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Leva T, Whitmire CJ, Sauve I, Bokiniec P, Memler C, Horn BM, Vestergaard M, Carta M, Poulet JFA. The spatial representation of temperature in the thalamus. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.13.580167. [PMID: 38405930 PMCID: PMC10888919 DOI: 10.1101/2024.02.13.580167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Although distinct thalamic nuclei encode sensory information for almost all sensory modalities, the existence of a thalamic representation of temperature is debated and the role of the thalamus in thermal perception remains unclear. To address this, we used high-density electrophysiological recordings across mouse forepaw somatosensory thalamus, and identified an anterior and a posterior representation of temperature that spans three thalamic nuclei. These parallel representations show fundamental differences in the cellular encoding of temperature that reflect their cortical output targets, with the anterior representation encoding cool only and the posterior both cool and warm. Moreover, their inactivation profoundly altered thermal perception. Together our data identifies a novel posterior thalamic representation of temperature and a principal role of the thalamus in thermal perception.
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Leva TM, Whitmire CJ. Thermosensory thalamus: parallel processing across model organisms. Front Neurosci 2023; 17:1210949. [PMID: 37901427 PMCID: PMC10611468 DOI: 10.3389/fnins.2023.1210949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Accepted: 09/15/2023] [Indexed: 10/31/2023] Open
Abstract
The thalamus acts as an interface between the periphery and the cortex, with nearly every sensory modality processing information in the thalamocortical circuit. Despite well-established thalamic nuclei for visual, auditory, and tactile modalities, the key thalamic nuclei responsible for innocuous thermosensation remains under debate. Thermosensory information is first transduced by thermoreceptors located in the skin and then processed in the spinal cord. Temperature information is then transmitted to the brain through multiple spinal projection pathways including the spinothalamic tract and the spinoparabrachial tract. While there are fundamental studies of thermal transduction via thermosensitive channels in primary sensory afferents, thermal representation in the spinal projection neurons, and encoding of temperature in the primary cortical targets, comparatively little is known about the intermediate stage of processing in the thalamus. Multiple thalamic nuclei have been implicated in thermal encoding, each with a corresponding cortical target, but without a consensus on the role of each pathway. Here, we review a combination of anatomy, physiology, and behavioral studies across multiple animal models to characterize the thalamic representation of temperature in two proposed thermosensory information streams.
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Affiliation(s)
- Tobias M. Leva
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin, Germany
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany
- Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Clarissa J. Whitmire
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin, Germany
- Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Berlin, Germany
- Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia
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3
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Ueta Y, Miyata M. Functional and structural synaptic remodeling mechanisms underlying somatotopic organization and reorganization in the thalamus. Neurosci Biobehav Rev 2023; 152:105332. [PMID: 37524138 DOI: 10.1016/j.neubiorev.2023.105332] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 05/09/2023] [Accepted: 07/27/2023] [Indexed: 08/02/2023]
Abstract
The somatosensory system organizes the topographic representation of body maps, termed somatotopy, at all levels of an ascending hierarchy. Postnatal maturation of somatotopy establishes optimal somatosensation, whereas deafferentation in adults reorganizes somatotopy, which underlies pathological somatosensation, such as phantom pain and complex regional pain syndrome. Here, we focus on the mouse whisker somatosensory thalamus to study how sensory experience shapes the fine topography of afferent connectivity during the critical period and what mechanisms remodel it and drive a large-scale somatotopic reorganization after peripheral nerve injury. We will review our findings that, following peripheral nerve injury in adults, lemniscal afferent synapses onto thalamic neurons are remodeled back to immature configuration, as if the critical period reopens. The remodeling process is initiated with local activation of microglia in the brainstem somatosensory nucleus downstream to injured nerves and heterosynaptically controlled by input from GABAergic and cortical neurons to thalamic neurons. These fruits of thalamic studies complement well-studied cortical mechanisms of somatotopic organization and reorganization and unveil potential intervention points in treating pathological somatosensation.
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Affiliation(s)
- Yoshifumi Ueta
- Division of Neurophysiology, Department of Physiology, School of Medicine, Tokyo Women's Medical University, Tokyo 162-8666, Japan
| | - Mariko Miyata
- Division of Neurophysiology, Department of Physiology, School of Medicine, Tokyo Women's Medical University, Tokyo 162-8666, Japan.
