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Lindeman S, Fu X, Reinert JK, Fukunaga I. Value-related learning in the olfactory bulb occurs through pathway-dependent perisomatic inhibition of mitral cells. PLoS Biol 2024; 22:e3002536. [PMID: 38427708 PMCID: PMC10936853 DOI: 10.1371/journal.pbio.3002536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Revised: 03/13/2024] [Accepted: 02/05/2024] [Indexed: 03/03/2024] Open
Abstract
Associating values to environmental cues is a critical aspect of learning from experiences, allowing animals to predict and maximise future rewards. Value-related signals in the brain were once considered a property of higher sensory regions, but their wide distribution across many brain regions is increasingly recognised. Here, we investigate how reward-related signals begin to be incorporated, mechanistically, at the earliest stage of olfactory processing, namely, in the olfactory bulb. In head-fixed mice performing Go/No-Go discrimination of closely related olfactory mixtures, rewarded odours evoke widespread inhibition in one class of output neurons, that is, in mitral cells but not tufted cells. The temporal characteristics of this reward-related inhibition suggest it is odour-driven, but it is also context-dependent since it is absent during pseudo-conditioning and pharmacological silencing of the piriform cortex. Further, the reward-related modulation is present in the somata but not in the apical dendritic tuft of mitral cells, suggesting an involvement of circuit components located deep in the olfactory bulb. Depth-resolved imaging from granule cell dendritic gemmules suggests that granule cells that target mitral cells receive a reward-related extrinsic drive. Thus, our study supports the notion that value-related modulation of olfactory signals is a characteristic of olfactory processing in the primary olfactory area and narrows down the possible underlying mechanisms to deeper circuit components that contact mitral cells perisomatically.
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Affiliation(s)
- Sander Lindeman
- Sensory and Behavioural Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Xiaochen Fu
- Sensory and Behavioural Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Janine Kristin Reinert
- Sensory and Behavioural Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Izumi Fukunaga
- Sensory and Behavioural Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
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2
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McLaren AMR, Kawaja MD. Olfactory Dysfunction and Alzheimer's Disease: A Review. J Alzheimers Dis 2024; 99:811-827. [PMID: 38728185 DOI: 10.3233/jad-231377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2024]
Abstract
Alzheimer's disease is the most common cause of dementia, and it is one of the leading causes of death globally. Identification and validation of biomarkers that herald the onset and progression of Alzheimer's disease is of paramount importance for early reliable diagnosis and effective pharmacological therapy commencement. A substantial body of evidence has emerged demonstrating that olfactory dysfunction is a preclinical symptom of neurodegenerative diseases including Alzheimer's disease. While a correlation between olfactory dysfunction and Alzheimer's disease onset and progression in humans exists, the mechanism underlying this relationship remains unknown. The aim of this article is to review the current state of knowledge regarding the range of potential factors that may contribute to the development of Alzheimer's disease-related olfactory dysfunction. This review predominantly focuses on genetic mutations associated with Alzheimer's disease including amyloid-β protein precursor, presenilin 1 and 2, and apolipoprotein E mutations, that may (in varying ways) drive the cellular events that lead to and sustain olfactory dysfunction.
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Affiliation(s)
| | - Michael D Kawaja
- Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, ON, Canada
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, ON, Canada
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3
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Li LX, Chu JH, Chen XW, Gao PC, Wang ZY, Liu C, Fan RF. Selenium ameliorates mercuric chloride-induced brain damage through activating BDNF/TrKB/PI3K/AKT and inhibiting NF-κB signaling pathways. J Inorg Biochem 2022; 229:111716. [DOI: 10.1016/j.jinorgbio.2022.111716] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 12/27/2021] [Accepted: 01/01/2022] [Indexed: 02/07/2023]
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Ahnaou A, Chave L, Manyakov NV, Drinkenburg WHIM. Odour Retrieval Processing in Mice: Cholinergic Modulation of Oscillatory Coupling in Olfactory Bulb-Piriform Networks. Neuropsychobiology 2022; 80:374-392. [PMID: 33588406 DOI: 10.1159/000513511] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 11/26/2020] [Indexed: 11/19/2022]
Abstract
BACKGROUND/AIMS Olfactory dysfunction can provide valuable insight into early pathophysiological processes of brain disorders. Olfactory processing of chemosensory and odour sensitivity relies on segregating salient odours from background odours cues. Odour-evoked fast oscillations in the olfactory bulb (OB) are hypothesized to be an important index of odour quality coding. The present preclinical work aimed at better understanding connectivity associated with odour coding and behavioural odour discrimination. METHODS Network oscillations and functional connectivity (FC) were measured in C57BL/6 mice performing the olfactory associative odour learning (OL) test, using multichannel local field potential recordings in key olfactory networks. Cholinergic modulation of odour processing was investigated using the muscarinic antagonist scopolamine. RESULTS At the behavioural level, olfactory memory, which refers to the acquisition and recollection of a reference odour by reduced exploration time, was observed in animals that correctly learned the task. Significant decrease in mean investigation and retrieval time of the associated odour-food reward was observed between trials. At the network level, the associated odour during sniffing behaviour was associated with enhanced coherence in the β and γ frequency oscillations across the olfactory pathway, with marked changes observed between the OB and anterior piriform cortex (PC). The enhanced phase-amplitude cross-frequency coupling in the OB and the weak coupling index in the hippocampal CA1 suggests a role of the OB network in olfaction encoding and processing. Scopolamine impaired behavioural and FC underlying recall and retrieval of the associated odour. CONCLUSION The results suggest that the acquisition and formation of odour reference memory rely primarily on FC at the OB-PC network and confirm the role of muscarinic receptors in olfactory retrieval processing.
