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Yang D, Xu J, Xu K, Xu P. Skeletal interoception in osteoarthritis. Bone Res 2024; 12:22. [PMID: 38561376 PMCID: PMC10985098 DOI: 10.1038/s41413-024-00328-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 03/02/2024] [Accepted: 03/16/2024] [Indexed: 04/04/2024] Open
Abstract
The interoception maintains proper physiological conditions and metabolic homeostasis by releasing regulatory signals after perceving changes in the internal state of the organism. Among its various forms, skeletal interoception specifically regulates the metabolic homeostasis of bones. Osteoarthritis (OA) is a complex joint disorder involving cartilage, subchondral bone, and synovium. The subchondral bone undergoes continuous remodeling to adapt to dynamic joint loads. Recent findings highlight that skeletal interoception mediated by aberrant mechanical loads contributes to pathological remodeling of the subchondral bone, resulting in subchondral bone sclerosis in OA. The skeletal interoception is also a potential mechanism for chronic synovial inflammation in OA. In this review, we offer a general overview of interoception, specifically skeletal interoception, subchondral bone microenviroment and the aberrant subchondral remedeling. We also discuss the role of skeletal interoception in abnormal subchondral bone remodeling and synovial inflammation in OA, as well as the potential prospects and challenges in exploring novel OA therapies that target skeletal interoception.
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Affiliation(s)
- Dinglong Yang
- Department of Joint Surgery, Honghui Hospital, Xi'an Jiaotong University, Xi'an, 710054, China
| | - Jiawen Xu
- Department of Orthopedic Surgery and Orthopedic Research Institute, West China Hospital, Sichuan University, Chengdu, 610041, China
| | - Ke Xu
- Department of Joint Surgery, Honghui Hospital, Xi'an Jiaotong University, Xi'an, 710054, China
| | - Peng Xu
- Department of Joint Surgery, Honghui Hospital, Xi'an Jiaotong University, Xi'an, 710054, China.
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Luettich A, Sievers C, Alfaro Almagro F, Allen M, Jbabdi S, Smith SM, Pattinson KTS. Functional connectivity between interoceptive brain regions is associated with distinct health-related domains: A population-based neuroimaging study. Hum Brain Mapp 2023; 44:3210-3221. [PMID: 36939141 PMCID: PMC10171512 DOI: 10.1002/hbm.26275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 02/08/2023] [Accepted: 02/27/2023] [Indexed: 03/21/2023] Open
Abstract
Interoception is the sensation, perception, and integration of signals from within the body. It has been associated with a broad range of physiological and psychological processes. Further, interoceptive variables are related to specific regions and networks in the human brain. However, it is not clear whether or how these networks relate empirically to different domains of physiological and psychological health at the population level. We analysed a data set of 19,020 individuals (10,055 females, 8965 males; mean age: 63 years, age range: 45-81 years), who have participated in the UK Biobank Study, a very large-scale prospective epidemiological health study. Using canonical correlation analysis (CCA), allowing for the examination of associations between two sets of variables, we related the functional connectome of brain regions implicated in interoception to a selection of nonimaging health and lifestyle related phenotypes, exploring their relationship within modes of population co-variation. In one integrated and data driven analysis, we obtained four statistically significant modes. Modes could be categorised into domains of arousal and affect and cardiovascular health, respiratory health, body mass, and subjective health (all p < .0001) and were meaningfully associated with distinct neural circuits. Circuits represent specific neural "fingerprints" of functional domains and set the scope for future studies on the neurobiology of interoceptive involvement in different lifestyle and health-related phenotypes. Therefore, our research contributes to the conceptualisation of interoception and may lead to a better understanding of co-morbid conditions in the light of shared interoceptive structures.
