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Warfield AE, Gupta P, Ruhmann MM, Jeffs QL, Guidone GC, Rhymes HW, Thompson MI, Todd WD. A brainstem to circadian system circuit links Tau pathology to sundowning-related disturbances in an Alzheimer's disease mouse model. Nat Commun 2023; 14:5027. [PMID: 37596279 PMCID: PMC10439113 DOI: 10.1038/s41467-023-40546-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 07/26/2023] [Indexed: 08/20/2023] Open
Abstract
Alzheimer's disease (AD) patients exhibit progressive disruption of entrained circadian rhythms and an aberrant circadian input pathway may underlie such dysfunction. Here we examine AD-related pathology and circadian dysfunction in the APPSwe-Tau (TAPP) model of AD. We show these mice exhibit phase delayed body temperature and locomotor activity with increases around the active-to-rest phase transition. Similar AD-related disruptions are associated with sundowning, characterized by late afternoon and early evening agitation and aggression, and we show TAPP mice exhibit increased aggression around this transition. We show such circadian dysfunction and aggression coincide with hyperphosphorylated Tau (pTau) development in lateral parabrachial (LPB) neurons, with these disturbances appearing earlier in females. Finally, we show LPB neurons, including those expressing dynorphin (LPBdyn), project to circadian structures and are affected by pTau, and LPBdyn ablations partially recapitulate the hyperthermia of TAPP mice. Altogether we link pTau in a brainstem circadian input pathway to AD-related disturbances relevant to sundowning.
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Affiliation(s)
- Andrew E Warfield
- Department of Zoology and Physiology, Program in Neuroscience, University of Wyoming, Laramie, WY, USA
| | - Pooja Gupta
- Department of Zoology and Physiology, Program in Neuroscience, University of Wyoming, Laramie, WY, USA
| | - Madison M Ruhmann
- Department of Zoology and Physiology, Program in Neuroscience, University of Wyoming, Laramie, WY, USA
| | - Quiana L Jeffs
- Department of Zoology and Physiology, Program in Neuroscience, University of Wyoming, Laramie, WY, USA
| | - Genevieve C Guidone
- Department of Zoology and Physiology, Program in Neuroscience, University of Wyoming, Laramie, WY, USA
| | - Hannah W Rhymes
- Department of Zoology and Physiology, Program in Neuroscience, University of Wyoming, Laramie, WY, USA
| | - McKenzi I Thompson
- Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, USA
| | - William D Todd
- Department of Zoology and Physiology, Program in Neuroscience, University of Wyoming, Laramie, WY, USA.
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Warfield AE, Prather JF, Todd WD. Systems and Circuits Linking Chronic Pain and Circadian Rhythms. Front Neurosci 2021; 15:705173. [PMID: 34276301 PMCID: PMC8284721 DOI: 10.3389/fnins.2021.705173] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 06/10/2021] [Indexed: 12/15/2022] Open
Abstract
Research over the last 20 years regarding the link between circadian rhythms and chronic pain pathology has suggested interconnected mechanisms that are not fully understood. Strong evidence for a bidirectional relationship between circadian function and pain has been revealed through inflammatory and immune studies as well as neuropathic ones. However, one limitation of many of these studies is a focus on only a few molecules or cell types, often within only one region of the brain or spinal cord, rather than systems-level interactions. To address this, our review will examine the circadian system as a whole, from the intracellular genetic machinery that controls its timing mechanism to its input and output circuits, and how chronic pain, whether inflammatory or neuropathic, may mediate or be driven by changes in these processes. We will investigate how rhythms of circadian clock gene expression and behavior, immune cells, cytokines, chemokines, intracellular signaling, and glial cells affect and are affected by chronic pain in animal models and human pathologies. We will also discuss key areas in both circadian rhythms and chronic pain that are sexually dimorphic. Understanding the overlapping mechanisms and complex interplay between pain and circadian mediators, the various nuclei they affect, and how they differ between sexes, will be crucial to move forward in developing treatments for chronic pain and for determining how and when they will achieve their maximum efficacy.
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Affiliation(s)
| | | | - William D. Todd
- Program in Neuroscience, Department of Zoology and Physiology, University of Wyoming, Laramie, WY, United States
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4
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Functional MRI of the Reserpine-Induced Putative Rat Model of Fibromyalgia Reveals Discriminatory Patterns of Functional Augmentation to Acute Nociceptive Stimuli. Sci Rep 2017; 7:38325. [PMID: 28079057 PMCID: PMC5228122 DOI: 10.1038/srep38325] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 11/08/2016] [Indexed: 11/23/2022] Open
Abstract
Functional neuroimaging, applied to pre-clinical models of chronic pain, offers unique advantages in the drive to discover new treatments for this prevalent and oppressive condition. The high spatial and temporal resolution of fMRI affords detailed mapping of regional pharmacodynamics that underlie mechanisms of pain suppression by new analgesics. Despite evidence supporting the translational relevance of this approach, relatively few studies have investigated fMRI abnormalities in rodent models of chronic pain. In this study, we used fMRI to map the BOLD response in a recently developed putative rat model of fibromyalgia to innocuous and acute nociceptive stimuli by applying a step-wise graded electrical forepaw stimulation paradigm, with comparison to healthy controls. We observed discriminatory functional signatures (p < 0.001) to 2 mA electrical forepaw stimulation, found to be innocuous in the control group. As such, this translational approach provides sensitive and quantitative neural correlates of the underlying chronic disease. The regional patterns of functional augmentation were found to be concordant with previous studies of nociception in the anaesthetised rat brain, supporting the specificity of this approach in the study of altered central pain processing in reserpine induced myalgia. The methodology introduced in this work represents a novel platform for emerging treatment evaluation in highly experimentally controlled conditions.