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Affiliation(s)
- Abdallah Ahnaou
- Department of Neuroscience, Janssen Research & Development, a Division of Janssen Pharmaceutica NV, Beerse, Belgium,
| | - Lucile Chave
- Department of Neuroscience, Janssen Research & Development, a Division of Janssen Pharmaceutica NV, Beerse, Belgium
| | - Nikolay V Manyakov
- Department of Neuroscience, Janssen Research & Development, a Division of Janssen Pharmaceutica NV, Beerse, Belgium
| | - Wilhelmus H I M Drinkenburg
- Department of Neuroscience, Janssen Research & Development, a Division of Janssen Pharmaceutica NV, Beerse, Belgium
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Arakawa H. Dynamic regulation of oxytocin neuronal circuits in the sequential processes of prosocial behavior in rodent models. CURRENT RESEARCH IN NEUROBIOLOGY 2021; 2:100011. [PMID: 36246512 PMCID: PMC9559098 DOI: 10.1016/j.crneur.2021.100011] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 03/08/2021] [Accepted: 03/31/2021] [Indexed: 12/16/2022] Open
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Dopamine-Dependent QR2 Pathway Activation in CA1 Interneurons Enhances Novel Memory Formation. J Neurosci 2020; 40:8698-8714. [PMID: 33046554 DOI: 10.1523/jneurosci.1243-20.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 09/18/2020] [Accepted: 09/21/2020] [Indexed: 01/18/2023] Open
Abstract
The formation of memory for a novel experience is a critical cognitive capacity. The ability to form novel memories is sensitive to age-related pathologies and disease, to which prolonged metabolic stress is a major contributing factor. Presently, we describe a dopamine-dependent redox modulation pathway within the hippocampus of male mice that promotes memory consolidation. Namely, following novel information acquisition, quinone reductase 2 (QR2) is suppressed by miRNA-182 (miR-182) in the CA1 region of the hippocampus via dopamine D1 receptor (D1R) activation, a process largely facilitated by locus coeruleus activity. This pathway activation reduces ROS generated by QR2 enzymatic activity, a process that alters the intrinsic properties of CA1 interneurons 3 h following learning, in a form of oxidative eustress. Interestingly, novel experience decreases QR2 expression predominately in inhibitory interneurons. Additionally, we find that in aged animals this newly described QR2 pathway is chronically under activated, resulting in miR-182 underexpression and QR2 overexpression. This leads to accumulative oxidative stress, which can be seen in CA1 via increased levels of oxidized, inactivated potassium channel Kv2.1, which undergoes disulfide bridge oligomerization. This newly described interneuron-specific molecular pathway lies alongside the known mRNA translation-dependent processes necessary for long-term memory formation, entrained by dopamine in CA1. It is a process crucial for the distinguishing features of novel memory, and points to a promising new target for memory enhancement in aging and age-dependent diseases.SIGNIFICANCE STATEMENT One way in which evolution dictates which sensory information will stabilize as an internal representation, relies on information novelty. Dopamine is a central neuromodulator involved in this process in the mammalian hippocampus. Here, we describe for the first time a dopamine D1 receptor-dependent quinone reductase 2 pathway in interneurons. This is a targeted redox event necessary to delineate a novel experience to a robust long-term internal representation. Activation of this pathway alone can explain the effect novelty has on "flashbulb" memories, and it can become dysfunctional with age and diseases, such as Alzheimer's disease.
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Ma L, Chen W, Yu D, Han Y. Brain-Wide Mapping of Afferent Inputs to Accumbens Nucleus Core Subdomains and Accumbens Nucleus Subnuclei. Front Syst Neurosci 2020; 14:15. [PMID: 32317941 PMCID: PMC7150367 DOI: 10.3389/fnsys.2020.00015] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Accepted: 03/02/2020] [Indexed: 12/20/2022] Open
Abstract
The nucleus accumbens (NAc) is the ventral part of the striatum and the interface between cognition, emotion, and action. It is composed of three major subnuclei: i.e., NAc core (NAcC), lateral shell (NAcLS), and medial shell (NAcMS), which exhibit functional heterogeneity. Thus, determining the synaptic inputs of the subregions of the NAc is important for understanding the circuit mechanisms involved in regulating different functions. Here, we simultaneously labeled subregions of the NAc with cholera toxin subunit B conjugated with multicolor Alexa Fluor, then imaged serial sections of the whole brain with a fully automated slide scanning system. Using the interactive WholeBrain framework, we characterized brain-wide inputs to the NAcC subdomains, including the rostral, caudal, dorsal, and ventral subdomains (i.e., rNAcC, cNAcC, dNAcC, and vNAcC, respectively) and the NAc subnuclei. We found diverse brain regions, distributed from the cerebrum to brain stem, projecting to the NAc. Of the 57 brain regions projecting to the NAcC, the anterior olfactory nucleus (AON) exhibited the greatest inputs. The input neurons of rNAcC and cNAcC are two distinct populations but share similar distribution over the same upstream brain regions, whereas the input neurons of dNAcC and vNAcC exhibit slightly different distributions over the same upstream regions. Of the 55 brain regions projecting to the NAcLS, the piriform area contributed most of the inputs. Of the 72 brain regions projecting to the NAcMS, the lateral septal nucleus contributed most of the inputs. The input neurons of NAcC and NAcLS share similar distributions, whereas the NAcMS exhibited brain-wide distinct distribution. Thus, the NAcC subdomains appeared to share the same upstream brain regions, although with distinct input neuron populations and slight differences in the input proportions, whereas the NAcMS subnuclei received distinct inputs from multiple upstream brain regions. These results lay an anatomical foundation for understanding the different functions of NAcC subdomains and NAc subnuclei.
