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Yu H, Miao W, Ji E, Huang S, Jin S, Zhu X, Liu MZ, Sun YG, Xu F, Yu X. Social touch-like tactile stimulation activates a tachykinin 1-oxytocin pathway to promote social interactions. Neuron 2022; 110:1051-1067.e7. [PMID: 35045339 DOI: 10.1016/j.neuron.2021.12.022] [Citation(s) in RCA: 56] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 08/29/2021] [Accepted: 12/15/2021] [Indexed: 12/21/2022]
Abstract
It is well known that affective and pleasant touch promotes individual well-being and facilitates affiliative social communication, although the neural circuit that mediates this process is largely unknown. Here, we show that social-touch-like tactile stimulation (ST) enhances firing of oxytocin neurons in the mouse paraventricular hypothalamus (PVH) and promotes social interactions and positively reinforcing place preference. These results link pleasant somatosensory stimulation to increased social interactions and positive affective valence. We further show that tachykinin 1 (Tac1+) neurons in the lateral and ventrolateral periaqueductal gray (l/vlPAG) send monosynaptic excitatory projections to PVH oxytocin neurons. Functionally, activation of PVH-projecting Tac1+ neurons increases firing of oxytocin neurons, promotes social interactions, and increases preference for the social touch context, whereas reducing activity of Tac1+ neurons abolishes ST-induced oxytocin neuronal firing. Together, these results identify a dipeptidergic pathway from l/vlPAG Tac1+ neurons to PVH oxytocin neurons, through which pleasant sensory experience promotes social behavior.
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Affiliation(s)
- Hang Yu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wanying Miao
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - En Ji
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shajin Huang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Sen Jin
- Brain Cognition and Brain Disease Institute, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen 518055, China
| | - Xutao Zhu
- Brain Cognition and Brain Disease Institute, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen 518055, China
| | - Ming-Zhe Liu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yan-Gang Sun
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Fuqiang Xu
- University of Chinese Academy of Sciences, Beijing 100049, China; Brain Cognition and Brain Disease Institute, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen 518055, China
| | - Xiang Yu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China; School of Life Sciences, Peking-Tsinghua Center for Life Sciences, and Peking University McGovern Institute, Peking University, Beijing 100871, China; Autism Research Center of Peking University Health Science Center, Beijing 100191, China; Chinese Institute for Brain Research, Beijing 102206, China.
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52
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Wu H, Niu C, Qu Y, Sun X, Wang K. Selective activation of TRPA1 ion channels by nitrobenzene skin sensitizers DNFB and DNCB. J Biol Chem 2021; 298:101555. [PMID: 34973335 PMCID: PMC8800105 DOI: 10.1016/j.jbc.2021.101555] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 12/17/2021] [Accepted: 12/28/2021] [Indexed: 12/21/2022] Open
Abstract
2, 4-dinitrofluorobenzene (DNFB) and 2, 4-dinitrochlorobenzene (DNCB) are well known as skin sensitizers that can cause dermatitis. DNFB has shown to more potently sensitize skin; however, how DNFB and DNCB cause skin inflammation at a molecular level and why this difference in their sensitization ability is observed remains unknown. In this study, we aimed to identify the molecular targets and mechanisms on which DNFB and DNCB act. We used a fluorescent calcium imaging plate reader in an initial screening assay before patch-clamp recordings for validation. Molecular docking in combination with site-directed mutagenesis was then carried out to investigate DNFB and DNCB binding sites in the TRPA1 ion channel that may be selectively activated by these tow sensitizers. We found that DNFB and DNCB selectively activated TRPA1 channel with EC50 values of 2.3 ± 0.7 μM μM and 42.4 ± 20.9 μM, respectively. Single-channel recordings revealed that DNFB and DNCB increase the probability of channel opening and acts on three residues (C621, E625 and Y658) critical for TRPA1 activation. Our findings may not only help explain the molecular mechanism underlying the dermatitis and pruritus caused by chemicals like DNFB and DNCB, but also provide a molecular tool 7.5-fold more potent than the current TRPA1 activator allyl isothiocyanate (AITC) used for investigating TRPA1 channel pharmacology and pathology.
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Affiliation(s)
- Han Wu
- Department of Pharmacology, School of Pharmacy, Qingdao University, #1 Ningde Road, Qingdao 266073
| | - Canyang Niu
- Department of Pharmacology, School of Pharmacy, Qingdao University, #1 Ningde Road, Qingdao 266073
| | - Yaxuan Qu
- Department of Pharmacology, School of Pharmacy, Qingdao University, #1 Ningde Road, Qingdao 266073
| | - Xiaoying Sun
- Department of Pharmacology, School of Pharmacy, Qingdao University, #1 Ningde Road, Qingdao 266073; Institue of Innovative Drugs, Qingdao University, 38 Dengzhou Road, Qingdao 266021, China.
| | - KeWei Wang
- Department of Pharmacology, School of Pharmacy, Qingdao University, #1 Ningde Road, Qingdao 266073; Institue of Innovative Drugs, Qingdao University, 38 Dengzhou Road, Qingdao 266021, China.
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53
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Abstract
Itch is one of the most primal sensations, being both ubiquitous and important for the well-being of animals. For more than a century, a desire to understand how itch is encoded by the nervous system has prompted the advancement of many theories. Within the past 15 years, our understanding of the molecular and neural mechanisms of itch has undergone a major transformation, and this remarkable progress continues today without any sign of abating. Here I describe accumulating evidence that indicates that itch is distinguished from pain through the actions of itch-specific neuropeptides that relay itch information to the spinal cord. According to this model, classical neurotransmitters transmit, inhibit and modulate itch information in a context-, space- and time-dependent manner but do not encode itch specificity. Gastrin-releasing peptide (GRP) is proposed to be a key itch-specific neuropeptide, with spinal neurons expressing GRP receptor (GRPR) functioning as a key part of a convergent circuit for the conveyance of peripheral itch information to the brain.
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54
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Mu D, Sun YG. Circuit Mechanisms of Itch in the Brain. J Invest Dermatol 2021; 142:23-30. [PMID: 34662562 DOI: 10.1016/j.jid.2021.09.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/21/2021] [Accepted: 09/21/2021] [Indexed: 12/12/2022]
Abstract
Itch is an unpleasant somatic sensation with the desire to scratch, and it consists of sensory, affective, and motivational components. Acute itch serves as a critical protective mechanism because an itch-evoked scratching response will help to remove harmful substances invading the skin. Recently, exciting progress has been made in deciphering the mechanisms of itch at both the peripheral nervous system and the CNS levels. Key neuronal subtypes and circuits have been revealed for ascending transmission and the descending modulation of itch. In this review, we mainly summarize the current understanding of the central circuit mechanisms of itch in the brain.
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Affiliation(s)
- Di Mu
- Department of Anesthesiology, Shanghai General Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yan-Gang Sun
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology (CEBSIT), Chinese Academy of Sciences, Shanghai, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai, China.
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Wimalasena NK, Milner G, Silva R, Vuong C, Zhang Z, Bautista DM, Woolf CJ. Dissecting the precise nature of itch-evoked scratching. Neuron 2021; 109:3075-3087.e2. [PMID: 34411514 PMCID: PMC8497439 DOI: 10.1016/j.neuron.2021.07.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 06/10/2021] [Accepted: 07/26/2021] [Indexed: 01/17/2023]
Abstract
Itch is a discrete and irritating sensation tightly coupled to a drive to scratch. Acute scratching developed evolutionarily as an adaptive defense against skin irritants, pathogens, or parasites. In contrast, the itch-scratch cycle in chronic itch is harmful, inducing escalating itch and skin damage. Clinically and preclinically, scratching incidence is currently evaluated as a unidimensional motor parameter and believed to reflect itch severity. We propose that scratching, when appreciated as a complex, multidimensional motor behavior, will yield greater insight into the nature of itch and the organization of neural circuits driving repetitive motor patterns. We outline the limitations of standard measurements of scratching in rodent models and present new approaches to observe and quantify itch-evoked scratching. We argue that accurate quantitative measurements of scratching are critical for dissecting the molecular, cellular, and circuit mechanisms underlying itch and for preclinical development of therapeutic interventions for acute and chronic itch disorders.