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Asad ABA, Seah S, Baumgartner R, Feng D, Jensen A, Manigbas E, Henry B, Houghton A, Evelhoch JL, Derbyshire SWG, Chin CL. Distinct BOLD fMRI Responses of Capsaicin-Induced Thermal Sensation Reveal Pain-Related Brain Activation in Nonhuman Primates. PLoS One 2016; 11:e0156805. [PMID: 27309348 PMCID: PMC4911046 DOI: 10.1371/journal.pone.0156805] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2015] [Accepted: 05/18/2016] [Indexed: 01/05/2023] Open
Abstract
Background Approximately 20% of the adult population suffer from chronic pain that is not adequately treated by current therapies, highlighting a great need for improved treatment options. To develop effective analgesics, experimental human and animal models of pain are critical. Topically/intra-dermally applied capsaicin induces hyperalgesia and allodynia to thermal and tactile stimuli that mimics chronic pain and is a useful translation from preclinical research to clinical investigation. Many behavioral and self-report studies of pain have exploited the use of the capsaicin pain model, but objective biomarker correlates of the capsaicin augmented nociceptive response in nonhuman primates remains to be explored. Methodology Here we establish an aversive capsaicin-induced fMRI model using non-noxious heat stimuli in Cynomolgus monkeys (n = 8). BOLD fMRI data were collected during thermal challenge (ON:20 s/42°C; OFF:40 s/35°C, 4-cycle) at baseline and 30 min post-capsaicin (0.1 mg, topical, forearm) application. Tail withdrawal behavioral studies were also conducted in the same animals using 42°C or 48°C water bath pre- and post- capsaicin application (0.1 mg, subcutaneous, tail). Principal Findings Group comparisons between pre- and post-capsaicin application revealed significant BOLD signal increases in brain regions associated with the ‘pain matrix’, including somatosensory, frontal, and cingulate cortices, as well as the cerebellum (paired t-test, p<0.02, n = 8), while no significant change was found after the vehicle application. The tail withdrawal behavioral study demonstrated a significant main effect of temperature and a trend towards capsaicin induced reduction of latency at both temperatures. Conclusions These findings provide insights into the specific brain regions involved with aversive, ‘pain-like’, responses in a nonhuman primate model. Future studies may employ both behavioral and fMRI measures as translational biomarkers to gain deeper understanding of pain processing and evaluate the preclinical efficacy of novel analgesics.
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Affiliation(s)
- Abu Bakar Ali Asad
- Translational Biomarkers, Merck Research Laboratories, MSD, Singapore, Singapore
- * E-mail:
| | - Stephanie Seah
- Translational Biomarkers, Merck Research Laboratories, MSD, Singapore, Singapore
| | - Richard Baumgartner
- Biometrics Research, Biostatistics & Research Decision Sciences, Merck Research Laboratories, Merck & Co., Rahway, NJ, United States of America
| | - Dai Feng
- Biometrics Research, Biostatistics & Research Decision Sciences, Merck Research Laboratories, Merck & Co., Rahway, NJ, United States of America
| | - Andres Jensen
- Early Discovery Pharmacology, Merck Research Laboratories, MSD, Singapore, Singapore
| | | | - Brian Henry
- Early Discovery Pharmacology, Merck Research Laboratories, MSD, Singapore, Singapore
| | - Andrea Houghton
- Early Discovery Pharmacology, Merck Research Laboratories, Merck & Co., West Point, PA, United States of America
| | - Jeffrey L. Evelhoch
- Translational Biomarkers, Merck Research Laboratories, Merck & Co., West Point, PA, United States of America
| | - Stuart W. G. Derbyshire
- Dept of Psychology, National University of Singapore, Singapore, Singapore
- A*STAR-NUS Clinical Imaging Research Centre, Singapore, Singapore
| | - Chih-Liang Chin
- Translational Biomarkers, Merck Research Laboratories, MSD, Singapore, Singapore
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Abaei M, Sagar DR, Stockley EG, Spicer CH, Prior M, Chapman V, Auer DP. Neural correlates of hyperalgesia in the monosodium iodoacetate model of osteoarthritis pain. Mol Pain 2016; 12:12/0/1744806916642445. [PMID: 27068285 PMCID: PMC4956384 DOI: 10.1177/1744806916642445] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 03/07/2016] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND The mechanisms driving osteoarthritic pain remain poorly understood, but there is increasing evidence for a role of the central nervous system in the chronification of pain. We used functional magnetic resonance imaging to investigate the influence of a model of unilateral knee osteoarthritis on nociceptive processing. RESULTS Four to five weeks post intra-articular injection of monosodium iodoacetate (MIA, 1 mg) into the left knee, Sprague Dawley rats were anesthetized for functional magnetic resonance imaging studies to characterize the neural response to a noxious stimulus (intra-articular capsaicin injection). In a two-arm cross-over design, 5 µM/50 µl capsaicin was injected into either the left knee (n = 8, CAPS-MIA) or right control knee (n = 8, CAPS-CON), preceded by contralateral vehicle (SAL) injection. To assess neural correlates of mechanical hyperalgesia, hindpaws were stimulated with von Frey hairs (8 g: MIA; 15 g: control knee, based on behavioral withdrawal responses). The CAPS-MIA group exhibited significant activation of the periaqueductal gray, unilateral thalamus and bilateral mensencephalon, superior-colliculus, and hippocampus, with no significant activation in the other groups/conditions. Capsaicin injection increased functional connectivity in the mid-brain network and mediodorsal thalamic nucleus, hippocampus, and globus pallidus, which was significantly stronger in CAPS-MIA compared to CAPS-CON groups. Mechanical stimulation of the hyperalgesic (ipsilateral to MIA knee) and normalgesic (contralateral) hindpaws evoked qualitatively different brain activation with more widespread brainstem and anterior cingulate (ACC) activation when stimulating the hyperalgesic paw, and clearer frontal sensory activation from the normalgesic paw. CONCLUSIONS We provide evidence for modulation of nociceptive processing in a chronic knee osteoarthritis pain model with stronger brain activation and alteration of brain networks induced by the pro-nociceptive stimulus. We also report a shift to a medial pain activation pattern following stimulation of the hyperalgesic hindpaw. Taken together, our data support altered neural pain processing as a result of peripheral and central pain sensitization in this model.
