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Schwarzenauer M, Rukwied RM, Lampert A, Rolke R, Namer B. Electrical matrix stimulation suppresses acute itch independently of activation of sleeping nociceptors. Eur J Pain 2024; 28:285-296. [PMID: 37715607 DOI: 10.1002/ejp.2177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 07/24/2023] [Accepted: 08/19/2023] [Indexed: 09/17/2023]
Abstract
INTRODUCTION Itch can be reduced by pain. Activation of sleeping nociceptors (CMi) is a crucial mechanism for the peripheral component of intense and long-lasting pain. Thus, activation of CMi might be especially effective in itch reduction. Electrical stimulation using sinusoidal pulses activates CMi with tolerable pain intensity, whereas short rectangular pulses with low intensity do not. In humans, histaminergic itch is mediated by histamine-sensitive CMi, whereas other pruritogens activate polymodal nociceptors (CM). METHODS In a psychophysical approach in a balanced crossover repeated-measures design in healthy volunteers, we activated nociceptors by two different electrical stimulation paradigms via a matrix electrode: 4 Hz sinusoidal pulses that activate C-nociceptors including CMi or 4 Hz rectangular stimuli to activate nociceptors excluding CMi. After 5-min stimulation, itch was induced by either histamine iontophoresis or application of cowhage spicules. Itch ratings were assessed via a numerical rating scale (NRS). RESULTS Electrical 4 Hz sine wave stimulation (0.1 mA) with low pain ratings of 1.5 (NRS; 0-10) induced an axon reflex erythema (3 cm2 ), indicating activation of CMi, whereas rectangular 0.2 ms pulses (average 0.91 mA) with the same pain rating did not. Both electrical stimulation paradigms reduced itch magnitude over time evoked by either histamine or cowhage to a similar extent. Peak maximum itch evoked by histamine was reduced by both stimulation paradigms, but not cowhage maximum itch. DISCUSSION Since electrical stimulation with the rectangular pulse paradigm reduces itch to a similar extent as the sine wave stimulation paradigm, the input of CMi is not necessarily required for itch suppression. The input of A-fibres and polymodal nociceptors, similarly, as also achieved by scratching, seems to be sufficient for both forms of chemically evoked itch. SIGNIFICANCE Since activation of CMi does not provide additional benefit for itch suppression, spinal pain pathways transmitted via CM versus CMi have differential effects on itch-processing circuits. This is important knowledge for using electrical matrix stimulation as itch suppressor since activation of sleeping nociceptors either requires significantly painful stimulation paradigms or specialized stimulation paradigms as sinusoidal pulses. An alternative approach using half-sine wave pulses with low pain intensity activating specifically polymodal nociceptors to suppress itch via matrix electrode stimulation may be considered.
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Affiliation(s)
- M Schwarzenauer
- IZKF Research Group Neuroscience, Medical Faculty RWTH Aachen University, Aachen, Germany
- Department of Palliative Medicine, Medical Faculty RWTH Aachen University, Aachen, Germany
| | - R M Rukwied
- Department of Experimental Pain Research, Mannheim Center for Translation Neuroscience (MCTN), Medical Faculty Mannheim, University of Heidelberg, Heidelberg, Germany
| | - A Lampert
- Department for Neurophysiology, Medical Faculty RWTH Aachen University, Aachen, Germany
| | - R Rolke
- Department of Palliative Medicine, Medical Faculty RWTH Aachen University, Aachen, Germany
| | - B Namer
- IZKF Research Group Neuroscience, Medical Faculty RWTH Aachen University, Aachen, Germany
- Department for Neurophysiology, Medical Faculty RWTH Aachen University, Aachen, Germany
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Kupari J, Ernfors P. Molecular taxonomy of nociceptors and pruriceptors. Pain 2023; 164:1245-1257. [PMID: 36718807 PMCID: PMC10184562 DOI: 10.1097/j.pain.0000000000002831] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 11/10/2022] [Accepted: 11/21/2022] [Indexed: 02/01/2023]
Affiliation(s)
- Jussi Kupari
- Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Patrik Ernfors
- Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