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4
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Pan Q, Guo SS, Chen M, Su XY, Gao ZL, Wang Q, Xu TL, Liu MG, Hu J. Representation and control of pain and itch by distinct prefrontal neural ensembles. Neuron 2023:S0896-6273(23)00342-2. [PMID: 37224813 DOI: 10.1016/j.neuron.2023.04.032] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 02/18/2023] [Accepted: 04/27/2023] [Indexed: 05/26/2023]
Abstract
Pain and itch are two closely related but essentially distinct sensations that elicit different behavioral responses. However, it remains mysterious how pain and itch information is encoded in the brain to produce differential perceptions. Here, we report that nociceptive and pruriceptive signals are separately represented and processed by distinct neural ensembles in the prelimbic (PL) subdivision of the medial prefrontal cortex (mPFC) in mice. Pain- and itch-responsive cortical neural ensembles were found to significantly differ in electrophysiological properties, input-output connectivity profiles, and activity patterns to nociceptive or pruriceptive stimuli. Moreover, these two groups of cortical neural ensembles oppositely modulate pain- or itch-related sensory and emotional behaviors through their preferential projections to specific downstream regions such as the mediodorsal thalamus (MD) and basolateral amygdala (BLA). These findings uncover separate representations of pain and itch by distinct prefrontal neural ensembles and provide a new framework for understanding somatosensory information processing in the brain.
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Affiliation(s)
- Qian Pan
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Su-Shan Guo
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Ming Chen
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Xin-Yu Su
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Zi-Long Gao
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Qi Wang
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Tian-Le Xu
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China; Songjiang Hospital and Songjiang Research Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 201600, China; Shanghai Research Center for Brain Science and Brain-Inspired Intelligence, Shanghai 201210, China.
| | - Ming-Gang Liu
- 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 Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai 200030, China.
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5
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Cronin SJF, Tejada MA, Song R, Laval K, Cikes D, Ji M, Brai A, Stadlmann J, Novatchikova M, Perlot T, Ali OH, Botta L, Decker T, Lazovic J, Hagelkruys A, Enquist L, Rao S, Koyuncu OO, Penninger JM. Pseudorabies virus hijacks DDX3X, initiating an addictive "mad itch" and immune suppression, to facilitate viral spread. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.09.539956. [PMID: 37214906 PMCID: PMC10197578 DOI: 10.1101/2023.05.09.539956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Infections with defined Herpesviruses, such as Pseudorabies virus (PRV) and Varicella zoster virus (VZV) can cause neuropathic itch, referred to as "mad itch" in multiple species. The underlying mechanisms involved in neuropathic "mad itch" are poorly understood. Here, we show that PRV infections hijack the RNA helicase DDX3X in sensory neurons to facilitate anterograde transport of the virus along axons. PRV induces re-localization of DDX3X from the cell body to the axons which ultimately leads to death of the infected sensory neurons. Inducible genetic ablation of Ddx3x in sensory neurons results in neuronal death and "mad itch" in mice. This neuropathic "mad itch" is propagated through activation of the opioid system making the animals "addicted to itch". Moreover, we show that PRV co-opts and diverts T cell development in the thymus via a sensory neuron-IL-6-hypothalamus-corticosterone stress pathway. Our data reveal how PRV, through regulation of DDX3X in sensory neurons, travels along axons and triggers neuropathic itch and immune deviations to initiate pathophysiological programs which facilitate its spread to enhance infectivity.
