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Kaneko T, Oura A, Imai Y, Kusumoto-Yoshida I, Kanekura T, Okuno H, Kuwaki T, Kashiwadani H. Orexin neurons play contrasting roles in itch and pain neural processing via projecting to the periaqueductal gray. Commun Biol 2024; 7:290. [PMID: 38459114 PMCID: PMC10923787 DOI: 10.1038/s42003-024-05997-x] [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: 08/04/2023] [Accepted: 02/28/2024] [Indexed: 03/10/2024] Open
Abstract
Pain and itch are recognized as antagonistically regulated sensations; pain suppresses itch, whilst pain inhibition enhances itch. The neural mechanisms at the central nervous system (CNS) underlying these pain-itch interactions still need to be explored. Here, we revealed the contrasting role of orexin-producing neurons (ORX neurons) in the lateral hypothalamus (LH), which suppresses pain while enhancing itch neural processing, by applying optogenetics to the acute pruritus and pain model. We also revealed that the circuit of ORX neurons from LH to periaqueductal gray regions served in the contrasting modulation of itch and pain processing using optogenetic terminal inhibition techniques. Additionally, by using an atopic dermatitis model, we confirmed the involvement of ORX neurons in regulating chronic itch processing, which could lead to a novel therapeutic target for persistent pruritus in clinical settings. Our findings provide new insight into the mechanism of antagonistic regulation between pain and itch in the CNS.
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Affiliation(s)
- Tatsuroh Kaneko
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan.
| | - Asuka Oura
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Yoshiki Imai
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Ikue Kusumoto-Yoshida
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Takuro Kanekura
- Department of Dermatology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Hiroyuki Okuno
- Laboratory of Biochemistry and Molecular Biology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Tomoyuki Kuwaki
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Hideki Kashiwadani
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan.
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2
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Obara S, Oishi R, Nakano Y, Kurosawa S, Inoue S. Marked improvement in severe postherpetic itching following an epidural block: a case report. JA Clin Rep 2023; 9:24. [PMID: 37184726 DOI: 10.1186/s40981-023-00618-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 05/04/2023] [Accepted: 05/06/2023] [Indexed: 05/16/2023] Open
Affiliation(s)
- Shinju Obara
- Department of Anesthesiology, Fukushima Medical University, 1 Hikarigaoka, Fukushima, Fukushima, 960-1295, Japan.
- Center for Pain Management, Fukushima Medical University Hospital, 1 Hikarigaoka, Fukushima, Fukushima, 960-1295, Japan.
| | - Rieko Oishi
- Department of Anesthesiology, Fukushima Medical University, 1 Hikarigaoka, Fukushima, Fukushima, 960-1295, Japan
| | - Yuko Nakano
- Department of Anesthesiology, Fukushima Medical University, 1 Hikarigaoka, Fukushima, Fukushima, 960-1295, Japan
| | - Shin Kurosawa
- Department of Anesthesiology, Fukushima Medical University, 1 Hikarigaoka, Fukushima, Fukushima, 960-1295, Japan
| | - Satoki Inoue
- Department of Anesthesiology, Fukushima Medical University, 1 Hikarigaoka, Fukushima, Fukushima, 960-1295, Japan
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3
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Zhang TT, Guo SS, Wang HY, Jing Q, Yi X, Hu ZH, Yu XR, Xu TL, Liu MG, Zhao X. An Anterior Cingulate Cortex-to-Midbrain Projection Controls Chronic Itch in Mice. Neurosci Bull 2022; 39:793-807. [PMID: 36528690 PMCID: PMC10169993 DOI: 10.1007/s12264-022-00996-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 08/26/2022] [Indexed: 12/23/2022] Open
Abstract
AbstractItch is an unpleasant sensation that provokes the desire to scratch. While acute itch serves as a protective system to warn the body of external irritating agents, chronic itch is a debilitating but poorly-treated clinical disease leading to repetitive scratching and skin lesions. However, the neural mechanisms underlying the pathophysiology of chronic itch remain mysterious. Here, we identified a cell type-dependent role of the anterior cingulate cortex (ACC) in controlling chronic itch-related excessive scratching behaviors in mice. Moreover, we delineated a neural circuit originating from excitatory neurons of the ACC to the ventral tegmental area (VTA) that was critically involved in chronic itch. Furthermore, we demonstrate that the ACC→VTA circuit also selectively modulated histaminergic acute itch. Finally, the ACC neurons were shown to predominantly innervate the non-dopaminergic neurons of the VTA. Taken together, our findings uncover a cortex–midbrain circuit for chronic itch-evoked scratching behaviors and shed novel insights on therapeutic intervention.
