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Coates KE, Calle-Schuler SA, Helmick LM, Knotts VL, Martik BN, Salman F, Warner LT, Valla SV, Bock DD, Dacks AM. The Wiring Logic of an Identified Serotonergic Neuron That Spans Sensory Networks. J Neurosci 2020; 40:6309-6327. [PMID: 32641403 PMCID: PMC7424878 DOI: 10.1523/jneurosci.0552-20.2020] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 06/16/2020] [Accepted: 06/25/2020] [Indexed: 12/21/2022] Open
Abstract
Serotonergic neurons project widely throughout the brain to modulate diverse physiological and behavioral processes. However, a single-cell resolution understanding of the connectivity of serotonergic neurons is currently lacking. Using a whole-brain EM dataset of a female Drosophila, we comprehensively determine the wiring logic of a broadly projecting serotonergic neuron (the CSDn) that spans several olfactory regions. Within the antennal lobe, the CSDn differentially innervates each glomerulus, yet surprisingly, this variability reflects a diverse set of presynaptic partners, rather than glomerulus-specific differences in synaptic output, which is predominately to local interneurons. Moreover, the CSDn has distinct connectivity relationships with specific local interneuron subtypes, suggesting that the CSDn influences distinct aspects of local network processing. Across olfactory regions, the CSDn has different patterns of connectivity, even having different connectivity with individual projection neurons that also span these regions. Whereas the CSDn targets inhibitory local neurons in the antennal lobe, the CSDn has more distributed connectivity in the LH, preferentially synapsing with principal neuron types based on transmitter content. Last, we identify individual novel synaptic partners associated with other sensory domains that provide strong, top-down input to the CSDn. Together, our study reveals the complex connectivity of serotonergic neurons, which combine the integration of local and extrinsic synaptic input in a nuanced, region-specific manner.SIGNIFICANCE STATEMENT All sensory systems receive serotonergic modulatory input. However, a comprehensive understanding of the synaptic connectivity of individual serotonergic neurons is lacking. In this study, we use a whole-brain EM microscopy dataset to comprehensively determine the wiring logic of a broadly projecting serotonergic neuron in the olfactory system of Drosophila Collectively, our study demonstrates, at a single-cell level, the complex connectivity of serotonergic neurons within their target networks, identifies specific cell classes heavily targeted for serotonergic modulation in the olfactory system, and reveals novel extrinsic neurons that provide strong input to this serotonergic system outside of the context of olfaction. Elucidating the connectivity logic of individual modulatory neurons provides a ground plan for the seemingly heterogeneous effects of modulatory systems.
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Affiliation(s)
- Kaylynn E Coates
- Department of Biology, West Virginia University, Morgantown, West Virginia 26506
| | | | - Levi M Helmick
- Department of Biology, West Virginia University, Morgantown, West Virginia 26506
| | - Victoria L Knotts
- Department of Biology, West Virginia University, Morgantown, West Virginia 26506
| | - Brennah N Martik
- Department of Biology, West Virginia University, Morgantown, West Virginia 26506
| | - Farzaan Salman
- Department of Biology, West Virginia University, Morgantown, West Virginia 26506
| | - Lauren T Warner
- Department of Biology, West Virginia University, Morgantown, West Virginia 26506
| | - Sophia V Valla
- Department of Biology, West Virginia University, Morgantown, West Virginia 26506
| | - Davi D Bock
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia 20147
- Department of Neurological Sciences, Larner College of Medicine, University of Vermont, Burlington, Vermont 05405
| | - Andrew M Dacks
- Department of Biology, West Virginia University, Morgantown, West Virginia 26506
- Department of Neuroscience, West Virginia University, Morgantown, West Virginia 26506
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2
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Sizemore TR, Hurley LM, Dacks AM. Serotonergic modulation across sensory modalities. J Neurophysiol 2020; 123:2406-2425. [PMID: 32401124 PMCID: PMC7311732 DOI: 10.1152/jn.00034.2020] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 05/04/2020] [Accepted: 05/12/2020] [Indexed: 12/24/2022] Open
Abstract
The serotonergic system has been widely studied across animal taxa and different functional networks. This modulatory system is therefore well positioned to compare the consequences of neuromodulation for sensory processing across species and modalities at multiple levels of sensory organization. Serotonergic neurons that innervate sensory networks often bidirectionally exchange information with these networks but also receive input representative of motor events or motivational state. This convergence of information supports serotonin's capacity for contextualizing sensory information according to the animal's physiological state and external events. At the level of sensory circuitry, serotonin can have variable effects due to differential projections across specific sensory subregions, as well as differential serotonin receptor type expression within those subregions. Functionally, this infrastructure may gate or filter sensory inputs to emphasize specific stimulus features or select among different streams of information. The near-ubiquitous presence of serotonin and other neuromodulators within sensory regions, coupled with their strong effects on stimulus representation, suggests that these signaling pathways should be considered integral components of sensory systems.