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Affiliation(s)
- Alexander Luettich
- Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
- Wellcome Centre for Integrative NeuroimagingUniversity of OxfordOxfordUK
| | - Carolin Sievers
- Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
- Wellcome Centre for Integrative NeuroimagingUniversity of OxfordOxfordUK
| | - Fidel Alfaro Almagro
- Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
- Wellcome Centre for Integrative NeuroimagingUniversity of OxfordOxfordUK
| | - Micah Allen
- Center of Functionally Integrative NeuroscienceAarhus UniversityAarhusDenmark
- Aarhus Institute of Advanced StudiesAarhus UniversityAarhusDenmark
- Cambridge PsychiatryUniversity of CambridgeCambridgeUK
| | - Saad Jbabdi
- Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
- Wellcome Centre for Integrative NeuroimagingUniversity of OxfordOxfordUK
| | - Stephen M. Smith
- Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
- Wellcome Centre for Integrative NeuroimagingUniversity of OxfordOxfordUK
| | - Kyle T. S. Pattinson
- Nuffield Department of Clinical NeurosciencesUniversity of OxfordOxfordUK
- Wellcome Centre for Integrative NeuroimagingUniversity of OxfordOxfordUK
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Bassi JK, Connelly AA, Butler AG, Liu Y, Ghanbari A, Farmer DGS, Jenkins MW, Melo MR, McDougall SJ, Allen AM. Analysis of the distribution of vagal afferent projections from different peripheral organs to the nucleus of the solitary tract in rats. J Comp Neurol 2022; 530:3072-3103. [PMID: 35988033 PMCID: PMC9804483 DOI: 10.1002/cne.25398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 07/26/2022] [Accepted: 08/02/2022] [Indexed: 01/05/2023]
Abstract
Anatomical tracing studies examining the vagal system can conflate details of sensory afferent and motor efferent neurons. Here, we used a serotype of adeno-associated virus that transports retrogradely and exhibits selective tropism for vagal afferents, to map their soma location and central termination sites within the nucleus of the solitary tract (NTS). We examined the vagal sensory afferents innervating the trachea, duodenum, stomach, or heart, and in some animals, from two organs concurrently. We observed no obvious somatotopy in the somata distribution within the nodose ganglion. The central termination patterns of afferents from different organs within the NTS overlap substantially. Convergence of vagal afferent inputs from different organs onto single NTS neurons is observed. Abdominal and thoracic afferents terminate throughout the NTS, including in the rostral NTS, where the 7th cranial nerve inputs are known to synapse. To address whether the axonal labeling produced by viral transduction is so widespread because it fills axons traveling to their targets, and not just terminal fields, we labeled pre and postsynaptic elements of vagal afferents in the NTS . Vagal afferents form multiple putative synapses as they course through the NTS, with each vagal afferent neuron distributing sensory signals to multiple second-order NTS neurons. We observe little selectivity between vagal afferents from different visceral targets and NTS neurons with common neurochemical phenotypes, with afferents from different organs making close appositions with the same NTS neuron. We conclude that specific viscerosensory information is distributed widely within the NTS and that the coding of this input is probably determined by the intrinsic properties and projections of the second-order neuron.
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Affiliation(s)
- Jaspreet K. Bassi
- Department of Anatomy and PhysiologyThe University of MelbourneParkvilleVictoriaAustralia
| | - Angela A. Connelly
- Department of Anatomy and PhysiologyThe University of MelbourneParkvilleVictoriaAustralia
| | - Andrew G. Butler
- Department of Anatomy and PhysiologyThe University of MelbourneParkvilleVictoriaAustralia
| | - Yehe Liu
- Department of Biomedical EngineeringCase Western Reserve UniversityClevelandOhioUSA
| | - Anahita Ghanbari
- Department of Anatomy and PhysiologyThe University of MelbourneParkvilleVictoriaAustralia,Department of Queensland Brain InstituteThe University of QueenslandSt LuciaQueenslandAustralia
| | - David G. S. Farmer
- Department of Anatomy and PhysiologyThe University of MelbourneParkvilleVictoriaAustralia
| | - Michael W. Jenkins
- Department of Biomedical EngineeringCase Western Reserve UniversityClevelandOhioUSA
| | - Mariana R. Melo
- Department of Anatomy and PhysiologyThe University of MelbourneParkvilleVictoriaAustralia
| | - Stuart J. McDougall
- Department of Florey Institute of Neuroscience and Mental HealthThe University of MelbourneParkvilleVictoriaAustralia
| | - Andrew M. Allen
