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Genaro K, Prado WA. The role of the anterior pretectal nucleus in pain modulation: A comprehensive review. Eur J Neurosci 2021; 54:4358-4380. [PMID: 33909941 DOI: 10.1111/ejn.15255] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 04/16/2021] [Accepted: 04/18/2021] [Indexed: 11/27/2022]
Abstract
Descending pain modulation involves multiple encephalic sites and pathways that range from the cerebral cortex to the spinal cord. Behavioral studies conducted in the 1980s revealed that electrical stimulation of the pretectal area causes antinociception dissociation from aversive responses. Anatomical and physiological studies identified the anterior pretectal nucleus and its descending projections to several midbrain, pontine, and medullary structures. The anterior pretectal nucleus is morphologically divided into a dorsal part that contains a dense neuron population (pars compacta) and a ventral part that contains a dense fiber band network (pars reticulata). Connections of the two anterior pretectal nucleus parts are broad and include prominent projections to and from major encephalic systems associated with somatosensory processes. Since the first observation that acute or chronic noxious stimuli activate the anterior pretectal nucleus, it has been established that numerous mediators participate in this response through distinct pathways. Recent studies have confirmed that at least two pain inhibitory pathways are activated from the anterior pretectal nucleus. This review focuses on rodent anatomical, behavioral, molecular, and neurochemical data that have helped to identify mediators of the anterior pretectal nucleus and pathways related to its role in pain modulation.
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Affiliation(s)
- Karina Genaro
- Department of Anesthesiology, University of California, Irvine, CA, USA
| | - Wiliam A Prado
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
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Roles of prefrontal cortex and paraventricular thalamus in affective and mechanical components of visceral nociception. Pain 2016; 156:2479-2491. [PMID: 26262826 DOI: 10.1097/j.pain.0000000000000318] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Visceral pain represents a major clinical challenge in the management of many gastrointestinal disorders, eg, pancreatitis. However, cerebral neurobiological mechanisms underlying visceral nociception are poorly understood. As a representative model of visceral nociception, we applied cerulein hyperstimulation in C57BL6 mice to induce acute pancreatitis and performed a behavioral test battery and c-Fos staining of brains. We observed a specific pain phenotype and a significant increase in c-Fos immunoreactivity in the paraventricular nucleus of the thalamus (PVT), the periaqueductal gray, and the medial prefrontal cortex (mPFC). Using neuronal tracing, we observed projections of the PVT to cortical layers of the mPFC with contacts to inhibitory GABAergic neurons. These inhibitory neurons showed more activation after cerulein treatment suggesting thalamocortical "feedforward inhibition" in visceral nociception. The activity of neurons in pancreatitis-related pain centers was pharmacogenetically modulated by designer receptors exclusively activated by designer drugs, selectively and cell type specifically expressed in target neurons using adeno-associated virus-mediated gene transfer. Pharmacogenetic inhibition of PVT but not periaqueductal gray neurons attenuated visceral pain and induced an activation of the descending inhibitory pain pathway. Activation of glutamatergic principle neurons in the mPFC, but not inhibitory neurons, also reversed visceral nociception. These data reveal novel insights into central pain processing that underlies visceral nociception and may trigger the development of novel, potent centrally acting analgesic drugs.
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Hubbard CS, Karpowicz JM, Furman AJ, da Silva JT, Seminowicz DA, Traub RJ. Estrogen-dependent visceral hypersensitivity following stress in rats: An fMRI study. Mol Pain 2016; 12:12/0/1744806916654145. [PMID: 27317579 PMCID: PMC4956385 DOI: 10.1177/1744806916654145] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 05/11/2016] [Indexed: 12/17/2022] Open
Abstract
We used functional MRI and a longitudinal design to investigate the brain mechanisms in a previously reported estrogen-dependent visceral hypersensitivity model. We hypothesized that noxious visceral stimulation would be associated with activation of the insula, anterior cingulate cortex, and amygdala, and that estrogen-dependent, stress-induced visceral hypersensitivity would both enhance activation of these regions and recruit activation of other brain areas mediating affect and reward processing. Ovariectomized rats were treated with estrogen (17 β-estradiol, E2) or vehicle (n = 5 per group) and scanned in a 7T MRI at three different time points: pre-stress (baseline), 2 days post-stress, and 18 days post-stress. Stress was induced via a forced-swim paradigm. In a separate group of ovariectomized rats, E2 treatment induced visceral hypersensitivity at the 2 days post-stress time point, and this hypersensitivity returned to baseline at the 18 days post-stress time point. Vehicle-treated rats show no hypersensitivity following stress. During the MRI scans, rats were exposed to noxious colorectal distention. Across groups and time points, noxious visceral stimulation led to activations in the insula, anterior cingulate, and left amygdala, parabrachial nuclei, and cerebellum. A group-by-time interaction was seen in the right amygdala, ventral striatum-pallidum, cerebellum, hippocampus, mediodorsal thalamus, and pontine nuclei. Closer inspection of the data revealed that vehicle-treated rats showed consistent activations and deactivations across time, whereas estrogen-treated animals showed minimal deactivation with noxious visceral stimulation. This unexpected finding suggests that E2 may dramatically alter visceral nociceptive processing in the brain following an acute stressor. This study is the first to examine estrogen-stress dependent interactions in response to noxious visceral stimulation using functional MRI. Future studies that include other control groups and larger sample sizes are needed to fully understand the interactions between sex hormones, stress, and noxious stimulation on brain activity.