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Affiliation(s)
- Tyler R Sizemore
- Department of Biology, West Virginia University, Morgantown, West Virginia
| | - Laura M Hurley
- Department of Biology, Indiana University, Bloomington, Indiana
| | - Andrew M Dacks
- Department of Biology, West Virginia University, Morgantown, West Virginia
- Department of Neuroscience, West Virginia University, Morgantown, West Virginia
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3
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Serotonergic afferents from the dorsal raphe decrease the excitability of pyramidal neurons in the anterior piriform cortex. Proc Natl Acad Sci U S A 2020; 117:3239-3247. [PMID: 31992641 DOI: 10.1073/pnas.1913922117] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The olfactory system receives extensive serotonergic inputs from the dorsal raphe, a nucleus involved in control of behavior, regulation of mood, and modulation of sensory processing. Although many studies have investigated how serotonin modulates the olfactory bulb, few have focused on the anterior piriform cortex (aPC), a region important for olfactory learning and encoding of odor identity and intensity. Specifically, the mechanism and functional significance of serotonergic modulation of the aPC remain largely unknown. Here we used pharmacologic, optogenetic, and fiber photometry techniques to examine the serotonergic modulation of neural activity in the aPC in vitro and in vivo. We found that serotonin (5-HT) reduces the excitability of pyramidal neurons directly via 5-HT2C receptors, phospholipase C, and calcium-activated potassium (BK) channels. Furthermore, endogenous serotonin attenuates odor-evoked calcium responses in aPC pyramidal neurons. These findings identify the mechanism underlying serotonergic modulation of the aPC and shed light on its potential role.
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4
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Upreti C, Konstantinov E, Kassabov SR, Bailey CH, Kandel ER. Serotonin Induces Structural Plasticity of Both Extrinsic Modulating and Intrinsic Mediating Circuits In Vitro in Aplysia Californica. Cell Rep 2019; 28:2955-2965.e3. [PMID: 31509754 DOI: 10.1016/j.celrep.2019.08.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 11/27/2018] [Accepted: 07/31/2019] [Indexed: 01/29/2023] Open
Abstract
Long-term sensitization of the gill withdrawal reflex in Aplysia requires heterosynaptic, modulatory input that is mediated in part by the growth of new synaptic connections between sensory neurons and their follower cells (intrinsic mediating circuit). Whether modulatory interneurons (the extrinsic modulatory circuit) also display learning-related structural synaptic plasticity remains unknown. To test this idea, we added a bona fide serotonergic modulatory neuron, the metacerebral cell (MCC), to sensory-motor neuron co-cultures and examined the modulating presynaptic varicosities of MCCs before and after repeated pulses of serotonin (5-HT) that induced long-term facilitation (LTF). We observed robust growth of new serotonergic varicosities that were positive for serotonin and capable of synaptic recycling. Our findings demonstrate that, in addition to structural changes in the intrinsic mediating circuit, there are also significant learning-related structural changes in the extrinsic modulating circuit, and these changes might provide a cellular mechanism for savings and for spread of memory.
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Affiliation(s)
- Chirag Upreti
- Department of Neuroscience, Columbia University, New York, NY 10027, USA; New York State Psychiatric Institute, New York, NY 10032, USA
| | | | - Stefan R Kassabov
- Department of Neuroscience, Columbia University, New York, NY 10027, USA
| | - Craig H Bailey
- Department of Neuroscience, Columbia University, New York, NY 10027, USA; New York State Psychiatric Institute, New York, NY 10032, USA; Kavli Institute for Brain Science, New York, NY 10027, USA
| | - Eric R Kandel
- Department of Neuroscience, Columbia University, New York, NY 10027, USA; New York State Psychiatric Institute, New York, NY 10032, USA; Kavli Institute for Brain Science, New York, NY 10027, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10027, USA.