- Department of Anatomy and PhysiologyThe University of MelbourneParkvilleVictoriaAustralia,Department of Florey Institute of Neuroscience and Mental HealthThe University of MelbourneParkvilleVictoriaAustralia
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An NTS-CeA projection modulates depression-like behaviors in a mouse model of chronic pain. Neurobiol Dis 2022; 174:105893. [DOI: 10.1016/j.nbd.2022.105893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 09/28/2022] [Accepted: 10/08/2022] [Indexed: 11/22/2022] Open
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Forstenpointner J, Maallo AMS, Elman I, Holmes S, Freeman R, Baron R, Borsook D. The Solitary Nucleus Connectivity to Key Autonomic Regions in Humans MRI and Literature based Considerations. Eur J Neurosci 2022; 56:3938-3966. [PMID: 35545280 DOI: 10.1111/ejn.15691] [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: 10/13/2021] [Revised: 05/04/2022] [Accepted: 05/05/2022] [Indexed: 11/03/2022]
Abstract
The nucleus tractus solitarius (NTS), is a key brainstem structure relaying interoceptive peripheral information to the interrelated brain centers for eliciting rapid autonomic responses and for shaping longer-term neuroendocrine and motor patterns. Structural and functional NTS' connectivity has been extensively investigated in laboratory animals. But there is limited information about NTS' connectome in humans. Using MRI, we examined diffusion and resting state data from 20 healthy participants in the Human Connectome Project. The regions within the brainstem (n=8), subcortical (n=6), cerebellar (n=2) and cortical (n=5) parts of the brain were selected via a systematic review of the literature and their white matter NTS connections were evaluated via probabilistic tractography along with functional and directional (i.e., Granger-causality) analyses. The underlying study confirms previous results from animal models and provides novel aspects on NTS integration in humans. Two key findings can be summarized: (i) the NTS predominantly processes afferent input and (ii) a lateralization towards a predominantly left-sided NTS processing. Our results lay the foundations for future investigations into the NTS' tripartite role comprised of interoreceptors' input integration, the resultant neurochemical outflow and cognitive/affective processing. The implications of these data add to the understanding of NTS' role in specific aspects of autonomic functions.
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Affiliation(s)
- Julia Forstenpointner
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA.,Division of Neurological Pain Research and Therapy, Department of Neurology, University Hospital Schleswig-Holstein, Kiel, Germany
| | - Anne Margarette S Maallo
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA
| | - Igor Elman
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA.,Cambridge Health Alliance, Harvard Medical School, Cambridge, MA, USA
| | - Scott Holmes
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA
| | - Roy Freeman
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - Ralf Baron
- Division of Neurological Pain Research and Therapy, Department of Neurology, University Hospital Schleswig-Holstein, Kiel, Germany
| | - David Borsook
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA.,Department of Radiology and Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
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6
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Forstenpointner J, Elman I, Freeman R, Borsook D. The Omnipresence of Autonomic Modulation in Health and Disease. Prog Neurobiol 2022; 210:102218. [PMID: 35033599 DOI: 10.1016/j.pneurobio.2022.102218] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 12/13/2021] [Accepted: 01/10/2022] [Indexed: 10/19/2022]
Abstract
The Autonomic Nervous System (ANS) is a critical part of the homeostatic machinery with both central and peripheral components. However, little is known about the integration of these components and their joint role in the maintenance of health and in allostatic derailments leading to somatic and/or neuropsychiatric (co)morbidity. Based on a comprehensive literature search on the ANS neuroanatomy we dissect the complex integration of the ANS: (1) First we summarize Stress and Homeostatic Equilibrium - elucidating the responsivity of the ANS to stressors; (2) Second we describe the overall process of how the ANS is involved in Adaptation and Maladaptation to Stress; (3) In the third section the ANS is hierarchically partitioned into the peripheral/spinal, brainstem, subcortical and cortical components of the nervous system. We utilize this anatomical basis to define a model of autonomic integration. (4) Finally, we deploy the model to describe human ANS involvement in (a) Hypofunctional and (b) Hyperfunctional states providing examples in the healthy state and in clinical conditions.