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Affiliation(s)
- Nivanthika K Wimalasena
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA; Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - George Milner
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA
| | - Ricardo Silva
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Cliff Vuong
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Zihe Zhang
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA; Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Diana M Bautista
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Hellen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA.
| | - Clifford J Woolf
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA; Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
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56
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G-Protein-Coupled Estrogen Receptor (GPER) in the Rostral Ventromedial Medulla Is Essential for Mobilizing Descending Inhibition of Itch. J Neurosci 2021; 41:7727-7741. [PMID: 34349001 DOI: 10.1523/jneurosci.2592-20.2021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 07/19/2021] [Accepted: 07/28/2021] [Indexed: 11/21/2022] Open
Abstract
Chronic itch is a troublesome condition and often difficult to cure. Emerging evidence suggests that the periaqueductal gray (PAG)-rostral ventromedial medulla (RVM) pathway may play an important role in the regulation of itch, but the cellular organization and molecular mechanisms remain incompletely understood. Here, we report that a group of RVM neurons distinctively express the G-protein-coupled estrogen receptor (GPER), which mediates descending inhibition of itch. We found that GPER+ neurons in the RVM were activated in chronic itch conditions in rats and mice. Selective ablation or chemogenetic suppression of RVM GPER+ neurons resulted in mechanical alloknesis and increased scratching in response to pruritogens, whereas chemogenetic activation of GPER+ neurons abrogated itch responses, indicating that GPER+ neurons are antipruritic. Moreover, GPER-deficient mice and rats of either sex exhibited hypersensitivity to mechanical and chemical itch, a phenotype reversible by the µ type opioid receptor (MOR) antagonism. Additionally, significant MOR phosphorylation in the RVM was detected in chronic itch models in wild-type but not in GPER-/- rats. Therefore, GPER not only identifies a population of medullary antipruritic neurons but may also determine the descending antipruritic tone through regulating µ opioid signaling.SIGNIFICANCE STATEMENT Therapeutic options for itch are limited because of an as yet incomplete understanding of the mechanisms of itch processing. Our data have provided novel insights into the cellular organization and molecular mechanisms of descending regulation of itch in normal and pathologic conditions. GPER+ neurons (largely GABAergic) in the RVM are antipruritic neurons under tonic opioidergic inhibition, activation of GPER promotes phosphorylation of MOR and disinhibition of the antipruritic GPER+ neurons from inhibitory opioidergic inputs, and failure to mobilize GPER+ neurons may result in the exacerbation of itch. Our data also illuminate on some of the outstanding questions in the field, such as the mechanisms underlying sex bias in itch, pain, and opioid analgesia and the paradoxical effects of morphine on pain and itch.
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57
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Aroke EN, Overstreet DS, Penn TM, Crossman DK, Jackson P, Tollefsbol TO, Quinn TL, Yi N, Goodin BR. Identification of DNA methylation associated enrichment pathways in adults with non-specific chronic low back pain. Mol Pain 2021; 16:1744806920972889. [PMID: 33169629 PMCID: PMC7658508 DOI: 10.1177/1744806920972889] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Chronic low back pain (cLBP) that cannot be attributable to a specific pathoanatomical change is associated with high personal and societal costs. Still, the underlying mechanism that causes and sustains such a phenotype is largely unknown. Emerging evidence suggests that epigenetic changes play a role in chronic pain conditions. Using reduced representation bisulfite sequencing (RRBS), we evaluated DNA methylation profiles of adults with non-specific cLBP (n = 50) and pain-free controls (n = 48). We identified 28,325 hypermethylated and 36,936 hypomethylated CpG sites (p < 0.05). After correcting for multiple testing, we identified 159 DMRs (q < 0.01and methylation difference > 10%), the majority of which were located in CpG island (50%) and promoter regions (48%) on the associated genes. The genes associated with the differentially methylated regions were highly enriched in biological processes that have previously been implicated in immune signaling, endochondral ossification, and G-protein coupled transmissions. Our findings support inflammatory alterations and the role of bone maturation in cLBP. This study suggests that epigenetic regulation has an important role in the pathophysiology of non-specific cLBP and a basis for future studies in biomarker development and targeted interventions.
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Affiliation(s)
- Edwin N Aroke
- School of Nursing, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Demario S Overstreet
- Department of Psychology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Terence M Penn
- Department of Psychology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - David K Crossman
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Pamela Jackson
- School of Nursing, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Trygve O Tollefsbol
- Department of Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Tammie L Quinn
- Department of Psychology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Nengjun Yi
- Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Burel R Goodin
- School of Nursing, University of Alabama at Birmingham, Birmingham, AL, USA.,Department of Psychology, University of Alabama at Birmingham, Birmingham, AL, USA
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58
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Wu ZH, Shao HY, Fu YY, Wu XB, Cao DL, Yan SX, Sha WL, Gao YJ, Zhang ZJ. Descending Modulation of Spinal Itch Transmission by Primary Somatosensory Cortex. Neurosci Bull 2021; 37:1345-1350. [PMID: 34057697 DOI: 10.1007/s12264-021-00713-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 02/19/2021] [Indexed: 11/28/2022] Open
Affiliation(s)
- Zi-Han Wu
- Department of Human Anatomy, School of Medicine, Nantong University, Nantong, 226001, China.,Institute of Pain Medicine, Institute of Nautical Medicine, Nantong University, Nantong, 226019, China
| | - Han-Yu Shao
- Department of Human Anatomy, School of Medicine, Nantong University, Nantong, 226001, China.,Institute of Pain Medicine, Institute of Nautical Medicine, Nantong University, Nantong, 226019, China
| | - Yuan-Yuan Fu
- Department of Human Anatomy, School of Medicine, Nantong University, Nantong, 226001, China.,Institute of Pain Medicine, Institute of Nautical Medicine, Nantong University, Nantong, 226019, China
| | - Xiao-Bo Wu
- Institute of Pain Medicine, Institute of Nautical Medicine, Nantong University, Nantong, 226019, China
| | - De-Li Cao
- Institute of Pain Medicine, Institute of Nautical Medicine, Nantong University, Nantong, 226019, China
| | - Sheng-Xiang Yan
- Institute of Pain Medicine, Institute of Nautical Medicine, Nantong University, Nantong, 226019, China
| | - Wei-Lin Sha
- Institute of Pain Medicine, Institute of Nautical Medicine, Nantong University, Nantong, 226019, China
| | - Yong-Jing Gao
- Institute of Pain Medicine, Institute of Nautical Medicine, Nantong University, Nantong, 226019, China. .,Co-innovation Center of Neuroregeneration, Nantong University, Nantong, 226001, China.
| | - Zhi-Jun Zhang
- Department of Human Anatomy, School of Medicine, Nantong University, Nantong, 226001, China. .,Institute of Pain Medicine, Institute of Nautical Medicine, Nantong University, Nantong, 226019, China.