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Affiliation(s)
- Shane J F Cronin
- Institute of Molecular Biotechnology Austria (IMBA), Dr. Bohrgasse 3, A-1030 Vienna, Austria
| | - Miguel A Tejada
- Institute of Molecular Biotechnology Austria (IMBA), Dr. Bohrgasse 3, A-1030 Vienna, Austria
| | - Ren Song
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
| | - Kathlyn Laval
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
- Department of Translational Physiology, Infectiology and Public Health, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Domagoj Cikes
- Institute of Molecular Biotechnology Austria (IMBA), Dr. Bohrgasse 3, A-1030 Vienna, Austria
| | - Ming Ji
- Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
| | - Annalaura Brai
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, I-53100 Siena, Italy
| | - Johannes Stadlmann
- Institute of Molecular Biotechnology Austria (IMBA), Dr. Bohrgasse 3, A-1030 Vienna, Austria
| | - Maria Novatchikova
- Institute of Molecular Biotechnology Austria (IMBA), Dr. Bohrgasse 3, A-1030 Vienna, Austria
| | - Thomas Perlot
- Institute of Molecular Biotechnology Austria (IMBA), Dr. Bohrgasse 3, A-1030 Vienna, Austria
| | - Omar Hasan Ali
- Department of Medical Genetics, Life Sciences Institute, University of British Columbia, Vancouver, Canada
- Institute of Immunobiology, Cantonal Hospital St. Gallen, Rorschacher Strasse 95, 9007 St. Gallen, Switzerland
- Department of Dermatology, University of Zurich, University Hospital Zurich, Rämistrasse 100, 8091 Zurich, Switzerland
| | - Lorenzo Botta
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, I-53100 Siena, Italy
| | - Thomas Decker
- Max F. Perutz Laboratories, Department of Microbiology, Immunobiology and Genetics, University of Vienna, Vienna Biocenter, Vienna, Austria
| | - Jelena Lazovic
- Institute of Molecular Biotechnology Austria (IMBA), Dr. Bohrgasse 3, A-1030 Vienna, Austria
| | - Astrid Hagelkruys
- Institute of Molecular Biotechnology Austria (IMBA), Dr. Bohrgasse 3, A-1030 Vienna, Austria
| | - Lynn Enquist
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
| | - Shuan Rao
- Department of Thoracic Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Orkide O Koyuncu
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California, Irvine, Irvine, CA 92697-4025, USA
| | - Josef M Penninger
- Institute of Molecular Biotechnology Austria (IMBA), Dr. Bohrgasse 3, A-1030 Vienna, Austria
- Department of Medical Genetics, Life Sciences Institute, University of British Columbia, Vancouver, Canada
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6
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Beauchene C, Zurn CA, Ehrens D, Duff I, Duan W, Caterina M, Guan Y, Sarma SV. Steering Toward Normative Wide-Dynamic-Range Neuron Activity in Nerve-Injured Rats With Closed-Loop Peripheral Nerve Stimulation. Neuromodulation 2023; 26:552-562. [PMID: 36402658 PMCID: PMC10081946 DOI: 10.1016/j.neurom.2022.09.011] [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: 07/02/2022] [Revised: 09/08/2022] [Accepted: 09/30/2022] [Indexed: 11/18/2022]
Abstract
OBJECTIVES Chronic pain is primarily treated with pharmaceuticals, but the effects remain unsatisfactory. A promising alternative therapy is peripheral nerve stimulation (PNS), but it has been associated with suboptimal efficacy because its modulation mechanisms are not clear and the current therapies are primarily open loop (ie, manually adjusting the stimulation parameters). In this study, we developed a proof-of-concept computational modeling as the first step toward implementing closed-loop PNS in future biological studies. When developing new pain therapies, a useful pain biomarker is the wide-dynamic-range (WDR) neuron activity in the dorsal horn. In healthy animals, the WDR neuron activity occurs in a stereotyped manner; however, this response profile can vary widely after nerve injury to create a chronic pain condition. We hypothesized that if injury-induced changes of neuronal response can be normalized to resemble those of a healthy condition, the pathological aspects of pain may be treated while maintaining protective physiological nociception. MATERIALS AND METHODS Using an in vivo electrophysiology data set of WDR neuron recordings obtained in nerve-injured rats and naïve rats, we constructed sets of linear phenomenologic models of WDR firing rate during windup stimulation for both conditions. Then, we applied robust control systems techniques to identify a closed-loop PNS controller, which can drive the dynamics of WDR neuron response in neuropathic pain model into ranges associated with normal physiological pain. RESULTS The sets of identified linear models can accurately predict, in silico, nonlinear neural responses to electrical stimulation of the peripheral nerve. In addition, we showed that continuous closed-loop control of PNS can be used to normalize WDR neuron firing responses in three injured cases. CONCLUSIONS In this proof-of-concept study, we show how tractable, linear mathematical models of pain-related neurotransmission can be used to inform the development of closed-loop PNS. This new application of robust control to neurotechnology may also be expanded and applied across other neuromodulation applications.