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Affiliation(s)
- Liping Ma
- Department of Neurobiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science & Technology, Wuhan, China
| | - Wenqi Chen
- Department of Neurobiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science & Technology, Wuhan, China
| | - Danfang Yu
- Department of Neurobiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science & Technology, Wuhan, China.,Department of Neurology, Provincial Hospital of Integrated Chinese and Western Medicine, Wuhan, China
| | - Yunyun Han
- Department of Neurobiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science & Technology, Wuhan, China.,Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
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8
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Abstract
The gustatory system contributes to the flavor of foods and beverages and communicates information about nutrients and poisons. This system has evolved to detect and ultimately respond to hydrophilic molecules dissolved in saliva. Taste receptor cells, located in taste buds and distributed throughout the oral cavity, activate nerve afferents that project to the brainstem. From here, information propagates to thalamic, subcortical, and cortical areas, where it is integrated with information from other sensory systems and with homeostatic, visceral, and affective processes. There is considerable divergence, as well as convergence, of information between multiple regions of the central nervous system that interact with the taste pathways, with reciprocal connections occurring between the involved regions. These widespread interactions among multiple systems are crucial for the perception of food. For example, memory, hunger, satiety, and visceral changes can directly affect and can be affected by the experience of tasting. In this chapter, we review the literature on the central processing of taste with a specific focus on the anatomic and physiologic responses of single neurons. Emphasis is placed on how information is distributed along multiple systems with the goal of better understanding how the rich and complex sensations associated with flavor emerge from large-scale, systems-wide, interactions.
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Abstract
PURPOSE OF REVIEW The sense of smell is today one of the focuses of interest in aging and neurodegenerative disease research. In several neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease, the olfactory dysfunction is one of the initial symptoms appearing years before motor symptoms and cognitive decline, being considered a clinical marker of these diseases' early stages and a marker of disease progression and cognitive decline. Overall and under the umbrella of precision medicine, attention to olfactory function may help to improve chances of success for neuroprotective and disease-modifying therapeutic strategies. RECENT FINDINGS The use of olfaction, as clinical marker for neurodegenerative diseases is helpful in the characterization of prodromal stages of these diseases, early diagnostic strategies, differential diagnosis, and potentially prediction of treatment success. Understanding the mechanisms underlying olfactory dysfunction is central to determine its association with neurodegenerative disorders. Several anatomical systems and environmental factors may underlie or contribute to olfactory loss associated with neurological diseases, although the direct biological link to each disorder remains unclear and, thus, requires further investigation. In this review, we describe the neurobiology of olfaction, and the most common olfactory function measurements in neurodegenerative diseases. We also highlight the evidence for the presence of olfactory dysfunction in several neurodegenerative diseases, its value as a clinical marker for early stages of the diseases when combined with other clinical, biological, and neuroimage markers, and its role as a useful symptom for the differential diagnosis and follow-up of disease. The neuropathological correlations and the changes in neurotransmitter systems related with olfactory dysfunction in the neurodegenerative diseases are also described.
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Rey NL, Wesson DW, Brundin P. The olfactory bulb as the entry site for prion-like propagation in neurodegenerative diseases. Neurobiol Dis 2018; 109:226-248. [PMID: 28011307 PMCID: PMC5972535 DOI: 10.1016/j.nbd.2016.12.013] [Citation(s) in RCA: 183] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 12/13/2016] [Accepted: 12/15/2016] [Indexed: 02/07/2023] Open
Abstract
Olfactory deficits are present in numerous neurodegenerative disorders and are accompanied by pathology in related brain regions. In several of these disorders, olfactory disturbances appear early and are considered as prodromal symptoms of the disease. In addition, pathological protein aggregates affect olfactory regions prior to other regions, suggesting that the olfactory system might be particularly vulnerable to neurodegenerative diseases. Exposed to the external environment, the olfactory epithelium and olfactory bulb allow pathogen and toxin penetration into the brain, a process that has been proposed to play a role in neurodegenerative diseases. Determining whether the olfactory bulb could be a starting point of pathology and of pathology spread is crucial to understanding how neurodegenerative diseases evolve. We argue that pathological changes following environmental insults contribute to the initiation of protein aggregation in the olfactory bulb, which then triggers the spread of the pathology within the brain by a templating mechanism in a prion-like manner. We review the evidence for the early involvement of olfactory structures in neurodegenerative diseases and the relationship between neuropathology and olfactory function. We discuss the vulnerability and putative underlying mechanisms by which pathology could be initiated in the olfactory bulb, from the entry of pathogens (promoted by increased permeability of the olfactory epithelium with aging or inflammation) to the sensitivity of the olfactory system to oxidative stress and inflammation. Finally, we review changes in protein expression and neural excitability triggered by pathogenic proteins that can promote pathogenesis in the olfactory bulb and beyond.