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59
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Samineni VK, Grajales-Reyes JG, Grajales-Reyes GE, Tycksen E, Copits BA, Pedersen C, Ankudey ES, Sackey JN, Sewell SB, Bruchas MR, Gereau RW. Cellular, circuit and transcriptional framework for modulation of itch in the central amygdala. eLife 2021; 10:e68130. [PMID: 34032210 PMCID: PMC8172243 DOI: 10.7554/elife.68130] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 05/24/2021] [Indexed: 01/06/2023] Open
Abstract
Itch is an unpleasant sensation that elicits robust scratching and aversive experience. However, the identity of the cells and neural circuits that organize this information remains elusive. Here, we show the necessity and sufficiency of chloroquine-activated neurons in the central amygdala (CeA) for both itch sensation and associated aversion. Further, we show that chloroquine-activated CeA neurons play important roles in itch-related comorbidities, including anxiety-like behaviors, but not in some aversive and appetitive behaviors previously ascribed to CeA neurons. RNA-sequencing of chloroquine-activated CeA neurons identified several differentially expressed genes as well as potential key signaling pathways in regulating pruritis. Finally, viral tracing experiments demonstrate that these neurons send projections to the ventral periaqueductal gray that are critical in modulation of itch. These findings reveal a cellular and circuit signature of CeA neurons orchestrating behavioral and affective responses to pruritus in mice.
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Affiliation(s)
- Vijay K Samineni
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
| | - Jose G Grajales-Reyes
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
- Medical Scientist Training Program, Washington University School of MedicineSt. LouisUnited States
- Neuroscience Program, Washington University School of MedicineSt. LouisUnited States
| | - Gary E Grajales-Reyes
- Department of Pathology & Immunology, Washington University School of MedicineSt. LouisUnited States
| | - Eric Tycksen
- Genome Technology Access Center, Washington University School of MedicineSeattleUnited States
| | - Bryan A Copits
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
| | - Christian Pedersen
- Department of Biomedical Engineering, University of WashingtonSeattleUnited States
| | - Edem S Ankudey
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
| | - Julian N Sackey
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
| | - Sienna B Sewell
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
| | - Michael R Bruchas
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
- Departments of Anesthesiology and Pharmacology, University of WashingtonSeattleUnited States
- Departmentsof Neuroscience and Biomedical Engineering, Washington University School of MedicineSt.LouisUnited States
| | - Robert W Gereau
- Washington University Pain Center and Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
- Department of Biomedical Engineering, University of WashingtonSeattleUnited States
- Departmentsof Neuroscience and Biomedical Engineering, Washington University School of MedicineSt.LouisUnited States
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Projections from the lateral parabrachial nucleus to the lateral and ventral lateral periaqueductal gray subregions mediate the itching sensation. Pain 2021; 162:1848-1863. [PMID: 33449512 DOI: 10.1097/j.pain.0000000000002193] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 12/30/2020] [Indexed: 11/25/2022]
Abstract
ABSTRACT Lateral and ventral lateral subregions of the periaqueductal gray (l/vlPAG) have been proved to be pivotal components in descending circuitry of itch processing, and their effects are related to the subclassification of neurons that were meditated. In this study, lateral parabrachial nucleus (LPB), one of the most crucial relay stations in the ascending pathway, was taken as the input nucleus to examine the modulatory effect of l/vlPAG neurons that received LPB projections. Anatomical tracing, chemogenetic, optogenetic, and local pharmacological approaches were used to investigate the participation of the LPB-l/vlPAG pathway in itch and pain sensation in mice. First, morphological evidence for projections from vesicular glutamate transporter-2-containing neurons in the LPB to l/vlPAG involved in itch transmission has been provided. Furthermore, chemogenetic and optogenetic activation of the LPB-l/vlPAG pathway resulted in both antipruritic effect and analgesic effect, whereas pharmacogenetic inhibition strengthened nociceptive perception without affecting spontaneous scratching behavior. Finally, in vivo pharmacology was combined with optogenetics which revealed that AMPA receptor-expressing neurons in l/vlPAG might play a more essential role in pathway modulation. These findings provide a novel insight about the connections between 2 prominent transmit nuclei, LPB and l/vlPAG, in both pruriceptive and nociceptive sensations and deepen the understanding of l/vlPAG modulatory roles in itch sensation by chosen LPB as source of ascending efferent projections.
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Abstract
PURPOSE OF REVIEW The current review aims to update the important findings about molecular and cellular biology of mammalian bombesin-like peptides (BLPs) and their receptors. RECENT FINDINGS Recent identification of synaptic communication between gastrin-releasing peptide (GRP) neurons and GRP receptor (GRPR) neurons in spinal itch relay provides us novel insights into physiology of itch sensation. Neuromedin B (NMB) neurons were found to form connections with subcortical areas associated with arousal, hippocampal theta oscillation, and premotor processing and project to multiple downstream stations to regulate locomotion and hippocampal theta power. In addition to researches regarding the roles of BLPs and their receptors in central nervous system, recent findings reveal that NMB receptor is expressed on helminth-induced type 2 innate lymphoid cells and is regulated by basophils, suggesting an important function of NMB in helminth-induced immune responses. Bombesin transactivates epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), and HER3 receptors on human nonsmall-cell lung cancer (NSCLC) cells and elicits downstream signaling cascades and induces formation of both human epidermal growthfactor receptor 3 (HER3)/EGFR and HER3/HER2 heterodimers. Several high-affinity ligands for bombesin receptors were characterized, providing useful tools in investigation of biological roles of those peptides and their receptors. SUMMARY The most exciting findings of BLPs and their receptors in the past year come from studies in central nervous system. In addition, more researches are still underway to probe the molecular mechanisms of those peptides in peripheral tissues and characterize novel synthetic ligands with high affinity for mammalian bombesin receptors.
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Affiliation(s)
- Xiaoqun Qin
- Department of Physiology, Xiangya School of Medicine, Central South University, Changsha, Hunan, PR China
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62
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Li Y, Zhang W, Sun T, Liu B, Manyande A, Xu W, Xiang HB. The Role of Gut Microbiota in Chronic Itch-Evoked Novel Object Recognition-Related Cognitive Dysfunction in Mice. Front Med (Lausanne) 2021; 8:616489. [PMID: 33614682 PMCID: PMC7892771 DOI: 10.3389/fmed.2021.616489] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 01/06/2021] [Indexed: 01/01/2023] Open
Abstract
The high incidence of patients with chronic itch highlights the importance of fundamental research. Recent advances in the interface of gut microbiota have shed new light into exploring this phenomenon. However, it is unknown whether gut microbiota plays a role in chronic itch in rodents with or without cognitive dysfunction. In this study, the role of gut microbiota in diphenylcyclopropenone (DCP)-evoked chronic itch was investigated in mice and hierarchical cluster analysis of novel object recognition test (ORT) results were used to classify DCP-evoked itch model in mice with or without cognitive dysfunction (CD)-like phenotype and 16S ribosomal RNA (rRNA) gene sequencing was used to compare gut bacterial composition between CD (Susceptible) and Non-CD phenotypes (Unsusceptible) in chronic itch mice. Results showed that the microbiota composition was significantly altered by DCP-evoked chronic itch and chronic itch induced novel object recognition-related CD. However, abnormal gut microbiota composition induced by chronic itch may not be correlated with novel object recognition-related CD.
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Affiliation(s)
- Yujuan Li
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Wencui Zhang
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Tainning Sun
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Baowen Liu
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Anne Manyande
- School of Human and Social Sciences, University of West London, London, United Kingdom
| | - Weiguo Xu
- Department of Orthopedics, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hong-Bing Xiang
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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63
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Agostinelli LJ, Bassuk AG. Novel inhibitory brainstem neurons with selective projections to spinal lamina I reduce both pain and itch. J Comp Neurol 2020; 529:2125-2137. [PMID: 33247430 PMCID: PMC8009815 DOI: 10.1002/cne.25076] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 11/18/2020] [Accepted: 11/20/2020] [Indexed: 12/18/2022]
Abstract
Sensory information is transmitted from peripheral nerves, through the spinal cord, and up to the brain (“bottom up” pathway). Some of this information may be modulated by “top‐down” projections from the brain to the spinal cord. Discovering endogenous mechanisms for reducing pain and itch holds enormous potential for developing new treatments. However, neurons mediating the top‐down inhibition of pain are not well understood, nor has any such pathway been identified for itch sensation. Here, we identify a novel population of GABAergic neurons in the ventral brainstem, distinguished by prodynorphin expression, which we named LJA5. LJA5 neurons provide the only known inhibitory projection specifically to lamina I of the spinal cord, which contains sensory neurons that transmit pain and itch information up to the brain. Chemogenetically activating LJA5 neurons in male mice reduces capsaicin‐induced pain and histamine‐induced itch. Identifying this new pathway opens new treatment opportunities for chronic, refractory pain, and pruritis.