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Affiliation(s)
- Ting-Ting Zhang
- Department of Anesthesiology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, 200072, China
| | - Su-Shan Guo
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Hui-Ying Wang
- Department of Anesthesiology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, 200072, China
| | - Qi Jing
- Department of Anesthesiology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, 200072, China
| | - Xin Yi
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Zi-Han Hu
- Department of Anesthesiology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, 200072, China
| | - Xin-Ren Yu
- Department of Anesthesiology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, 200072, China
| | - Tian-Le Xu
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
- Center for Brain Science of Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Ming-Gang Liu
- Department of Anatomy and Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
- Center for Brain Science of Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China.
| | - Xuan Zhao
- Department of Anesthesiology, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, 200072, China.
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4
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Park C, John H, Lee J, Hong S, Kim M, Park S, Kim JH. The relative frequency of pruritus in postherpetic neuralgia patients presenting to the pain clinic and associative factors. Medicine (Baltimore) 2022; 101:e30208. [PMID: 36107606 PMCID: PMC9439806 DOI: 10.1097/md.0000000000030208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Postherpetic neuralgia (PHN) is the most common complication of herpes zoster, whereas postherpetic pruritus (PHP) a rare one. Although PHN has been extensively studied, few studies have investigated PHP. The purpose of this study was to investigate PHP incidence and associated factors in patients with PHN. This was a retrospective study of patients with PHN. A total of 645 patients were included. This study conducted in a single university hospital. Data included age, sex, height, weight, pain score, PHN site, medications, nerve blocks, and pulsed radiofrequency treatment. Data also included PHP onset and duration among those with PHP. We divided patients into 2 groups: the control group (group C), comprising those without PHP, and pruritus group (group P), comprising those with PHP. The correlation of PHP with other factors was analyzed. Of 207 patients, 58 were in group P whereas 149 in group C. The mean onset time and duration of PHP were 96.5 and 278.6 days, respectively. Pain scores were lower in group P than in group C after 3 and 4 months following vesicle formation. Patients with PHN in the trigeminal nerve had a higher incidence of PHP compared to those with PHN in others. Twenty-eight percent of patients with PHN developed PHP. At 3 and 4 months after vesicle formation, patients with PHP had greater pain improvement compared to those without. Patients with PHN in the trigeminal nerve also had a higher incidence of PHP compared to others.
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Affiliation(s)
- Cheolhwan Park
- Department of Anesthesiology and Pain Medicine, Konkuk University School of Medicine, Seoul, Korea
| | - Hyunji John
- Department of Anesthesiology and Pain Medicine, Konkuk University School of Medicine, Seoul, Korea
| | - Jaemoon Lee
- Department of Anesthesiology and Pain Medicine, Konkuk University School of Medicine, Seoul, Korea
| | - Seungwan Hong
- Department of Anesthesiology and Pain Medicine, Konkuk University School of Medicine, Seoul, Korea
| | - Minjung Kim
- Department of Anesthesiology and Pain Medicine, Konkuk University School of Medicine, Seoul, Korea
| | - Sangtae Park
- Department of Anesthesiology and Pain Medicine, Konkuk University School of Medicine, Seoul, Korea
| | - Jae Hun Kim
- Department of Anesthesiology and Pain Medicine, Konkuk University School of Medicine, Seoul, Korea
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Badwy M, Baart SJ, Thio HB, Huygen FJPM, de Vos CC. Electrical neurostimulation for the treatment of chronic pruritus: A systematic review. Exp Dermatol 2021; 31:280-289. [PMID: 34637585 PMCID: PMC9299998 DOI: 10.1111/exd.14468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 07/06/2021] [Accepted: 09/30/2021] [Indexed: 11/30/2022]
Abstract
Approximately one fifth of the world population experiences continuous itch for 6 weeks or more during their life, that is chronic itch. It is diverse in its aetiologies, and it is notoriously hard to treat. Because itch and pain have largely overlapping pathophysiology and the demonstrated efficacy of neurostimulation in treatment of selected chronic pain conditions, we conducted a systematic review to investigate whether neurostimulation could be an effective treatment for chronic itch. We identified two randomized controlled trials and 17 open label studies or case reports investigating various neurostimulation modalities for the treatment of refractory itch of various aetiologies. Transcutaneous electrical nerve stimulation (TENS) was the most investigated modality (n = 17), and in the largest number of conditions. Other modalities were cutaneous field stimulation (n = 2), painscrambler (n = 1), transcranial direct current stimulation (n = 1) and peripheral nerve field stimulation (n = 1). Atopic dermatitis was the most studied condition (n = 5). Despite the large heterogeneity in used stimulation paradigms and outcome parameters, all studies reported a positive effect of at least one neurostimulation modality. Our review indicates that electrical neurostimulation could be considered for the treatment of refractory chronic itch of selected aetiologies, such as atopic dermatitis or burn pruritus. However, better understanding of the mechanisms of action of the neurostimulation modalities and regimens in various pruritic conditions is necessary.