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5
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Zhang X, Coates K, Dacks A, Günay C, Lauritzen JS, Li F, Calle-Schuler SA, Bock D, Gaudry Q. Local synaptic inputs support opposing, network-specific odor representations in a widely projecting modulatory neuron. eLife 2019; 8:46839. [PMID: 31264962 PMCID: PMC6660217 DOI: 10.7554/elife.46839] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 07/01/2019] [Indexed: 12/14/2022] Open
Abstract
Serotonin plays different roles across networks within the same sensory modality. Previously, we used whole-cell electrophysiology in Drosophila to show that serotonergic neurons innervating the first olfactory relay are inhibited by odorants (Zhang and Gaudry, 2016). Here we show that network-spanning serotonergic neurons segregate information about stimulus features, odor intensity and identity, by using opposing coding schemes in different olfactory neuropil. A pair of serotonergic neurons (the CSDns) innervate the antennal lobe and lateral horn, which are first and second order neuropils. CSDn processes in the antennal lobe are inhibited by odors in an identity independent manner. In the lateral horn, CSDn processes are excited in an odor identity dependent manner. Using functional imaging, modeling, and EM reconstruction, we demonstrate that antennal lobe derived inhibition arises from local GABAergic inputs and acts as a means of gain control on branch-specific inputs that the CSDns receive within the lateral horn.
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Affiliation(s)
- Xiaonan Zhang
- Department of Biology, University of Maryland, College Park, United States
| | - Kaylynn Coates
- Department of Biology, West Virginia University, Morgantown, United States
| | - Andrew Dacks
- Department of Biology, West Virginia University, Morgantown, United States
| | - Cengiz Günay
- School of Science and Technology, Georgia Gwinnett College, Lawrenceville, United States
| | - J Scott Lauritzen
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Feng Li
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | | | - Davi Bock
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, United States.,Department of Neurological Sciences, Larner College of Medicine, University of Vermont, Burlington, United States
| | - Quentin Gaudry
- Department of Biology, University of Maryland, College Park, United States
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6
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Vinograd A, Tasaka GI, Kreines L, Weiss Y, Mizrahi A. The Pre-synaptic Landscape of Mitral/Tufted Cells of the Main Olfactory Bulb. Front Neuroanat 2019; 13:58. [PMID: 31244618 PMCID: PMC6563787 DOI: 10.3389/fnana.2019.00058] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 05/21/2019] [Indexed: 12/21/2022] Open
Abstract
In olfaction, all volatile odor information is tunneled through the main olfactory bulb (OB). Odor information is then processed before it is transferred to higher brain centers. Odor processing in the OB is carried out by numerous local inhibitory circuits and modulated by top-down input. Top-down modulation of OB function has been shown to act via interneurons but evidence also exists for its direct impact onto the principle mitral and tufted cells (M/Ts). Here, we used monosynaptic rabies trans-synaptic tracing from the OB to map and quantify the local and top-down pre-synaptic landscape of M/Ts and local inhibitory interneurons. We found that M/Ts receive a significant amount of top-down inputs from various brain regions that match qualitatively but not quantitatively those that synapse onto local inhibitory inter-neurons. These results show that M/Ts are direct targets of top-down inputs.