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Affiliation(s)
- Catherine S Hubbard
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA Center for Pain and the Brain, Department of Anesthesiology, Perioperative and Pain Medicine, Boston Children's Hospital, Boston, MA, USA Department of Anaesthesia, Harvard Medical School, Boston, MA, USA
| | - Jane M Karpowicz
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA
| | - Andrew J Furman
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA
| | - Joyce Teixeira da Silva
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA Department of Anaesthesia, Harvard Medical School, Boston, MA, USA Department of Anatomy, Institute of Biomedical Science-III, University of Sao Paulo, Sao Paulo, Brazil
| | - David A Seminowicz
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA Center to Advance Chronic Pain Research, University of Maryland, Baltimore, MD, USA
| | - Richard J Traub
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA Center to Advance Chronic Pain Research, University of Maryland, Baltimore, MD, USA
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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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Reis GM, Fais RS, Prado WA. The antinociceptive effect of stimulating the retrosplenial cortex in the rat tail-flick test but not in the formalin test involves the rostral anterior cingulate cortex. Pharmacol Biochem Behav 2015; 131:112-8. [DOI: 10.1016/j.pbb.2015.02.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 02/02/2015] [Accepted: 02/06/2015] [Indexed: 10/24/2022]
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A systematic review of the evidence for central nervous system plasticity in animal models of inflammatory-mediated gastrointestinal pain. Inflamm Bowel Dis 2014; 20:176-95. [PMID: 24284415 DOI: 10.1097/01.mib.0000437499.52922.b1] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Abdominal pain frequently accompanies inflammatory disorders of the gastrointestinal tract (GIT), and animal models of GIT inflammation have been developed to explore the role of the central nervous system (CNS) in this process. Here, we summarize the evidence from animal studies for CNS plasticity following GIT inflammation. METHODS A systematic review was conducted to identify studies that: (1) used inflammation of GIT organs, (2) assessed pain or visceral hypersensitivity, and (3) presented evidence of CNS involvement. Two hundred and eight articles were identified, and 79 were eligible for analysis. RESULTS Rats were most widely used (76%). Most studies used adult animals (42%) with a bias toward males (74%). Colitis was the most frequently used model (78%) and 2,4,6-trinitrobenzenesulfonic acid the preferred inflammatory agent (33%). Behavioral (58%), anatomical/molecular (44%), and physiological (24%) approaches were used alone or in combination to assess CNS involvement during or after GIT inflammation. Measurement times varied widely (<1 h-> 2 wk after inflammation). Blinded outcomes were used in 42% studies, randomization in 10%, and evidence of visceral inflammation in 54%. Only 3 studies fulfilled our criteria for high methodological quality, and no study reported sample size calculations. CONCLUSIONS The included studies provide strong evidence for CNS plasticity following GIT inflammation, specifically in the spinal cord dorsal horn. This evidence includes altered visceromotor responses and indices of referred pain, elevated neural activation and peptide content, and increased neuronal excitability. This evidence supports continued use of this approach for preclinical studies; however, there is substantial scope to improve study design.