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Affiliation(s)
- Nolwen L Rey
- Center for Neurodegenerative Science, Van Andel Research Institute, Grand Rapids, MI 49503, USA.
| | - Daniel W Wesson
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Patrik Brundin
- Center for Neurodegenerative Science, Van Andel Research Institute, Grand Rapids, MI 49503, USA
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Enhancement of Gustatory Neural Responses by Parasympathetic Nerve in the Frog. Cell Mol Neurobiol 2017; 38:883-890. [PMID: 29103093 DOI: 10.1007/s10571-017-0562-5] [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: 07/28/2017] [Accepted: 10/30/2017] [Indexed: 10/18/2022]
Abstract
The autonomic nervous system affects the gustatory responses in animals. Frog glossopharyngeal nerve (GPN) contains the parasympathetic nerve. We checked the effects of electrical stimulation (ES) of the parasympathetic nerves on the gustatory neural responses. The gustatory neural impulses of the GPNs were recorded using bipolar AgCl wires under normal blood circulation and integrated with a time constant of 1 s. Electrical stimuli were applied to the proximal side of the GPN with a pair of AgCl wires. The parasympathetic nerves of the GPN were strongly stimulated for 10 s with 6 V at 30 Hz before taste stimulation. The integrated neural responses to 0.5 M NaCl, 2.5 mM CaCl2, water, and 1 M sucrose were enhanced to 130-140% of the controls. On the other hand, the responses for 1 mM Q-HCl and 0.3 mM acetic acid were not changed by the preceding applied ES. After hexamethonium (a blocker of nicotinic ACh receptor) was intravenously injected, ES of the parasympathetic nerve did not modulate the responses for all six taste stimuli. The mechanism for enhancement of the gustatory neural responses is discussed.
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Misiak MM, Hipolito MS, Ressom HW, Obisesan TO, Manaye KF, Nwulia EA. Apo E4 Alleles and Impaired Olfaction as Predictors of Alzheimer's Disease. CLINICAL AND EXPERIMENTAL PSYCHOLOGY 2017; 3:169. [PMID: 29423459 PMCID: PMC5800509 DOI: 10.4172/2471-2701.1000169] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Alzheimer's disease (AD) is the most common form of dementia that affects more than 5 million Americans. It is the only disease among the 10 causes of death that cannot be slowed or cured, thus raising the need for identification of early preclinical markers that could be the focus of preventative efforts. Although evidence is escalating that abnormalities in olfactory structure and function precede AD development and early cognitive impairments by one or more decades, the importance of olfaction is largely overlooked in AD, and such testing is not routinely performed in neurology clinics. Nevertheless, research using the olfactory model, has begun to advance our understanding of the preclinical pathophysiology of AD. Notably, an interesting series of studies is beginning to illuminate the relationship between Apolipoprotein E (ApoE) ε4 polymorphism and olfactory dysfunction and late-onset Alzheimer's disease. In this article, we reviewed present research on the significance of ApoE and olfaction to AD, summarized current studies on the associations and mechanisms of ApoE and olfactory dysfunction, and highlighted important gaps for future work to further advance the translational application of the olfactory paradigm to early, preclinical diagnosis and treatment of AD.
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Affiliation(s)
- Magdalena M Misiak
- Department of Psychiatry and Behavioral Sciences, Howard University, Washington DC, USA
- Department of Physiology, Howard University, Washington DC, USA
| | - MariaMananita S Hipolito
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC, USA
| | - Habtom W Ressom
- Department of Medicine, Howard University, Washington DC, USA
| | | | | | - Evaristus A Nwulia
- Department of Psychiatry and Behavioral Sciences, Howard University, Washington DC, USA
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC, USA
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GABAB Receptors Tune Cortical Feedback to the Olfactory Bulb. J Neurosci 2017; 36:8289-304. [PMID: 27511004 DOI: 10.1523/jneurosci.3823-15.2016] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 06/09/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Sensory perception emerges from the confluence of sensory inputs that encode the composition of external environment and top-down feedback that conveys information from higher brain centers. In olfaction, sensory input activity is initially processed in the olfactory bulb (OB), serving as the first central relay before being transferred to the olfactory cortex. In addition, the OB receives dense connectivity from feedback projections, so the OB has the capacity to implement a wide array of sensory neuronal computation. However, little is known about the impact and the regulation of this cortical feedback. Here, we describe a novel mechanism to gate glutamatergic feedback selectively from the anterior olfactory cortex (AOC) to the OB. Combining in vitro and in vivo electrophysiological recordings, optogenetics, and fiber-photometry-based calcium imaging applied to wild-type and conditional transgenic mice, we explore the functional consequences of circuit-specific GABA type-B receptor (GABABR) manipulation. We found that activation of presynaptic GABABRs specifically depresses synaptic transmission from the AOC to OB inhibitory interneurons, but spares direct excitation to principal neurons. As a consequence, feedforward inhibition of spontaneous and odor-evoked activity of principal neurons is diminished. We also show that tunable cortico-bulbar feedback is critical for generating beta, but not gamma, OB oscillations. Together, these results show that GABABRs on cortico-bulbar afferents gate excitatory transmission in a target-specific manner and thus shape how the OB integrates sensory inputs and top-down information. SIGNIFICANCE STATEMENT The olfactory bulb (OB) receives top-down inputs from the olfactory cortex that produce direct excitation and feedforward inhibition onto mitral and tufted cells, the principal neurons. The functional role of this feedback and the mechanisms regulating the balance of feedback excitation and inhibition remain unknown. We found that GABAB receptors are expressed in cortico-bulbar axons that synapse on granule cells and receptor activation reduces the feedforward inhibition of spontaneous and odor-driven mitral and tufted cells' firing activity. In contrast, direct excitatory inputs to these principal neurons remain unchanged. This study demonstrates that activation of GABAB receptors biases the excitation/inhibition balance provided by cortical inputs to the OB, leading to profound effects on early stages of sensory information processing.