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Affiliation(s)
- Lindsay J Agostinelli
- Department of Neurology, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, Iowa, USA
| | - Alexander G Bassuk
- Department of Neurology, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, Iowa, USA.,Department of Pediatrics, University of Iowa, Iowa City, Iowa, USA
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64
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Spinal Inhibitory Ptf1a-Derived Neurons Prevent Self-Generated Itch. Cell Rep 2020; 33:108422. [PMID: 33238109 DOI: 10.1016/j.celrep.2020.108422] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 04/27/2020] [Accepted: 11/02/2020] [Indexed: 01/13/2023] Open
Abstract
Chronic itch represents an incapacitating burden on patients suffering from a spectrum of diseases. Despite recent advances in our understanding of the cells and circuits implicated in the processing of itch information, chronic itch often presents itself without an apparent cause. Here, we identify a spinal subpopulation of inhibitory neurons defined by the expression of Ptf1a, involved in gating mechanosensory information self-generated during movement. These neurons receive tactile and motor input and establish presynaptic inhibitory contacts on mechanosensory afferents. Loss of Ptf1a neurons leads to increased hairy skin sensitivity and chronic itch, partially mediated by the classic itch pathway involving gastrin-releasing peptide receptor (GRPR) spinal neurons. Conversely, chemogenetic activation of GRPR neurons elicits itch, which is suppressed by concomitant activation of Ptf1a neurons. These findings shed light on the circuit mechanisms implicated in chronic itch and open novel targets for therapy developments.
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65
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Fenno LE, Ramakrishnan C, Kim YS, Evans KE, Lo M, Vesuna S, Inoue M, Cheung KYM, Yuen E, Pichamoorthy N, Hong ASO, Deisseroth K. Comprehensive Dual- and Triple-Feature Intersectional Single-Vector Delivery of Diverse Functional Payloads to Cells of Behaving Mammals. Neuron 2020; 107:836-853.e11. [PMID: 32574559 PMCID: PMC7687746 DOI: 10.1016/j.neuron.2020.06.003] [Citation(s) in RCA: 85] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 05/08/2020] [Accepted: 05/29/2020] [Indexed: 01/12/2023]
Abstract
The resolution and dimensionality with which biologists can characterize cell types have expanded dramatically in recent years, and intersectional consideration of such features (e.g., multiple gene expression and anatomical parameters) is increasingly understood to be essential. At the same time, genetically targeted technology for writing in and reading out activity patterns for cells in living organisms has enabled causal investigation in physiology and behavior; however, cell-type-specific delivery of these tools (including microbial opsins for optogenetics and genetically encoded Ca2+ indicators) has thus far fallen short of versatile targeting to cells jointly defined by many individually selected features. Here, we develop a comprehensive intersectional targeting toolbox including 39 novel vectors for joint-feature-targeted delivery of 13 molecular payloads (including opsins, indicators, and fluorophores), systematic approaches for development and optimization of new intersectional tools, hardware for in vivo monitoring of expression dynamics, and the first versatile single-virus tools (Triplesect) that enable targeting of triply defined cell types.
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Affiliation(s)
- Lief E Fenno
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA 94305, USA; Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Charu Ramakrishnan
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Yoon Seok Kim
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Kathryn E Evans
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Maisie Lo
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Sam Vesuna
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Masatoshi Inoue
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Kathy Y M Cheung
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Elle Yuen
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | | | - Alice S O Hong
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Karl Deisseroth
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA 94305, USA; Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA.
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66
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Posterior Thalamic Nucleus Mediates Facial Histaminergic Itch. Neuroscience 2020; 444:54-63. [PMID: 32750381 DOI: 10.1016/j.neuroscience.2020.07.048] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 07/13/2020] [Accepted: 07/27/2020] [Indexed: 11/24/2022]
Abstract
Itch induces a desire to scratch and leads to skin damage in some severe conditions. Much progress has been made in the peripheral and spinal level, and recent findings suggested that we need to focus on the central circuitry mechanism. However, the functional role of the thalamus in itch signal processing remains largely unknown. We showed that the posterior thalamic nucleus (Po) played a vital role in modulating facial histaminergic itch signal processing. We found that the calcium signal of Po neurons was increased during the histaminergic itch-induced scratching behavior in the cheek model, and pharmacogenetic suppression of Po neurons reduced the scratching behaviors. Retrograde mapping results suggested that the Po receives information from the somatosensory cortex, motor cortex, parabrachial nucleus (PBN), the principal sensory trigeminal nucleus (PrV) and the spinal trigeminal nucleus (SpV), which participate in itch signal transmission from head and body. Thus, our study indicates that the Po is critical in modulating facial histaminergic itch signal processing.
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67
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Agostinelli LJ, Mix MR, Hefti MM, Scammell TE, Bassuk AG. Input-output connections of LJA5 prodynorphin neurons. J Comp Neurol 2020; 529:635-654. [PMID: 32602558 PMCID: PMC7769903 DOI: 10.1002/cne.24974] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Revised: 06/22/2020] [Accepted: 06/25/2020] [Indexed: 12/21/2022]
Abstract
Sensory information is transmitted from peripheral nerves, through the spinal cord, and up to the brain. Sensory information may be modulated by projections from the brain to the spinal cord, but the neural substrates for top‐down sensory control are incompletely understood. We identified a novel population of inhibitory neurons in the mouse brainstem, distinguished by their expression of prodynorphin, which we named LJA5. Here, we identify a similar group of Pdyn+ neurons in the human brainstem, and we define the efferent and afferent projection patterns of LJA5 neurons in mouse. Using specific genetic tools, we selectively traced the projections of the Pdyn‐expressing LJA5 neurons through the brain and spinal cord. Terminal fields were densest in the lateral and ventrolateral periaqueductal gray (PAG), lateral parabrachial nucleus (LPB), caudal pressor area, and lamina I of the spinal trigeminal nucleus and all levels of the spinal cord. We then labeled cell types in the PAG, LPB, medulla, and spinal cord to better define the specific targets of LJA5 boutons. LJA5 neurons send the only known inhibitory descending projection specifically to lamina I of the spinal cord, which transmits afferent pain, temperature, and itch information up to the brain. Using retrograde tracing, we found LJA5 neurons receive inputs from sensory and stress areas such as somatosensory/insular cortex, preoptic area, paraventricular nucleus, dorsomedial nucleus and lateral hypothalamus, PAG, and LPB. This pattern of inputs and outputs suggest LJA5 neurons are uniquely positioned to be activated by sensation and stress, and in turn, inhibit pain and itch.