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Affiliation(s)
- Julia Forstenpointner
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA; Division of Neurological Pain Research and Therapy, Department of Neurology, University Hospital Schleswig-Holstein, Campus Kiel, SH, Germany.
| | - Igor Elman
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA; Cambridge Health Alliance, Harvard Medical School, Cambridge, MA, USA
| | - Roy Freeman
- Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - David Borsook
- Center for Pain and the Brain, Boston Children's Hospital, Department of Anesthesia, Critical Care and Pain Medicine, Harvard Medical School, Boston, MA, USA; Departments of Psychiatry and Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
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Fawley JA, Hegarty DM, Aicher SA, Beaumont E, Andresen MC. Dedicated C-fiber vagal sensory afferent pathways to the paraventricular nucleus of the hypothalamus. Brain Res 2021; 1769:147625. [PMID: 34416255 DOI: 10.1016/j.brainres.2021.147625] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/24/2021] [Accepted: 08/12/2021] [Indexed: 12/22/2022]
Abstract
The nucleus of the solitary tract (NTS) receives viscerosensory information from the vagus nerve to regulate diverse homeostatic reflex functions. The NTS projects to a wide network of other brain regions, including the paraventricular nucleus of the hypothalamus (PVN). Here we examined the synaptic characteristics of primary afferent pathways to PVN-projecting NTS neurons in rat brainstem slices.Expression of the Transient Receptor Potential Vanilloid receptor (TRPV1+ ) distinguishes C-fiber afferents within the solitary tract (ST) from A-fibers (TRPV1-). We used resiniferatoxin (RTX), a TRPV1 agonist, to differentiate the two. The variability in the latency (jitter) of evoked excitatory postsynaptic currents (ST-EPSCs) distinguished monosynaptic from polysynaptic ST-EPSCs. Rhodamine injected into PVN was retrogradely transported to identify PVN-projecting NTS neurons within brainstem slices. Graded shocks to the ST elicited all-or-none EPSCs in rhodamine-positive NTS neurons with latencies that had either low jitter (<200 µs - monosynaptic), high jitter (>200 µs - polysynaptic inputs) or both. RTX blocked ST-evoked TRPV1 + EPSCs whether mono- or polysynaptic. Most PVN-projecting NTS neurons (17/21 neurons) had at least one input polysynaptically connected to the ST. Compared to unlabeled NTS neurons, PVN-projecting NTS neurons were more likely to receive indirect inputs and be higher order. Surprisingly, sEPSC rates for PVN-projecting neurons were double that of unlabeled NTS neurons. The ST synaptic responses for PVN-projecting NTS neurons were either all TRPV1+ or all TRPV1-, including neurons that received both direct and indirect inputs. Overall, PVN-projecting NTS neurons received direct and indirect vagal afferent information with strict segregation regarding TRPV1 expression.
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Affiliation(s)
- Jessica A Fawley
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR 97239, United States
| | - Deborah M Hegarty
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR 97239, United States
| | - Sue A Aicher
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR 97239, United States
| | - Eric Beaumont
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, United States
| | - Michael C Andresen
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, OR 97239, United States.
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Berntson GG, Khalsa SS. Neural Circuits of Interoception. Trends Neurosci 2021; 44:17-28. [PMID: 33378653 DOI: 10.1016/j.tins.2020.09.011] [Citation(s) in RCA: 124] [Impact Index Per Article: 41.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 06/30/2020] [Accepted: 09/25/2020] [Indexed: 12/11/2022]
Abstract
The present paper considers recent progress in our understanding of the afferent/ascending neural pathways and neural circuits of interoception. Of particular note is the extensive role of rostral neural systems, including cortical systems, in the recognition of internal body states, and the reciprocal role of efferent/descending systems in the regulation of those states. Together these reciprocal interacting networks entail interoceptive circuits that play an important role in a broad range of functions beyond the homeostatic maintenance of physiological steady-states. These include the regulation of behavioral, cognitive, and affective processes across conscious and nonconscious levels of processing. We highlight recent advances and knowledge gaps that are important for accelerating progress in the study of interoception.