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Ko J. Neuroanatomical Substrates of Rodent Social Behavior: The Medial Prefrontal Cortex and Its Projection Patterns. Front Neural Circuits 2017; 11:41. [PMID: 28659766 PMCID: PMC5468389 DOI: 10.3389/fncir.2017.00041] [Citation(s) in RCA: 123] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 05/29/2017] [Indexed: 12/30/2022] Open
Abstract
Social behavior encompasses a number of distinctive and complex constructs that form the core elements of human imitative culture, mainly represented as either affiliative or antagonistic interactions with conspecifics. Traditionally considered in the realm of psychology, social behavior research has benefited from recent advancements in neuroscience that have accelerated identification of the neural systems, circuits, causative genes and molecular mechanisms that underlie distinct social cognitive traits. In this review article, I summarize recent findings regarding the neuroanatomical substrates of key social behaviors, focusing on results from experiments conducted in rodent models. In particular, I will review the role of the medial prefrontal cortex (mPFC) and downstream subcortical structures in controlling social behavior, and discuss pertinent future research perspectives.
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Affiliation(s)
- Jaewon Ko
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST)Daegu, South Korea
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15
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Behavioral Status Influences the Dependence of Odorant-Induced Change in Firing on Prestimulus Firing Rate. J Neurosci 2017; 37:1835-1852. [PMID: 28093474 DOI: 10.1523/jneurosci.3132-16.2017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Revised: 01/07/2017] [Accepted: 01/08/2017] [Indexed: 11/21/2022] Open
Abstract
The firing rate of the mitral/tufted cells in the olfactory bulb is known to undergo significant trial-to-trial variability and is affected by anesthesia. Here we ask whether odorant-elicited changes in firing rate depend on the rate before application of the stimulus in the awake and anesthetized mouse. We find that prestimulus firing rate varies widely on a trial-to-trial basis and that the stimulus-induced change in firing rate decreases with increasing prestimulus firing rate. Interestingly, this prestimulus firing rate dependence was different when the behavioral task did not involve detecting the valence of the stimulus. Finally, when the animal was learning to associate the odor with reward, the prestimulus firing rate was smaller for false alarms compared with correct rejections, suggesting that intrinsic activity reflects the anticipatory status of the animal. Thus, in this sensory modality, changes in behavioral status alter the intrinsic prestimulus activity, leading to a change in the responsiveness of the second-order neurons. We speculate that this trial-to-trial variability in odorant responses reflects sampling of the massive parallel input by subsets of mitral cells.SIGNIFICANCE STATEMENT The olfactory bulb must deal with processing massive parallel input from ∼1200 distinct olfactory receptors. In contrast, the visual system receives input from a small number of photoreceptors and achieves recognition of complex stimuli by allocating processing for distinct spatial locations to different brain areas. Here we find that the change in firing rate elicited by the odorant in second-order mitral cells depends on the intrinsic activity leading to a change of magnitude in the responsiveness of these neurons relative to this prestimulus activity. Further, we find that prestimulus firing rate is influenced by behavioral status. This suggests that there is top-down modulation allowing downstream brain processing areas to perform dynamic readout of olfactory information.
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16
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Doyle WI, Meeks JP. Heterogeneous effects of norepinephrine on spontaneous and stimulus-driven activity in the male accessory olfactory bulb. J Neurophysiol 2017; 117:1342-1351. [PMID: 28053247 DOI: 10.1152/jn.00871.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 12/09/2016] [Accepted: 01/03/2017] [Indexed: 11/22/2022] Open
Abstract
Norepinephrine (NE) release has been linked to experience-dependent plasticity in many model systems and brain regions. Among these is the rodent accessory olfactory system (AOS), which is crucial for detecting and processing socially relevant environmental cues. The accessory olfactory bulb (AOB), the first site of chemosensory information processing in the AOS, receives dense centrifugal innervation by noradrenergic fibers originating in the locus coeruleus. Although NE release has been linked to behavioral plasticity through its actions in the AOB, the impacts of noradrenergic modulation on AOB information processing have not been thoroughly studied. We made extracellular single-unit recordings of AOB principal neurons in ex vivo preparations of the early AOS taken from adult male mice. We analyzed the impacts of bath-applied NE (10 μM) on spontaneous and stimulus-driven activity. In the presence of NE, we observed overall suppression of stimulus-driven neuronal activity with limited impact on spontaneous activity. NE-associated response suppression in the AOB came in two forms: one that was strong and immediate (21%) and one other that involved gradual, stimulus-dependent monotonic response suppression (47%). NE-associated changes in spontaneous activity were more modest, with an overall increase in spontaneous spike frequency observed in 25% of neurons. Neurons with increased spontaneous activity demonstrated a net decrease in chemosensory discriminability. These results reveal that noradrenergic signaling in the AOB causes cell-specific changes in chemosensory tuning, even among similar projection neurons.NEW & NOTEWORTHY Norepinephrine (NE) is released throughout the brain in many behavioral contexts, but its impacts on information processing are not well understood. We studied the impact of NE on chemosensory tuning in the mouse accessory olfactory bulb (AOB). Electrophysiological recordings from AOB neurons in ex vivo preparations revealed that NE, on balance, inhibited mitral cell responses to chemosensory cues. However, NE's effects were heterogeneous, indicating that NE signaling reshapes AOB output in a cell- and stimulus-specific manner.
