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Yao D, Chen Y, Chen G. The role of pain modulation pathway and related brain regions in pain. Rev Neurosci 2023; 34:899-914. [PMID: 37288945 DOI: 10.1515/revneuro-2023-0037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Accepted: 05/18/2023] [Indexed: 06/09/2023]
Abstract
Pain is a multifaceted process that encompasses unpleasant sensory and emotional experiences. The essence of the pain process is aversion, or perceived negative emotion. Central sensitization plays a significant role in initiating and perpetuating of chronic pain. Melzack proposed the concept of the "pain matrix", in which brain regions associated with pain form an interconnected network, rather than being controlled by a singular brain region. This review aims to investigate distinct brain regions involved in pain and their interconnections. In addition, it also sheds light on the reciprocal connectivity between the ascending and descending pathways that participate in pain modulation. We review the involvement of various brain areas during pain and focus on understanding the connections among them, which can contribute to a better understanding of pain mechanisms and provide opportunities for further research on therapies for improved pain management.
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Affiliation(s)
- Dandan Yao
- Department of Anesthesiology, School of Medicine, Shaoxing University, Shaoxing, Zhejiang, China
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Yeru Chen
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Gang Chen
- Department of Anesthesiology, School of Medicine, Shaoxing University, Shaoxing, Zhejiang, China
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310058, China
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Komboz F, Mehsein Z, Kobaïter-Maarrawi S, Chehade HD, Maarrawi J. Epidural Posterior Insular Stimulation Alleviates Neuropathic Pain Manifestations in Rats With Spared Nerve Injury Through Endogenous Opioid System. Neuromodulation 2023; 26:1602-1611. [PMID: 35219569 DOI: 10.1016/j.neurom.2022.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 01/05/2022] [Accepted: 01/09/2022] [Indexed: 10/19/2022]
Abstract
OBJECTIVES Neuropathic pain (NP) is defined as constant disabling pain secondary to a lesion or disease of the somatosensory nervous system. This condition is particularly difficult to treat because it often remains resistant to most treatment strategies. Despite the recent diversification of neurostimulation methods, some patients still suffer from refractory pain syndromes. The central role of the posterior insular cortex (PI) in the modulation of pain signaling and perception has been repeatedly suggested. The objective of this study is to assess whether epidural insular stimulation (IS) could reverse NP behavior. MATERIALS AND METHODS A total of 53 adult Sprague-Dawley rats received left-sided spared nerve injury (SNI) or Sham-SNI to induce NP symptoms. Afterward, epidural electrodes were implanted over the right PI. After two weeks of postoperative recovery, three groups of SNI-operated rats each received a different stimulation modality: Sham-IS, low-frequency-IS (LF-IS), or high-frequency-IS (HF-IS). Behavioral and functional tests were conducted before and after IS. They comprised the acetone test, pinprick test, von Frey test, and sciatic functional index. An additional LF-IS group received a dose of opioid antagonist naloxone before IS. Intergroup means were compared through independent-samples t-tests, and pre- and post-IS means in the same group were compared through paired t-tests. RESULTS We found a significant reduction of cold allodynia (p = 0.019), mechanical hyperalgesia (p = 0.040), and functional disability (p = 0.005) after LF-IS but not HF-IS. Mechanical allodynia only showed a tendency to decrease after LF-IS. The observed analgesic effects were reversed by opioid antagonist administration. CONCLUSION These results suggest a significant reversal of NP symptoms after LF-IS and offer additional evidence that IS might be beneficial in the treatment of resistant NP syndromes through endogenous opioid secretion. Relying on our novel epidural IS model, further fine tuning of stimulation parameters might be necessary to achieve optimal therapeutic effects.
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Affiliation(s)
- Fares Komboz
- Laboratory of Research in Neuroscience, Pôle Technologie Santé, Faculty of Medicine, Saint Joseph University of Beirut, Beirut, Lebanon
| | - Zeinab Mehsein
- Laboratory of Research in Neuroscience, Pôle Technologie Santé, Faculty of Medicine, Saint Joseph University of Beirut, Beirut, Lebanon
| | - Sandra Kobaïter-Maarrawi
- Laboratory of Research in Neuroscience, Pôle Technologie Santé, Faculty of Medicine, Saint Joseph University of Beirut, Beirut, Lebanon.
