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Abstract
Pain has a strong emotional component and is defined by its unpleasantness. Chronic pain represents a complex disorder with anxio-depressive symptoms and cognitive deficits. Underlying mechanisms are still not well understood but an important role for interactions between prefrontal cortical areas and subcortical limbic structures has emerged. Evidence from preclinical studies in the rodent brain suggests that neuroplastic changes in prefrontal (anterior cingulate, prelimbic and infralimbic) cortical and subcortical (amygdala and nucleus accumbens) brain areas and their interactions (corticolimbic circuitry) contribute to the complexity and persistence of pain and may be predetermining factors as has been proposed in recent human neuroimaging studies.
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Affiliation(s)
- Jeremy M Thompson
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, School of Medicine, Lubbock, TX, United States
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, School of Medicine, Lubbock, TX, United States; Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX, United States.
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52
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Li JN, Sheets PL. The central amygdala to periaqueductal gray pathway comprises intrinsically distinct neurons differentially affected in a model of inflammatory pain. J Physiol 2018; 596:6289-6305. [PMID: 30281797 DOI: 10.1113/jp276935] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 09/19/2018] [Indexed: 01/15/2023] Open
Abstract
KEY POINTS The central nucleus of the amygdala (CeA) encompasses the main output pathways of the amygdala, a temporal lobe structure essential in affective and cognitive dimensions of pain. A major population of neurons in the CeA send projections to the periaqueductal gray (PAG), a key midbrain structure that mediates coping strategies in response to threat or stress. CeA-PAG neurons are topographically organized based on their targeted subregion within the PAG. PAG-projecting neurons in the central medial (CeM) and central lateral (CeL) regions of CeA are intrinsically distinct. CeL-PAG neurons are a homogeneous population of intrinsically distinct neurons while CeM-PAG neurons are intrinsically heterogeneous. Membrane properties of distinct CeM-PAG subtypes are altered in the complete Freund's adjuvant model of inflammatory pain. ABSTRACT A major population of neurons in the central nucleus of amygdala (CeA) send projections to the periaqueductal gray (PAG), a key midbrain structure that mediates coping strategies in response to threat or stress. While the CeA-PAG pathway has proved to be a component of descending anti-nociceptive circuitry, the functional organization of CeA-PAG neurons remains unclear. We identified CeA-PAG neurons in C57BL/6 mice of both sexes using intracranial injection of a fluorescent retrograde tracer into the PAG. In acute brain slices, we investigated the topographical and intrinsic characteristics of retrogradely labelled CeA-PAG neurons using epifluorescence and whole-cell electrophysiology. We also measured changes to CeA-PAG neurons in the complete Freund's adjuvant (CFA) model of inflammatory pain. Neurons in the central lateral (CeL) and central medial (CeM) amygdala project primarily to different regions of the PAG. CeL-PAG neurons consist of a relatively homogeneous population of intrinsically distinct neurons while CeM-PAG neurons are intrinsically heterogeneous. Membrane properties of distinct CeM-PAG subtypes are altered 1 day after induction of the CFA inflammatory pain model. Collectively, our results provide insight into pain-induced changes to a specific population of CeA neurons that probably play a key role in the integration of noxious input with endogenous analgesia and behavioural coping response.
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Affiliation(s)
- Jun-Nan Li
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA.,Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Patrick L Sheets
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, USA.,Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
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53
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Kiritoshi T, Neugebauer V. Pathway-Specific Alterations of Cortico-Amygdala Transmission in an Arthritis Pain Model. ACS Chem Neurosci 2018; 9:2252-2261. [PMID: 29630339 PMCID: PMC6146017 DOI: 10.1021/acschemneuro.8b00022] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Medial prefrontal cortex (mPFC) and amygdala are closely interconnected brain areas that play a key role in cognitive-affective aspects of pain through their reciprocal interactions. Clinical and preclinical evidence suggests that dysfunctions in the mPFC-amygdala circuitry underlie pain-related cognitive-affective deficits. However, synaptic mechanisms of pain-related changes in these long-range pathways are largely unknown. Here we used optogenetics and brain slice physiology to analyze synaptic transmission in different types of amygdala neurons driven by inputs from infralimbic (IL) and prelimbic (PL) subdivisions of the mPFC. We found that IL inputs evoked stronger synaptic inhibition of neurons in the latero-capsular division of the central nucleus (CeLC) of the amygdala than PL inputs, and this inhibition was impaired in an arthritis pain model. Furthermore, inhibition-excitation ratio in basolateral amygdala neurons was increased in the pain model in the IL pathway but not in the PL pathway. These results suggest that IL rather than PL controls CeLC activity, and that changes in this acute pain model occur predominantly in the IL-amygdala pathway.