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Affiliation(s)
- Maryam Abaei
- Radiological Sciences, Division of Clinical Neuroscience, University of Nottingham, Nottingham, UK
| | - Devi R Sagar
- Arthritis Research UK Pain Centre, University of Nottingham, Nottingham, UK School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Elizabeth G Stockley
- Arthritis Research UK Pain Centre, University of Nottingham, Nottingham, UK School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Clare H Spicer
- School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Malcolm Prior
- Medical Imaging Unit, School of Medicine, University of Nottingham, Nottingham, UK
| | - Victoria Chapman
- Arthritis Research UK Pain Centre, University of Nottingham, Nottingham, UK School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Dorothee P Auer
- Radiological Sciences, Division of Clinical Neuroscience, University of Nottingham, Nottingham, UK Arthritis Research UK Pain Centre, University of Nottingham, Nottingham, UK Medical Imaging Unit, School of Medicine, University of Nottingham, Nottingham, UK
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Maracle EC, Hung LY, Fell SI, Osmond MR, Brown SHM, Srbely JZ. A Comparison of the Sensitivity of Brush Allodynia and Semmes-Weinstein Monofilament Testing in the Detection of Allodynia Within Regions of Secondary Hyperalgesia in Humans. Pain Pract 2016; 17:16-24. [PMID: 26936430 DOI: 10.1111/papr.12418] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 10/22/2015] [Indexed: 01/04/2023]
Abstract
BACKGROUND Two of the most common Quantitative Sensory Techniques (QST) employed to detect allodynia include mechanical brush allodynia and Semmes-Weinstein monofilaments. However, their relative sensitivity at detecting allodynia is poorly understood. The purpose of this study was to compare the sensitivity of brush allodynia against Semmes-Weinstein monofilament technique for detecting allodynia within regions of secondary hyperalgesia in humans. METHODS Twenty subjects (10 males, 10 females; 21.1 ± 0.9 years) were recruited and randomly allocated to allodynia or monofilament groups. Topical capsaicin (Zostrix 0.075%) was applied to a target region defined by C4-C7 dermatomes. Allodynia testing was performed at 0- (baseline) and 10 minutes postcapsaicin. The Semmes-Weinstein group assessed changes in skin sensitivity 8 cm inferior to target region and 2 cm lateral to the spinous process, while brush allodynia was employed to detect the point inferior to the target region where subjects reported changes in skin sensitivity. The distance (cm) from this point to the inferior border of the target region was termed the Allodynia Score. RESULTS Statistically significant increases in the Allodynia Score were observed at 10 minutes postcapsaicin compared to baseline (P < 0.001). No differences in monofilament scores were observed between 10 minutes postcapsaicin and baseline (P = 0.125). Brush allodynia also demonstrated superior sensitivity, detecting allodynia in 100% of cases compared to 60% in the Semmes-Weinstein group. CONCLUSION Brush allodynia is more sensitive than Semmes-Weinstein monofilaments for detecting mechanical allodynia in regions of secondary hyperalgesia. Brush allodynia may be preferred over Semmes-Weinstein monofilaments for clinical applications requiring reliable detection of allodynia.
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Affiliation(s)
- Emmalee C Maracle
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Laurie Y Hung
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Sabrina I Fell
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Michael R Osmond
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Stephen H M Brown
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - John Z Srbely
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
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Amirmohseni S, Segelcke D, Reichl S, Wachsmuth L, Görlich D, Faber C, Pogatzki-Zahn E. Characterization of incisional and inflammatory pain in rats using functional tools of MRI. Neuroimage 2016; 127:110-122. [DOI: 10.1016/j.neuroimage.2015.11.052] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 11/04/2015] [Accepted: 11/23/2015] [Indexed: 02/07/2023] Open
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Yee JR, Kenkel W, Caccaviello JC, Gamber K, Simmons P, Nedelman M, Kulkarni P, Ferris CF. Identifying the integrated neural networks involved in capsaicin-induced pain using fMRI in awake TRPV1 knockout and wild-type rats. Front Syst Neurosci 2015; 9:15. [PMID: 25745388 PMCID: PMC4333803 DOI: 10.3389/fnsys.2015.00015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 01/31/2015] [Indexed: 12/18/2022] Open
Abstract
In the present study, we used functional MRI in awake rats to investigate the pain response that accompanies intradermal injection of capsaicin into the hindpaw. To this end, we used BOLD imaging together with a 3D segmented, annotated rat atlas and computational analysis to identify the integrated neural circuits involved in capsaicin-induced pain. The specificity of the pain response to capsaicin was tested in a transgenic model that contains a biallelic deletion of the gene encoding for the transient receptor potential cation channel subfamily V member 1 (TRPV1). Capsaicin is an exogenous ligand for the TRPV1 receptor, and in wild-type rats, activated the putative pain neural circuit. In addition, capsaicin-treated wild-type rats exhibited activation in brain regions comprising the Papez circuit and habenular system, systems that play important roles in the integration of emotional information, and learning and memory of aversive information, respectively. As expected, capsaicin administration to TRPV1-KO rats failed to elicit the robust BOLD activation pattern observed in wild-type controls. However, the intradermal injection of formalin elicited a significant activation of the putative pain pathway as represented by such areas as the anterior cingulate, somatosensory cortex, parabrachial nucleus, and periaqueductal gray. Notably, comparison of neural responses to capsaicin in wild-type vs. knock-out rats uncovered evidence that capsaicin may function in an antinociceptive capacity independent of TRPV1 signaling. Our data suggest that neuroimaging of pain in awake, conscious animals has the potential to inform the neurobiological basis of full and integrated perceptions of pain.