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Affiliation(s)
- Amit Vinograd
- Department of Neurobiology, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel.,The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Gen-Ichi Tasaka
- The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Lena Kreines
- Department of Neurobiology, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Yair Weiss
- Department of Neurobiology, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Adi Mizrahi
- Department of Neurobiology, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel.,The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
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7
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Crespo C, Liberia T, Blasco-Ibáñez JM, Nácher J, Varea E. Cranial Pair I: The Olfactory Nerve. Anat Rec (Hoboken) 2018; 302:405-427. [PMID: 29659152 DOI: 10.1002/ar.23816] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 05/29/2017] [Accepted: 06/15/2017] [Indexed: 12/13/2022]
Abstract
The olfactory nerve constitutes the first cranial pair. Compared with other cranial nerves, it depicts some atypical features. First, the olfactory nerve does not form a unique bundle. The olfactory axons join other axons and form several small bundles or fascicles: the fila olfactoria. These fascicles leave the nasal cavity, pass through the lamina cribrosa of the ethmoid bone and enter the brain. The whole of these fascicles is what is known as the olfactory nerve. Second, the olfactory sensory neurons, whose axons integrate the olfactory nerve, connect the nasal cavity and the brain without any relay. Third, the olfactory nerve is composed by unmyelinated axons. Fourth, the olfactory nerve contains neither Schwann cells nor oligodendrocytes wrapping its axons. But it contains olfactory ensheathing glia, which is a type of glia unique to this nerve. Fifth, the olfactory axons participate in the circuitry of certain spherical structures of neuropil that are unique in the brain: the olfactory glomeruli. Sixth, the axons of the olfactory nerve are continuously replaced and their connections in the central nervous system are remodeled continuously. Therefore, the olfactory nerve is subject to lifelong plasticity. Finally seventh, the olfactory nerve can be a gateway for the direct entrance of viruses, neurotoxins and other xenobiotics to the brain. In the same way, it can be used as a portal of entry to the brain for therapeutic substances, bypassing the blood-brain barrier. In this article, we analyze some features of the anatomy and physiology of the first cranial pair. Anat Rec, 302:405-427, 2019. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Carlos Crespo
- Department of Cell Biology, Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), University of Valencia, Spain
| | - Teresa Liberia
- Departments of Neurosurgery and Neuroscience, Yale University School of Medicine, New Haven, Connecticut
| | - José Miguel Blasco-Ibáñez
- Department of Cell Biology, Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), University of Valencia, Spain
| | - Juan Nácher
- Department of Cell Biology, Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), University of Valencia, Spain
| | - Emilio Varea
- Department of Cell Biology, Interdisciplinary Research Structure for Biotechnology and Biomedicine (BIOTECMED), University of Valencia, Spain
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8
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Kiyokage E, Kobayashi K, Toida K. Spatial distribution of synapses on tyrosine hydroxylase-expressing juxtaglomerular cells in the mouse olfactory glomerulus. J Comp Neurol 2017; 525:1059-1074. [DOI: 10.1002/cne.24147] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 10/13/2016] [Accepted: 10/13/2016] [Indexed: 01/17/2023]
Affiliation(s)
- Emi Kiyokage
- Department of Anatomy; Kawasaki Medical School; Kurashiki Okayama 701-0192 Japan
| | - Kazuto Kobayashi
- Department of Molecular Genetics; Institute of Biomedical Sciences, Fukushima Medical University School of Medicine; Fukushima 960-1295 Japan
| | - Kazunori Toida
- Department of Anatomy; Kawasaki Medical School; Kurashiki Okayama 701-0192 Japan
- Research Center for Ultra-High Voltage Electron Microscopy; Osaka University; Mihogaoka, Ibaraki Osaka 567-0047 Japan
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9
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Abstract
Despite the fact that pigs are reputed to have excellent olfactory abilities, few studies have examined regions of the pig brain involved in the sense of smell. The present study provides an overview of the olfactory bulb, anterior olfactory nucleus, and piriform cortex of adult pigs using several approaches. Nissl, myelin, and Golgi stains were used to produce a general overview of the organization of the regions and confocal microscopy was employed to examine 1) projection neurons, 2) GABAergic local circuit neurons that express somatostatin, parvalbumin, vasoactive intestinal polypeptide, or calretinin, 3) neuromodulatory fibers (cholinergic and serotonergic), and 4) glia (astrocytes and microglia). The findings revealed that pig olfactory structures are quite large, highly organized and follow the general patterns observed in mammals.