| | - Hiba-Douja Chehade
- Laboratory of Research in Neuroscience, Pôle Technologie Santé, Faculty of Medicine, Saint Joseph University of Beirut, Beirut, Lebanon
| | - Joseph Maarrawi
- Laboratory of Research in Neuroscience, Pôle Technologie Santé, Faculty of Medicine, Saint Joseph University of Beirut, Beirut, Lebanon; Department of Neurosurgery, Hôtel-Dieu de France Hospital, Beirut, Lebanon
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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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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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CB1-cannabinoid-, TRPV1-vanilloid- and NMDA-glutamatergic-receptor-signalling systems interact in the prelimbic cerebral cortex to control neuropathic pain symptoms. Brain Res Bull 2020; 165:118-128. [DOI: 10.1016/j.brainresbull.2020.09.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 08/20/2020] [Accepted: 09/16/2020] [Indexed: 12/28/2022]
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Sun Y, Wang J, Liang SH, Ge J, Lu YC, Li JN, Chen YB, Luo DS, Li H, Li YQ. Involvement of the Ventrolateral Periaqueductal Gray Matter-Central Medial Thalamic Nucleus-Basolateral Amygdala Pathway in Neuropathic Pain Regulation of Rats. Front Neuroanat 2020; 14:32. [PMID: 32792913 PMCID: PMC7394700 DOI: 10.3389/fnana.2020.00032] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Accepted: 05/28/2020] [Indexed: 11/27/2022] Open
Abstract
The central medial nucleus (CM), a prominent cell group of the intralaminar nuclei (ILN) of the thalamus, and the ventrolateral periaqueductal gray matter (vlPAG) are two major components of the medial pain system. Whether vlPAG and CM are input sources of nociceptive information to the basolateral amygdala (BLA) and whether they are involved in neuropathic pain regulation remain unclear. Clarifying the hierarchical organization of these subcortical nuclei (vlPAG, CM, and BLA) can enhance our understanding on the neural circuits for pain regulation. Behavioral test results showed that a CM lesion made by kainic acid (KA) injection could effectively alleviate mechanical hyperalgesia 4, 6, and 8 days after spared nerve injury (SNI) surgery, with the symptoms returning after 10 days. Morphological studies revealed that: (1) the CM received afferents from vlPAG and sent efferents to BLA, indicating that an indirect vlPAG–CM–BLA pathway exists; (2) such CM–BLA projections were primarily excitatory glutamatergic neurons as revealed by fluorescence in situ hybridization; (3) the fibers originated from the CM-formed close contacts with both excitatory and inhibitory neurons in the BLA; and (4) BLA-projecting CM neurons expressed Fos induced by SNI and formed close contacts with fibers from vlPAG, suggesting that the vlPAG–CM–BLA indirect pathway was activated in neuropathic pain conditions. Finally, the vlPAG–CM–BLA indirect pathway was further confirmed using anterograde and monosynaptic virus tracing investigation. In summary, our present results provide behavioral and morphological evidence that the indirect vlPAG–CM–BLA pathway might be a novel pain pathway involved in neuropathic pain regulation.
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Affiliation(s)
- Yi Sun
- Department of Human Anatomy, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Jian Wang
- Department of Cardiovascular Surgery, the General Hospital of Western Theater Command, Chengdu, China
| | - Shao-Hua Liang
- Department of Human Anatomy, Binzhou Medical University, Yantai, China
| | - Jun Ge
- Department of Anatomy, Histology and Embryology and K.K. Leung Brain Research Centre, Air Force Medical University, Xi'an, China
| | - Ya-Cheng Lu
- Department of Anatomy, Histology and Embryology and K.K. Leung Brain Research Centre, Air Force Medical University, Xi'an, China
| | - Jia-Ni Li
- Department of Anatomy, Histology and Embryology and K.K. Leung Brain Research Centre, Air Force Medical University, Xi'an, China
| | - Yan-Bing Chen
- Department of Human Anatomy, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Dao-Shu Luo
- Department of Human Anatomy, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Hui Li
- Department of Anatomy, Histology and Embryology and K.K. Leung Brain Research Centre, Air Force Medical University, Xi'an, China
| | - Yun-Qing Li
- Department of Human Anatomy, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China.,Department of Anatomy, Histology and Embryology and K.K. Leung Brain Research Centre, Air Force Medical University, Xi'an, China.,Key Laboratory of Brain Science Research and Transformation in Tropical Environment of Hainan Province, Haikou, China.,Department of Human Anatomy, College of Basic Medicine, Dali University, Dali, China