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Lu P, Zhao Y, Xie Z, Zhou H, Dong X, Wu GF, Kim BS, Feng J, Hu H. MrgprA3-expressing pruriceptors drive pruritogen-induced alloknesis through mechanosensitive Piezo2 channel. Cell Rep 2023; 42:112283. [PMID: 36961815 PMCID: PMC10514240 DOI: 10.1016/j.celrep.2023.112283] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 01/29/2023] [Accepted: 03/03/2023] [Indexed: 03/25/2023] Open
Abstract
Although touch and itch are coded by distinct neuronal populations, light touch also provokes itch in the presence of exogenous pruritogens, resulting in a phenomenon called alloknesis. However, the cellular and molecular mechanisms underlying the initiation of pruritogen-induced mechanical itch sensitization are poorly understood. Here, we show that intradermal injections of histamine or chloroquine (CQ) provoke alloknesis through activation of TRPV1- and MrgprA3-expressing prurioceptors, and functional ablation of these neurons reverses pruritogen-induced alloknesis. Moreover, genetic ablation of mechanosensitive Piezo2 channel function from MrgprA3-expressing prurioceptors also dampens pruritogen-induced alloknesis. Mechanistically, histamine and CQ sensitize Piezo2 channel function, at least in part, through activation of the phospholipase C (PLC) and protein kinase C-δ (PKCδ) signaling. Collectively, our data find a TRPV1+/MrgprA3+ prurioceptor-Piezo2 signaling axis in the initiation of pruritogen-induced mechanical itch sensitization in the skin.
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Affiliation(s)
- Ping Lu
- Department of Anesthesiology, The Center for the Study of Itch & Sensory Disorders, Washington University School of Medicine, St. Louis, MO, USA; Dermatology Hospital, Southern Medical University, Guangzhou, China
| | - Yonghui Zhao
- Department of Anesthesiology, The Center for the Study of Itch & Sensory Disorders, Washington University School of Medicine, St. Louis, MO, USA
| | - Zili Xie
- Department of Anesthesiology, The Center for the Study of Itch & Sensory Disorders, Washington University School of Medicine, St. Louis, MO, USA
| | - Huan Zhou
- Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Science, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Gregory F Wu
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA
| | - Brian S Kim
- Kimberly and Eric J. Waldman Department of Dermatology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jing Feng
- Department of Anesthesiology, The Center for the Study of Itch & Sensory Disorders, Washington University School of Medicine, St. Louis, MO, USA; Center for Neurological and Psychiatric Research and Drug Discovery, Shanghai Institute of Materia Medica, Chinese Academy of Science, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China.
| | - Hongzhen Hu
- Department of Anesthesiology, The Center for the Study of Itch & Sensory Disorders, Washington University School of Medicine, St. Louis, MO, USA.
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de Almeida C, Chabbah N, Eyraud C, Fasano C, Bernard V, Pietrancosta N, Fabre V, El Mestikawy S, Daumas S. Absence of VGLUT3 Expression Leads to Impaired Fear Memory in Mice. eNeuro 2023; 10:ENEURO.0304-22.2023. [PMID: 36720646 PMCID: PMC9953049 DOI: 10.1523/eneuro.0304-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 01/08/2023] [Accepted: 01/10/2023] [Indexed: 02/02/2023] Open
Abstract
Fear is an emotional mechanism that helps to cope with potential hazards. However, when fear is generalized, it becomes maladaptive and represents a core symptom of posttraumatic stress disorder (PTSD). Converging lines of research show that dysfunction of glutamatergic neurotransmission is a cardinal feature of trauma and stress related disorders such as PTSD. However, the involvement of glutamatergic co-transmission in fear is less well understood. Glutamate is accumulated into synaptic vesicles by vesicular glutamate transporters (VGLUTs). The atypical subtype, VGLUT3, is responsible for the co-transmission of glutamate with acetylcholine, serotonin, or GABA. To understand the involvement of VGLUT3-dependent co-transmission in aversive memories, we used a Pavlovian fear conditioning paradigm in VGLUT3-/- mice. Our results revealed a higher contextual fear memory in these mice, despite a facilitation of extinction. In addition, the absence of VGLUT3 leads to fear generalization, probably because of a pattern separation deficit. Our study suggests that the VGLUT3 network plays a crucial role in regulating emotional memories. Hence, VGLUT3 is a key player in the processing of aversive memories and therefore a potential therapeutic target in stress-related disorders.