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Affiliation(s)
- Christine Beauchene
- Department of Biomedical Engineering, Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD, USA.
| | - Claire A Zurn
- Department of Biomedical Engineering, Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Daniel Ehrens
- Department of Biomedical Engineering, Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Irina Duff
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Wanru Duan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Michael Caterina
- Department of Neurosurgery, Neurosurgery Pain Research Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Yun Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Neurosurgery, Neurosurgery Pain Research Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Sridevi V Sarma
- Department of Biomedical Engineering, Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD, USA.
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7
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Modulation of itch and pain signals processing in ventrobasal thalamus by thalamic reticular nucleus. iScience 2022; 25:103625. [PMID: 35106466 PMCID: PMC8786640 DOI: 10.1016/j.isci.2021.103625] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 11/16/2021] [Accepted: 12/10/2021] [Indexed: 01/03/2023] Open
Abstract
Thalamic reticular nucleus (TRN) is known to be crucial for dynamically modulating sensory processing. Recently, the functional role of TRN in itch and pain sensation processing has drawn much attention. We found that ventrobasal thalamus (VB) neurons exhibited scratching behavior-related and nociceptive behavior-related neuronal activity changes, and most of VB neurons responsive to pruritic stimulus were also activated by nociceptive stimulus. Inhibition of VB could relieve itch-induced scratching behaviors and pathological pain without affecting basal nociceptive thresholds, and activation of VB could facilitate scratching behaviors. Tracing and electrophysiology recording results showed that VB mainly received inhibitory inputs from ventral TRN. Furthermore, optogenetic activation of TRN-VB projections suppressed scratching behaviors, and ablation of TRN enhanced scratching behaviors. In addition, activation of TRN-VB projections relieved the pathological pain without affecting basal nociceptive thresholds. Thus, our study indicates that TRN modulates itch and pain signals processing via TRN-VB inhibitory projections. VB is involved in both itch and pain signals processing Manipulation of VB or TRN-VB inhibitory projections modulates both itch and pain Enhancing the inhibitory tone might be a strategy for treating itch and pain
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8
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Chen XJ, Liu YH, Xu NL, Sun YG. Itch perception is reflected by neuronal ignition in the primary somatosensory cortex. Natl Sci Rev 2021; 9:nwab218. [PMID: 35769233 PMCID: PMC9232292 DOI: 10.1093/nsr/nwab218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Revised: 11/26/2021] [Accepted: 11/26/2021] [Indexed: 11/19/2022] Open
Abstract
Multiple cortical areas including the primary somatosensory cortex (S1) are activated during itch signal processing, yet cortical representation of itch perception remains unknown. Using novel miniature two-photon microscopic imaging in free-moving mice, we investigated the coding of itch perception in S1. We found that pharmacological inactivation of S1 abolished itch-induced scratching behavior, and the itch-induced scratching behavior could be well predicted by the activity of a fraction of layer 2/3 pyramidal neurons, suggesting that a subpopulation of S1 pyramidal neurons encoded itch perception, as indicated by immediate subsequent scratching behaviors. With a newly established optogenetics-based paradigm that allows precisely controlled pruritic stimulation, we found that a small fraction of S1 neurons exhibited an ignition-like pattern at the detection threshold of itch perception. Our study revealed the neural mechanism underlying itch perceptual coding in S1, thus paving the way for the study of cortical representation of itch perception at the single-neuron level in freely moving animals.