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Sun X, Pan X, Ni K, Ji C, Wu J, Yan C, Luo Y. Aberrant Thalamic-Centered Functional Connectivity in Patients with Persistent Somatoform Pain Disorder. Neuropsychiatr Dis Treat 2020; 16:273-281. [PMID: 32158212 PMCID: PMC6986177 DOI: 10.2147/ndt.s231555] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 01/11/2020] [Indexed: 12/26/2022] Open
Abstract
PURPOSE Recent task-based fMRI studies have shown that Persistent Somatoform Pain Disorder (PSPD) patients demonstrated aberrant activity in a wide range of brain regions associated with sensation, cognition and emotion. However, these specific task-based studies could not clearly uncover the alterations in the spontaneous brain networks that were associated with the general pain-related symptoms in PSPD. PATIENTS AND METHODS In the present study, 13 PSPD patients and 23 matched healthy controls (HCs) were enrolled. Resting state and 3D structural imaging data were collected during magnetic resonance imaging (MRI) scans. Ninety regions of interest (ROIs) were selected from the automated anatomical labeling (AAL) template. The functional connectivity toolbox "CONN" was used to calculate the functional connectivity (FC) coefficients. RESULTS Our results showed that PSPD patients exhibited increased FCs between the left thalamus and the right amygdala, the right hippocampus, and multiple sub-regions of the occipital lobe when compared to HCs. Correlation analysis revealed a negative correlation between the left thalamus-right amygdala FC and the level of anxiety in PSPD patients. CONCLUSION These findings suggest that the altered FC between thalamus and amygdala may be the neural mechanisms underlying the pain-related anxiety in PSPD.
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Affiliation(s)
- Xia Sun
- Department of Psychological Medicine, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China
| | - Xiandi Pan
- Shanghai Pudong New Area Mental Health Center, Tongji University School of Medicine, Shanghai, People's Republic of China
| | - Kaiji Ni
- Department of Psychological Medicine, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China
| | - Chenfeng Ji
- Department of Psychological Medicine, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China
| | - Jiaxin Wu
- Department of Psychiatry, Tongji Hospital of Tongji University, Shanghai, People's Republic of China
| | - Chao Yan
- Key Laboratory of Brain Functional Genomics (MOE&STCSM), Shanghai Changning-ECNU Mental Health Center, School of Psychology and Cognitive Science, East China Normal University, Shanghai, People's Republic of China
| | - Yanli Luo
- Department of Psychological Medicine, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China
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Pan P, Zhong J, Shang H, Zhu Y, Xiao P, Dai Z, Shi H. Quantitative meta-analysis of grey matter anomalies in neuropathic pain. Eur J Pain 2015; 19:1224-31. [PMID: 25708697 DOI: 10.1002/ejp.670] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/21/2014] [Indexed: 02/05/2023]
Affiliation(s)
- P.L. Pan
- Department of Neurology; Affiliated Yancheng Hospital of Southeast University; China
| | - J.G. Zhong
- Department of Neurology; Affiliated Yancheng Hospital of Southeast University; China
| | - H.F. Shang
- Department of Neurology; West China Hospital; Sichuan University; Chengdu China
| | - Y.L. Zhu
- Department of Neurology; Affiliated Yancheng Hospital of Southeast University; China
| | - P.R. Xiao
- Department of Neurology; Affiliated Yancheng Hospital of Southeast University; China
| | - Z.Y. Dai
- Department of Radiology; Affiliated Yancheng Hospital of Southeast University; China
| | - H.C. Shi
- Department of Neurology; Affiliated Yancheng Hospital of Southeast University; China
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9
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Yen CT, Lu PL. Thalamus and pain. ACTA ACUST UNITED AC 2013; 51:73-80. [DOI: 10.1016/j.aat.2013.06.011] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 05/13/2013] [Indexed: 02/02/2023]