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Affiliation(s)
- Lindsay J Agostinelli
- Department of Neurology, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, Iowa, USA.,Department of Pediatrics, University of Iowa, Iowa City, Iowa, USA.,Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Madison R Mix
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, USA
| | - Marco M Hefti
- Department of Pathology, University of Iowa, Iowa City, Iowa, USA
| | - Thomas E Scammell
- Department of Neurology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
| | - Alexander G Bassuk
- Department of Neurology, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, Iowa, USA.,Department of Pediatrics, University of Iowa, Iowa City, Iowa, USA
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68
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Deng J, Zhou H, Lin JK, Shen ZX, Chen WZ, Wang LH, Li Q, Mu D, Wei YC, Xu XH, Sun YG. The Parabrachial Nucleus Directly Channels Spinal Nociceptive Signals to the Intralaminar Thalamic Nuclei, but Not the Amygdala. Neuron 2020; 107:909-923.e6. [PMID: 32649865 DOI: 10.1016/j.neuron.2020.06.017] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 03/26/2020] [Accepted: 06/15/2020] [Indexed: 12/18/2022]
Abstract
The parabrachial nucleus (PBN) is one of the major targets of spinal projection neurons and plays important roles in pain. However, the architecture of the spinoparabrachial pathway underlying its functional role in nociceptive information processing remains elusive. Here, we report that the PBN directly relays nociceptive signals from the spinal cord to the intralaminar thalamic nuclei (ILN). We demonstrate that the spinal cord connects with the PBN in a bilateral manner and that the ipsilateral spinoparabrachial pathway is critical for nocifensive behavior. We identify Tacr1-expressing neurons as the major neuronal subtype in the PBN that receives direct spinal input and show that these neurons are critical for processing nociceptive information. Furthermore, PBN neurons receiving spinal input form functional monosynaptic excitatory connections with neurons in the ILN, but not the amygdala. Together, our results delineate the neural circuit underlying nocifensive behavior, providing crucial insight into the circuit mechanism underlying nociceptive information processing.
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Affiliation(s)
- Juan Deng
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China.
| | - Hua Zhou
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China
| | - Jun-Kai Lin
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China; University of Chinese Academy of Sciences, 19A Yu-quan Road, Beijing 100049, China
| | - Zi-Xuan Shen
- Department of Biotechnology, East China University of Science and Technology, 130 Mei-long Road, Shanghai 200237, China
| | - Wen-Zhen Chen
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China; University of Chinese Academy of Sciences, 19A Yu-quan Road, Beijing 100049, China
| | - Lin-Han Wang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China; University of Chinese Academy of Sciences, 19A Yu-quan Road, Beijing 100049, China
| | - Qing Li
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China
| | - Di Mu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China
| | - Yi-Chao Wei
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China
| | - Xiao-Hong Xu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China
| | - Yan-Gang Sun
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China.
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69
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Abstract
Itch is a unique sensation that helps organisms scratch away external threats; scratching itself induces an immune response that can contribute to more itchiness. Itch is induced chemically in the peripheral nervous system via a wide array of receptors. Given the superficial localization of itch neuron terminals, cells that dwell close to the skin contribute significantly to itch. Certain mechanical stimuli mediated by recently discovered circuits also contribute to the itch sensation. Ultimately, in the spinal cord, and likely in the brain, circuits that mediate touch, pain, and itch engage in cross modulation. Much of itch perception is still a mystery, but we present in this review the known ligands and receptors associated with itch. We also describe experiments and findings from investigations into the spinal and supraspinal circuitry responsible for the sensation of itch.
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Affiliation(s)
- Mark Lay
- The Solomon H. Snyder Department of Neuroscience and the Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA;,
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience and the Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA;,
- Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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70
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Cevikbas F, Lerner EA. Physiology and Pathophysiology of Itch. Physiol Rev 2020; 100:945-982. [PMID: 31869278 PMCID: PMC7474262 DOI: 10.1152/physrev.00017.2019] [Citation(s) in RCA: 126] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 10/31/2019] [Accepted: 12/04/2019] [Indexed: 02/06/2023] Open
Abstract
Itch is a topic to which everyone can relate. The physiological roles of itch are increasingly understood and appreciated. The pathophysiological consequences of itch impact quality of life as much as pain. These dynamics have led to increasingly deep dives into the mechanisms that underlie and contribute to the sensation of itch. When the prior review on the physiology of itching was published in this journal in 1941, itch was a black box of interest to a small number of neuroscientists and dermatologists. Itch is now appreciated as a complex and colorful Rubik's cube. Acute and chronic itch are being carefully scratched apart and reassembled by puzzle solvers across the biomedical spectrum. New mediators are being identified. Mechanisms blur boundaries of the circuitry that blend neuroscience and immunology. Measures involve psychophysics and behavioral psychology. The efforts associated with these approaches are positively impacting the care of itchy patients. There is now the potential to markedly alleviate chronic itch, a condition that does not end life, but often ruins it. We review the itch field and provide a current understanding of the pathophysiology of itch. Itch is a disease, not only a symptom of disease.
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Affiliation(s)
- Ferda Cevikbas
- Dermira, Inc., Menlo Park, California; and Harvard Medical School and the Cutaneous Biology Research Center at Massachusetts General Hospital, Charlestown, Massachusetts
| | - Ethan A Lerner
- Dermira, Inc., Menlo Park, California; and Harvard Medical School and the Cutaneous Biology Research Center at Massachusetts General Hospital, Charlestown, Massachusetts
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71
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Abstract
Itch, in particular chronic forms, has been widely recognized as an important clinical problem, but much less is known about the mechanisms of itch in comparison with other sensory modalities such as pain. Recently, considerable progress has been made in dissecting the circuit mechanisms of itch at both the spinal and supraspinal levels. Major components of the spinal neural circuit underlying both chemical and mechanical itch have now been identified, along with the circuits relaying ascending transmission and the descending modulation of itch. In this review, we summarize the progress in elucidating the neural circuit mechanism of itch at spinal and supraspinal levels.
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Affiliation(s)
- Xiao-Jun Chen
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, 200031, Shanghai, China
- University of Chinese Academy of Sciences, 19A Yu-quan Road, 100049, Beijing, China
| | - Yan-Gang Sun
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, 200031, Shanghai, China.
- Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, 201210, Shanghai, China.
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72
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Harding EK, Fung SW, Bonin RP. Insights Into Spinal Dorsal Horn Circuit Function and Dysfunction Using Optical Approaches. Front Neural Circuits 2020; 14:31. [PMID: 32595458 PMCID: PMC7303281 DOI: 10.3389/fncir.2020.00031] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 05/01/2020] [Indexed: 12/13/2022] Open
Abstract
Somatosensation encompasses a variety of essential modalities including touch, pressure, proprioception, temperature, pain, and itch. These peripheral sensations are crucial for all types of behaviors, ranging from social interaction to danger avoidance. Somatosensory information is transmitted from primary afferent fibers in the periphery into the central nervous system via the dorsal horn of the spinal cord. The dorsal horn functions as an intermediary processing center for this information, comprising a complex network of excitatory and inhibitory interneurons as well as projection neurons that transmit the processed somatosensory information from the spinal cord to the brain. It is now known that there can be dysfunction within this spinal cord circuitry in pathological pain conditions and that these perturbations contribute to the development and maintenance of pathological pain. However, the complex and heterogeneous network of the spinal dorsal horn has hampered efforts to further elucidate its role in somatosensory processing. Emerging optical techniques promise to illuminate the underlying organization and function of the dorsal horn and provide insights into the role of spinal cord sensory processing in shaping the behavioral response to somatosensory input that we ultimately observe. This review article will focus on recent advances in optogenetics and fluorescence imaging techniques in the spinal cord, encompassing findings from both in vivo and in vitro preparations. We will also discuss the current limitations and difficulties of employing these techniques to interrogate the spinal cord and current practices and approaches to overcome these challenges.
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Affiliation(s)
- Erika K Harding
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, AB, Canada
| | - Samuel Wanchi Fung
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada
| | - Robert P Bonin
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada.,University of Toronto Centre for the Study of Pain, University of Toronto, Toronto, ON, Canada
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73
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Zhang XY, Dou YN, Yuan L, Li Q, Zhu YJ, Wang M, Sun YG. Different neuronal populations mediate inflammatory pain analgesia by exogenous and endogenous opioids. eLife 2020; 9:55289. [PMID: 32519950 PMCID: PMC7311172 DOI: 10.7554/elife.55289] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Accepted: 06/10/2020] [Indexed: 02/06/2023] Open
Abstract
Mu-opioid receptors (MORs) are crucial for analgesia by both exogenous and endogenous opioids. However, the distinct mechanisms underlying these two types of opioid analgesia remain largely unknown. Here, we demonstrate that analgesic effects of exogenous and endogenous opioids on inflammatory pain are mediated by MORs expressed in distinct subpopulations of neurons in mice. We found that the exogenous opioid-induced analgesia of inflammatory pain is mediated by MORs in Vglut2+ glutamatergic but not GABAergic neurons. In contrast, analgesia by endogenous opioids is mediated by MORs in GABAergic rather than Vglut2+ glutamatergic neurons. Furthermore, MORs expressed at the spinal level is mainly involved in the analgesic effect of morphine in acute pain, but not in endogenous opioid analgesia during chronic inflammatory pain. Thus, our study revealed distinct mechanisms underlying analgesia by exogenous and endogenous opioids, and laid the foundation for further dissecting the circuit mechanism underlying opioid analgesia.