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Affiliation(s)
- Peter C Brunjes
- Department Psychology, University of Virginia, 102 Gilmer Hall, PO Box 400400, Charlottesville, VA 22904, USA and
| | - Sanford Feldman
- Department of Comparative Medicine, University of Virginia, 102 Gilmer Hall, PO Box 400400, Charlottesville, VA 22904, USA
| | - Stephen K Osterberg
- Department Psychology, University of Virginia, 102 Gilmer Hall, PO Box 400400, Charlottesville, VA 22904, USA and
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10
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Activation of raphe nuclei triggers rapid and distinct effects on parallel olfactory bulb output channels. Nat Neurosci 2016; 19:271-82. [PMID: 26752161 PMCID: PMC4948943 DOI: 10.1038/nn.4219] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 11/30/2015] [Indexed: 12/14/2022]
Abstract
The serotonergic raphe nuclei are involved in regulating brain states over timescales of minutes and hours. We examined more rapid effects of raphe activation on two classes of principal neurons in the mouse olfactory bulb, mitral and tufted cells, which send olfactory information to distinct targets. Brief stimulation of the raphe nuclei led to excitation of tufted cells at rest and potentiation of their odor responses. While mitral cells at rest were also excited by raphe activation, their odor responses were bidirectionally modulated, leading to improved pattern separation of odors. In vitro whole-cell recordings revealed that specific optogenetic activation of raphe axons affected bulbar neurons through dual release of serotonin and glutamate. Therefore, the raphe nuclei, in addition to their role in neuromodulation of brain states, are also involved in fast, sub-second top-down modulation similar to cortical feedback. This modulation can selectively and differentially sensitize or decorrelate distinct output channels.
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11
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Ono D, Honma S, Honma KI. Circadian PER2::LUC rhythms in the olfactory bulb of freely moving mice depend on the suprachiasmatic nucleus but not on behaviour rhythms. Eur J Neurosci 2015; 42:3128-37. [DOI: 10.1111/ejn.13111] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2015] [Revised: 10/07/2015] [Accepted: 10/15/2015] [Indexed: 11/30/2022]
Affiliation(s)
- Daisuke Ono
- Photonic Bioimaging Section; Research Center for Cooperative Projects; Hokkaido University Graduate School of Medicine; Sapporo Japan
| | - Sato Honma
- Department of Chronomedicine; Hokkaido University Graduate School of Medicine; North 15, West 7, Kita-ku Sapporo 060-8638 Japan
| | - Ken-ichi Honma
- Department of Chronomedicine; Hokkaido University Graduate School of Medicine; North 15, West 7, Kita-ku Sapporo 060-8638 Japan
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12
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Brill J, Shao Z, Puche AC, Wachowiak M, Shipley MT. Serotonin increases synaptic activity in olfactory bulb glomeruli. J Neurophysiol 2015; 115:1208-19. [PMID: 26655822 DOI: 10.1152/jn.00847.2015] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 12/09/2015] [Indexed: 11/22/2022] Open
Abstract
Serotoninergic fibers densely innervate olfactory bulb glomeruli, the first sites of synaptic integration in the olfactory system. Acting through 5HT2A receptors, serotonin (5HT) directly excites external tufted cells (ETCs), key excitatory glomerular neurons, and depolarizes some mitral cells (MCs), the olfactory bulb's main output neurons. We further investigated 5HT action on MCs and determined its effects on the two major classes of glomerular interneurons: GABAergic/dopaminergic short axon cells (SACs) and GABAergic periglomerular cells (PGCs). In SACs, 5HT evoked a depolarizing current mediated by 5HT2C receptors but did not significantly impact spike rate. 5HT had no measurable direct effect in PGCs. Serotonin increased spontaneous excitatory and inhibitory postsynaptic currents (sEPSCs and sIPSCs) in PGCs and SACs. Increased sEPSCs were mediated by 5HT2A receptors, suggesting that they are primarily due to enhanced excitatory drive from ETCs. Increased sIPSCs resulted from elevated excitatory drive onto GABAergic interneurons and augmented GABA release from SACs. Serotonin-mediated GABA release from SACs was action potential independent and significantly increased miniature IPSC frequency in glomerular neurons. When focally applied to a glomerulus, 5HT increased MC spontaneous firing greater than twofold but did not increase olfactory nerve-evoked responses. Taken together, 5HT modulates glomerular network activity in several ways: 1) it increases ETC-mediated feed-forward excitation onto MCs, SACs, and PGCs; 2) it increases inhibition of glomerular interneurons; 3) it directly triggers action potential-independent GABA release from SACs; and 4) these network actions increase spontaneous MC firing without enhancing responses to suprathreshold sensory input. This may enhance MC sensitivity while maintaining dynamic range.