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Pitcher GM, Ritchie J, Henry JL. Peripheral neuropathy induces cutaneous hypersensitivity in chronically spinalized rats. PAIN MEDICINE 2013; 14:1057-71. [PMID: 23855791 DOI: 10.1111/pme.12123] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND/OBJECTIVES The present study was aimed at the issue of whether peripheral nerve injury-induced chronic pain is maintained by supraspinal structures governing descending facilitation to the spinal dorsal horn, or whether altered peripheral nociceptive mechanisms sustain central hyperexcitability and, in turn, neuropathic pain. We examined this question by determining the contribution of peripheral/spinal mechanisms, isolated from supraspinal influence(s), in cutaneous hypersensitivity in an animal model of peripheral neuropathy. METHODS Adult rats were spinalized at T8-T9; 8 days later, peripheral neuropathy was induced by implanting a 2-mm polyethylene cuff around the left sciatic nerve. Hind paw withdrawal responses to mechanical or thermal plantar stimulation were evaluated using von Frey filaments or a heat lamp, respectively. RESULTS Spinalized rats without cuff implantation exhibited a moderate decrease in mechanical withdrawal threshold on ~day 10 (P < 0.05) and in thermal withdrawal threshold on ~day 18 (P < 0.05). However, cuff-implanted spinalized rats developed a more rapid and significant decrease in mechanical (~day 4; P < 0.001) and thermal (~day 10; P < 0.05) withdrawal thresholds that remained significantly decreased through the duration of the study. CONCLUSIONS Our findings demonstrate an aberrant peripheral/spinal mechanism that induces and maintains thermal and to a greater degree tactile cutaneous hypersensitivity in the cuff model of neuropathic pain, and raise the prospect that altered peripheral/spinal nociceptive mechanisms in humans with peripheral neuropathy may have a pathologically relevant role in both inducing and sustaining neuropathic pain.
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Affiliation(s)
- Graham M Pitcher
- Departments of Physiology and Psychiatry, McGill University, Montreal, Quebec, Canada.
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Benison AM, Chumachenko S, Harrison JA, Maier SF, Falci SP, Watkins LR, Barth DS. Caudal granular insular cortex is sufficient and necessary for the long-term maintenance of allodynic behavior in the rat attributable to mononeuropathy. J Neurosci 2011; 31:6317-28. [PMID: 21525272 PMCID: PMC3089761 DOI: 10.1523/jneurosci.0076-11.2011] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Revised: 03/02/2011] [Accepted: 03/09/2011] [Indexed: 12/22/2022] Open
Abstract
Mechanical allodynia, the perception of innocuous tactile stimulation as painful, is a severe symptom of chronic pain often produced by damage to peripheral nerves. Allodynia affects millions of people and remains highly resistant to classic analgesics and therapies. Neural mechanisms for the development and maintenance of allodynia have been investigated in the spinal cord, brainstem, thalamus, and forebrain, but manipulations of these regions rarely produce lasting effects. We found that long-term alleviation of allodynic manifestations is produced by discreetly lesioning a newly discovered somatosensory representation in caudal granular insular cortex (CGIC) in the rat, either before or after a chronic constriction injury of the sciatic nerve. However, CGIC lesions alone have no effect on normal mechanical stimulus thresholds. In addition, using electrophysiological techniques, we reveal a corticospinal loop that could be the anatomical source of the influence of CGIC on allodynia.
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Affiliation(s)
- Alexander M. Benison
- Department of Psychology and Neuroscience, University of Colorado, Boulder, Colorado 80309-0345
| | - Serhiy Chumachenko
- Department of Psychology and Neuroscience, University of Colorado, Boulder, Colorado 80309-0345
| | - Jacqueline A. Harrison
- Department of Psychology and Neuroscience, University of Colorado, Boulder, Colorado 80309-0345
| | - Steven F. Maier
- Department of Psychology and Neuroscience, University of Colorado, Boulder, Colorado 80309-0345
| | - Scott P. Falci
- Department of Psychology and Neuroscience, University of Colorado, Boulder, Colorado 80309-0345
| | - Linda R. Watkins
- Department of Psychology and Neuroscience, University of Colorado, Boulder, Colorado 80309-0345
| | - Daniel S. Barth
- Department of Psychology and Neuroscience, University of Colorado, Boulder, Colorado 80309-0345
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Tran TD, Wang H, Tandon A, Hernandez-Garcia L, Casey KL. Temporal summation of heat pain in humans: Evidence supporting thalamocortical modulation. Pain 2010; 150:93-102. [PMID: 20494516 DOI: 10.1016/j.pain.2010.04.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Revised: 03/21/2010] [Accepted: 04/05/2010] [Indexed: 12/29/2022]
