recurrent and lateral inhibition. Sparse MTC synchronization supralinearly increases this high-fidelity inhibition, while sensory afferent activation combined with single-cell silencing reveals that individual FSIs account for a substantial fraction of total network-driven MTC lateral inhibition. OB output is thus powerfully shaped by detonation-driven high-fidelity perisomatic inhibition.
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Affiliation(s)
- Shawn D. Burton
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, USA
| | | | - Nathaniel N. Urban
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, USA
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7
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Lorenzon P, Antos K, Tripathi A, Vedin V, Berghard A, Medini P. In vivo spontaneous activity and coital-evoked inhibition of mouse accessory olfactory bulb output neurons. iScience 2023; 26:107545. [PMID: 37664596 PMCID: PMC10470370 DOI: 10.1016/j.isci.2023.107545] [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: 03/30/2023] [Revised: 04/11/2023] [Accepted: 08/01/2023] [Indexed: 09/05/2023] Open
Abstract
Little is known about estrous effects on brain microcircuits. We examined the accessory olfactory bulb (AOB) in vivo, in anesthetized naturally cycling females, as model microcircuit receiving coital somatosensory information. Whole-cell recordings demonstrate that output neurons are relatively hyperpolarized in estrus and unexpectedly fire high frequency bursts of action potentials. To mimic coitus, a calibrated artificial vagino-cervical stimulation (aVCS) protocol was devised. aVCS evoked stimulus-locked local field responses in the interneuron layer independent of estrous stage. The response is sensitive to α1-adrenergic receptor blockade, as expected since aVCS increases norepinephrine release in AOB. Intriguingly, only in estrus does aVCS inhibit AOB spike output. Estrus-specific output reduction coincides with prolonged aVCS activation of inhibitory interneurons. Accordingly, in estrus the AOB microcircuit sets the stage for coital stimulation to inhibit the output neurons, possibly via high frequency bursting-dependent enhancement of reciprocal synapse efficacy between inter- and output neurons.
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Affiliation(s)
- Paolo Lorenzon
- Department of Integrative Medical Biology, Umeå University, SE90187 Umeå, Sweden
| | - Kamil Antos
- Department of Integrative Medical Biology, Umeå University, SE90187 Umeå, Sweden
| | - Anushree Tripathi
- Department of Integrative Medical Biology, Umeå University, SE90187 Umeå, Sweden
| | - Viktoria Vedin
- Department of Molecular Biology, Umeå University, SE90187 Umeå, Sweden
| | - Anna Berghard
- Department of Molecular Biology, Umeå University, SE90187 Umeå, Sweden
| | - Paolo Medini
- Department of Integrative Medical Biology, Umeå University, SE90187 Umeå, Sweden
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Brunert D, Quintela RM, Rothermel M. The anterior olfactory nucleus revisited - an emerging role for neuropathological conditions? Prog Neurobiol 2023:102486. [PMID: 37343762 DOI: 10.1016/j.pneurobio.2023.102486] [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: 12/23/2022] [Revised: 06/14/2023] [Accepted: 06/16/2023] [Indexed: 06/23/2023]
Abstract
Olfaction is an important sensory modality for many species and greatly influences animal and human behavior. Still, much about olfactory perception remains unknown. The anterior olfactory nucleus is one of the brain's central early olfactory processing areas. Located directly posterior to the olfactory bulb in the olfactory peduncle with extensive in- and output connections and unique cellular composition, it connects olfactory processing centers of the left and right hemispheres. Almost 20 years have passed since the last comprehensive review on the anterior olfactory nucleus has been published and significant advances regarding its anatomy, function, and pathophysiology have been made in the meantime. Here we briefly summarize previous knowledge on the anterior olfactory nucleus, give detailed insights into the progress that has been made in recent years, and map out its emerging importance in translational research of neurological diseases.
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Affiliation(s)
- Daniela Brunert
- Institute of Physiology, Medical Faculty, Otto-von-Guericke-University, 39120 Magdeburg, Germany
| | | | - Markus Rothermel
- Institute of Physiology, Medical Faculty, Otto-von-Guericke-University, 39120 Magdeburg, Germany.