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Affiliation(s)
- Gary G Berntson
- Department of Psychology, Ohio State University, Columbus, OH, USA.
| | - Sahib S Khalsa
- Laureate Institute for Brain Research, Tulsa, OK, USA; Oxley College of Health Sciences, University of Tulsa, Tulsa, OK, USA
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Pagliusi M, Bonet IJM, Lemes JBP, Oliveira ALL, Carvalho NS, Tambeli CH, Parada CA, Sartori CR. Social defeat stress-induced hyperalgesia is mediated by nav 1.8 + nociceptive fibers. Neurosci Lett 2020; 729:135006. [PMID: 32387758 DOI: 10.1016/j.neulet.2020.135006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 04/17/2020] [Accepted: 04/20/2020] [Indexed: 10/24/2022]
Abstract
Recently the voltage-gated sodium (Nav) channels began to be studied as possible targets for analgesic drugs. In addition, specific Nav 1.8 blockers are currently being used to treat some types of chronic pain pathologies such as neuropathies and fibromyalgia. Nav 1.8+ fibers convey nociceptive information to brain structures belonging to the limbic system, which is involved in the pathophysiology of major depressive disorders. From this, using a model of chronic social defeat stress (SDS) and intrathecal injections of Nav 1.8 antisense, this study investigated the possible involvement of Nav 1.8+ nociceptive fibers in SDS- induced hyperalgesia in C57/BL mice. Our results showed that SDS induced a depressive-like behavior of social avoidance and increased the sensitivity to mechanical (electronic von Frey test) and chemical (capsaicin test) nociceptive stimuli. We also showed that intrathecal injection of Nav 1.8 antisense reversed the SDS-induced hyperalgesia as demonstrated by both, mechanical and chemical nociceptive tests. We confirmed the antisense efficacy and specificity in a separate no-defeated cohort through real-time PCR, which showed a significant reduction of Nav 1.8 mRNA and no reduction of Nav 1.7 and Nav 1.9 in the L4, L5 and L6 dorsal root ganglia (DRG). The present study advances the understanding of SDS-induced hyperalgesia, which seems to be dependent on Nav 1.8+ nociceptive fibers.
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Affiliation(s)
- Marco Pagliusi
- Department of Structural and Functional Biology, State University of Campinas, Rua Monteiro Lobato, 255, Cidade Universitaria Zeferino Vaz, Box 6109, Campinas, SP 13083-865, Brazil
| | - Ivan José Magayewski Bonet
- Department of Oral and Maxillofacial Surgery,University of California San Francisco, 513 Parnassus Ave, Box 0440 S709, San Francisco, CA 94143, United States
| | - Júlia Borges Paes Lemes
- Department of Structural and Functional Biology, State University of Campinas, Rua Monteiro Lobato, 255, Cidade Universitaria Zeferino Vaz, Box 6109, Campinas, SP 13083-865, Brazil
| | - Anna Lethicia Lima Oliveira
- Department of Structural and Functional Biology, State University of Campinas, Rua Monteiro Lobato, 255, Cidade Universitaria Zeferino Vaz, Box 6109, Campinas, SP 13083-865, Brazil
| | - Nathalia Santos Carvalho
- Department of Structural and Functional Biology, State University of Campinas, Rua Monteiro Lobato, 255, Cidade Universitaria Zeferino Vaz, Box 6109, Campinas, SP 13083-865, Brazil
| | - Claudia Herrera Tambeli
- Department of Structural and Functional Biology, State University of Campinas, Rua Monteiro Lobato, 255, Cidade Universitaria Zeferino Vaz, Box 6109, Campinas, SP 13083-865, Brazil
| | - Carlos Amilcar Parada
- Department of Structural and Functional Biology, State University of Campinas, Rua Monteiro Lobato, 255, Cidade Universitaria Zeferino Vaz, Box 6109, Campinas, SP 13083-865, Brazil
| | - Cesar Renato Sartori
- Department of Structural and Functional Biology, State University of Campinas, Rua Monteiro Lobato, 255, Cidade Universitaria Zeferino Vaz, Box 6109, Campinas, SP 13083-865, Brazil.