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Affiliation(s)
- Moustafa Badwy
- Center for pain Medicine, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Sara J Baart
- Center for pain Medicine, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.,Department of Biostatistics, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Hok B Thio
- Department of Dermatology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Frank J P M Huygen
- Center for pain Medicine, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Cecile C de Vos
- Center for pain Medicine, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
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6
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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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7
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Patnaik S, Imms JB, Varadi G. The neuropathic itch: Don't scratch your head too hard! Clin Case Rep 2021; 9:914-916. [PMID: 33598271 PMCID: PMC7869385 DOI: 10.1002/ccr3.3688] [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: 10/15/2020] [Accepted: 12/04/2020] [Indexed: 11/30/2022] Open
Abstract
Postherpetic complications can sometimes result in significant debility. A multidisciplinary approach is crucial in deciding the appropriate treatment strategy in these patients.
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Affiliation(s)
- Soumya Patnaik
- Department of MedicineEinstein Medical CenterPhiladelphiaPAUSA
| | - John Brady Imms
- Department of MedicineEinstein Medical CenterPhiladelphiaPAUSA
| | - Gabor Varadi
- Division of HematooncologyEinstein Medical CenterPhiladelphiaPAUSA
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8
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Ständer S, Schmelz M. [Neuropathic pruritus]. Schmerz 2020; 34:525-535. [PMID: 33025226 DOI: 10.1007/s00482-020-00502-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 07/14/2020] [Accepted: 07/15/2020] [Indexed: 11/26/2022]
Abstract
In the past 10 years specific pathways for pruritus have been characterized on a cellular and molecular level but their exact role in the pathophysiology of neuropathic pruritus remains unclear. This also applies to the question which of the competing theories for pruritus, e.g. specificity, temporal/spatial pattern or intensity, would best apply. While experimental trials on mice have mostly confirmed the theory of specificity, the results on humans indicate a role of spatial and temporal patterns. The skin innervation is greatly reduced by the neuropathy and could provide a "spatial contrast pattern" and the axotomy could induce a de novo expression of gastrin-releasing peptide (GRP) in primarily afferent nociceptors and thus modulate spinal pruritus processing. In addition, the overlap of pruritus and pain in neuropathy patients complicates the direct translation from animal experiments and requires collaboration at the clinical level between pain medicine and dermatology.
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Affiliation(s)
- Sonja Ständer
- Kompetenzzentrum Chronischer Pruritus, Universitätsklinikum Münster, Münster, Deutschland
| | - Martin Schmelz
- Experimentelle Schmerzforschung, MCTN, Medizinische Fakultät Mannheim, Universität Heidelberg, Ludolf-Krehl-Str. 13-17, 68167, Mannheim, Deutschland.
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9
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Xu G, Zhou CS, Tang WZ, Xu J, Xu G, Cheng C, Wang LD, Ding KH. Local Administration of Methylcobalamin for Subacute Ophthalmic Herpetic Neuralgia: A Randomized, Phase III Clinical Trial. Pain Pract 2020; 20:838-849. [PMID: 32372561 DOI: 10.1111/papr.12909] [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: 12/31/2019] [Revised: 04/13/2020] [Accepted: 04/29/2020] [Indexed: 10/24/2022]
Abstract
OBJECTIVES The ophthalmic branch of the trigeminal nerve is one of the most frequently involved sites of postherpetic neuralgia. A single-center randomized controlled study was conducted to evaluate the efficacy of local methylcobalamin injection for subacute ophthalmic herpetic neuralgia (SOHN). METHODS One hundred and five patients with a pain score of 4 or greater were randomized to receive a combination of methylcobalamin and lidocaine via local injection (LM group, n = 35), intramuscular methylcobalamin and local lidocaine injection (IM group, n = 35), and oral methylcobalamin tablet and lidocaine local injection (OM group, n = 35) for 4 weeks. Multilevel mixed modeling was employed to examine treatment responses. RESULTS Pain scores were reduced in all groups, but this reduction was significantly greater in the LM group (6.7 at baseline vs. 2.8 at endpoint) when compared with systemic administration (IM group 6.8 vs. 4.9, OM group 6.7 vs. 5.1). Clinically relevant reduction of pain (>30%) was seen in 91% of patients in the LM group, a significantly greater proportion than in the systemic groups (66% IM group, 57% OM group). Analgesic use reduced significantly in the LM group (94% at baseline vs. 6% at endpoint) but not in systemic groups (IM group 97% vs. 86%, OM group 94% vs. 80%). Health-related quality of life was higher in the LM group than in the systemic groups. In mixed modelling, increased age was associated with a lower response to methylcobalamin. CONCLUSIONS This study indicates that local injection of methylcobalamin produces significant pain relief from SOHN and is superior to systemic administration.