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Affiliation(s)
- Xin-Yan Zhang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yan-Nong Dou
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
| | - Lei Yuan
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Qing Li
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
| | - Yan-Jing Zhu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
| | - Meng Wang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, Shanghai, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yan-Gang Sun
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science & Intelligence Technology, Chinese Academy of Sciences, Shanghai, China.,Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai, China
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74
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Zhang XY, Li Q, Dong Y, Yan W, Song K, Lin YQ, Sun YG. Mu-Opioid Receptors Expressed in Glutamatergic Neurons are Essential for Morphine Withdrawal. Neurosci Bull 2020; 36:1095-1106. [PMID: 32451910 DOI: 10.1007/s12264-020-00515-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 02/11/2020] [Indexed: 01/09/2023] Open
Abstract
Although opioids still remain the most powerful pain-killers, the chronic use of opioid analgesics is largely limited by their numerous side-effects, including opioid dependence. However, the mechanism underlying this dependence is largely unknown. In this study, we used the withdrawal symptoms precipitated by naloxone to characterize opioid dependence in mice. We determined the functional role of mu-opioid receptors (MORs) expressed in different subpopulations of neurons in the development of morphine withdrawal. We found that conditional deletion of MORs from glutamatergic neurons expressing vesicular glutamate transporter 2 (Vglut2+) largely eliminated the naloxone-precipitated withdrawal symptoms. In contrast, conditional deletion of MORs expressed in GABAergic neurons had a limited effect on morphine withdrawal. Consistently, mice with MORs deleted from Vglut2+ glutamatergic neurons also showed no morphine-induced locomotor hyperactivity. Furthermore, morphine withdrawal and morphine-induced hyperactivity were not significantly affected by conditional knockout of MORs from dorsal spinal neurons. Taken together, our data indicate that the development of morphine withdrawal is largely mediated by MORs expressed in Vglut2+ glutamatergic neurons.
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Affiliation(s)
- Xin-Yan Zhang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
- University of the Chinese Academy of Sciences, Beijing, 100049, China
| | - Qing Li
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Ye Dong
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Wei Yan
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
- University of the Chinese Academy of Sciences, Beijing, 100049, China
| | - Kun Song
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
- University of the Chinese Academy of Sciences, Beijing, 100049, China
| | - Yong-Qin Lin
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
- University of the Chinese Academy of Sciences, Beijing, 100049, China
| | - Yan-Gang Sun
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China.
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75
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Falkner AL, Wei D, Song A, Watsek LW, Chen I, Chen P, Feng JE, Lin D. Hierarchical Representations of Aggression in a Hypothalamic-Midbrain Circuit. Neuron 2020; 106:637-648.e6. [PMID: 32164875 DOI: 10.1016/j.neuron.2020.02.014] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 12/20/2019] [Accepted: 02/10/2020] [Indexed: 12/13/2022]
Abstract
Although the ventromedial hypothalamus ventrolateral area (VMHvl) is now well established as a critical locus for the generation of conspecific aggression, its role is complex, with neurons responding during multiple phases of social interactions with both males and females. It has been previously unclear how the brain uses this complex multidimensional signal and coordinates a discrete action: the attack. Here, we find a hypothalamic-midbrain circuit that represents hierarchically organized social signals during aggression. Optogenetic-assisted circuit mapping reveals a preferential projection from VMHvlvGlut2 to lPAGvGlut2 cells, and inactivation of downstream lPAGvGlut2 populations results in aggression-specific deficits. lPAG neurons are selective for attack action and exhibit short-latency, time-locked spiking relative to the activity of jaw muscles during biting. Last, we find that this projection conveys male-biased signals from the VMHvl to downstream lPAGvGlut2 neurons that are sensitive to features of ongoing activity, suggesting that action selectivity is generated by a combination of pre- and postsynaptic mechanisms.
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Affiliation(s)
- Annegret L Falkner
- Princeton Neuroscience Institute, Princeton, NJ 08540, USA; Neuroscience Institute, New York University School of Medicine, New York, NY 10016, USA.
| | - Dongyu Wei
- Neuroscience Institute, New York University School of Medicine, New York, NY 10016, USA
| | - Anjeli Song
- Boston University School of Medicine, Boston, MA 02118, USA
| | - Li W Watsek
- Neuroscience Institute, New York University School of Medicine, New York, NY 10016, USA
| | - Irene Chen
- Neuroscience Institute, New York University School of Medicine, New York, NY 10016, USA
| | - Patricia Chen
- Princeton Neuroscience Institute, Princeton, NJ 08540, USA
| | - James E Feng
- Neuroscience Institute, New York University School of Medicine, New York, NY 10016, USA
| | - Dayu Lin
- Neuroscience Institute, New York University School of Medicine, New York, NY 10016, USA; Department of Psychiatry, New York University School of Medicine, New York, NY 10016, USA; Center for Neural Science, New York University, New York, NY 10003, USA
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76
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Li NQ, Tang Y, Huang ST, Liu XT, Zeng LP, Li H, Wan L. Modulation of NR1 receptor by CaMKIIα plays an important role in chronic itch development in mice. Brain Res Bull 2020; 158:66-76. [PMID: 32112850 DOI: 10.1016/j.brainresbull.2020.02.011] [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: 12/13/2019] [Revised: 02/22/2020] [Accepted: 02/24/2020] [Indexed: 10/24/2022]
Abstract
Intractable scratching is the characteristic of chronic itch, which represents a great challenge in clinical practice. However, the mechanism underlying chronic itch development is largely unknown. In the present study, we investigated the role of NMDA receptor in acute itch and in development of chronic itch. A mouse model was developed by painting DNFB to induce allergic contact dermatitis (ACD). We found that the expression of pNR1, which is a subunit of NMDA receptor, was significantly increased in the dorsal root ganglion in the DNFB model. The DNFB-evoked spontaneous scratching was blocked by the NMDA antagonist D-AP-5, the calcium-calmodulin-dependent protein kinase (CaMK) inhibitor KN-93, a CaMKIIα siRNA and the PKC inhibitor LY317615. Moreover, activation of PKC did not reverse the CaMKIIα knockdown-induced decrease in scratching, suggesting that PKC functions upstream of CaMKIIα. Thus, our study indicates that modulation of NR1 receptor by CaMKIIα plays an important role in the development of chronic itch.
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Affiliation(s)
- Nan-Qi Li
- Department of Pain Management, The State Key Clinical Specialty in Pain Medicine, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, P.R. China
| | - Yang Tang
- Department of Pain Management, The State Key Clinical Specialty in Pain Medicine, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, P.R. China
| | - Si-Ting Huang
- Department of Pain Management, The State Key Clinical Specialty in Pain Medicine, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, P.R. China
| | - Xue-Ting Liu
- Guangdong Provincial Key Laboratory of Allergy & Clinic Immunology, Sino-French Hoffmann Institute, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, P.R. China
| | - Li-Ping Zeng
- Guangdong Provincial Key Laboratory of Allergy & Clinic Immunology, Sino-French Hoffmann Institute, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, P.R. China
| | - Hui Li
- Department of Anatomy, Histology and Embryology & K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Li Wan
- Department of Pain Management, The State Key Clinical Specialty in Pain Medicine, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510260, P.R. China.