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Extensive Inhibitory Gating of Viscerosensory Signals by a Sparse Network of Somatostatin Neurons. J Neurosci 2019; 39:8038-8050. [PMID: 31471471 DOI: 10.1523/jneurosci.3036-18.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 08/07/2019] [Accepted: 08/10/2019] [Indexed: 01/07/2023] Open
Abstract
Integration and modulation of primary afferent sensory information begins at the first terminating sites within the CNS, where central inhibitory circuits play an integral role. Viscerosensory information is conveyed to the nucleus of the solitary tract (NTS) where it initiates neuroendocrine, behavioral, and autonomic reflex responses that ensure optimal internal organ function. This excitatory input is modulated by diverse, local inhibitory interneurons, whose functions are not clearly understood. Here we show that, in male rats, 65% of somatostatin-expressing (SST) NTS neurons also express GAD67, supporting their likely role as inhibitory interneurons. Using whole-cell recordings of NTS neurons, from horizontal brainstem slices of male and female SST-yellow fluorescent protein (YFP) and SST-channelrhodopsin 2 (ChR2)-YFP mice, we quantified the impact of SST-NTS neurons on viscerosensory processing. Light-evoked excitatory photocurrents were reliably obtained from SST-ChR2-YFP neurons (n = 16) and the stimulation-response characteristics determined. Most SST neurons (57%) received direct input from solitary tract (ST) afferents, indicating that they form part of a feedforward circuit. All recorded SST-negative NTS neurons (n = 72) received SST-ChR2 input. ChR2-evoked PSCs were largely inhibitory and, in contrast to previous reports, were mediated by both GABA and glycine. When timed to coincide, the ChR2-activated SST input suppressed ST-evoked action potentials at second-order NTS neurons, demonstrating strong modulation of primary viscerosensory input. These data indicate that the SST inhibitory network innervates broadly within the NTS, with the potential to gate viscerosensory input to powerfully alter autonomic reflex function and other behaviors.SIGNIFICANCE STATEMENT Sensory afferent input is modulated according to state. For example the baroreflex is altered during a stress response or exercise, but the basic mechanisms underpinning this sensory modulation are not fully understood in any sensory system. Here we demonstrate that the neuronal processing of viscerosensory information begins with synaptic gating at the first central synapse with second-order neurons in the NTS. These data reveal that the somatostatin subclass of inhibitory interneurons are driven by visceral sensory input to play a major role in gating viscerosensory signals, placing them within a feedforward circuit within the NTS.
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Litvin DG, Dick TE, Smith CB, Jacono FJ. Lung-injury depresses glutamatergic synaptic transmission in the nucleus tractus solitarii via discrete age-dependent mechanisms in neonatal rats. Brain Behav Immun 2018; 70:398-422. [PMID: 29601943 PMCID: PMC6075724 DOI: 10.1016/j.bbi.2018.03.031] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 03/20/2018] [Accepted: 03/26/2018] [Indexed: 12/26/2022] Open
Abstract
Transition periods (TPs) are brief stages in CNS development where neural circuits can exhibit heightened vulnerability to pathologic conditions such as injury or infection. This susceptibility is due in part to specialized mechanisms of synaptic plasticity, which may become activated by inflammatory mediators released under pathologic conditions. Thus, we hypothesized that the immune response to lung injury (LI) mediated synaptic changes through plasticity-like mechanisms that depended on whether LI occurred just before or after a TP. We studied the impact of LI on brainstem 2nd-order viscerosensory neurons located in the nucleus tractus solitarii (nTS) during a TP for respiratory control spanning (postnatal day (P) 11-15). We injured the lungs of Sprague-Dawley rats by intratracheal instillation of Bleomycin (or saline) just before (P9-11) or after (P17-19) the TP. A week later, we prepared horizontal slices of the medulla and recorded spontaneous and evoked excitatory postsynaptic currents (sEPSCs/eEPSCs) in vitro from neurons in the nTS that received monosynaptic glutamatergic input from the tractus solitarii (TS). In rats injured before the TP (pre-TP), neurons exhibited blunted sEPSCs and TS-eEPSCs compared to controls. The decreased TS-eEPSCs were mediated by differences in postsynaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic-acid receptors (AMPAR). Specifically, compared to controls, LI rats had more Ca2+-impermeable AMPARs (CI-AMPARs) as indicated by: 1) the absence of current-rectification, 2) decreased sensitivity to polyamine, 1-Naphthyl-acetyl-spermine-trihydrochloride (NASPM) and 3) augmented immunoreactive staining for the CI-AMPAR GluA2. Thus, pre-TP-LI acts postsynaptically to blunt glutamatergic transmission. The neuroimmune response to pre-TP-LI included microglia hyper-ramification throughout the nTS. Daily intraperitoneal administration of minocycline, an inhibitor of microglial/macrophage function prevented hyper-ramification and abolished the pre-TP-LI evoked synaptic changes. In contrast, rat-pups injured after the TP (post-TP) exhibited microglia hypo-ramification in the nTS and had increased sEPSC amplitudes/frequencies, and decreased TS-eEPSC amplitudes compared to controls. These synaptic changes were not associated with changes in CI-AMPARs, and instead involved greater TS-evoked use-dependent depression (reduced paired pulse ratio), which is a hallmark of presynaptic plasticity. Thus we conclude that LI regulates the efficacy of TS → nTS synapses through discrete plasticity-like mechanisms that are immune-mediated and depend on whether the injury occurs before or after the TP for respiratory control.