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Affiliation(s)
- Gang Xu
- Rehabilitation Medicine Department, Zoster-associated Pain Research Center, Affiliated Tenth People's Hospital of Tongji University, Shanghai Tenth People's Hospital, Shanghai, China.,Rehabilitation Medicine Department, Chongming Branch of Shanghai Tenth People's Hospital, Shanghai, China
| | - Chao Sheng Zhou
- Rehabilitation Medicine Department, Zoster-associated Pain Research Center, Affiliated Tenth People's Hospital of Tongji University, Shanghai Tenth People's Hospital, Shanghai, China
| | - Wei Zhen Tang
- Rehabilitation Medicine Department, Zoster-associated Pain Research Center, Affiliated Tenth People's Hospital of Tongji University, Shanghai Tenth People's Hospital, Shanghai, China
| | - Jie Xu
- Rehabilitation Medicine Department, Zoster-associated Pain Research Center, Affiliated Tenth People's Hospital of Tongji University, Shanghai Tenth People's Hospital, Shanghai, China
| | - Gang Xu
- Rehabilitation Medicine Department, Zoster-associated Pain Research Center, Affiliated Tenth People's Hospital of Tongji University, Shanghai Tenth People's Hospital, Shanghai, China
| | - Chao Cheng
- Rehabilitation Medicine Department, Zoster-associated Pain Research Center, Affiliated Tenth People's Hospital of Tongji University, Shanghai Tenth People's Hospital, Shanghai, China
| | - Li Dong Wang
- Rehabilitation Medicine Department, Chongming Branch of Shanghai Tenth People's Hospital, Shanghai, China
| | - Kai Hua Ding
- Rehabilitation Medicine Department, Chongming Branch of Shanghai Tenth People's Hospital, Shanghai, China
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10
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Abstract
Itching can result from activity of specialized primary afferent neurons (“pruriceptors”) that have been shown to express certain molecular markers such as B-type natriuretic peptide and several members of the Mrgpr-family in rodents. On the other hand, neurons involved in pain processing (“nociceptors”) can also provoke itching when the activation site is restricted to an isolated tiny spot within the epidermis. Individuals classified as having sensitive skin report increased itching and pain sensations upon weak external stimuli that are not painful or itchy in the control group. Numerous possible factors could contribute to sensitive skin along the pathway of transduction of the external stimuli into peripheral neuronal signals, followed by neuronal processing, finally resulting in the perception: (a) reduced local protective factors leading to impaired skin barrier function, (b) increased production of excitatory skin mediators, (c) sensitized peripheral neurons, (d) facilitated spinal and central processing, and (e) reduced descending inhibition from the central nervous system. For all of those pathophysiological mechanisms there are clinical examples such as atopic dermatitis (a,b,c), neuropathic itching (c,e), and restless leg syndrome (d,e). However, none of these factors have been directly linked to the occurrence of sensitive skin. Moreover, individuals reporting sensitive skin are heterogeneous and a subpopulation with defined pathophysiology has not yet been identified. Given that the condition is reported in about 50% of women, and thereby includes many healthy individuals, it appears problematic to assign a definitive pathophysiological mechanism to it.
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Affiliation(s)
- Martin Schmelz
- Department Experimental Pain Research, CBTM, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
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11
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Abstract
Neuropathic itch is clinically important but has received much less attention as compared to neuropathic pain. In the past decade, itch-specific pathways have been characterized on a cellular and molecular level, but their exact role in the pathophysiology of neuropathic itch is still unclear. Traditionally, mutually exclusive theories for itch such as labeled line, temporal/spatial pattern, or intensity theory have been proposed, and experimental studies in mice mainly favor the specificity theory of itch. By contrast, results in humans also suggest a role for spatial and temporal patterns in neuropathic itch. Rarefication of skin innervation in neuropathy could provide a "spatial contrast" discharge pattern, and axotomy could induce de novo expression of the itch-specific spinal neuropeptide, gastrin-releasing peptide, in primary afferent nociceptors, thereby modulating itch processing in the dorsal horn. Thus, clinical neuropathy may generate itch by changes in the spatial and temporal discharge patterns of nociceptors, hijacking the labeled line processing of itch and abandoning the canonical scheme of mutual exclusive itch theories. Moreover, the overlap between itch and pain symptoms in neuropathy patients complicates direct translation from animal experiments and, on a clinical level, necessitates collaboration between medical specialities, such as dermatologists, anesthesiologists, and neurologists.
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