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77
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Aguilar Garcia IG, Dueñas-Jiménez JM, Castillo L, Osuna-Carrasco LP, De La Torre Valdovinos B, Castañeda-Arellano R, López-Ruiz JR, Toro-Castillo C, Treviño M, Mendizabal-Ruiz G, Duenas-Jimenez SH. Fictive Scratching Patterns in Brain Cortex-Ablated, Midcollicular Decerebrate, and Spinal Cats. Front Neural Circuits 2020; 14:1. [PMID: 32174815 PMCID: PMC7056700 DOI: 10.3389/fncir.2020.00001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 01/03/2020] [Indexed: 11/13/2022] Open
Abstract
Background: The spinal cord’s central pattern generators (CPGs) have been explained by the symmetrical half-center hypothesis, the bursts generator, computational models, and more recently by connectome circuits. Asymmetrical models, at odds with the half-center paradigm, are composed of extensor and flexor CPG modules. Other models include not only flexor and extensor motoneurons but also motoneuron pools controlling biarticular muscles. It is unknown whether a preferred model can explain some particularities that fictive scratching (FS) in the cat presents. The first aim of this study was to investigate FS patterns considering the aiming and the rhythmic periods, and second, to examine the effects of serotonin (5HT) on and segmental inputs to FS. Methods: The experiments were carried out first in brain cortex-ablated cats (BCAC), then spinalized (SC), and for the midcollicular (MCC) preparation. Subjects were immobilized and the peripheral nerves were used to elicit the Monosynaptic reflex (MR), to modify the scratching patterns and for electroneurogram recordings. Results: In BCAC, FS was produced by pinna stimulation and, in some cases, by serotonin. The scratching aiming phase (AP) initiates with the activation of either flexor or extensor motoneurons. Serotonin application during the AP produced simultaneous extensor and flexor bursts. Furthermore, WAY 100635 (5HT1A antagonist) produced a brief burst in the tibialis anterior (TA) nerve, followed by a reduction in its electroneurogram (ENG), while the soleus ENG remained silent. In SC, rhythmic phase (RP) activity was recorded in the soleus motoneurons. Serotonin or WAY produced FS bouts. The electrical stimulation of Ia afferent fibers produced heteronymous MRes waxing and waning during the scratch cycle. In MCC, FS began with flexor activity. Electrical stimulation of either deep peroneus (DP) or superficial peroneus (SP) nerves increased the duration of the TA electroneurogram. Medial gastrocnemius (MG) stretching or MG nerve electrical stimulation produced a reduction in the TA electroneurogram and an initial MG extensor burst. MRes waxed and waned during the scratch cycle. Conclusion: Descending pathways and segmental afferent fibers, as well as 5-HT and WAY, can change the FS pattern. To our understanding, the half-center hypothesis is the most suitable for explaining the AP in MCC.
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Affiliation(s)
| | | | - Luis Castillo
- Centro Básico, Universidad de Aguascalientes, Aguascalientes, Mexico
| | | | | | | | | | - Carmen Toro-Castillo
- Departmento de Electrónica y Computación, CUCEI, Universidad de Guadalajara, Guadalajara, Mexico
| | - Mario Treviño
- Laboratorio de Plasticidad Cortical y Aprendizaje Perceptual, Instituto de Neurociencias, Universidad de Guadalajara, Guadalajara, Mexico
| | - Gerardo Mendizabal-Ruiz
- Departmento de Electrónica y Computación, CUCEI, Universidad de Guadalajara, Guadalajara, Mexico
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78
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Vincenzi B, Trower M, Duggal A, Guglielmini P, Harris P, Jackson D, Lacouture ME, Ratti E, Tonini G, Wood A, Ständer S. Neurokinin-1 antagonist orvepitant for EGFRI-induced pruritus in patients with cancer: a randomised, placebo-controlled phase II trial. BMJ Open 2020; 10:e030114. [PMID: 32034016 PMCID: PMC7045265 DOI: 10.1136/bmjopen-2019-030114] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
OBJECTIVE To evaluate the efficacy of orvepitant (10 or 30 mg given once daily, orally for 4 weeks), a neurokinin-1 receptor antagonist, compared with placebo in reducing the intensity of epidermal growth factor receptor inhibitor (EGFRI)-induced intense pruritus. DESIGN Randomised, double-blind, placebo-controlled clinical trial. SETTING 15 hospitals in Italy and five hospitals in the UK. PARTICIPANTS 44 patients aged ≥18 years receiving an EGFRI for a histologically confirmed malignant solid tumour and experiencing moderate or intense pruritus after EGFRI treatment. INTERVENTION 30 or 10 mg orvepitant or placebo tablets once daily for 4 weeks (randomised 1:1:1). PRIMARY AND SECONDARY OUTCOME MEASURES The primary endpoint was change from baseline in mean patient-recorded numerical rating scale (NRS) score (over the last three recordings) at week 4. Secondary outcome measures were NRS score, verbal rating scale score, Skindex-16 and Leeds Sleep Evaluation Questionnaire at each study visit (baseline, weeks 1, 4, 8); rescue medication use; EGFRI dose reduction; and study withdrawal because of intense uncontrolled pruritus. RESULTS The trial was terminated early because of recruitment challenges; only 44 of the planned 90 patients were randomised. All patients were analysed for efficacy and safety. Mean NRS score change from baseline to week 4 was -2.78 (SD: 2.64) points in the 30 mg group, -3.04 (SD: 3.06) points in the 10 mg group and -3.21 (SD: 1.77) points in the placebo group; the difference between orvepitant and placebo was not statistically significant. No safety signal was detected. Adverse events related to orvepitant (asthenia, dizziness, dry mouth, hyperhidrosis) were all of mild or moderate severity. CONCLUSIONS Orvepitant was safe and well tolerated. No difference in NRS score between the orvepitant and placebo groups was observed at the week 4 primary endpoint. A number of explanations for this outcome are possible. TRIAL REGISTRATION NUMBER EudraCT2013-002763-25.
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Affiliation(s)
- Bruno Vincenzi
- Medical Oncology, Universita Campus Bio-Medico di Roma Facolta di Medicina e Chirurgia, Roma, Italy
| | | | - Ajay Duggal
- Adnovate Clinical Development Strategies, East Sussex, UK
| | | | | | | | - Mario E Lacouture
- Department of Dermatology, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | | | - Giuseppe Tonini
- Medical Oncology, Universita Campus Bio-Medico di Roma Facolta di Medicina e Chirurgia, Roma, Italy
| | | | - Sonja Ständer
- Center for Chronic Pruritus, University Hospital Münster, Münster, Germany
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79
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Abstract
Basic mechanisms and pathways of itch signaling are reviewed, with an emphasis on the progress to date as well as remaining challenges in translating current knowledge to the clinical treatment of chronic itch. Recent studies reveal 3 subsets of pruriceptive sensory neurons highly expressing itch-related genes. Their fibers project into the spinal cord to activate neurons expressing gastrin releasing peptide (GRP) and its receptor (GRPR), which connect to neurons that express the substance P (NK-1) receptor and project to the parabrachial nucleus and thalamus. Spinal inhibitory interneurons release GABA, glycine and dynorphin to modulate segmental itch transmission. However, nearly all pruriceptive neurons also respond to algogens such as capsaicin. Alternative theories of itch-pain discrimination, such as intensity or spatial contrast, are based on the observation that focal stimulation of nociceptive nerve endings elicits itch while more widespread stimulation elicits pain. These findings cloud the issue of a labeled line for itch- a long-debated but currently unresolved challenge. In higher primates there is a dichotomy of histaminergic and non-histaminergic itch-signaling pathways which is less demarcated in rodents, suggesting species differences. A cardinal symptom of chronic itch is alloknesis, i.e., mechanical or touch-evoked itch. Recent evidence indicates that low-threshold mechanosensory afferents can access the spinal itch pathway, but are normally kept in check by inhibitory interneurons expressing neuropeptide Y (NPY). In chronic itch, NPY-mediated inhibition is reduced, allowing touch to excite itch-signaling pathways. These recent advances provide novel targets for development of therapeutic strategies to relieve chronic itch.