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Projections from the insular cortex to pain-receptive trigeminal caudal subnucleus (medullary dorsal horn) and other lower brainstem areas in rats. Neuroscience 2013; 233:9-27. [DOI: 10.1016/j.neuroscience.2012.12.024] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 12/13/2012] [Accepted: 12/17/2012] [Indexed: 11/18/2022]
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Suzuki H, Sumiyoshi A, Kawashima R, Shimokawa H. Different brain activation under left and right ventricular stimulation: an fMRI study in anesthetized rats. PLoS One 2013; 8:e56990. [PMID: 23451129 PMCID: PMC3579932 DOI: 10.1371/journal.pone.0056990] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 01/16/2013] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Myocardial ischemia in the anterior wall of the left ventricule (LV) and in the inferior wall and/or right ventricle (RV) shows different manifestations that can be explained by the different innervations of cardiac afferent nerves. However, it remains unclear whether information from different areas of the heart, such as the LV and RV, are differently processed in the brain. In this study, we investigated the brain regions that process information from the LV or RV using cardiac electrical stimulation and functional magnetic resonance imaging (fMRI) in anesthetized rats because the combination of these two approaches cannot be used in humans. METHODOLOGY/PRINCIPAL FINDINGS An electrical stimulation catheter was inserted into the LV or RV (n = 12 each). Brain fMRI scans were recorded during LV or RV stimulation (9 Hz and 0.3 ms width) over 10 blocks consisting of alternating periods of 2 mA for 30 sec followed by 0.2 mA for 60 sec. The validity of fMRI signals was confirmed by first and second-level analyses and temporal profiles. Increases in fMRI signals were observed in the anterior cingulate cortex and the right somatosensory cortex under LV stimulation. In contrast, RV stimulation activated the right somatosensory cortex, which was identified more anteriorly compared with LV stimulation but did not activate the anterior cingulate cortex. CONCLUSION/SIGNIFICANCE This study provides the first evidence for differences in brain activation under LV and RV stimulation. These different brain processes may be associated with different clinical manifestations between anterior wall and inferoposterior wall and/or RV myocardial ischemia.
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Affiliation(s)
- Hideaki Suzuki
- Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan.
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Pais-Vieira M, Aguiar P, Lima D, Galhardo V. Inflammatory pain disrupts the orbitofrontal neuronal activity and risk-assessment performance in a rodent decision-making task. Pain 2012; 153:1625-1635. [DOI: 10.1016/j.pain.2012.04.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 04/10/2012] [Accepted: 04/10/2012] [Indexed: 11/28/2022]
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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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Coffeenl U, Ortega-Legaspil JM, López-Muñozl FJ, Simón-Arceol K, Jaimesl O, Pellicerl F. Insular cortex lesion diminishes neuropathic and inflammatory pain-like behaviours. Eur J Pain 2012; 15:132-8. [DOI: 10.1016/j.ejpain.2010.06.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Revised: 05/27/2010] [Accepted: 06/06/2010] [Indexed: 10/19/2022]
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González-Pardo H, Conejo N, Lana G, Arias J. Different brain networks underlying the acquisition and expression of contextual fear conditioning: a metabolic mapping study. Neuroscience 2012; 202:234-42. [DOI: 10.1016/j.neuroscience.2011.11.064] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 11/28/2011] [Accepted: 11/28/2011] [Indexed: 01/17/2023]
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Rossaneis AC, Reis GM, Prado WA. Stimulation of the occipital or retrosplenial cortex reduces incision pain in rats. Pharmacol Biochem Behav 2011; 100:220-7. [DOI: 10.1016/j.pbb.2011.08.024] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Revised: 08/26/2011] [Accepted: 08/29/2011] [Indexed: 10/17/2022]
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Staahl C, Krarup AL, Olesen AE, Brock C, Graversen C, Drewes AM. Is Electrical Brain Activity a Reliable Biomarker for Opioid Analgesia in the Gut? Basic Clin Pharmacol Toxicol 2011; 109:321-7. [DOI: 10.1111/j.1742-7843.2011.00727.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Yang PF, Chen DY, Hu JW, Chen JH, Yen CT. Functional tracing of medial nociceptive pathways using activity-dependent manganese-enhanced MRI. Pain 2011; 152:194-203. [DOI: 10.1016/j.pain.2010.10.027] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2009] [Revised: 10/09/2010] [Accepted: 10/20/2010] [Indexed: 11/30/2022]
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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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Ji G, Neugebauer V. Reactive oxygen species are involved in group I mGluR-mediated facilitation of nociceptive processing in amygdala neurons. J Neurophysiol 2010; 104:218-29. [PMID: 20463194 DOI: 10.1152/jn.00223.2010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent biochemical and behavioral data implicate reactive oxygen species (ROS) in peripheral and spinal pain mechanisms. However, pain-related functions of ROS in the brain and mechanisms of pain-related ROS activation remain to be determined. Our previous studies showed that the amygdala plays a key role in emotional-affective pain responses and pain modulation. Hyperactivity of amygdala neurons in an animal pain model depends on group I metabotropic glutamate receptors (subtypes mGluR1 and mGluR5), but their signaling pathway remains to be determined. Here we tested the hypothesis that activation of group I mGluRs increases nociceptive processing in amygdala neurons through a mechanism that involves ROS. Extracellular single-unit recordings were made from neurons in the laterocapsular division of the central nucleus of the amygdala (CeLC) in anesthetized adult male rats. Administration of a group I mGluR agonist (DHPG) into the CeLC by microdialysis increased the responses to innocuous and noxious somatosensory (knee joint compression) and visceral (colorectal distention [CRD]) stimuli. A ROS scavenger (PBN) and a superoxide dismutase mimetic (TEMPOL) reversed the facilitatory effects of DHPG. An mGluR5 antagonist (MPEP) also inhibited the effects of DHPG on the responses to innocuous and noxious somatosensory and visceral stimuli, whereas an mGluR1 antagonist (LY367385) decreased only the responses to visceral stimulation. The results show for the first time that ROS mediate group I mGluR-induced facilitation of nociceptive processing in amygdala neurons. The antagonist data may suggest differential contributions of subtypes mGluR1 and mGluR5 to the processing of somatosensory and visceral nociceptive information in the amygdala.