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9
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Aghvami SS, Kubota Y, Egger V. Anatomical and Functional Connectivity at the Dendrodendritic Reciprocal Mitral Cell-Granule Cell Synapse: Impact on Recurrent and Lateral Inhibition. Front Neural Circuits 2022; 16:933201. [PMID: 35937203 PMCID: PMC9355734 DOI: 10.3389/fncir.2022.933201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Accepted: 05/27/2022] [Indexed: 11/16/2022] Open
Abstract
In the vertebrate olfactory bulb, reciprocal dendrodendritic interactions between its principal neurons, the mitral and tufted cells, and inhibitory interneurons in the external plexiform layer mediate both recurrent and lateral inhibition, with the most numerous of these interneurons being granule cells. Here, we used recently established anatomical parameters and functional data on unitary synaptic transmission to simulate the strength of recurrent inhibition of mitral cells specifically from the reciprocal spines of rat olfactory bulb granule cells in a quantitative manner. Our functional data allowed us to derive a unitary synaptic conductance on the order of 0.2 nS. The simulations predicted that somatic voltage deflections by even proximal individual granule cell inputs are below the detection threshold and that attenuation with distance is roughly linear, with a passive length constant of 650 μm. However, since recurrent inhibition in the wake of a mitral cell action potential will originate from hundreds of reciprocal spines, the summated recurrent IPSP will be much larger, even though there will be substantial mutual shunting across the many inputs. Next, we updated and refined a preexisting model of connectivity within the entire rat olfactory bulb, first between pairs of mitral and granule cells, to estimate the likelihood and impact of recurrent inhibition depending on the distance between cells. Moreover, to characterize the substrate of lateral inhibition, we estimated the connectivity via granule cells between any two mitral cells or all the mitral cells that belong to a functional glomerular ensemble (i.e., which receive their input from the same glomerulus), again as a function of the distance between mitral cells and/or entire glomerular mitral cell ensembles. Our results predict the extent of the three regimes of anatomical connectivity between glomerular ensembles: high connectivity within a glomerular ensemble and across the first four rings of adjacent glomeruli, substantial connectivity to up to eleven glomeruli away, and negligible connectivity beyond. Finally, in a first attempt to estimate the functional strength of granule-cell mediated lateral inhibition, we combined this anatomical estimate with our above simulation results on attenuation with distance, resulting in slightly narrowed regimes of a functional impact compared to the anatomical connectivity.
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Affiliation(s)
- S. Sara Aghvami
- School of Cognitive Sciences, Institute for Research in Fundamental Sciences (IPM), Tehran, Iran
| | - Yoshiyuki Kubota
- Division of Cerebral Circuitry, National Institute for Physiological Sciences (NIPS), Okazaki, Japan
| | - Veronica Egger
- Neurophysiology, Institute of Zoology, Regensburg University, Regensburg, Germany
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10
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Schubert C, Schulz K, Träger S, Plath AL, Omriouate A, Rosenkranz SC, Morellini F, Friese MA, Hirnet D. Neuronal Adenosine A1 Receptor is Critical for Olfactory Function but Unable to Attenuate Olfactory Dysfunction in Neuroinflammation. Front Cell Neurosci 2022; 16:912030. [PMID: 35846561 PMCID: PMC9279574 DOI: 10.3389/fncel.2022.912030] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Accepted: 06/08/2022] [Indexed: 11/13/2022] Open
Abstract
Adenine nucleotides, such as adenosine triphosphate (ATP), adenosine diphosphate (ADP), as well as the nucleoside adenosine are important modulators of neuronal function by engaging P1 and P2 purinergic receptors. In mitral cells, signaling of the G protein-coupled P1 receptor adenosine 1 receptor (A1R) affects the olfactory sensory pathway by regulating high voltage-activated calcium channels and two-pore domain potassium (K2P) channels. The inflammation of the central nervous system (CNS) impairs the olfactory function and gives rise to large amounts of extracellular ATP and adenosine, which act as pro-inflammatory and anti-inflammatory mediators, respectively. However, it is unclear whether neuronal A1R in the olfactory bulb modulates the sensory function and how this is impacted by inflammation. Here, we show that signaling via neuronal A1R is important for the physiological olfactory function, while it cannot counteract inflammation-induced hyperexcitability and olfactory deficit. Using neuron-specific A1R-deficient mice in patch-clamp recordings, we found that adenosine modulates spontaneous dendro-dendritic signaling in mitral and granule cells via A1R. Furthermore, neuronal A1R deficiency resulted in olfactory dysfunction in two separate olfactory tests. In mice with experimental autoimmune encephalomyelitis (EAE), we detected immune cell infiltration and microglia activation in the olfactory bulb as well as hyperexcitability of mitral cells and olfactory dysfunction. However, neuron-specific A1R activity was unable to attenuate glutamate excitotoxicity in the primary olfactory bulb neurons in vitro or EAE-induced olfactory dysfunction and disease severity in vivo. Together, we demonstrate that A1R modulates the dendro-dendritic inhibition (DDI) at the site of mitral and granule cells and impacts the processing of the olfactory sensory information, while A1R activity was unable to counteract inflammation-induced hyperexcitability.