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Affiliation(s)
- Wayne I Doyle
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Julian P Meeks
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas
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Olfactory Bulb Deep Short-Axon Cells Mediate Widespread Inhibition of Tufted Cell Apical Dendrites. J Neurosci 2016; 37:1117-1138. [PMID: 28003347 DOI: 10.1523/jneurosci.2880-16.2016] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 11/14/2016] [Accepted: 12/03/2016] [Indexed: 01/10/2023] Open
Abstract
In the main olfactory bulb (MOB), the first station of sensory processing in the olfactory system, GABAergic interneuron signaling shapes principal neuron activity to regulate olfaction. However, a lack of known selective markers for MOB interneurons has strongly impeded cell-type-selective investigation of interneuron function. Here, we identify the first selective marker of glomerular layer-projecting deep short-axon cells (GL-dSACs) and investigate systematically the structure, abundance, intrinsic physiology, feedforward sensory input, neuromodulation, synaptic output, and functional role of GL-dSACs in the mouse MOB circuit. GL-dSACs are located in the internal plexiform layer, where they integrate centrifugal cholinergic input with highly convergent feedforward sensory input. GL-dSAC axons arborize extensively across the glomerular layer to provide highly divergent yet selective output onto interneurons and principal tufted cells. GL-dSACs are thus capable of shifting the balance of principal tufted versus mitral cell activity across large expanses of the MOB in response to diverse sensory and top-down neuromodulatory input. SIGNIFICANCE STATEMENT The identification of cell-type-selective molecular markers has fostered tremendous insight into how distinct interneurons shape sensory processing and behavior. In the main olfactory bulb (MOB), inhibitory circuits regulate the activity of principal cells precisely to drive olfactory-guided behavior. However, selective markers for MOB interneurons remain largely unknown, limiting mechanistic understanding of olfaction. Here, we identify the first selective marker of a novel population of deep short-axon cell interneurons with superficial axonal projections to the sensory input layer of the MOB. Using this marker, together with immunohistochemistry, acute slice electrophysiology, and optogenetic circuit mapping, we reveal that this novel interneuron population integrates centrifugal cholinergic input with broadly tuned feedforward sensory input to modulate principal cell activity selectively.
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Galindo-Villegas J, Garcia-Garcia E, Mulero V. Role of histamine in the regulation of intestinal immunity in fish. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2016; 64:178-186. [PMID: 26872545 DOI: 10.1016/j.dci.2016.02.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 02/02/2016] [Accepted: 02/08/2016] [Indexed: 06/05/2023]
Abstract
In mammals, during the acute inflammatory response, the complex interrelationship and cross-talk among histamine and the immune system has been fairly well characterized. There is a substantial body of information on its structure, metabolism, receptors, signal transduction, physiologic and pathologic effects. However, for early vertebrates, there is little such knowledge. In the case of teleost fish, this lack of knowledge has been due to the widely held belief that histamine is not present in this phylogenetic group. However, it has been recently demonstrated, that granules of mast cells in perciforms contain biologically active histamine. More importantly, the inflammatory response was clearly demonstrated to be regulated by the direct action of histamine on professional phagocytes. Nevertheless, the molecular basis and exact role of this biogenic amine in perciforms is still a matter of speculation. Therefore, this review intends to summarize recent experimental evidence regarding fish mast cells and correlate the same with their mammalian counterparts to establish the possible role of histamine in the fish intestinal inflammatory response.
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Affiliation(s)
- Jorge Galindo-Villegas
- Department of Cell Biology and Histology, Faculty of Biology, University of Murcia, IMIB-Arrixaca, Campus Universitario de Espinardo, Murcia 30100, Spain.
| | - Erick Garcia-Garcia
- Department of Cell Biology and Histology, Faculty of Biology, University of Murcia, IMIB-Arrixaca, Campus Universitario de Espinardo, Murcia 30100, Spain
| | - Victoriano Mulero
- Department of Cell Biology and Histology, Faculty of Biology, University of Murcia, IMIB-Arrixaca, Campus Universitario de Espinardo, Murcia 30100, Spain.
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19
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Marlin BJ, Froemke RC. Oxytocin modulation of neural circuits for social behavior. Dev Neurobiol 2016; 77:169-189. [PMID: 27626613 DOI: 10.1002/dneu.22452] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 09/07/2016] [Accepted: 09/12/2016] [Indexed: 01/04/2023]
Abstract
Oxytocin is a hypothalamic neuropeptide that has gained attention for the effects on social behavior. Recent findings shed new light on the mechanisms of oxytocin in synaptic plasticity and adaptively modifying neural circuits for social interactions such as conspecific recognition, pair bonding, and maternal care. Here, we review several of these newer studies on oxytocin in the context of previous findings, with an emphasis on social behavior and circuit plasticity in various brain regions shown to be enriched for oxytocin receptors. We provide a framework that highlights current circuit-level mechanisms underlying the widespread action of oxytocin. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 169-189, 2017.