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Affiliation(s)
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience
- Center of Excellence for Translational Neuroscience and Therapeutics Texas Tech University Health Sciences Center (TTUHSC), School of Medicine 3601 4th Street, Lubbock, TX 79430-6592
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54
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Weston CSE. Amygdala Represents Diverse Forms of Intangible Knowledge, That Illuminate Social Processing and Major Clinical Disorders. Front Hum Neurosci 2018; 12:336. [PMID: 30186129 PMCID: PMC6113401 DOI: 10.3389/fnhum.2018.00336] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 08/02/2018] [Indexed: 01/21/2023] Open
Abstract
Amygdala is an intensively researched brain structure involved in social processing and multiple major clinical disorders, but its functions are not well understood. The functions of a brain structure are best hypothesized on the basis of neuroanatomical connectivity findings, and of behavioral, neuroimaging, neuropsychological and physiological findings. Among the heaviest neuroanatomical interconnections of amygdala are those with perirhinal cortex (PRC), but these are little considered in the theoretical literature. PRC integrates complex, multimodal, meaningful and fine-grained distributed representations of objects and conspecifics. Consistent with this connectivity, amygdala is hypothesized to contribute meaningful and fine-grained representations of intangible knowledge for integration by PRC. Behavioral, neuroimaging, neuropsychological and physiological findings further support amygdala mediation of a diversity of such representations. These representations include subjective valence, impact, economic value, noxiousness, importance, ingroup membership, social status, popularity, trustworthiness and moral features. Further, the formation of amygdala representations is little understood, and is proposed to be often implemented through embodied cognition mechanisms. The hypothesis builds on earlier work, and makes multiple novel contributions to the literature. It highlights intangible knowledge, which is an influential but insufficiently researched factor in social and other behaviors. It contributes to understanding the heavy but neglected amygdala-PRC interconnections, and the diversity of amygdala-mediated intangible knowledge representations. Amygdala is a social brain region, but it does not represent species-typical social behaviors. A novel proposal to clarify its role is postulated. The hypothesis is also suggested to illuminate amygdala's involvement in several core symptoms of autism spectrum disorder (ASD). Specifically, novel and testable explanations are proposed for the ASD symptoms of disorganized visual scanpaths, apparent social disinterest, preference for concrete cognition, aspects of the disorder's heterogeneity, and impairment in some activities of daily living. Together, the presented hypothesis demonstrates substantial explanatory potential in the neuroscience, social and clinical domains.
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55
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Kim H, Thompson J, Ji G, Ganapathy V, Neugebauer V. Monomethyl fumarate inhibits pain behaviors and amygdala activity in a rat arthritis model. Pain 2018; 158:2376-2385. [PMID: 28832396 DOI: 10.1097/j.pain.0000000000001042] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Neuroplasticity in the amygdala, a brain center for emotions, leads to increased neuronal activity and output that can generate emotional-affective behaviors and modulate nocifensive responses. Mechanisms of increased activity in the amygdala output region (central nucleus, CeA) include increased reactive oxygen species, and so we explored beneficial effects of monomethyl fumarate (MMF), which can have neuroprotective effects through the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) antioxidant response pathway. Systemic (intraperitoneal) MMF dose-dependently inhibited vocalizations and mechanosensitivity (hindlimb withdrawal reflexes) of rats in an arthritis pain model (kaolin-carrageenan-induced monoarthritis in the knee). Stereotaxic administration of MMF into the CeA by microdialysis also inhibited vocalizations but had a limited effect on mechanosensitivity, suggesting a differential contribution to emotional-affective vs sensory pain aspects. Extracellular single-unit recordings of CeA neurons in anesthetized rats showed that stereotaxic administration of MMF into the CeA by microdialysis inhibited background activity and responses of CeA neurons to knee joint stimulation in the arthritis pain model. Monomethyl fumarate had no effect on behaviors and neuronal activity under normal conditions. The results suggest that MMF can inhibit emotional-affective responses in an arthritis pain model through an action that involves the amygdala (CeA).
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Affiliation(s)
- Hyunyoung Kim
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center (TTUHSC), School of Medicine, Lubbock, TX, USA
| | - Jeremy Thompson
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center (TTUHSC), School of Medicine, Lubbock, TX, USA
| | - Guangchen Ji
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center (TTUHSC), School of Medicine, Lubbock, TX, USA
| | - Vadivel Ganapathy
- Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center (TTUHSC), Lubbock, TX, USA.,Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center (TTUHSC), Lubbock, TX, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center (TTUHSC), School of Medicine, Lubbock, TX, USA.,Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center (TTUHSC), Lubbock, TX, USA
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56
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Emotional and Motivational Pain Processing: Current State of Knowledge and Perspectives in Translational Research. Pain Res Manag 2018; 2018:5457870. [PMID: 30123398 PMCID: PMC6079355 DOI: 10.1155/2018/5457870] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Accepted: 06/03/2018] [Indexed: 01/13/2023]
Abstract
Pain elicits fear and anxiety and promotes escape, avoidance, and adaptive behaviors that are essential for survival. When pain persists, motivational priority and attention shift to pain-related information. Such a shift often results in impaired functionality, leading to maladaptive pain-related fear and anxiety and escape and avoidance behaviors. Neuroimaging studies in chronic pain patients have established that brain activity, especially in cortical and mesolimbic regions, is different from activity observed during acute pain in control subjects. In this review, we discuss the psychophysiological and neuronal factors that may be associated with the transition to chronic pain. We review information from human studies on neural circuits involved in emotional and motivational pain processing and how these circuits are altered in chronic pain conditions. We then highlight findings from animal research that can increase our understanding of the molecular and cellular mechanisms underlying emotional-motivational pain processing in the brain. Finally, we discuss how translational approaches incorporating results from both human and animal investigations may aid in accelerating the discovery of therapies.