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Affiliation(s)
- David G Litvin
- Department of Physiology & Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Division of Pulmonary, Critical Care and Sleep Medicine, Louis Stokes VA Medical Center, Cleveland, OH 44106, United States
| | - Thomas E Dick
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States
| | - Corey B Smith
- Department of Physiology & Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States
| | - Frank J Jacono
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Division of Pulmonary, Critical Care and Sleep Medicine, Louis Stokes VA Medical Center, Cleveland, OH 44106, United States.
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Central Network Dynamics Regulating Visceral and Humoral Functions. J Neurosci 2017; 37:10848-10854. [PMID: 29118214 DOI: 10.1523/jneurosci.1833-17.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 10/03/2017] [Accepted: 10/08/2017] [Indexed: 02/07/2023] Open
Abstract
The brain processes information from the periphery and regulates visceral and immune activity to maintain internal homeostasis, optimally respond to a dynamic external environment, and integrate these functions with ongoing behavior. In addition to its relevance for survival, this integration underlies pathology as evidenced by diseases exhibiting comorbid visceral and psychiatric symptoms. Advances in neuroanatomical mapping, genetically specific neuronal manipulation, and neural network recording are overcoming the challenges of dissecting complex circuits that underlie this integration and deciphering their function. Here we focus on reciprocal communication between the brain and urological, gastrointestinal, and immune systems. These studies are revealing how autonomic activity becomes integrated into behavior as part of a social strategy, how the brain regulates innate immunity in response to stress, and how drugs impact emotion and gastrointestinal function. These examples highlight the power of the functional organization of circuits at the interface of the brain and periphery.
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Carter DA, Guo H, Connelly AA, Bassi JK, Fong AY, Allen AM, McDougall SJ. Viscerosensory input drives angiotensin II type 1A receptor-expressing neurons in the solitary tract nucleus. Am J Physiol Regul Integr Comp Physiol 2017; 314:R282-R293. [PMID: 29118020 DOI: 10.1152/ajpregu.00290.2017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Homeostatic regulation of visceral organ function requires integrated processing of neural and neurohormonal sensory signals. The nucleus of the solitary tract (NTS) is the primary sensory nucleus for cranial visceral sensory afferents. Angiotensin II (ANG II) is known to modulate peripheral visceral reflexes, in part, by activating ANG II type 1A receptors (AT1AR) in the NTS. AT1AR-expressing NTS neurons occur throughout the NTS with a defined subnuclear distribution, and most of these neurons are depolarized by ANG II. In this study we determined whether AT1AR-expressing NTS neurons receive direct visceral sensory input, and whether this input is modulated by ANG II. Using AT1AR-GFP mice to make targeted whole cell recordings from AT1AR-expressing NTS neurons, we demonstrate that two-thirds (37 of 56) of AT1AR-expressing neurons receive direct excitatory, visceral sensory input. In half of the neurons tested (4 of 8) the excitatory visceral sensory input was significantly reduced by application of the transient receptor potential vallinoid type 1 receptor agonist, capsaicin, indicating AT1AR-expressing neurons can receive either C- or A-fiber-mediated input. Application of ANG II to a subset of second-order AT1AR-expressing neurons did not affect spontaneous, evoked, or asynchronous glutamate release from visceral sensory afferents. Thus it is unlikely that AT1AR-expressing viscerosensory neurons terminate on AT1AR-expressing NTS neurons. Our data suggest that ANG II is likely to modulate multiple visceral sensory modalities by altering the excitability of second-order AT1AR-expressing NTS neurons.