Abstract
Noxious cutaneous contact heat stimuli (48 degrees C) are perceived as increasingly painful when the stimulus duration is extended from 5 to 10s, reflecting the temporal summation of central neuronal activity mediating heat pain. However, the sensation of increasing heat pain disappears, reaching a plateau as stimulus duration increases from 10 to 20s. We used functional magnetic resonance imaging (fMRI) in 10 healthy subjects to determine if active central mechanisms could contribute to this psychophysical plateau. During heat pain durations ranging from 5 to 20s, activation intensities in the bilateral orbitofrontal cortices and the activation volume in the left primary (S1) somatosensory cortex correlated only with perceived stimulus intensity and not with stimulus duration. Activation volumes increased with both stimulus duration and perceived intensity in the left lateral thalamus, posterior insula, inferior parietal cortex, and hippocampus. In contrast, during the psychophysical plateau, both the intensity and volume of thalamic and cortical activations in the right medial thalamus, right posterior insula, and left secondary (S2) somatosensory cortex continued to increase with stimulus duration but not with perceived stimulus intensity. Activation volumes in the left medial and right lateral thalamus, and the bilateral mid-anterior cingulate, left orbitofrontal, and right S2 cortices also increased only with stimulus duration. The increased activity of specific thalamic and cortical structures as stimulus duration, but not perceived intensity, increases is consistent with the recruitment of a thalamocortical mechanism that participates in the modulation of pain-related cortical responses and the temporal summation of heat pain.
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Affiliation(s)
- Tuan D Tran
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA Neurology Research Laboratory, VA Medical Center, Ann Arbor, MI 48105, USA Department of Pediatrics, University of Medicine and Pharmacy of Ho Chi Minh City, Ho Chi Minh City, Vietnam Medical School, University of Michigan, Ann Arbor, MI 48105, USA Department of Biomedical Engineering and Functional MRI Laboratory, University of Michigan, Ann Arbor, MI 48109, USA
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Spinal cord injuries containing asymmetrical damage in the ventrolateral funiculus is associated with a higher incidence of at-level allodynia. THE JOURNAL OF PAIN 2010; 11:864-75. [PMID: 20338826 DOI: 10.1016/j.jpain.2009.12.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Revised: 10/09/2009] [Accepted: 12/10/2009] [Indexed: 01/13/2023]
Abstract
UNLABELLED Approximately 70% of male rats receiving severe T8 spinal contusions develop allodynia in T5-7 dermatomes (at-level) beginning 2 weeks after injury. In contrast, rats having either complete transections or dorsal hemisections do not develop allodynia at-level after chronic spinal cord injury (SCI). In the present study, incomplete laceration and contusion injuries were made to test for neuroanatomical correlates between areas of white matter damage/sparing at the lesion epicenter and the presence/absence of allodynia. After incomplete laceration lesions and 6 weeks of behavioral testing, histological reconstruction and analysis of the lesion epicenters revealed a significant difference (P < .001) in the amount of ventrolateral funiculus (VLF) asymmetry between rats showing pain-like responses evoked by touch (74.5% +/- 8.4% side-to-side difference in VLF damage) versus those not responding to touch (11.3% +/- 4.4% side-to-side difference in VLF damage). A 5-week mean allodynia score for each rat that incorporates a full range of forces that are all innocuous in intact controls revealed that the degree of hypersensitivity at level is related to the extent of VLF asymmetry after SCI. No other damaged spinal white matter or gray matter area was correlated with sensitivity to touch. Similar findings were obtained for rats receiving T8 contusions, a more clinically relevant injury. These data suggest that different extents of damage/sparing between the 2 sides of VLF probably are a requisite for the development of allodynia after SCI. PERSPECTIVE A side-to-side lesion asymmetry after chronic SCI in a rodent model was found to be highly correlated with the presence and degree of allodynia. Greater insight of key factors contributing to the development and maintenance of chronic neuropathic pain is important for improving quality of life.