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57
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Kissiwaa SA, Bagley EE. Central sensitization of the spino-parabrachial-amygdala pathway that outlasts a brief nociceptive stimulus. J Physiol 2018; 596:4457-4473. [PMID: 30004124 PMCID: PMC6138295 DOI: 10.1113/jp273976] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Accepted: 06/29/2018] [Indexed: 12/22/2022] Open
Abstract
KEY POINTS Chronic pain is disabling because sufferers form negative associations between pain and activities, such as work, leading to the sufferer limiting these activities. Pain information arriving in the amygdala is responsible for forming these associations and contributes to us feeling bad when we are in pain. Ongoing injuries enhance the delivery of pain information to the amygdala. If we want to understand why chronic pain can continue without ongoing injury, it is important to know whether this facilitation continues once the injury has healed. In the present study, we show that a 2 min noxious heat stimulus, without ongoing injury, is able to enhance delivery of pain information to the amygdala for 3 days. If the noxious heat stimulus is repeated, this enhancement persists even longer. These changes may prime this information pathway so that subsequent injuries may feel even worse and the associative learning that results in pain-related avoidance may be promoted. ABSTRACT Pain is an important defence against dangers in our environment; however, some clinical conditions produce pain that outlasts this useful role and persists even after the injury has healed. The experience of pain consists of somatosensory elements of intensity and location, negative emotional/aversive feelings and subsequent restrictions on lifestyle as a result of a learned association between certain activities and pain. The amygdala contributes negative emotional value to nociceptive sensory information and forms the association between an aversive response and the environment in which it occurs. It is able to form this association because it receives nociceptive information via the spino-parabrachio-amygdaloid pathway and polymodal sensory information via cortical and thalamic inputs. Synaptic plasticity occurs at the parabrachial-amygdala synapse and other brain regions in chronic pain conditions with ongoing injury; however, very little is known about how plasticity occurs in conditions with no ongoing injury. Using immunohistochemistry, electrophysiology and behavioural assays, we show that a brief nociceptive stimulus with no ongoing injury is able to produce long-lasting synaptic plasticity at the rat parabrachial-amygdala synapse. We show that this plasticity is caused by an increase in postsynaptic AMPA receptors with a transient change in the AMPA receptor subunit, similar to long-term potentiation. Furthermore, this synaptic potentiation primes the synapse so that a subsequent noxious stimulus causes prolonged potentiation of the nociceptive information flow into the amygdala. As a result, a second injury could have an increased negative emotional value and promote associative learning that results in pain-related avoidance.
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Affiliation(s)
- Sarah A Kissiwaa
- Discipline of Pharmacology and Charles Perkins CentreUniversity of SydneySydneyNSW2006Australia
| | - Elena E Bagley
- Discipline of Pharmacology and Charles Perkins CentreUniversity of SydneySydneyNSW2006Australia
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58
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Thompson JM, Yakhnitsa V, Ji G, Neugebauer V. Small conductance calcium activated potassium (SK) channel dependent and independent effects of riluzole on neuropathic pain-related amygdala activity and behaviors in rats. Neuropharmacology 2018; 138:219-231. [PMID: 29908238 DOI: 10.1016/j.neuropharm.2018.06.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 05/04/2018] [Accepted: 06/11/2018] [Indexed: 01/17/2023]
Abstract
BACKGROUND AND PURPOSE Chronic neuropathic pain is an important healthcare issue with significant emotional components. The amygdala is a brain region involved in pain and emotional-affective states and disorders. The central amygdala output nucleus (CeA) contains small-conductance calcium-activated potassium (SK) channels that can control neuronal activity. A clinically available therapeutic, riluzole can activate SK channels and may have antinociceptive effects through a supraspinal action. We tested the hypothesis that riluzole inhibits neuropathic pain behaviors by inhibiting pain-related changes in CeA neurons, in part at least through SK channel activation. EXPERIMENTAL APPROACH Brain slice physiology and behavioral assays were done in adult Sprague Dawley rats. Audible and ultrasonic vocalizations and von Frey thresholds were measured in sham and neuropathic rats 4 weeks after left L5 spinal nerve ligation (SNL model). Whole cell patch-clamp recordings of regular firing CeA neurons in brain slices were used to measure synaptic transmission and neuronal excitability. KEY RESULTS In brain slices, riluzole increased the SK channel-mediated afterhyperpolarization and synaptic inhibition, but inhibited neuronal excitability through an SK channel independent action. SNL rats had increased vocalizations and decreased withdrawal thresholds compared to sham rats, and intra-CeA administration of riluzole inhibited vocalizations and depression-like behaviors but did not affect withdrawal thresholds. Systemic riluzole administration also inhibited these changes, demonstrating the clinical utility of this strategy. SK channel blockade in the CeA attenuated the inhibitory effects of systemic riluzole on vocalizations, confirming SK channel involvement in these effects. CONCLUSIONS AND IMPLICATIONS The results suggest that riluzole has beneficial effects on neuropathic pain behaviors through SK channel dependent and independent mechanisms in the amygdala.
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Affiliation(s)
- Jeremy M Thompson
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, School of Medicine, Lubbock, TX, USA
| | - Vadim Yakhnitsa
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, School of Medicine, Lubbock, TX, USA
| | - Guangchen Ji
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, School of Medicine, Lubbock, TX, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, School of Medicine, Lubbock, TX, USA; Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX, USA.