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Affiliation(s)
- Camille de Almeida
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), Paris 75005, France
| | - Nida Chabbah
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), Paris 75005, France
| | - Camille Eyraud
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), Paris 75005, France
| | - Caroline Fasano
- Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montréal QC H4H 1R3, Quebec, Canada
| | - Véronique Bernard
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), Paris 75005, France
| | - Nicolas Pietrancosta
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), Paris 75005, France
| | - Véronique Fabre
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), Paris 75005, France
| | - Salah El Mestikawy
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), Paris 75005, France
- Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montréal QC H4H 1R3, Quebec, Canada
| | - Stephanie Daumas
- Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, Centre National de la Recherche Scientifique, Neuroscience Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), Paris 75005, France
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Chemogenetic activation of VGLUT3-expressing neurons decreases movement. Eur J Pharmacol 2022; 935:175298. [PMID: 36198338 DOI: 10.1016/j.ejphar.2022.175298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/16/2022] [Accepted: 09/21/2022] [Indexed: 11/24/2022]
Abstract
Vesicular glutamate transporters (VGLUTs) are responsible for the storage of glutamate into secretory vesicles. The VGLUT3 isoform is mainly expressed in neurons that secrete other classical neurotransmitters, including the cholinergic interneurons in the striatum, and VGLUT3-expressing neurons often secrete two distinct neurotransmitters. VGLUT3 is discretely distributed throughout the brain and is found in subpopulations of spinal cord interneurons, in subset of neurons in the dorsal root ganglion, and in Merkel cells. Mice with a global loss of VGLUT3 are hyperactive and the modulation of specific VGLUT3-expressing circuits can lead to changes in movement. In this study, we tested the hypothesis that increased activity of VGLUT3-expressing neurons is associated with decreased movement. Using a mouse line expressing excitatory designer receptor exclusively activated by designer drugs (hM3Dq-DREADD) on VGLUT3-expressing neurons, we showed that activation of hM3Dq signalling acutely decreased locomotor activity. This decreased locomotion was likely not due to circuit changes mediated by glutamate nor acetylcholine released from VGLUT3-expressing neurons, as activation of hM3Dq signalling in mice that do not release glutamate or acetylcholine from VGLUT3-expressing neurons also decreased locomotor activity. This suggests that other neurotransmitters are likely driving this hypoactive phenotype. We used these mouse lines to compare the effects of DREADD agonists in vivo. We observed that clozapine-N-oxide (CNO), clozapine, compound 21 and perlapine show small differences in the speed at which they prompt behavioural responses but the four of them are selective DREADD ligands.
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Irie H, Kabashima K. The interaction between the immune system and the peripheral sensory nerves in pruritus. Int Immunol 2021; 33:737-742. [PMID: 34611710 DOI: 10.1093/intimm/dxab076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 09/28/2021] [Indexed: 12/16/2022] Open
Abstract
Pruritus is a skin-specific sensation that is observed in various skin diseases, especially in inflammatory skin diseases such as atopic dermatitis, and is deeply involved in their pathogenesis. Pruritus also adversely affects patients' sleep and mental health, placing a heavy burden on daily life. As such, pruritus control is important to the maintenance of health. The mechanism of pruritus has recently been clarified and the discovery of various pruritus mediators, the identification of specific nerves that transmit pruritus and the accumulation of knowledge on pruritus perception have led to a better understanding of all aspects of pruritus generation, transmission and recognition. In the case of pruritus caused by dermatitis, immune cells infiltrating the skin secrete inflammatory cytokines, which also act on peripheral nerves as pruritus mediators and induce an inflammatory response. Interestingly, there has been accumulating evidence that peripheral nerves are also involved in the inflammation via neuropeptides. In this article, we summarize the findings on pruritus mediators secreted by immune cells and the roles of peripheral nerves in pruritus in terms of their interactions with immunity.