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Affiliation(s)
- Bianca J Marlin
- Department of Neuroscience, Columbia University, New York, New York, 10032.,Howard Hughes Medical Institute, College of Physicians and Surgeons, Columbia University, New York, New York, 10032
| | - Robert C Froemke
- Department of Otolaryngology, Skirball Institute for Biomolecular Medicine, Neuroscience Institute, New York University School of Medicine, New York, New York.,Department of Neuroscience and Physiology Skirball Institute for Biomolecular Medicine, Neuroscience Institute New York University School of Medicine, New York, New York.,Center for Neural Science, New York University, New York, New York
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20
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Carlson KS, Whitney MS, Gadziola MA, Deneris ES, Wesson DW. Preservation of Essential Odor-Guided Behaviors and Odor-Based Reversal Learning after Targeting Adult Brain Serotonin Synthesis. eNeuro 2016; 3:ENEURO.0257-16.2016. [PMID: 27896310 PMCID: PMC5112565 DOI: 10.1523/eneuro.0257-16.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Revised: 10/18/2016] [Accepted: 10/24/2016] [Indexed: 01/02/2023] Open
Abstract
The neurotransmitter serotonin (5-HT) is considered a powerful modulator of sensory system organization and function in a wide range of animals. The olfactory system is innervated by midbrain 5-HT neurons into both its primary and secondary odor-processing stages. Facilitated by this circuitry, 5-HT and its receptors modulate olfactory system function, including odor information input to the olfactory bulb. It is unknown, however, whether the olfactory system requires 5-HT for even its most basic behavioral functions. To address this question, we established a conditional genetic approach to specifically target adult brain tryptophan hydroxylase 2 (Tph2), encoding the rate-limiting enzyme in brain 5-HT synthesis, and nearly eliminate 5-HT from the mouse forebrain. Using this novel model, we investigated the behavior of 5-HT-depleted mice during performance in an olfactory go/no-go task. Surprisingly, the near elimination of 5-HT from the forebrain, including the olfactory bulbs, had no detectable effect on the ability of mice to perform the odor-based task. Tph2-targeted mice not only were able to learn the task, but also had levels of odor acuity similar to those of control mice when performing coarse odor discrimination. Both groups of mice spent similar amounts of time sampling odors during decision-making. Furthermore, odor reversal learning was identical between 5-HT-depleted and control mice. These results suggest that 5-HT neurotransmission is not necessary for the most essential aspects of olfaction, including odor learning, discrimination, and certain forms of cognitive flexibility.
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Affiliation(s)
| | | | - Marie A. Gadziola
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH, 44106
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21
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Neuropeptides Modulate Female Chemosensory Processing upon Mating in Drosophila. PLoS Biol 2016; 14:e1002455. [PMID: 27145127 PMCID: PMC4856363 DOI: 10.1371/journal.pbio.1002455] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Accepted: 04/07/2016] [Indexed: 11/19/2022] Open
Abstract
A female's reproductive state influences her perception of odors and tastes along with her changed behavioral state and physiological needs. The mechanism that modulates chemosensory processing, however, remains largely elusive. Using Drosophila, we have identified a behavioral, neuronal, and genetic mechanism that adapts the senses of smell and taste, the major modalities for food quality perception, to the physiological needs of a gravid female. Pungent smelling polyamines, such as putrescine and spermidine, are essential for cell proliferation, reproduction, and embryonic development in all animals. A polyamine-rich diet increases reproductive success in many species, including flies. Using a combination of behavioral analysis and in vivo physiology, we show that polyamine attraction is modulated in gravid females through a G-protein coupled receptor, the sex peptide receptor (SPR), and its neuropeptide ligands, MIPs (myoinhibitory peptides), which act directly in the polyamine-detecting olfactory and taste neurons. This modulation is triggered by an increase of SPR expression in chemosensory neurons, which is sufficient to convert virgin to mated female olfactory choice behavior. Together, our data show that neuropeptide-mediated modulation of peripheral chemosensory neurons increases a gravid female's preference for important nutrients, thereby ensuring optimal conditions for her growing progeny.
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22
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Oettl LL, Ravi N, Schneider M, Scheller MF, Schneider P, Mitre M, da Silva Gouveia M, Froemke RC, Chao MV, Young WS, Meyer-Lindenberg A, Grinevich V, Shusterman R, Kelsch W. Oxytocin Enhances Social Recognition by Modulating Cortical Control of Early Olfactory Processing. Neuron 2016; 90:609-21. [PMID: 27112498 DOI: 10.1016/j.neuron.2016.03.033] [Citation(s) in RCA: 226] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2015] [Revised: 02/17/2016] [Accepted: 03/15/2016] [Indexed: 11/19/2022]
Abstract
Oxytocin promotes social interactions and recognition of conspecifics that rely on olfaction in most species. The circuit mechanisms through which oxytocin modifies olfactory processing are incompletely understood. Here, we observed that optogenetically induced oxytocin release enhanced olfactory exploration and same-sex recognition of adult rats. Consistent with oxytocin's function in the anterior olfactory cortex, particularly in social cue processing, region-selective receptor deletion impaired social recognition but left odor discrimination and recognition intact outside a social context. Oxytocin transiently increased the drive of the anterior olfactory cortex projecting to olfactory bulb interneurons. Cortical top-down recruitment of interneurons dynamically enhanced the inhibitory input to olfactory bulb projection neurons and increased the signal-to-noise of their output. In summary, oxytocin generates states for optimized information extraction in an early cortical top-down network that is required for social interactions with potential implications for sensory processing deficits in autism spectrum disorders.