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59
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Zussy C, Gómez-Santacana X, Rovira X, De Bundel D, Ferrazzo S, Bosch D, Asede D, Malhaire F, Acher F, Giraldo J, Valjent E, Ehrlich I, Ferraguti F, Pin JP, Llebaria A, Goudet C. Dynamic modulation of inflammatory pain-related affective and sensory symptoms by optical control of amygdala metabotropic glutamate receptor 4. Mol Psychiatry 2018; 23:509-520. [PMID: 27994221 DOI: 10.1038/mp.2016.223] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 10/06/2016] [Accepted: 10/14/2016] [Indexed: 12/30/2022]
Abstract
Contrary to acute pain, chronic pain does not serve as a warning signal and must be considered as a disease per se. This pathology presents a sensory and psychological dimension at the origin of affective and cognitive disorders. Being largely refractory to current pharmacotherapies, identification of endogenous systems involved in persistent and chronic pain is crucial. The amygdala is a key brain region linking pain sensation with negative emotions. Here, we show that activation of a specific intrinsic neuromodulatory system within the amygdala associated with type 4 metabotropic glutamate receptors (mGlu4) abolishes sensory and affective symptoms of persistent pain such as hypersensitivity to pain, anxiety- and depression-related behaviors, and fear extinction impairment. Interestingly, neuroanatomical and synaptic analysis of the amygdala circuitry suggests that the effects of mGlu4 activation occur outside the central nucleus via modulation of multisensory thalamic inputs to lateral amygdala principal neurons and dorso-medial intercalated cells. Furthermore, we developed optogluram, a small diffusible photoswitchable positive allosteric modulator of mGlu4. This ligand allows the control of endogenous mGlu4 activity with light. Using this photopharmacological approach, we rapidly and reversibly inhibited behavioral symptoms associated with persistent pain through optical control of optogluram in the amygdala of freely behaving animals. Altogether, our data identify amygdala mGlu4 signaling as a mechanism that bypasses central sensitization processes to dynamically modulate persistent pain symptoms. Our findings help to define novel and more precise therapeutic interventions for chronic pain, and exemplify the potential of optopharmacology to study the dynamic activity of endogenous neuromodulatory mechanisms in vivo.
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Affiliation(s)
- C Zussy
- Institut de Génomique Fonctionnelle, CNRS, UMR-5203, Université de Montpellier, Montpellier, France.,INSERM, U1191, Montpellier, France
| | - X Gómez-Santacana
- MCS, Laboratory of Medicinal Chemistry, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain.,Laboratory of Molecular Neuropharmacology and Bioinformatics, Institut de Neurociències and Unitat de Bioestadística, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - X Rovira
- Institut de Génomique Fonctionnelle, CNRS, UMR-5203, Université de Montpellier, Montpellier, France.,INSERM, U1191, Montpellier, France
| | - D De Bundel
- Institut de Génomique Fonctionnelle, CNRS, UMR-5203, Université de Montpellier, Montpellier, France.,INSERM, U1191, Montpellier, France
| | - S Ferrazzo
- Department of Pharmacology, Innsbruck Medical University, Innsbruck, Austria
| | - D Bosch
- Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.,Werner Reichardt Centre for Integrative Neuroscience, University of Tübingen, Tübingen, Germany
| | - D Asede
- Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.,Werner Reichardt Centre for Integrative Neuroscience, University of Tübingen, Tübingen, Germany
| | - F Malhaire
- Institut de Génomique Fonctionnelle, CNRS, UMR-5203, Université de Montpellier, Montpellier, France.,INSERM, U1191, Montpellier, France
| | - F Acher
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, CNRS UMR8601, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - J Giraldo
- Laboratory of Molecular Neuropharmacology and Bioinformatics, Institut de Neurociències and Unitat de Bioestadística, Universitat Autònoma de Barcelona, Bellaterra, Spain.,Network Biomedical Research Center on Mental Health (CIBERSAM), Madrid, Spain
| | - E Valjent
- Institut de Génomique Fonctionnelle, CNRS, UMR-5203, Université de Montpellier, Montpellier, France.,INSERM, U1191, Montpellier, France
| | - I Ehrlich
- Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.,Werner Reichardt Centre for Integrative Neuroscience, University of Tübingen, Tübingen, Germany
| | - F Ferraguti
- Department of Pharmacology, Innsbruck Medical University, Innsbruck, Austria
| | - J-P Pin
- Institut de Génomique Fonctionnelle, CNRS, UMR-5203, Université de Montpellier, Montpellier, France.,INSERM, U1191, Montpellier, France
| | - A Llebaria
- MCS, Laboratory of Medicinal Chemistry, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain
| | - C Goudet
- Institut de Génomique Fonctionnelle, CNRS, UMR-5203, Université de Montpellier, Montpellier, France.,INSERM, U1191, Montpellier, France
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60
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Abstract
Chronic pain is frequently associated with anxiety, depression, and cognitive dysfunction. This review discusses recent work in rodents that contributes to the understanding of their neurobiological links. Brain regions that contain circuits that mediate persistent changes in behavior that are caused by nerve injury or joint inflammation include the rostral anterior cingulate and other parts of the medial prefrontal cortex, the basolateral and central nucleus of the amygdala, and the nucleus accumbens. Functional changes, including increases in the activity within specific neuronal pathways and in the levels of specific synaptic components, that are associated with the behavior changes, or are in some cases necessary for them, have recently been identified. Broadly projecting modulatory systems and widely expressed factors such as cytokines and growth factors also contribute to pain-associated behavior. Integrating these observations and determining their causal relationships is now critical for the identification of therapeutic targets and the design of appropriate interventions.