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Affiliation(s)
- Jason R Yee
- Center for Translational NeuroImaging, Department of Psychology, Northeastern University Boston, MA, USA
| | - William Kenkel
- Center for Translational NeuroImaging, Department of Psychology, Northeastern University Boston, MA, USA
| | - John C Caccaviello
- Center for Translational NeuroImaging, Department of Psychology, Northeastern University Boston, MA, USA
| | | | | | | | - Praveen Kulkarni
- Center for Translational NeuroImaging, Department of Psychology, Northeastern University Boston, MA, USA
| | - Craig F Ferris
- Center for Translational NeuroImaging, Department of Psychology, Northeastern University Boston, MA, USA
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Andrade DC, Borges I, Bravo GL, Bolognini N, Fregni F. Therapeutic time window of noninvasive brain stimulation for pain treatment: inhibition of maladaptive plasticity with early intervention. Expert Rev Med Devices 2014; 10:339-52. [PMID: 23668706 DOI: 10.1586/erd.12.90] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Neuromodulatory effects of noninvasive brain stimulation (NIBS) have been extensively studied in chronic disorders such as major depression, chronic pain and stroke. However, few studies have explored the use of these techniques in acute conditions. A possible use of NIBS in acute disorders is to prevent or reverse ongoing maladaptive plastic alterations, seemingly responsible for treatment refractoriness and detrimental behavioral changes. In this review, the authors discuss the potential role of NIBS in blocking maladaptive plasticity using the transition of acute to chronic pain in conditions such as postsurgical pain, central poststroke pain, pain after spinal cord injury and pain after traumatic brain injury as a model. The authors also present suggestions for clinical trial design using NIBS in the acute stage of illnesses.
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Affiliation(s)
- Dafne C Andrade
- Laboratory of Neuromodulation, Spaulding Rehabilitation Hospital, 125 Nashua Street 727, Boston, MA 02114, USA
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Tsurugizawa T, Nogusa Y, Ando Y, Uneyama H. Different TRPV1-mediated brain responses to intragastric infusion of capsaicin and capsiate. Eur J Neurosci 2013; 38:3628-35. [PMID: 24102723 DOI: 10.1111/ejn.12365] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 07/24/2013] [Accepted: 08/25/2013] [Indexed: 12/20/2022]
Abstract
Capsaicin and capsiate, which is an analogue of capsaicin, are agonists of capsaicin-binding transient potential vanilloid 1 (TRPV1) receptors. However, their physiological effects are different. Capsaicin induces thermogenesis and nociception, while the different kinetics of capsiate result in thermogenesis without nociception in the oral cavity. In the present study, using functional magnetic resonance imaging, we compared the brain activation after intragastric infusion of non-nociceptive levels of capsaicin and capsiate in wild-type and TRPV1-knockout (KO) mice. Capsaicin activated several brain regions, such as the periaqueductal grey (PAG), thalamic nuclei and hypothalamus, including the medial preoptic area (mPOA) and ventromedial hypothalamus (VMH). Most of these areas were not activated in TRPV1-KO mice. Capsiate activated several regions, including the thalamic nuclei, mPOA and VMH but not PAG in wild-type mice. Most of the activated areas were not activated by intragastric capsiate infusion in TRPV1-KO mice. These results demonstrate that TRPV1 is critical for the induction of activation in the hypothalamus by capsaicin and capsiate, and these distinct brain activations could help to explain the individual physiological reactions of capsaicin and capsiate.
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Affiliation(s)
- Tomokazu Tsurugizawa
- Institute for Innovation, Ajinomoto Co., Inc., Suzuki-cho 1-1, Kawasaki-ku, Kawasaki, 210-8601, Japan
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Cortright DN, Matson DJ, Broom DC. New frontiers in assessing pain and analgesia in laboratory animals. Expert Opin Drug Discov 2013; 3:1099-108. [PMID: 23506182 DOI: 10.1517/17460441.3.9.1099] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Translating promising analgesic compounds into reliable pain therapeutics in humans is made particularly challenging by the difficulty in measuring the pain quantitatively. This problem is manifest not only in clinical settings in which patient pain assessments involve mostly subjective measures but also in preclinical settings wherein laboratory animals, most commonly rodents, are typically evaluated in stimulus-evoked response tests. OBJECTIVE Given the limitations of traditional pain tests, we sought out new approaches to measure pain, and analgesia, in laboratory animals. METHODS We reviewed the peer reviewed literature to identify pain tests that could be utilized in preclinical settings to understand the effects of new and established analgesics. RESULTS/CONCLUSIONS The tests identified include weight bearing differential, suppression of feeding, reduction in locomotor activity, gait analysis, conditioning models and functional MRI. Although the pharmacology of known and new analgesics has not been broadly established in these models, they hold the promise of better predictive utility for the discovery of pain relievers.
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O'Neill J, Brock C, Olesen AE, Andresen T, Nilsson M, Dickenson AH. Unravelling the mystery of capsaicin: a tool to understand and treat pain. Pharmacol Rev 2013; 64:939-71. [PMID: 23023032 DOI: 10.1124/pr.112.006163] [Citation(s) in RCA: 220] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
A large number of pharmacological studies have used capsaicin as a tool to activate many physiological systems, with an emphasis on pain research but also including functions such as the cardiovascular system, the respiratory system, and the urinary tract. Understanding the actions of capsaicin led to the discovery its receptor, transient receptor potential (TRP) vanilloid subfamily member 1 (TRPV1), part of the superfamily of TRP receptors, sensing external events. This receptor is found on key fine sensory afferents, and so the use of capsaicin to selectively activate pain afferents has been exploited in animal studies, human psychophysics, and imaging studies. Its effects depend on the dose and route of administration and may include sensitization, desensitization, withdrawal of afferent nerve terminals, or even overt death of afferent fibers. The ability of capsaicin to generate central hypersensitivity has been valuable in understanding the consequences and mechanisms behind enhanced central processing of pain. In addition, capsaicin has been used as a therapeutic agent when applied topically, and antagonists of the TRPV1 receptor have been developed. Overall, the numerous uses for capsaicin are clear; hence, the rationale of this review is to bring together and discuss the different types of studies that exploit these actions to shed light upon capsaicin working both as a tool to understand pain but also as a treatment for chronic pain. This review will discuss the various actions of capsaicin and how it lends itself to these different purposes.