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80
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Synaptic control of spinal GRPR + neurons by local and long-range inhibitory inputs. Proc Natl Acad Sci U S A 2019; 116:27011-27017. [PMID: 31806757 DOI: 10.1073/pnas.1905658116] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Spinal gastrin-releasing peptide receptor-expressing (GRPR+) neurons play an essential role in itch signal processing. However, the circuit mechanisms underlying the modulation of spinal GRPR+ neurons by direct local and long-range inhibitory inputs remain elusive. Using viral tracing and electrophysiological approaches, we dissected the neural circuits underlying the inhibitory control of spinal GRPR+ neurons. We found that spinal galanin+ GABAergic neurons form inhibitory synapses with GRPR+ neurons in the spinal cord and play an important role in gating the GRPR+ neuron-dependent itch signaling pathway. Spinal GRPR+ neurons also receive inhibitory inputs from local neurons expressing neuronal nitric oxide synthase (nNOS). Moreover, spinal GRPR+ neurons are gated by strong inhibitory inputs from the rostral ventromedial medulla. Thus, both local and long-range inhibitory inputs could play important roles in gating itch processing in the spinal cord by directly modulating the activity of spinal GRPR+ neurons.
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81
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Sensitization Mechanisms of Chronic Itch. INTERNATIONAL JOURNAL OF DERMATOLOGY AND VENEREOLOGY 2019. [DOI: 10.1097/jd9.0000000000000045] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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82
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Pain Inhibits GRPR Neurons via GABAergic Signaling in the Spinal Cord. Sci Rep 2019; 9:15804. [PMID: 31676846 PMCID: PMC6825123 DOI: 10.1038/s41598-019-52316-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 10/11/2019] [Indexed: 11/30/2022] Open
Abstract
It has been known that algogens and cooling could inhibit itch sensation; however, the underlying molecular and neural mechanisms remain poorly understood. Here, we show that the spinal neurons expressing gastrin releasing peptide receptor (GRPR) primarily comprise excitatory interneurons that receive direct and indirect inputs from C and Aδ fibers and form contacts with projection neurons expressing the neurokinin 1 receptor (NK1R). Importantly, we show that noxious or cooling agents inhibit the activity of GRPR neurons via GABAergic signaling. By contrast, capsaicin, which evokes a mix of itch and pain sensations, enhances both excitatory and inhibitory spontaneous synaptic transmission onto GRPR neurons. These data strengthen the role of GRPR neurons as a key circuit for itch transmission and illustrate a spinal mechanism whereby pain inhibits itch by suppressing the function of GRPR neurons.
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83
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Samineni VK, Grajales-Reyes JG, Sundaram SS, Yoo JJ, Gereau RW. Cell type-specific modulation of sensory and affective components of itch in the periaqueductal gray. Nat Commun 2019; 10:4356. [PMID: 31554789 PMCID: PMC6761157 DOI: 10.1038/s41467-019-12316-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 08/28/2019] [Indexed: 01/07/2023] Open
Abstract
Itch is a distinct aversive sensation that elicits a strong urge to scratch. Despite recent advances in our understanding of the peripheral basis of itch, we know very little regarding how central neural circuits modulate acute and chronic itch processing. Here we establish the causal contributions of defined periaqueductal gray (PAG) neuronal populations in itch modulation in mice. Chemogenetic manipulations demonstrate bidirectional modulation of scratching by neurons in the PAG. Fiber photometry studies show that activity of GABAergic and glutamatergic neurons in the PAG is modulated in an opposing manner during chloroquine-evoked scratching. Furthermore, activation of PAG GABAergic neurons or inhibition of glutamatergic neurons resulted in attenuation of scratching in both acute and chronic pruritis. Surprisingly, PAG GABAergic neurons, but not glutamatergic neurons, may encode the aversive component of itch. Thus, the PAG represents a neuromodulatory hub that regulates both the sensory and affective aspects of acute and chronic itch.
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Affiliation(s)
- Vijay K Samineni
- Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA
- Washington University Pain Center, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA
| | - Jose G Grajales-Reyes
- Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA
- Washington University Pain Center, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA
- Medical Scientist Training Program, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA
- Neuroscience Program, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA
| | - Saranya S Sundaram
- Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA
- Washington University Pain Center, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA
| | - Judy J Yoo
- Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA
- Washington University Pain Center, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA
| | - Robert W Gereau
- Department of Anesthesiology, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA.
- Washington University Pain Center, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA.
- Department of Neuroscience, Department of Biomedical Engineering, Washington University School of Medicine, 660 S. Euclid Ave, Box 8054, St. Louis, MO, 63110, USA.
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84
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Su XY, Chen M, Yuan Y, Li Y, Guo SS, Luo HQ, Huang C, Sun W, Li Y, Zhu MX, Liu MG, Hu J, Xu TL. Central Processing of Itch in the Midbrain Reward Center. Neuron 2019; 102:858-872.e5. [PMID: 31000426 DOI: 10.1016/j.neuron.2019.03.030] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 12/28/2018] [Accepted: 03/19/2019] [Indexed: 10/27/2022]
Abstract
Itch is an aversive sensation that evokes a desire to scratch. Paradoxically, scratching the itch also produces a hedonic experience. The specific brain circuits processing these different aspects of itch, however, remain elusive. Here, we report that GABAergic (GABA) and dopaminergic (DA) neurons in the ventral tegmental area (VTA) are activated with different temporal patterns during acute and chronic itch. DA neuron activation lags behind GABA neurons and is dependent on scratching of the itchy site. Optogenetic manipulations of VTA GABA neurons rapidly modulated scratching behaviors through encoding itch-associated aversion. In contrast, optogenetic manipulations of VTA DA neurons revealed their roles in sustaining recurrent scratching episodes through signaling scratching-induced reward. A similar dichotomy exists for the role of VTA in chronic itch. These findings advance understanding of circuit mechanisms of the unstoppable itch-scratch cycles and shed important insights into chronic itch therapy.
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Affiliation(s)
- Xin-Yu Su
- Collaborative Innovation Center for Brain Science, Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Ming Chen
- iHuman Institute, ShanghaiTech University, Shanghai 201210, China
| | - Yuan Yuan
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Ying Li
- Collaborative Innovation Center for Brain Science, Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Su-Shan Guo
- Collaborative Innovation Center for Brain Science, Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Huo-Qing Luo
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Chen Huang
- Collaborative Innovation Center for Brain Science, Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Wenzhi Sun
- iHuman Institute, ShanghaiTech University, Shanghai 201210, China; School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China; Chinese Institute for Brain Research, Beijing 102206, China
| | - Yong Li
- Collaborative Innovation Center for Brain Science, Department of Biochemistry and Molecular Cell Biology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China; Shanghai Research Center for Brain Science and Brain-Inspired Intelligence, Shanghai 201210, China
| | - Michael X Zhu
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Ming-Gang Liu
- Collaborative Innovation Center for Brain Science, Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China.
| | - Ji Hu
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China; Shanghai Research Center for Brain Science and Brain-Inspired Intelligence, Shanghai 201210, China.
| | - Tian-Le Xu
- Collaborative Innovation Center for Brain Science, Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China; Shanghai Research Center for Brain Science and Brain-Inspired Intelligence, Shanghai 201210, China.
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85
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More than Scratching the Surface: Recent Progress in Brain Mechanisms Underlying Itch and Scratch. Neurosci Bull 2019; 36:85-88. [PMID: 30830669 DOI: 10.1007/s12264-019-00352-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 02/02/2019] [Indexed: 12/31/2022] Open
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