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Affiliation(s)
- Ted B Usdin
- Section on Fundamental Neuroscience, National Institute of Mental Health Intramural Research Program, Bethesda, MD, USA
| | - Eugene L Dimitrov
- Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA
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61
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Ji G, Yakhnitsa V, Kiritoshi T, Presto P, Neugebauer V. Fear extinction learning ability predicts neuropathic pain behaviors and amygdala activity in male rats. Mol Pain 2018; 14:1744806918804441. [PMID: 30209982 PMCID: PMC6172937 DOI: 10.1177/1744806918804441] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 08/15/2018] [Accepted: 09/02/2018] [Indexed: 12/14/2022] Open
Abstract
Background The amygdala plays a key role in fear learning and extinction and has emerged as an important node of emotional-affective aspects of pain and pain modulation. Impaired fear extinction learning, which involves prefrontal cortical control of amygdala processing, has been linked to neuropsychiatric disorders. Here, we tested the hypothesis that fear extinction learning ability can predict the magnitude of neuropathic pain. Results We correlated fear extinction learning in naive adult male rats with sensory and affective behavioral outcome measures (mechanical thresholds, vocalizations, and anxiety- and depression-like behaviors) before and after the induction of the spinal nerve ligation model of neuropathic pain compared to sham controls. Auditory fear conditioning, extinction learning, and extinction retention tests were conducted after baseline testing. All rats showed increased freezing responses after fear conditioning. During extinction training, the majority (75%) of rats showed a decline in freezing level to 50% in 5 min (fear extinction+), whereas 25% of the rats maintained a high freezing level (>50%, fear extinction-). Fear extinction- rats showed decreased open-arm preference in the elevated plus maze, reflecting anxiety-like behavior, but there were no significant differences in sensory thresholds, vocalizations, or depression-like behavior (forced swim test) between fear extinction+ and fear extinction- types. In the neuropathic pain model (four weeks after spinal nerve ligation), fear extinction- rats showed a greater increase in vocalizations and anxiety-like behavior than fear extinction+ rats. Fear extinction- rats, but not fear extinction+ rats, also developed depression-like behavior. Extracellular single unit recordings of amygdala (central nucleus) neurons in behaviorally tested rats (anesthetized with isoflurane) found greater increases in background activity, bursting, and evoked activity in fear extinction- rats than fear extinction+ rats in the spinal nerve ligation model compared to sham controls. Conclusion The data may suggest that fear extinction learning ability predicts the magnitude of neuropathic pain-related affective rather than sensory behaviors, which correlates with differences in amygdala activity changes.
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Affiliation(s)
- Guangchen Ji
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, School of Medicine, Lubbock, TX, USA
- Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Vadim Yakhnitsa
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, School of Medicine, Lubbock, TX, USA
| | - Takaki Kiritoshi
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, School of Medicine, Lubbock, TX, USA
| | - Peyton Presto
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, School of Medicine, Lubbock, TX, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, School of Medicine, Lubbock, TX, USA
- Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX, USA
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62
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Abstract
The amygdala is a limbic brain region that plays a key role in emotional processing, neuropsychiatric disorders, and the emotional-affective dimension of pain. Preclinical and clinical studies have identified amygdala hyperactivity as well as impairment of cortical control mechanisms in pain states. Hyperactivity of basolateral amygdala (BLA) neurons generates enhanced feedforward inhibition and deactivation of the medial prefrontal cortex (mPFC), resulting in pain-related cognitive deficits. The mPFC sends excitatory projections to GABAergic neurons in the intercalated cell mass (ITC) in the amygdala, which project to the laterocapsular division of the central nucleus of the amygdala (CeLC; output nucleus) and serve gating functions for amygdala output. Impairment of these cortical control mechanisms allows the development of amygdala pain plasticity. Mechanisms of abnormal amygdala activity in pain with particular focus on loss of cortical control mechanisms as well as new strategies to correct pain-related amygdala dysfunction will be discussed in the present review.
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63
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Chronic stress exacerbates neuropathic pain via the integration of stress-affect-related information with nociceptive information in the central nucleus of the amygdala. Pain 2017; 158:717-739. [PMID: 28225710 DOI: 10.1097/j.pain.0000000000000827] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Exacerbation of pain by chronic stress and comorbidity of pain with stress-related psychiatric disorders, including anxiety and depression, represent significant clinical challenges. However, the underlying mechanisms still remain unclear. Here, we investigated whether chronic forced swim stress (CFSS)-induced exacerbation of neuropathic pain is mediated by the integration of stress-affect-related information with nociceptive information in the central nucleus of the amygdala (CeA). We first demonstrated that CFSS indeed produces both depressive-like behaviors and exacerbation of spared nerve injury (SNI)-induced mechanical allodynia in rats. Moreover, we revealed that CFSS induces both sensitization of basolateral amygdala (BLA) neurons and augmentation of long-term potentiation (LTP) at the BLA-CeA synapse and meanwhile, exaggerates both SNI-induced sensitization of CeA neurons and LTP at the parabrachial (PB)-CeA synapse. In addition, we discovered that CFSS elevates SNI-induced functional up-regulation of GluN2B-containing NMDA (GluN2B-NMDA) receptors in the CeA, which is proved to be necessary for CFSS-induced augmentation of LTP at the PB-CeA synapse and exacerbation of pain hypersensitivity in SNI rats. Suppression of CFSS-elicited depressive-like behaviors by antidepressants imipramine or ifenprodil inhibits the CFSS-induced exacerbation of neuropathic pain. Collectively, our findings suggest that CFSS potentiates synaptic efficiency of the BLA-CeA pathway, leading to the activation of GluN2B-NMDA receptors and sensitization of CeA neurons, which subsequently facilitate pain-related synaptic plasticity of the PB-CeA pathway, thereby exacerbating SNI-induced neuropathic pain. We conclude that chronic stress exacerbates neuropathic pain via the integration of stress-affect-related information with nociceptive information in the CeA.