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Affiliation(s)
- Julia Brill
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland; and
| | - Zuoyi Shao
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland; and
| | - Adam C Puche
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland; and
| | - Matt Wachowiak
- Department of Neurobiology and Anatomy, and Brain Institute, University of Utah, Salt Lake City, Utah
| | - Michael T Shipley
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland; and
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Suzuki Y, Kiyokage E, Sohn J, Hioki H, Toida K. Structural basis for serotonergic regulation of neural circuits in the mouse olfactory bulb. J Comp Neurol 2014; 523:262-80. [PMID: 25234191 DOI: 10.1002/cne.23680] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 09/17/2014] [Accepted: 09/17/2014] [Indexed: 11/05/2022]
Abstract
Olfactory processing is well known to be regulated by centrifugal afferents from other brain regions, such as noradrenergic, acetylcholinergic, and serotonergic neurons. Serotonergic neurons widely innervate and regulate the functions of various brain regions. In the present study, we focused on serotonergic regulation of the olfactory bulb (OB), one of the most structurally and functionally well-defined brain regions. Visualization of a single neuron among abundant and dense fibers is essential to characterize and understand neuronal circuits. We accomplished this visualization by successfully labeling and reconstructing serotonin (5-hydroxytryptamine: 5-HT) neurons by infection with sindbis and adeno-associated virus into dorsal raphe nuclei (DRN) of mice. 5-HT synapses were analyzed by correlative confocal laser microscopy and serial-electron microscopy (EM) study. To further characterize 5-HT neuronal and network function, we analyzed whether glutamate was released from 5-HT synaptic terminals using immuno-EM. Our results are the first visualizations of complete 5-HT neurons and fibers projecting from DRN to the OB with bifurcations. We found that a single 5-HT axon can form synaptic contacts to both type 1 and 2 periglomerular cells within a single glomerulus. Through immunolabeling, we also identified vesicular glutamate transporter 3 in 5-HT neurons terminals, indicating possible glutamatergic transmission. Our present study strongly implicates the involvement of brain regions such as the DRN in regulation of the elaborate mechanisms of olfactory processing. We further provide a structure basis of the network for coordinating or linking olfactory encoding with other neural systems, with special attention to serotonergic regulation.
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Affiliation(s)
- Yoshinori Suzuki
- Department of Anatomy, Kawasaki Medical School, Okayama, 701-0192, Japan
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14
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Olfactory bulb monoamine concentrations vary with time of day. Neuroscience 2013; 247:234-41. [PMID: 23727009 DOI: 10.1016/j.neuroscience.2013.05.040] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2013] [Revised: 05/19/2013] [Accepted: 05/21/2013] [Indexed: 11/21/2022]
Abstract
The olfactory bulb (OB) has been recently identified as a circadian oscillator capable of operating independently of the master circadian pacemaker, the suprachiasmatic nuclei of the hypothalamus. OB oscillations manifest as rhythms in clock genes, electrical activity, and odor sensitivity. Dopamine, norepinephrine, and serotonin have been shown to modulate olfactory information processing by the OB and may be part of the mechanism that underlies diurnal changes in olfactory sensitivity. Rhythmic release of these neurotransmitters could generate OB rhythms in electrical activity and olfactory sensitivity. We hypothesized that these monoamines were rhythmically released in the OB. To test our hypotheses, we examined monoamine levels in the OB, over the course of a day, by high-performance liquid chromatography coupled to electrochemical detection. We observed that dopamine and its metabolite, 3-4-dihydroxyphenylacetic acid, rhythmically fluctuate over the day. In contrast, norepinephrine is arrhythmic. Serotonin and its metabolite hydroxyindoleacetic acid appear to rhythmically fluctuate. Each of these monoamines has been shown to alter OB circuit behavior and influence odor processing. Rhythmic release of serotonin may be a mechanism by which the suprachiasmatic nuclei communicate, indirectly, with the OB.
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15
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Liberia T, Blasco-Ibáñez JM, Nácher J, Varea E, Lanciego JL, Crespo C. Two types of periglomerular cells in the olfactory bulb of the macaque monkey (Macaca fascicularis). Brain Struct Funct 2012; 218:873-87. [DOI: 10.1007/s00429-012-0435-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 05/22/2012] [Indexed: 11/28/2022]
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