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Affiliation(s)
- Charlotte Schubert
- Institute of Neuroimmunology and Multiple Sclerosis (INIMS), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Kristina Schulz
- Division of Neurophysiology, Institute of Cell and Systems Biology of Animals, University of Hamburg, Hamburg, Germany
| | - Simone Träger
- Institute of Neuroimmunology and Multiple Sclerosis (INIMS), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Anna-Lena Plath
- Research Group Behavioral Biology, Center for Molecular Neurobiology (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Asina Omriouate
- Research Group Behavioral Biology, Center for Molecular Neurobiology (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Sina C. Rosenkranz
- Institute of Neuroimmunology and Multiple Sclerosis (INIMS), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Fabio Morellini
- Research Group Behavioral Biology, Center for Molecular Neurobiology (ZMNH), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Manuel A. Friese
- Institute of Neuroimmunology and Multiple Sclerosis (INIMS), University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- *Correspondence: Manuel A. Friese,
| | - Daniela Hirnet
- Division of Neurophysiology, Institute of Cell and Systems Biology of Animals, University of Hamburg, Hamburg, Germany
- Daniela Hirnet,
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11
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Wichmann C, Kuner T. Heterogeneity of glutamatergic synapses: cellular mechanisms and network consequences. Physiol Rev 2022; 102:269-318. [PMID: 34727002 DOI: 10.1152/physrev.00039.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Chemical synapses are commonly known as a structurally and functionally highly diverse class of cell-cell contacts specialized to mediate communication between neurons. They represent the smallest "computational" unit of the brain and are typically divided into excitatory and inhibitory as well as modulatory categories. These categories are subdivided into diverse types, each representing a different structure-function repertoire that in turn are thought to endow neuronal networks with distinct computational properties. The diversity of structure and function found among a given category of synapses is referred to as heterogeneity. The main building blocks for this heterogeneity are synaptic vesicles, the active zone, the synaptic cleft, the postsynaptic density, and glial processes associated with the synapse. Each of these five structural modules entails a distinct repertoire of functions, and their combination specifies the range of functional heterogeneity at mammalian excitatory synapses, which are the focus of this review. We describe synapse heterogeneity that is manifested on different levels of complexity ranging from the cellular morphology of the pre- and postsynaptic cells toward the expression of different protein isoforms at individual release sites. We attempt to define the range of structural building blocks that are used to vary the basic functional repertoire of excitatory synaptic contacts and discuss sources and general mechanisms of synapse heterogeneity. Finally, we explore the possible impact of synapse heterogeneity on neuronal network function.
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Affiliation(s)
- Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Institute for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
| | - Thomas Kuner
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, Heidelberg, Germany
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12
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Manzini I, Schild D, Di Natale C. Principles of odor coding in vertebrates and artificial chemosensory systems. Physiol Rev 2021; 102:61-154. [PMID: 34254835 DOI: 10.1152/physrev.00036.2020] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The biological olfactory system is the sensory system responsible for the detection of the chemical composition of the environment. Several attempts to mimic biological olfactory systems have led to various artificial olfactory systems using different technical approaches. Here we provide a parallel description of biological olfactory systems and their technical counterparts. We start with a presentation of the input to the systems, the stimuli, and treat the interface between the external world and the environment where receptor neurons or artificial chemosensors reside. We then delineate the functions of receptor neurons and chemosensors as well as their overall I-O relationships. Up to this point, our account of the systems goes along similar lines. The next processing steps differ considerably: while in biology the processing step following the receptor neurons is the "integration" and "processing" of receptor neuron outputs in the olfactory bulb, this step has various realizations in electronic noses. For a long period of time, the signal processing stages beyond the olfactory bulb, i.e., the higher olfactory centers were little studied. Only recently there has been a marked growth of studies tackling the information processing in these centers. In electronic noses, a third stage of processing has virtually never been considered. In this review, we provide an up-to-date overview of the current knowledge of both fields and, for the first time, attempt to tie them together. We hope it will be a breeding ground for better information, communication, and data exchange between very related but so far little connected fields.
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Affiliation(s)
- Ivan Manzini
- Animal Physiology and Molecular Biomedicine, Justus-Liebig-University Gießen, Gießen, Germany
| | - Detlev Schild
- Institute of Neurophysiology and Cellular Biophysics, University Medical Center, University of Göttingen, Göttingen, Germany
| | - Corrado Di Natale
- Department of Electronic Engineering, University of Rome Tor Vergata, Rome, Italy
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13
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Affiliation(s)
- Silke Sachse
- Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, 07745, Jena, Germany.
| | - Ivan Manzini
- Department of Animal Physiology and Molecular Biomedicine, Justus-Liebig-University Giessen, Giessen, Germany.
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