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Yeh LF, Watanabe M, Sulkes-Cuevas J, Johansen JP. Dysregulation of aversive signaling pathways: a novel circuit endophenotype for pain and anxiety disorders. Curr Opin Neurobiol 2017; 48:37-44. [PMID: 28965072 DOI: 10.1016/j.conb.2017.09.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 09/11/2017] [Indexed: 12/20/2022]
Abstract
Aversive experiences activate dedicated neural instructive pathways which trigger memory formation and change behavior. The strength of these aversive memories and the degree to which they alter behavior is proportional to the intensity of the aversive experience. Dysregulation of aversive learning circuits can lead to psychiatric pathology. Here we review recent findings elucidating aversive instructive signaling circuits for fear conditioning. We then examine how chronic pain as well as stress and anxiety disrupt these circuits and the implications this has for understanding and treating psychiatric disease. Together this review synthesizes current work on aversive instructive signaling circuits in health and disease and suggests a novel circuit based framework for understanding pain and anxiety syndromes.
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Affiliation(s)
- Li-Feng Yeh
- RIKEN Brain Science Institute, Laboratory for Neural Circuitry of Memory, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan; Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan
| | - Mayumi Watanabe
- RIKEN Brain Science Institute, Laboratory for Neural Circuitry of Memory, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan; Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan
| | - Jessica Sulkes-Cuevas
- RIKEN Brain Science Institute, Laboratory for Neural Circuitry of Memory, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan; Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan
| | - Joshua P Johansen
- RIKEN Brain Science Institute, Laboratory for Neural Circuitry of Memory, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan; Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan; RIKEN BSI-Kao Collaboration Center, Japan.
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Shinohara K, Watabe AM, Nagase M, Okutsu Y, Takahashi Y, Kurihara H, Kato F. Essential role of endogenous calcitonin gene-related peptide in pain-associated plasticity in the central amygdala. Eur J Neurosci 2017; 46:2149-2160. [PMID: 28833700 PMCID: PMC5698701 DOI: 10.1111/ejn.13662] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 08/04/2017] [Accepted: 08/14/2017] [Indexed: 12/16/2022]
Abstract
The role of the neuropeptide calcitonin gene‐related peptide (CGRP) is well established in nociceptive behaviors. CGRP is highly expressed in the projection pathway from the parabrachial nucleus to the laterocapsular region of the central amygdala (CeC), which plays a critical role in relaying nociceptive information. The CeC is a key structure in pain behavior because it integrates and modulates nociceptive information along with other sensory signals. Previous studies have demonstrated that blockade of the amygdalar CGRP‐signaling cascade attenuates nociceptive behaviors in pain models, while CGRP application facilitates amygdalar synaptic transmission and induces pain behaviors. Despite these lines of evidence, it remains unclear whether endogenous CGRP is involved in the development of nociceptive behaviors accompanied with amygdalar plasticity in a peripheral inflammation model in vivo. To directly address this, we utilized a previously generated CGRP knockout (KO) mouse to longitudinally study formalin‐induced plasticity and nociceptive behavior. We found that synaptic potentiation in the right PB‐CeC pathway that was observed in wild‐type mice was drastically attenuated in the CGRP KO mice 6 h post‐inflammation, when acute nociceptive behavior was no longer observed. Furthermore, the bilateral tactile allodynia 6 h post‐inflammation was significantly decreased in the CGRP KO mice. In contrast, the acute nociceptive behavior immediately after the formalin injection was reduced only at 20–25 min post‐injection in the CGRP KO mice. These results suggest that endogenous CGRP contributes to peripheral inflammation‐induced synaptic plasticity in the amygdala, and this plasticity may underlie the exaggerated nociception–emotion linkage in pain chronification.