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Affiliation(s)
- Guangchen Ji
- Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, Texas 77555-1069, USA
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Tai C, Wang J, Jin T, Wang P, Kim SG, Roppolo JR, de Groat WC. Brain switch for reflex micturition control detected by FMRI in rats. J Neurophysiol 2009; 102:2719-30. [PMID: 19741099 DOI: 10.1152/jn.00700.2009] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The functions of the lower urinary tract are controlled by complex pathways in the brain that act like switching circuits to voluntarily or reflexly shift the activity of various pelvic organs (bladder, urethra, urethral sphincter, and pelvic floor muscles) from urine storage to micturition. In this study, functional magnetic resonance imaging (fMRI) was used to visualize the brain switching circuits controlling reflex micturition in anesthetized rats. The fMRI images confirmed the hypothesis based on previous neuroanatomical and neurophysiological studies that the brain stem switch for reflex micturition control involves both the periaqueductal gray (PAG) and the pontine micturition center (PMC). During storage, the PAG was activated by afferent input from the urinary bladder while the PMC was inactive. When bladder volume increased to the micturition threshold, the switch from storage to micturition was associated with PMC activation and enhanced PAG activity. A complex brain network that may regulate the brain stem micturition switch and control storage and voiding was also identified. Storage was accompanied by activation of the motor cortex, somatosensory cortex, cingulate cortex, retrosplenial cortex, thalamus, putamen, insula, and septal nucleus. On the other hand, micturition was associated with: 1) increased activity of the motor cortex, thalamus, and putamen; 2) a shift in the locus of activity in the cingulate and insula; and 3) the emergence of activity in the hypothalamus, substantia nigra, globus pallidus, hippocampus, and inferior colliculus. Understanding brain control of reflex micturition is important for elucidating the mechanisms underlying neurogenic bladder dysfunctions including frequency, urgency, and incontinence.
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Affiliation(s)
- Changfeng Tai
- Department of Urology, University of Pittsburgh, 700 Kaufmann Building, Pittsburgh, PA 15213, USA.
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Ren Y, Zhang L, Lu Y, Yang H, Westlund KN. Central lateral thalamic neurons receive noxious visceral mechanical and chemical input in rats. J Neurophysiol 2009; 102:244-58. [PMID: 19369360 DOI: 10.1152/jn.90985.2008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Thalamic intralaminar and medial nuclei participate mainly in affective and motivational aspects of pain processing. Unique to the present study were identification and characterization of spontaneously active neurons in the central lateral nucleus (CL) of the intralaminar thalamus, which were found to respond only to viscerally evoked noxious stimuli in animals under pentobarbital anesthesia. Responses to noxious colorectal distention, intrapancreatic bradykinin, intraperitoneal dilute acetic acid, and greater splanchnic nerve electrical stimulation were characterized. Electrophysiological recordings revealed activity in most CL neurons (93%) was excited (69%) or inhibited (31%) in response to noxious visceral stimulation of visceral nerves. Expression of c-Fos observed in CL nucleus after intensive visceral stimulation confirmed the activation. However, excited CL neurons did not have somatic fields, except in 3 of 43 (7%) CL neurons tested for responses to somatic stimulation (innocuous brush and noxious pinch). Intrathecal administration of morphine significantly reduced the increased responses of CL neurons to colorectal and pancreatic stimuli and was naloxone reversible. High-level thoracic midline dorsal column (DC) myelotomy also dramatically reduced responses, identifying the DC as a major route of travel from the spinal cord for CL input, in addition to input traveling ventromedially in the spinothalamic tract identified anatomically in a previous study. Spinal cord and lower brain stem cells providing input to medial thalamus were mapped after stereotaxic injections of a retrograde dye. These data combined with our previous data suggest that the CL nucleus is an important component of a medial visceral nociceptive system that may mediate attentional, affective, endocrine, motor, and autonomic responses to noxious visceral stimuli.
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Affiliation(s)
- Yong Ren
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX, USA
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