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Affiliation(s)
- Xiao-Jun Chen
- 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 Chinese Academy of Sciences, Beijing 100049, China
| | - Yan-He Liu
- 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 Chinese Academy of Sciences, Beijing 100049, China
| | - Ning-Long Xu
- 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 Chinese Academy of Sciences, Beijing 100049, China
- Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China
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9
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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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10
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Dissecting the Tectal Output Channels for Orienting and Defense Responses. eNeuro 2020; 7:ENEURO.0271-20.2020. [PMID: 32928881 PMCID: PMC7540932 DOI: 10.1523/eneuro.0271-20.2020] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 08/31/2020] [Accepted: 09/05/2020] [Indexed: 12/01/2022] Open
Abstract
Electrical stimulation and lesion experiments in 1980’s suggested that the crossed descending pathway from the deeper layers of superior colliculus (SCd) controls orienting responses, while the uncrossed pathway mediates defense-like behavior. To overcome the limitation of these classical studies and explicitly dissect the structure and function of these two pathways, we performed selective optogenetic activation of each pathway in male mice with channelrhodopsin 2 (ChR2) expression by Cre driver using double viral vector techniques. Brief photostimulation of the crossed pathway evoked short latency contraversive orienting-like head turns, while extended stimulation induced body turn responses. In contrast, stimulation of the uncrossed pathway induced short-latency upward head movements followed by longer-latency defense-like behaviors including retreat and flight. The novel discovery was that while the evoked orienting responses were stereotyped, the defense-like responses varied considerably depending on the environment, suggesting that uncrossed output can be influenced by top-down modification of the SC or its target areas. This further suggests that the connection of the SCd-defense system with non-motor, affective and cognitive structures. Tracing the whole axonal trajectories of these two pathways revealed existence of both ascending and descending branches targeting different areas in the thalamus, midbrain, pons, medulla, and/or spinal cord, including projections which could not be detected in the classical studies; the crossed pathway has some ipsilaterally descending collaterals and the uncrossed pathway has some contralaterally descending collaterals. Some of the connections might explain the context-dependent modulation of the defense-like responses. Thus, the classical views on the tectal output systems are updated.
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11
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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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12
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Domocos D, Selescu T, Ceafalan LC, Iodi Carstens M, Carstens E, Babes A. Role of 5-HT1A and 5-HT3 receptors in serotonergic activation of sensory neurons in relation to itch and pain behavior in the rat. J Neurosci Res 2020; 98:1999-2017. [PMID: 32537854 DOI: 10.1002/jnr.24633] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 03/29/2020] [Accepted: 04/10/2020] [Indexed: 12/21/2022]
Abstract
Serotonin (5-hydroxytryptamine, 5-HT) released by platelets, mast cells, and immunocytes is a potent inflammatory mediator which modulates pain and itch sensing in the peripheral nervous system. The serotonergic receptors expressed by primary afferent neurons involved in these sensory functions are not fully identified and appear to be to a large extent species dependent. Moreover, the mechanisms through which 5-HT receptor activation is coupled to changes in neuronal excitability have not been completely revealed. Using a combination of in vitro (calcium and voltage imaging and patch-clamp) and in vivo behavioral methods, we used both male and female Wistar rats to provide evidence for the involvement of two 5-HT receptor subtypes, 5-HT1A and 5-HT3, in mediating the sustained and transient effects, respectively, of 5-HT on rat primary afferent neurons involved in pain and itch processing. In addition, our results are consistent with a model in which sustained serotonergic responses triggered via the 5-HT1A receptor are due to closure of background potassium channels, followed by membrane depolarization and action potentials, during which the activation of voltage-gated calcium channels leads to calcium entry. Our results may provide a better understanding of mammalian serotonergic itch signaling.