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Affiliation(s)
- Kei Shinohara
- Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo, Japan.,Department of Orthopaedic Surgery, Jikei University School of Medicine, Minato-ku, Tokyo, Japan.,Center for Neuroscience of Pain, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Ayako M Watabe
- Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo, Japan.,Center for Neuroscience of Pain, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Masashi Nagase
- Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo, Japan.,Center for Neuroscience of Pain, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Yuya Okutsu
- Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo, Japan.,Department of Orthopaedic Surgery, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Yukari Takahashi
- Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo, Japan.,Center for Neuroscience of Pain, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Hiroki Kurihara
- Department of Molecular Cell Biology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Fusao Kato
- Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo, Japan.,Center for Neuroscience of Pain, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
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66
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Shinohara K, Watabe AM, Nagase M, Okutsu Y, Takahashi Y, Kurihara H, Kato F. Essential role of endogenous calcitonin gene-related peptide in pain-associated plasticity in the central amygdala. Eur J Neurosci 2017. [PMID: 28833700 DOI: 10.1111/ejn.2017.46.issue-610.1111/ejn.13662] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2023]
Abstract
The role of the neuropeptide calcitonin gene-related peptide (CGRP) is well established in nociceptive behaviors. CGRP is highly expressed in the projection pathway from the parabrachial nucleus to the laterocapsular region of the central amygdala (CeC), which plays a critical role in relaying nociceptive information. The CeC is a key structure in pain behavior because it integrates and modulates nociceptive information along with other sensory signals. Previous studies have demonstrated that blockade of the amygdalar CGRP-signaling cascade attenuates nociceptive behaviors in pain models, while CGRP application facilitates amygdalar synaptic transmission and induces pain behaviors. Despite these lines of evidence, it remains unclear whether endogenous CGRP is involved in the development of nociceptive behaviors accompanied with amygdalar plasticity in a peripheral inflammation model in vivo. To directly address this, we utilized a previously generated CGRP knockout (KO) mouse to longitudinally study formalin-induced plasticity and nociceptive behavior. We found that synaptic potentiation in the right PB-CeC pathway that was observed in wild-type mice was drastically attenuated in the CGRP KO mice 6 h post-inflammation, when acute nociceptive behavior was no longer observed. Furthermore, the bilateral tactile allodynia 6 h post-inflammation was significantly decreased in the CGRP KO mice. In contrast, the acute nociceptive behavior immediately after the formalin injection was reduced only at 20-25 min post-injection in the CGRP KO mice. These results suggest that endogenous CGRP contributes to peripheral inflammation-induced synaptic plasticity in the amygdala, and this plasticity may underlie the exaggerated nociception-emotion linkage in pain chronification.
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Affiliation(s)
- Kei Shinohara
- Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
- Department of Orthopaedic Surgery, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
- Center for Neuroscience of Pain, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Ayako M Watabe
- Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
- Center for Neuroscience of Pain, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Masashi Nagase
- Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
- Center for Neuroscience of Pain, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Yuya Okutsu
- Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
- Department of Orthopaedic Surgery, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Yukari Takahashi
- Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
- Center for Neuroscience of Pain, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
| | - Hiroki Kurihara
- Department of Molecular Cell Biology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Fusao Kato
- Department of Neuroscience, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
- Center for Neuroscience of Pain, Jikei University School of Medicine, Minato-ku, Tokyo, Japan
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67
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Sadler KE, Gartland NM, Cavanaugh JE, Kolber BJ. Central amygdala activation of extracellular signal-regulated kinase 1 and age-dependent changes in inflammatory pain sensitivity in mice. Neurobiol Aging 2017; 56:100-107. [PMID: 28526294 DOI: 10.1016/j.neurobiolaging.2017.04.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 03/19/2017] [Accepted: 04/16/2017] [Indexed: 01/06/2023]
Abstract
Aging populations are more sensitive to noxious stimuli as a result of altered somatosensory systems. In these experiments, we examined pain-like behaviors in young, middle-aged, and old mice during peripheral inflammation to determine if the same sensitivity exists in preclinical animal models. Immediately following injury, middle-aged and old mice exhibited more spontaneous pain-like behaviors than young mice, matching pain prevalence in clinical populations. Middle-aged and old mice also developed persistent mechanical hypersensitivity in the injured paw. Furthermore, old mice developed mechanical hypersensitivity in the noninjured paw suggesting age-dependent changes in central nociceptive systems. To address this end, pain-related protein expression was examined in the central nucleus of the amygdala, a limbic brain region that modulates somatic pain. Following injury, increased phosphorylation of extracellular signal-regulated kinase 1, a protein with known nociceptive functions, was observed in the right central nucleus of the amygdala of old mice and not middle-aged or young animals. These findings suggest that age-dependent changes in supraspinal nociceptive systems may account for increased pain-like behaviors in aging populations.
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Affiliation(s)
- Katelyn E Sadler
- Department of Biological Sciences, Duquesne University, Pittsburgh, PA, USA; Chronic Pain Research Consortium, Duquesne University, Pittsburgh, PA, USA; Aging Research and Teaching Consortium, Duquesne University, Pittsburgh, PA, USA
| | - Nathan M Gartland
- Chronic Pain Research Consortium, Duquesne University, Pittsburgh, PA, USA; Division of Pharmacology, Duquesne University, Pittsburgh, PA, USA
| | - Jane E Cavanaugh
- Chronic Pain Research Consortium, Duquesne University, Pittsburgh, PA, USA; Aging Research and Teaching Consortium, Duquesne University, Pittsburgh, PA, USA; Division of Pharmacology, Duquesne University, Pittsburgh, PA, USA
| | - Benedict J Kolber
- Department of Biological Sciences, Duquesne University, Pittsburgh, PA, USA; Chronic Pain Research Consortium, Duquesne University, Pittsburgh, PA, USA; Aging Research and Teaching Consortium, Duquesne University, Pittsburgh, PA, USA.