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Affiliation(s)
- Hiroyuki Irie
- Department of Dermatology, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawahara, Sakyo, Kyoto, Japan
| | - Kenji Kabashima
- Department of Dermatology, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawahara, Sakyo, Kyoto, Japan.,Singapore Immunology Network and Skin Research Institute of Singapore, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
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Abstract
Mechanistic theories of itch are based on neuronal specificity, stimulus intensity, and temporal or spatial discharge patterns. Traditionally, these theories are conceptualized as mutually exclusive, assuming that finding evidence for one theory would exclude the others and could sufficiently explain itch. Current experimental data primarily support the specificity or pattern theory of itch. However, in contrast to an assumed inherent exclusivity, recent results have shown that even within itch-specific pathways in the spinal cord, temporal discharge patterns are important as sustained pruriceptor is required to allow successful transsynaptic signal progression. Also, optogenetic activation of pruriceptors suggest that the combination of neuronal specificity and temporal pattern determines the sensory effect: tonic activation of pruriceptors is required to induce scratching behavior whereas short-lasting stimulation rather causes withdrawal. In addition to the mere duration of discharge, also the temporal pattern or spatial aspects could critically contribute to elicit pruritus instead of pain. Basic neurophysiological studies trying to validate neuronal theories for pruritus in their pure form provide unitary concepts leading from neuronal discharge to the itch sensation. However, the crucial clinical questions have the opposite perspective: which mechanisms explain the chronic itch in a given patient or a given disease? In trying to solve these clinical problems we should not feel bound to the mutual exclusive nature of itch theories, but rather appreciate blending several theories and also accept combinations of itch and pain. Thus, blended versions of itch theories might better suffice for an explanation of chronic itch in patients and will improve the basis for mechanistic treatment options.
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Affiliation(s)
- Martin Schmelz
- Department of Experimental Pain Research, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
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Meijer LL, Schielen ZA, van Ree KY, Dijkerman HC. Affective Touch Reduces Electrically Induced Itch Experience. Front Med (Lausanne) 2021; 8:628020. [PMID: 33659264 PMCID: PMC7917120 DOI: 10.3389/fmed.2021.628020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 01/25/2021] [Indexed: 11/13/2022] Open
Abstract
Introduction: Itch is a common symptom in dermatologic and other diseases and can have a severe impact on quality of life and mental health. As a proportion of patients with itch-symptoms is resistant to commonly used anti-histamine treatments, development of new treatments is desirable. Past research on pain, itch and affective touch (i.e. slow, gentle stroking of the skin activating C-tactile fibers) revealed an inhibitory relationship between affective touch and pain and between pain and itch. Given the overlap in neural processing between these three sensory submodalities, a possible interaction between affective touch and itch might be expected. This study investigated whether there is a relationship between itch and affective touch, and if so, whether affective touch inhibits itch. Methodology: Itch was electrically induced with the use of electrodes that were placed at the ventral side of the wrist of 61 participants. A within-subject design was conducted with two conditions. An experimental -affective touch- condition (stroking the forearm with a soft brush at 3 cm/s) and a control -non-affective touch- condition (stroking the forearm with a soft brush at 18 cm/s). Touch was applied on the dorsal side of the forearm, the same arm as were the electrodes were placed. For each condition itch was induced for 20 min, with every 2 min a VAS-scale measurement of the level of experienced itch. Results: Both types of touch reduced the experienced itch compared to baseline (p < 0.01, partial η2 = 0.67). However, affective touch had an additional significant relieving effect compared to non-affective touch (p = 0.03, partial η2= 0.08). The alleviation of itch started after 2 min of stroking and continued to increase up till 6 min, where after the relieving effect stabilized but still persisted. Conclusion: This finding suggest that affective touch, as with acute pain, has a relieving effect on electrically induced itch.
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Affiliation(s)
- Larissa L Meijer
- Experimental Psychology/Helmholtz Institute, Utrecht University, Utrecht, Netherlands
| | - Zoë A Schielen
- Experimental Psychology/Helmholtz Institute, Utrecht University, Utrecht, Netherlands
| | - Kim Y van Ree
- Experimental Psychology/Helmholtz Institute, Utrecht University, Utrecht, Netherlands
| | - H Chris Dijkerman
- Experimental Psychology/Helmholtz Institute, Utrecht University, Utrecht, Netherlands
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