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Affiliation(s)
- Dan Domocos
- Department of Anatomy, Physiology and Biophysics, Faculty of Biology, University of Bucharest, Bucharest, Romania
| | - Tudor Selescu
- Department of Anatomy, Physiology and Biophysics, Faculty of Biology, University of Bucharest, Bucharest, Romania
| | - Laura Cristina Ceafalan
- Cell Biology, Neuroscience and Experimental Myology Laboratory, 'Victor Babeș' National Institute of Pathology, Bucharest, Romania.,Department of Cellular & Molecular Biology and Histology, School of Medicine, 'Carol Davila' University of Medicine and Pharmacy, Bucharest, Romania
| | - Mirela Iodi Carstens
- Department of Neurobiology, Physiology and Behavior, College of Biological Sciences, University of California, Davis, CA, USA
| | - Earl Carstens
- Department of Neurobiology, Physiology and Behavior, College of Biological Sciences, University of California, Davis, CA, USA
| | - Alexandru Babes
- Department of Anatomy, Physiology and Biophysics, Faculty of Biology, University of Bucharest, Bucharest, Romania
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13
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Khasabov SG, Truong H, Rogness VM, Alloway KD, Simone DA, Giesler GJ. Responses of neurons in the primary somatosensory cortex to itch- and pain-producing stimuli in rats. J Neurophysiol 2020; 123:1944-1954. [PMID: 32292106 DOI: 10.1152/jn.00038.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Understanding of cortical encoding of itch is limited. Injection of pruritogens and algogens into the skin of the cheek produces distinct behaviors, making the rodent cheek a useful model for understanding mechanisms of itch and pain. We examined responses of neurons in the primary somatosensory cortex by application of mechanical stimuli (brush, pressure, and pinch) and stimulations with intradermal injections of pruritic and algesic chemical of receptive fields located on the skin of the cheek in urethane-anesthetized rats. Stimuli included chloroquine, serotonin, β-alanine, histamine, capsaicin, and mustard oil. All 33 neurons studied were excited by noxious mechanical stimuli applied to the cheek. Based on mechanical stimulation most neurons were functionally classified as high threshold. Of 31 neurons tested for response to chemical stimuli, 84% were activated by one or more pruritogens/partial pruritogens. No cells were activated by all five substances. Histamine activated the greatest percentage of neurons and evoked the greatest mean discharge. Importantly, no cells were excited exclusively by pruritogens or partial pruritogens. The recording sites of all neurons that responded to chemical stimuli applied to the cheek were located in the dysgranular zone (DZ) and in deep laminae of the medial border of the vibrissal barrel fields (VBF). Therefore, neurons in the DZ/VBF of rats encode mechanical and chemical pruritogens and algogens. This cortical region appears to contain primarily nociceptive neurons as defined by responses to noxious pinching of the skin. Its role in encoding itch and pain from the cheek of the face needs further study.NEW & NOTEWORTHY Processing of information related to itch sensation at the level of cerebral cortex is not well understood. In this first single-unit electrophysiological study of pruriceptive cortical neurons, we show that neurons responsive to noxious and pruritic stimulation of the cheek of the face are concentrated in a small area of the dysgranular cortex, indicating that these neurons encode information related to itch and pain.
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Affiliation(s)
- Sergey G Khasabov
- Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, Minneapolis, Minnesota
| | - Hai Truong
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Victoria M Rogness
- Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, Minneapolis, Minnesota
| | - Kevin D Alloway
- Center for Neural Engineering, Penn State University, University Park, Pennsylvania.,Department of Neural and Behavioral Sciences, Penn State University, University Park, Pennsylvania
| | - Donald A Simone
- Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, Minneapolis, Minnesota
| | - Glenn J Giesler
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota
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Associative and plastic thalamic signaling to the lateral amygdala controls fear behavior. Nat Neurosci 2020; 23:625-637. [PMID: 32284608 DOI: 10.1038/s41593-020-0620-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 03/05/2020] [Indexed: 01/21/2023]
Abstract
Decades of research support the idea that associations between a conditioned stimulus (CS) and an unconditioned stimulus (US) are encoded in the lateral amygdala (LA) during fear learning. However, direct proof for the sources of CS and US information is lacking. Definitive evidence of the LA as the primary site for cue association is also missing. Here, we show that calretinin (Calr)-expressing neurons of the lateral thalamus (Calr+LT neurons) convey the association of fast CS (tone) and US (foot shock) signals upstream from the LA in mice. Calr+LT input shapes a short-latency sensory-evoked activation pattern of the amygdala via both feedforward excitation and inhibition. Optogenetic silencing of Calr+LT input to the LA prevents auditory fear conditioning. Notably, fear conditioning drives plasticity in Calr+LT neurons, which is required for appropriate cue and contextual fear memory retrieval. Collectively, our results demonstrate that Calr+LT neurons provide integrated CS-US representations to the LA that support the formation of aversive memories.
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15
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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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