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Affiliation(s)
- Jessica O'Neill
- Neuroscience, Physiology and Pharmacology, University College London, London.
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14
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Hayes DJ, Northoff G. Common brain activations for painful and non-painful aversive stimuli. BMC Neurosci 2012; 13:60. [PMID: 22676259 PMCID: PMC3464596 DOI: 10.1186/1471-2202-13-60] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Accepted: 04/18/2012] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Identification of potentially harmful stimuli is necessary for the well-being and self-preservation of all organisms. However, the neural substrates involved in the processing of aversive stimuli are not well understood. For instance, painful and non-painful aversive stimuli are largely thought to activate different neural networks. However, it is presently unclear whether there is a common aversion-related network of brain regions responsible for the basic processing of aversive stimuli. To help clarify this issue, this report used a cross-species translational approach in humans (i.e. meta-analysis) and rodents (i.e. systematic review of functional neuroanatomy). RESULTS Animal and human data combined to show a core aversion-related network, consisting of similar cortical (i.e. MCC, PCC, AI, DMPFC, RTG, SMA, VLOFC; see results section or abbreviation section for full names) and subcortical (i.e. Amyg, BNST, DS, Hab, Hipp/Parahipp, Hyp, NAc, NTS, PAG, PBN, raphe, septal nuclei, Thal, LC, midbrain) regions. In addition, a number of regions appeared to be more involved in pain-related (e.g. sensory cortex) or non-pain-related (e.g. amygdala) aversive processing. CONCLUSIONS This investigation suggests that aversive processing, at the most basic level, relies on similar neural substrates, and that differential responses may be due, in part, to the recruitment of additional structures as well as the spatio-temporal dynamic activity of the network. This network perspective may provide a clearer understanding of why components of this circuit appear dysfunctional in some psychiatric and pain-related disorders.
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Affiliation(s)
- Dave J Hayes
- Mind, Brain Imaging and Neuroethics Research Unit, Institute of Mental Health Research, University of Ottawa, 1145 Carling Avenue, Ottawa, K1Z 7K4, Canada
| | - Georg Northoff
- Mind, Brain Imaging and Neuroethics Research Unit, Institute of Mental Health Research, University of Ottawa, 1145 Carling Avenue, Ottawa, K1Z 7K4, Canada
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15
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Thompson SJ, Bushnell MC. Rodent functional and anatomical imaging of pain. Neurosci Lett 2012; 520:131-9. [PMID: 22445887 DOI: 10.1016/j.neulet.2012.03.015] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 03/06/2012] [Accepted: 03/07/2012] [Indexed: 02/07/2023]
Abstract
Human brain imaging has provided much information about pain processing and pain modulation, but brain imaging in rodents can provide information not attainable in human studies. First, the short lifespan of rats and mice, as well as the ability to have homogenous genetics and environments, allows for longitudinal studies of the effects of chronic pain on the brain. Second, brain imaging in animals allows for the testing of central actions of novel pharmacological and nonpharmacological analgesics before they can be tested in humans. The two most commonly used brain imaging methods in rodents are magnetic resonance imaging (MRI) and positron emission tomography (PET). MRI provides better spatial and temporal resolution than PET, but PET allows for the imaging of neurotransmitters and non-neuronal cells, such as astrocytes, in addition to functional imaging. One problem with rodent brain imaging involves methods for keeping the subject still in the scanner. Both anesthetic agents and restraint techniques have potential confounds. Some PET methods allow for tracer uptake before the animal is anesthetized, but imaging a moving animal also has potential confounds. Despite the challenges associated with the various techniques, the 31 studies using either functional MRI or PET to image pain processing in rodents have yielded surprisingly consistent results, with brain regions commonly activated in human pain imaging studies (somatosensory cortex, cingulate cortex, thalamus) also being activated in the majority of these studies. Pharmacological imaging in rodents shows overlapping activation patterns with pain and opiate analgesics, similar to what is found in humans. Despite the many structural imaging studies in human chronic pain patients, only one study has been performed in rodents, but that study confirmed human findings of decreased cortical thickness associated with chronic pain. Future directions in rodent pain imaging include miniaturized PET for the freely moving animal, as well as new MRI techniques that enable ongoing chronic pain imaging.
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Affiliation(s)
- Scott J Thompson
- Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC H3A 2T5, Canada
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Zhao F, Welsh D, Williams M, Coimbra A, Urban MO, Hargreaves R, Evelhoch J, Williams DS. fMRI of pain processing in the brain: a within-animal comparative study of BOLD vs. CBV and noxious electrical vs. noxious mechanical stimulation in rat. Neuroimage 2011; 59:1168-79. [PMID: 21856430 DOI: 10.1016/j.neuroimage.2011.08.002] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Revised: 07/01/2011] [Accepted: 08/02/2011] [Indexed: 11/19/2022] Open
Abstract
This study aims to identify fMRI signatures of nociceptive processing in whole brain of anesthetized rats during noxious electrical stimulation (NES) and noxious mechanical stimulation (NMS) of paw. Activation patterns for NES were mapped with blood oxygen level dependent (BOLD) and cerebral blood volume (CBV) fMRI, respectively, to investigate the spatially-dependent hemodynamic responses during nociception processing. A systematic evaluation of fMRI responses to varying frequencies of electrical stimulus was carried out to optimize the NES protocol. Both BOLD and CBV fMRI showed widespread activations, but with different spatial characteristics. While BOLD and CBV showed well-localized activations in ipsilateral dorsal column nucleus, contralateral primary somatosensory cortex (S1), and bilateral caudate putamen (CPu), CBV fMRI showed additional bilateral activations in the regions of pons, midbrain and thalamus compared to BOLD fMRI. CBV fMRI that offers higher sensitivity compared to BOLD was then used to compare the nociception processing during NES and NMS in the same animal. The activations in most regions were similar. In the medulla, however, NES induced a robust activation in the ipsilateral dorsal column nucleus while NMS showed no activation. This study demonstrates that (1) the hemodynamic response to nociception is spatial-dependent; (2) the widespread activations during nociception in CBV fMRI are similar to what have been observed in (14)C-2-deoxyglucose (2DG) autoradiography and PET; (3) the bilateral activations in the brain originate from the divergence of neural responses at supraspinal level; and (4) the similarity of activation patterns suggests that nociceptive processing in rats is similar during NES and NMS.