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Abstract
Hyperalgesia and allodynia are frequent symptoms of disease and may be useful adaptations to protect vulnerable tissues. Both may, however, also emerge as diseases in their own right. Considerable progress has been made in developing clinically relevant animal models for identifying the most significant underlying mechanisms. This review deals with experimental models that are currently used to measure (sect. II) or to induce (sect. III) hyperalgesia and allodynia in animals. Induction and expression of hyperalgesia and allodynia are context sensitive. This is discussed in section IV. Neuronal and nonneuronal cell populations have been identified that are indispensable for the induction and/or the expression of hyperalgesia and allodynia as summarized in section V. This review focuses on highly topical spinal mechanisms of hyperalgesia and allodynia including intrinsic and synaptic plasticity, the modulation of inhibitory control (sect. VI), and neuroimmune interactions (sect. VII). The scientific use of language improves also in the field of pain research. Refined definitions of some technical terms including the new definitions of hyperalgesia and allodynia by the International Association for the Study of Pain are illustrated and annotated in section I.
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Affiliation(s)
- Jürgen Sandkühler
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, Vienna, Austria
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Governing role of primary afferent drive in increased excitation of spinal nociceptive neurons in a model of sciatic neuropathy. Exp Neurol 2008; 214:219-28. [PMID: 18773893 DOI: 10.1016/j.expneurol.2008.08.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Revised: 07/31/2008] [Accepted: 08/10/2008] [Indexed: 01/07/2023]
Abstract
Previously we reported that the cuff model of peripheral neuropathy, in which a 2 mm polyethylene tube is implanted around the sciatic nerve, exhibits aspects of neuropathic pain behavior in rats similar to those in humans and causes robust hyperexcitation of spinal nociceptive dorsal horn neurons. The mechanisms mediating this increased excitation are not known and remain a key unresolved question in models of peripheral neuropathy. In anesthetized adult male Sprague-Dawley rats 2-6 weeks after cuff implantation we found that elevated discharge rate of single lumbar (L(3-4)) wide dynamic range (WDR) neurons persists despite acute spinal transection (T9) but is reversed by local conduction block of the cuff-implanted sciatic nerve; lidocaine applied distal to the cuff (i.e. between the cuff and the cutaneous receptive field) decreased spontaneous baseline discharge of WDR dorsal horn neurons approximately 40% (n=18) and when applied subsequently proximal to the cuff, i.e. between the cuff and the spinal cord, it further reduced spontaneous discharge by approximately 60% (n=19; P<0.05 proximal vs. distal) to a level that was not significantly different from that of naive rats. Furthermore, in cuff-implanted rats WDR neurons (n=5) responded to mechanical cutaneous stimulation with an exaggerated afterdischarge which was reversed entirely by proximal nerve conduction block. These results demonstrate that the hyperexcited state of spinal dorsal horn neurons observed in this model of peripheral neuropathy is not maintained by tonic descending facilitatory mechanisms. Rather, on-going afferent discharges originating from the sciatic nerve distal to, at, and proximal to the cuff maintain the synaptically-mediated gain in discharge of spinal dorsal horn WDR neurons and hyperresponsiveness of these neurons to cutaneous stimulation. Our findings reveal that ectopic afferent activity from multiple regions along peripheral nerves may drive CNS changes and the symptoms of pain associated with peripheral neuropathy.
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Nociceptive behavior in animal models for peripheral neuropathy: spinal and supraspinal mechanisms. Prog Neurobiol 2008; 86:22-47. [PMID: 18602968 DOI: 10.1016/j.pneurobio.2008.06.002] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Revised: 04/08/2008] [Accepted: 06/11/2008] [Indexed: 02/01/2023]
Abstract
Since the initial description by Wall [Wall, P.D., 1967. The laminar organization of dorsal horn and effects of descending impulses. J. Neurophysiol. 188, 403-423] of tonic descending inhibitory control of dorsal horn neurons, several studies have aimed to characterize the role of various brain centers in the control of nociceptive input to the spinal cord. The role of brainstem centers in pain inhibition has been well documented over the past four decades. Lesion to peripheral nerves results in hypersensitivity to mild tactile or cold stimuli (allodynia) and exaggerated response to nociceptive stimuli (hyperalgesia), both considered as cardinal signs of neuropathic pain. The increased interest in animal models for peripheral neuropathy has raised several questions concerning the rostral conduction of the neuropathic manifestations and the role of supraspinal centers, especially brainstem, in the inhibitory control or in the abnormal contribution to the maintenance and facilitation of neuropathic-like behavior. This review aims to summarize the data on the ascending and descending modulation of neuropathic manifestations and discusses the recent experimental data on the role of supraspinal centers in the control of neuropathic pain. In particular, the review emphasizes the importance of the reciprocal interconnections between the analgesic areas of the brainstem and the pain-related areas of the forebrain. The latter includes the cerebral limbic areas, the prefrontal cortex, the intralaminar thalamus and the hypothalamus and play a critical role in the control of pain considered as part of an integrated behavior related to emotions and various homeostatic regulations. We finally speculate that neuropathic pain, like extrapyramidal motor syndromes, reflects a disorder in the processing of somatosensory information.