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Affiliation(s)
- Lars-Lennart Oettl
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159 Mannheim, Germany
| | - Namasivayam Ravi
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159 Mannheim, Germany
| | - Miriam Schneider
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159 Mannheim, Germany
| | - Max F Scheller
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159 Mannheim, Germany
| | - Peggy Schneider
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159 Mannheim, Germany
| | - Mariela Mitre
- Skirball Institute for Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Miriam da Silva Gouveia
- Schaller Research Group on Neuropeptides, German Cancer Research Center, 69120 Heidelberg, Germany
| | - Robert C Froemke
- Skirball Institute for Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Moses V Chao
- Skirball Institute for Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - W Scott Young
- Section on Neural Gene Expression, National Institute of Mental Health, NIH, Bethesda, MD 20892, USA
| | - Andreas Meyer-Lindenberg
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159 Mannheim, Germany
| | - Valery Grinevich
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159 Mannheim, Germany; Schaller Research Group on Neuropeptides, German Cancer Research Center, 69120 Heidelberg, Germany
| | - Roman Shusterman
- Sagol Department of Neurobiology, University of Haifa, Haifa 3498838, Israel
| | - Wolfgang Kelsch
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159 Mannheim, Germany.
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Abstract
UNLABELLED Neuromodulation of olfactory circuits by acetylcholine (ACh) plays an important role in odor discrimination and learning. Early processing of chemosensory signals occurs in two functionally and anatomically distinct regions, the main and accessory olfactory bulbs (MOB and AOB), which receive extensive cholinergic input from the basal forebrain. Here, we explore the regulation of AOB and MOB circuits by ACh, and how cholinergic modulation influences olfactory-mediated behaviors in mice. Surprisingly, despite the presence of a conserved circuit, activation of muscarinic ACh receptors revealed marked differences in cholinergic modulation of output neurons: excitation in the AOB and inhibition in the MOB. Granule cells (GCs), the most abundant intrinsic neuron in the OB, also exhibited a complex muscarinic response. While GCs in the AOB were excited, MOB GCs exhibited a dual muscarinic action in the form of a hyperpolarization and an increase in excitability uncovered by cell depolarization. Furthermore, ACh influenced the input-output relationship of mitral cells in the AOB and MOB differently showing a net effect on gain in mitral cells of the MOB, but not in the AOB. Interestingly, despite the striking differences in neuromodulatory actions on output neurons, chemogenetic inhibition of cholinergic neurons produced similar perturbations in olfactory behaviors mediated by these two regions. Decreasing ACh in the OB disrupted the natural discrimination of molecularly related odors and the natural investigation of odors associated with social behaviors. Thus, the distinct neuromodulation by ACh in these circuits could underlie different solutions to the processing of general odors and semiochemicals, and the diverse olfactory behaviors they trigger. SIGNIFICANCE STATEMENT State-dependent cholinergic modulation of brain circuits is critical for several high-level cognitive functions, including attention and memory. Here, we provide new evidence that cholinergic modulation differentially regulates two parallel circuits that process chemosensory information, the accessory and main olfactory bulb (AOB and MOB, respectively). These circuits consist of remarkably similar synaptic arrangement and neuronal types, yet cholinergic regulation produced strikingly opposing effects in output and intrinsic neurons. Despite these differences, the chemogenetic reduction of cholinergic activity in freely behaving animals disrupted odor discrimination of simple odors, and the investigation of social odors associated with behaviors signaled by the Vomeronasal system.
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Steinfeld R, Herb JT, Sprengel R, Schaefer AT, Fukunaga I. Divergent innervation of the olfactory bulb by distinct raphe nuclei. J Comp Neurol 2015; 523:805-13. [PMID: 25420775 PMCID: PMC4328392 DOI: 10.1002/cne.23713] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 11/13/2014] [Accepted: 11/14/2014] [Indexed: 01/07/2023]
Abstract
The raphe nuclei provide serotonergic innervation widely in the brain, thought to mediate a variety of neuromodulatory effects. The mammalian olfactory bulb (OB) is a prominent recipient of serotonergic fibers, particularly in the glomerular layer (GL), where they are thought to gate incoming signals from the olfactory nerve. The dorsal raphe nucleus (DRN) and the median raphe nucleus (MRN) are known to densely innervate the OB. The majority of such projections are thought to terminate in the GL, but this has not been explicitly tested. We sought to investigate this using recombinant adeno-associated viruses (rAAV)-mediated expression of green fluorescent protein (GFP)-synaptophysin targeted specifically to neurons of the DRN or the MRN. With DRN injections, labeled fibers were found mostly in the granule cell layer (GCL), not the GL. Conversely, dense labeling in the GL was observed with MRN injections, suggesting that the source of GL innervation is the MRN, not the DRN, as previously thought. The two raphe nuclei thus give dual innervation within the OB, with distinct innervation patterns. J. Comp. Neurol. 523:805–813, 2015. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Raphael Steinfeld
- Behavioural Neurophysiology, Max Planck Institute for Medical Research, Heidelberg, 69120, Germany; Champalimaud Centre for Neuroscience, Lisbon, 1400-038, Portugal
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