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Affiliation(s)
- Fuqiang Zhao
- Imaging Department, Merck Research Laboratories, West Point, PA 19486, USA.
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Mazzanti ML, Walvick RP, Zhou X, Sun Y, Shah N, Mansour J, Gereige J, Albert MS. Distribution of hyperpolarized xenon in the brain following sensory stimulation: preliminary MRI findings. PLoS One 2011; 6:e21607. [PMID: 21789173 PMCID: PMC3137603 DOI: 10.1371/journal.pone.0021607] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Accepted: 06/03/2011] [Indexed: 11/18/2022] Open
Abstract
In hyperpolarized xenon magnetic resonance imaging (HP (129)Xe MRI), the inhaled spin-1/2 isotope of xenon gas is used to generate the MR signal. Because hyperpolarized xenon is an MR signal source with properties very different from those generated from water-protons, HP (129)Xe MRI may yield structural and functional information not detectable by conventional proton-based MRI methods. Here we demonstrate the differential distribution of HP (129)Xe in the cerebral cortex of the rat following a pain stimulus evoked in the animal's forepaw. Areas of higher HP (129)Xe signal corresponded to those areas previously demonstrated by conventional functional MRI (fMRI) methods as being activated by a forepaw pain stimulus. The percent increase in HP (129)Xe signal over baseline was 13-28%, and was detectable with a single set of pre and post stimulus images. Recent innovations in the production of highly polarized (129)Xe should make feasible the emergence of HP (129)Xe MRI as a viable adjunct method to conventional MRI for the study of brain function and disease.
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Affiliation(s)
- Mary L. Mazzanti
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Ronn P. Walvick
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Xin Zhou
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- Wuhan Center for Magnetic Resonance, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China
| | - Yanping Sun
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- Lurie Family Imaging Center, Center for Biomedical Imaging in Oncology, Dana Farber Cancer Institute, Massachusetts, United States of America
| | - Niral Shah
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Joey Mansour
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jessica Gereige
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Mitchell S. Albert
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- Thunder Bay Regional Research Institute, Thunder Bay, Ontario, Canada
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Holschneider DP, Bradesi S, Mayer EA. The role of experimental models in developing new treatments for irritable bowel syndrome. Expert Rev Gastroenterol Hepatol 2011; 5:43-57. [PMID: 21309671 PMCID: PMC3124306 DOI: 10.1586/egh.10.88] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Irritable bowel syndrome (IBS) is characterized by chronic, recurrent abdominal pain and altered bowel habits and is currently defined by symptom criteria and the absence of detectable organic disease. The underlying pathophysiology remains incompletely understood. Despite considerable efforts by the scientific community and the pharmaceutical industry to develop novel pharmacological treatments aimed at chronic visceral pain, the traditional approach to identifying and evaluating novel drugs for this target have largely failed to translate into effective IBS treatments. However, several novel drugs aimed at normalizing bowel movements have produced clinical effects, not only on the primary target, but also on pain and discomfort. While some of the commonly used experimental animal models for the pain dimension of IBS have some face and construct validity, the predictive validity of most of the models is either unknown, or has been disappointing. A reverse translational approach is proposed, which is based on identification and characterization of brain endophenotypes in patients, followed by translation of these endophenotypes for pharmacological studies in rodent models.
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Affiliation(s)
- Daniel P Holschneider
- VA Greater Los Angeles Healthcare System, LA, CA, USA,Departments of Psychiatry and the Behavioral Sciences, Neurology, Cell & Neurobiology, Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
| | - Sylvie Bradesi
- VA Greater Los Angeles Healthcare System, LA, CA, USA,UCLA Center for Neurobiology of Stress, Departments of Medicine, Physiology and Psychiatry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90024, USA,Author for correspondence:
| | - Emeran A Mayer
- VA Greater Los Angeles Healthcare System, LA, CA, USA,UCLA Center for Neurobiology of Stress, Departments of Medicine, Physiology and Psychiatry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90024, USA
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CNS activation maps in awake rats exposed to thermal stimuli to the dorsum of the hindpaw. Neuroimage 2011; 54:1355-66. [DOI: 10.1016/j.neuroimage.2010.08.056] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Revised: 08/19/2010] [Accepted: 08/21/2010] [Indexed: 01/08/2023] Open
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CNS animal fMRI in pain and analgesia. Neurosci Biobehav Rev 2010; 35:1125-43. [PMID: 21126534 DOI: 10.1016/j.neubiorev.2010.11.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Revised: 11/22/2010] [Accepted: 11/23/2010] [Indexed: 11/22/2022]
Abstract
Animal imaging of brain systems offers exciting opportunities to better understand the neurobiology of pain and analgesia. Overall functional studies have lagged behind human studies as a result of technical issues including the use of anesthesia. Now that many of these issues have been overcome including the possibility of imaging awake animals, there are new opportunities to study whole brain systems neurobiology of acute and chronic pain as well as analgesic effects on brain systems de novo (using pharmacological MRI) or testing in animal models of pain. Understanding brain networks in these areas may provide new insights into translational science, and use neural networks as a "language of translation" between preclinical to clinical models. In this review we evaluate the role of functional and anatomical imaging in furthering our understanding in pain and analgesia.