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Affiliation(s)
- D A Carter
- Department of Physiology, The University of Melbourne , Victoria , Australia
| | - H Guo
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne , Victoria , Australia
| | - A A Connelly
- Department of Physiology, The University of Melbourne , Victoria , Australia
| | - J K Bassi
- Department of Physiology, The University of Melbourne , Victoria , Australia
| | - A Y Fong
- Department of Physiology, The University of Melbourne , Victoria , Australia
| | - A M Allen
- Department of Physiology, The University of Melbourne , Victoria , Australia.,Florey Institute of Neuroscience and Mental Health, The University of Melbourne , Victoria , Australia
| | - S J McDougall
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne , Victoria , Australia
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Beaumont E, Campbell RP, Andresen MC, Scofield S, Singh K, Libbus I, KenKnight BH, Snyder L, Cantrell N. Cervical vagus nerve stimulation augments spontaneous discharge in second- and higher-order sensory neurons in the rat nucleus of the solitary tract. Am J Physiol Heart Circ Physiol 2017; 313:H354-H367. [PMID: 28476920 DOI: 10.1152/ajpheart.00070.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 05/01/2017] [Accepted: 05/01/2017] [Indexed: 02/07/2023]
Abstract
Vagus nerve stimulation (VNS) currently treats patients with drug-resistant epilepsy, depression, and heart failure. The mild intensities used in chronic VNS suggest that primary visceral afferents and central nervous system activation are involved. Here, we measured the activity of neurons in the nucleus of the solitary tract (NTS) in anesthetized rats using clinically styled VNS. Our chief findings indicate that VNS at threshold bradycardic intensity activated NTS neuron discharge in one-third of NTS neurons. This VNS directly activated only myelinated vagal afferents projecting to second-order NTS neurons. Most VNS-induced activity in NTS, however, was unsynchronized to vagal stimuli. Thus, VNS activated unsynchronized activity in NTS neurons that were second order to vagal afferent C-fibers as well as higher-order NTS neurons only polysynaptically activated by the vagus. Overall, cardiovascular-sensitive and -insensitive NTS neurons were similarly activated by VNS: 3/4 neurons with monosynaptic vagal A-fiber afferents, 6/42 neurons with monosynaptic vagal C-fiber afferents, and 16/21 polysynaptic NTS neurons. Provocatively, vagal A-fibers indirectly activated C-fiber neurons during VNS. Elevated spontaneous spiking was quantitatively much higher than synchronized activity and extended well into the periods of nonstimulation. Surprisingly, many polysynaptic NTS neurons responded to half the bradycardic intensity used in clinical studies, indicating that a subset of myelinated vagal afferents is sufficient to evoke VNS indirect activation. Our study uncovered a myelinated vagal afferent drive that indirectly activates NTS neurons and thus central pathways beyond NTS and support reconsideration of brain contributions of vagal afferents underpinning of therapeutic impacts.NEW & NOTEWORTHY Acute vagus nerve stimulation elevated activity in neurons located in the medial nucleus of the solitary tract. Such stimuli directly activated only myelinated vagal afferents but indirectly activated a subpopulation of second- and higher-order neurons, suggesting that afferent mechanisms and central neuron activation may be responsible for vagus nerve stimulation efficacy.
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Affiliation(s)
- Eric Beaumont
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee;
| | - Regenia P Campbell
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee
| | | | - Stephanie Scofield
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee
| | - Krishna Singh
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee.,James H. Quillen Veterans Affairs Medical Center, Johnson City, Tennessee; and
| | | | | | - Logan Snyder
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee
| | - Nathan Cantrell
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee
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