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Saadé NE, Al Amin H, Abdel Baki S, Chalouhi S, Jabbur SJ, Atweh SF. Reversible attenuation of neuropathic-like manifestations in rats by lesions or local blocks of the intralaminar or the medial thalamic nuclei. Exp Neurol 2006; 204:205-19. [PMID: 17134698 DOI: 10.1016/j.expneurol.2006.10.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Revised: 10/18/2006] [Accepted: 10/23/2006] [Indexed: 11/29/2022]
Abstract
BACKGROUND AND AIM Thalamic somatosensory nuclei have been classified into medial and lateral systems based on their role in nociception. An imbalance between these two systems may result in abnormal somatic sensations and spontaneous pain. This study aims to investigate the effects of transient or permanent block of the medial and intralaminar nuclear groups on the neuropathic-like behavior in a rat model for mononeuropathy. METHODS Neuropathy was induced on one hind paw in different groups of rats following the spared nerve injury model. When the resulting hyperalgesia and allodynia (tactile and cold) reached a maximum plateau, the rats received either chemical or electrolytic lesion or lidocaine (2%) microperfusion, placed in the various thalamic nuclear groups. RESULTS All procedures produced transient but significant decrease of neuropathic manifestations. The magnitude and duration of decrease depended on the type and the site of the block. These effects can be ranked in increasing order as follows, electrolytic<chemical<lidocaine micro-perfusion according to the procedure, and as rostro-medial<ventro-median<parafascicular nuclei, according to the site of the block. Thermal hyperalgesia was the most affected while cold allodynia showed the least attenuation. Neuropathic manifestations returned to their pre-lesion levels after 2-3 weeks, along with frequently observed delayed hyper-responsiveness to the hotplate test. CONCLUSION The observed results demonstrate the involvement of the medial and intralaminar thalamic nuclei in the processing of neuropathic-like manifestations, and the reversibility of the effects suggests the flexibility of the neural network involved in supraspinal processing of nociceptive information.
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Affiliation(s)
- N E Saadé
- Department of Human Morphology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.
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Saadé NE, Al Amin H, Chalouhi S, Baki SA, Jabbur SJ, Atweh SF. Spinal pathways involved in supraspinal modulation of neuropathic manifestations in rats. Pain 2006; 126:280-93. [PMID: 16945485 DOI: 10.1016/j.pain.2006.07.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2006] [Revised: 06/21/2006] [Accepted: 07/17/2006] [Indexed: 11/22/2022]
Abstract
Controversial results have been recently reported on the role of supraspinal centers in the modulation of nociceptive behavior in animal models of mononeuropathy. Our aim was to investigate the role of the various spinal pathways in the modulation of the neuropathic manifestations. Several groups of rats were subjected to selective spinal-tract lesions, either 2-3 weeks before or 2-3 weeks after the induction of mononeuropathy following the chronic constriction injury (CCI) or the spared nerve injury (SNI) models. Tactile and cold allodynias were assessed by Von Frey filaments and the acetone drops test, respectively. Thermal hyperalgesia was assessed by the paw withdrawal and the hot plate tests. The effects of unilateral and bilateral lesions of the dorso-lateral funiculus (DLF), the anterolateral column (ALC) or hemisection were tested over a period of 4-8 weeks. All spinal tract lesions produced reversible, but significant decrease of allodynia and hyperalgesia over a period of 1-3 weeks. The most pronounced effects were observed with bilateral lesions. The stronger attenuation was observed on thermal hyperalgesia, assessed by the paw withdrawal test, while cold allodynia was the least affected. Spinal lesions performed before the induction of neuropathy did not produce significant alterations in the temporal development of neuropathic manifestations. The present results allow the conclusion that all spinal tracts can be involved in the rostral transmission and the descending modulation of neuropathic manifestations. The recovery of symptoms following spinal lesions provides illustration on the plasticity of the neural network involved in the processing of the neuropathic syndromes.
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Affiliation(s)
- Nayef E Saadé
- Department of Human Morphology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.
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