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Central sensitization: a generator of pain hypersensitivity by central neural plasticity. THE JOURNAL OF PAIN 2009; 10:895-926. [PMID: 19712899 DOI: 10.1016/j.jpain.2009.06.012] [Citation(s) in RCA: 2235] [Impact Index Per Article: 149.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2009] [Revised: 06/08/2009] [Accepted: 06/08/2009] [Indexed: 02/08/2023]
Abstract
UNLABELLED Central sensitization represents an enhancement in the function of neurons and circuits in nociceptive pathways caused by increases in membrane excitability and synaptic efficacy as well as to reduced inhibition and is a manifestation of the remarkable plasticity of the somatosensory nervous system in response to activity, inflammation, and neural injury. The net effect of central sensitization is to recruit previously subthreshold synaptic inputs to nociceptive neurons, generating an increased or augmented action potential output: a state of facilitation, potentiation, augmentation, or amplification. Central sensitization is responsible for many of the temporal, spatial, and threshold changes in pain sensibility in acute and chronic clinical pain settings and exemplifies the fundamental contribution of the central nervous system to the generation of pain hypersensitivity. Because central sensitization results from changes in the properties of neurons in the central nervous system, the pain is no longer coupled, as acute nociceptive pain is, to the presence, intensity, or duration of noxious peripheral stimuli. Instead, central sensitization produces pain hypersensitivity by changing the sensory response elicited by normal inputs, including those that usually evoke innocuous sensations. PERSPECTIVE In this article, we review the major triggers that initiate and maintain central sensitization in healthy individuals in response to nociceptor input and in patients with inflammatory and neuropathic pain, emphasizing the fundamental contribution and multiple mechanisms of synaptic plasticity caused by changes in the density, nature, and properties of ionotropic and metabotropic glutamate receptors.
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Central representation of cold-evoked pain relief in capsaicin induced pain: An event-related fMRI study. Pain 2008; 139:416-430. [DOI: 10.1016/j.pain.2008.05.020] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2007] [Revised: 05/15/2008] [Accepted: 05/21/2008] [Indexed: 11/20/2022]
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Jones KL, Finn DP, Governo RJM, Prior MJ, Morris PG, Kendall DA, Marsden CA, Chapman V. Identification of discrete sites of action of chronic treatment with desipramine in a model of neuropathic pain. Neuropharmacology 2008; 56:405-13. [PMID: 18930746 DOI: 10.1016/j.neuropharm.2008.09.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2008] [Revised: 09/11/2008] [Accepted: 09/12/2008] [Indexed: 12/19/2022]
Abstract
Tricyclic antidepressants (TCAs) are an important analgesic treatment for neuropathic pain, though the neural substrates mediating these effects are poorly understood. We have used an integrative approach combining behavioural pharmacology with functional magnetic resonance imaging (fMRI) to investigate the effects of chronic treatment with the TCA desipramine, on touch-evoked pain (mechanical allodynia) and brain regional activity in the selective spinal nerve ligation (SNL) model of neuropathic pain. SNL and sham-operated rats received once daily i.p. administration of 10 mg/kg DMI, or saline, for 14 days. Withdrawal responses to the application of a normally non-noxious (10 g) stimulus were recorded in SNL and sham-operated rats over this period. On the final day of the study, SNL and sham-operated rats received a final challenge dose of DMI (10 mg/kg i.p.) during fMRI scanning. Chronic administration of desipramine (DMI) significantly attenuated mechancial allodynia in SNL rats. DMI challenge in chronic DMI-treated neuropathic rats produced significantly greater activation of the deep mesencephalic nucleus, primary somatosensory cortex, insular cortex, medial globus pallidus, inferior colliculus, perirhinal cortex and cerebellum compared to sham-operated rats and saline controls. By contrast, the spatial pattern of brain regional activation by chronic DMI treatment in sham controls encompassed a number of other areas including those associated with learning and memory processes. These novel findings identify key brain regions implicated in the analgesic and mood altering effects associated with chronic treatment with DMI.
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Affiliation(s)
- K L Jones
- Institute of Neuroscience, School of Biomedical Sciences, University of Nottingham, Nottingham NG7 2UH, UK
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Endo T, Spenger C, Hao J, Tominaga T, Wiesenfeld-Hallin Z, Olson L, Xu XJ. Functional MRI of the brain detects neuropathic pain in experimental spinal cord injury. Pain 2008; 138:292-300. [DOI: 10.1016/j.pain.2007.12.017] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2007] [Revised: 12/21/2007] [Accepted: 12/21/2007] [Indexed: 11/16/2022]
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Abstract
Lateral Heschl's gyrus (HG), a subdivision of the human auditory cortex, is commonly believed to represent a general “pitch center,” responding selectively to the pitch of sounds, irrespective of their spectral characteristics. However, most neuroimaging investigations have used only one specialized pitch-evoking stimulus: iterated-ripple noise (IRN). The present study used a novel experimental design in which a range of different pitch-evoking stimuli were presented to the same listeners. Pitch sites were identified by searching for voxels that responded well to the range of pitch-evoking stimuli. The first result suggested that parts of the planum temporale are more relevant for pitch processing than lateral HG. In some listeners, pitch responses occurred elsewhere, such as the temporo-parieto-occipital junction or prefrontal cortex. The second result demonstrated a different pattern of response to the IRN and raises the possibility that features of IRN unrelated to pitch might contribute to the earlier results. In conclusion, it seems premature to assign special status to lateral HG solely on the basis of neuroactivation patterns. Further work should consider the functional roles of these multiple pitch processing sites within the proposed network.
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Affiliation(s)
- Deborah A Hall
- MRC Institute of Hearing Research, University Park, Nottingham, UK.
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Borsook D, Bleakman D, Hargreaves R, Upadhyay J, Schmidt KF, Becerra L. A 'BOLD' experiment in defining the utility of fMRI in drug development. Neuroimage 2008; 42:461-6. [PMID: 18598770 DOI: 10.1016/j.neuroimage.2008.04.268] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Revised: 04/09/2008] [Accepted: 04/17/2008] [Indexed: 10/22/2022] Open
Affiliation(s)
- David Borsook
- Imaging Consortium for Drug Development, Brain Imaging Center, McLean Hospital, Belmont, USA.
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Gabapentin evoked changes in functional activity in nociceptive regions in the brain of the anaesthetized rat: an fMRI study. Br J Pharmacol 2008; 153:1558-67. [PMID: 18264121 DOI: 10.1038/bjp.2008.27] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE Gabapentin (GBP; 1-(aminomethyl)cyclohexane acetic acid) is used clinically in the treatment of pain. Nevertheless, the sites and mechanisms of action of GBP are poorly defined. Herein, the effects of GBP on brain activation have been studied. EXPERIMENTAL APPROACH Changes in blood oxygen level dependent (BOLD) haemodynamic signal following intravenous infusion of GBP (equivalent to 30 mg kg(-1) p.o., followed by 100 mg kg(-1) p.o.), compared to saline control, were studied in isofluorane anaesthetized rats (n=8 per group). Effects of GBP on mean arterial blood pressure (MAP) were also recorded. RESULTS Random effect analysis revealed that the lower dose of GBP produced significant (P<0.001) increases in BOLD signal intensity in several brain regions, including the thalamus and periaqueductal grey (PAG), compared to basal. This dose of GBP also produced significant (P<0.001) decreases in BOLD signal intensity in the amygdala and the entorhinal cortex. Increasing the dose of GBP (100 mg kg(-1)) produced significantly greater changes in BOLD signal intensity in several brain regions including the thalamus and PAG. MAP was not significantly altered by GBP, compared to saline. CONCLUSIONS AND IMPLICATIONS GBP had marked positive and negative effects on BOLD signal intensity in a number of brain regions in naïve rats. The activation of key areas involved in nociceptive processing indicate a supraspinal site of action of GBP and this may contribute to its well-described analgesic effects in animal models of pain and clinical studies.
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Schneider G, Ständer S, Burgmer M, Driesch G, Heuft G, Weckesser M. Significant differences in central imaging of histamine-induced itch between atopic dermatitis and healthy subjects. Eur J Pain 2008; 12:834-41. [PMID: 18203636 DOI: 10.1016/j.ejpain.2007.12.003] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Revised: 11/13/2007] [Accepted: 12/05/2007] [Indexed: 11/16/2022]
Abstract
BACKGROUND/AIM This is the first investigation of the central processing of itch in the brain in 8 subjects with atopic dermatitis (AD) in comparison to 6 healthy controls (HC), comparing histamine-induced itch related activations in the frontal, prefrontal, parietal, cingulate cortex, thalamus, basal ganglia and cerebellum. METHODS We employed 1% histamine-dihydrochlorid-iontophoresis of the left hand, recorded H2(15)O-PET-scans and perception of itch intensity on a numeric rating scale. RESULTS There was no significant difference in perceived itch intensity between AD and HC. Significant increase in rCBF was found in HC in the contralateral somatosensory and motor cortex, midcingulate gyrus, and ipsilateral prefrontal cortex; in AD: in the contralateral thalamus, somatosensory, motor and prefrontal cortex and cerebellum, in the ipsilateral precentral, prefrontal, orbitofrontal cortex, insula, pallidum and cerebellum. More brain sites were activated in AD than in HC. Activation in AD was significantly higher in the contralateral thalamus, ipsilateral caudate and pallidum. CONCLUSIONS We interpret our findings as possible central correlates of changes in the motor system in subjects with chronic itch, with activation of the basal ganglia possibly correlating to the vicious itch-scratch-circle in subjects with chronic itching skin diseases. However, further neuroimaging studies in healthy subjects and also in different skin diseases are needed to understand the complex mechanisms of the processing of itch.
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Affiliation(s)
- Gudrun Schneider
- Department of Psychosomatics and Psychotherapy, University of Münster, Domagkstr. 22, D-48149 Münster, Germany.
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Shih YYI, Chen YY, Chen CCV, Chen JC, Chang C, Jaw FS. Whole-brain functional magnetic resonance imaging mapping of acute nociceptive responses induced by formalin in rats using atlas registration-based event-related analysis. J Neurosci Res 2008; 86:1801-11. [DOI: 10.1002/jnr.21638] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Governo RJM, Prior MJW, Morris PG, Marsden CA, Chapman V. Validation of an automated punctate mechanical stimuli delivery system designed for fMRI studies in rodents. J Neurosci Methods 2007; 163:31-7. [PMID: 17368787 DOI: 10.1016/j.jneumeth.2007.02.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Accepted: 02/11/2007] [Indexed: 10/23/2022]
Abstract
Functional magnetic resonance imaging (fMRI) is increasingly being used for animal studies studying the transmission of nociceptive information. Application of noxious mechanical stimuli is widely used for animal and human assessment of pain processing. Any accessory hardware used in animal imaging studies must, however, be sufficiently small to fit in the magnet bore diameter and be non-magnetic. We have developed a system that can apply mechanical stimuli simultaneously with fMRI. This system consists of a standardized instrument to deliver mechanical stimuli (VonFrey monofilament) and a gas-pressured mechanical transducer. These components were integrated with a computer console that controlled the period of stimuli to match acquisition scans. Preliminary experiments demonstrated that the force-stimulus transducer did not influence MRI signal to noise ratio. Mechanical stimulation of the hindpaw significantly increased blood oxygen level dependent (BOLD) signal intensity in several midbrain regions involved in the processing of nociceptive information in the rat (p<0.001, uncorrected for multiple comparisons). This system can be applied to both animal and human imaging studies and has a wide range of applications for studies of nociceptive processing.
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