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68
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Missig G, Mei L, Vizzard MA, Braas KM, Waschek JA, Ressler KJ, Hammack SE, May V. Parabrachial Pituitary Adenylate Cyclase-Activating Polypeptide Activation of Amygdala Endosomal Extracellular Signal-Regulated Kinase Signaling Regulates the Emotional Component of Pain. Biol Psychiatry 2017; 81:671-682. [PMID: 28057459 PMCID: PMC5332340 DOI: 10.1016/j.biopsych.2016.08.025] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 07/15/2016] [Accepted: 08/16/2016] [Indexed: 01/11/2023]
Abstract
BACKGROUND Chronic pain and stress-related psychopathologies, such as depression and anxiety-associated abnormalities, are mutually reinforcing; however, the neuronal circuits and mechanisms that underlie this reinforcement are still not well understood. Pituitary adenylate cyclase-activating polypeptide (PACAP; Adcyap1) and its cognate PAC1 receptor (Adcyap1r1) are expressed in peripheral nociceptive pathways, participate in anxiety-related responses and have been have been linked to posttraumatic stress disorder and other mental health afflictions. METHODS Using immunocytochemistry, pharmacological treatments and behavioral testing techniques, we have used a rodent partial sciatic nerve chronic constriction injury model (n = 5-8 per group per experiment) to evaluate PACAP plasticity and signaling in nociceptive and stress-related behaviors. RESULTS We show that chronic neuropathic pain increases PACAP expression at multiple tiers along the spinoparabrachioamygdaloid tract. Furthermore, chronic constriction injury bilaterally augments nociceptive amygdala (in the central nucleus of the amygdala [CeA]) PACAP immunoreactivity, extracellular signal-regulated kinase phosphorylation, and c-Fos activation, in parallel with heightened anxiety-like behavior and nociceptive hypersensitivity. Acute CeA infusions with the PACAP receptor antagonist PACAP(6-38) blocked chronic constriction injury-induced behavioral responses. Additionally, pretreatments with inhibitors of mitogen-activated protein kinase enzymes or endocytosis to block endosomal PACAP receptor extracellular signal-regulated kinase signaling attenuated PACAP-induced CeA neuronal activation and nociceptive responses. CONCLUSIONS Our data suggest that chronic pain-induced PACAP neuroplasticity and signaling in spinoparabrachioamygdaloid projections have an impact on CeA stress- and nociception-associated maladaptive responses, which can be ameliorated upon receptor antagonism even during injury progression. Thus, the PACAP pathway provides for an important mechanism underlying the intersection of stress and chronic pain pathways via the amygdala.
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Affiliation(s)
- Galen Missig
- Department of Neurological Sciences, Burlington, Vermont
| | - Linda Mei
- Department of Neurological Sciences, Burlington, Vermont
| | | | - Karen M Braas
- Department of Neurological Sciences, Burlington, Vermont
| | - James A Waschek
- Department of Psychiatry and Behavioral Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California
| | - Kerry J Ressler
- Division of Depression and Anxiety, McLean Hospital-Harvard Medical School, Belmont, Massachusetts
| | - Sayamwong E Hammack
- Department of Psychological Science, University of Vermont College of Medicine, Burlington, Vermont
| | - Victor May
- Department of Neurological Sciences, Burlington, Vermont.
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Font J, López-Cano M, Notartomaso S, Scarselli P, Di Pietro P, Bresolí-Obach R, Battaglia G, Malhaire F, Rovira X, Catena J, Giraldo J, Pin JP, Fernández-Dueñas V, Goudet C, Nonell S, Nicoletti F, Llebaria A, Ciruela F. Optical control of pain in vivo with a photoactive mGlu 5 receptor negative allosteric modulator. eLife 2017; 6:e23545. [PMID: 28395733 PMCID: PMC5388536 DOI: 10.7554/elife.23545] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 03/19/2017] [Indexed: 12/22/2022] Open
Abstract
Light-operated drugs constitute a major target in drug discovery, since they may provide spatiotemporal resolution for the treatment of complex diseases (i.e. chronic pain). JF-NP-26 is an inactive photocaged derivative of the metabotropic glutamate type 5 (mGlu5) receptor negative allosteric modulator raseglurant. Violet light illumination of JF-NP-26 induces a photochemical reaction prompting the active-drug's release, which effectively controls mGlu5 receptor activity both in ectopic expressing systems and in striatal primary neurons. Systemic administration in mice followed by local light-emitting diode (LED)-based illumination, either of the thalamus or the peripheral tissues, induced JF-NP-26-mediated light-dependent analgesia both in neuropathic and in acute/tonic inflammatory pain models. These data offer the first example of optical control of analgesia in vivo using a photocaged mGlu5 receptor negative allosteric modulator. This approach shows potential for precisely targeting, in time and space, endogenous receptors, which may allow a better management of difficult-to-treat disorders.
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Affiliation(s)
- Joan Font
- MCS, Laboratory of Medicinal Chemistry, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain
- Institut de Neurociències, Universitat Autònoma de Barcelona, Bellaterra, Spain
- Unitat de Bioestadística, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Marc López-Cano
- Departament de Patologia i Terapèutica Experimental, Facultat de Medicina i Ciències de la Salut, IDIBELL, Universitat de Barcelona, Barcelona, Spain
- Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain
| | | | | | | | | | | | - Fanny Malhaire
- IGF, CNRS, INSERM, Univ. Montpellier, Montpellier, France
| | - Xavier Rovira
- IGF, CNRS, INSERM, Univ. Montpellier, Montpellier, France
| | - Juanlo Catena
- MCS, Laboratory of Medicinal Chemistry, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain
| | - Jesús Giraldo
- Institut de Neurociències, Universitat Autònoma de Barcelona, Bellaterra, Spain
- Unitat de Bioestadística, Universitat Autònoma de Barcelona, Bellaterra, Spain
- Network Biomedical Research Center on Mental Health (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
| | | | - Víctor Fernández-Dueñas
- Departament de Patologia i Terapèutica Experimental, Facultat de Medicina i Ciències de la Salut, IDIBELL, Universitat de Barcelona, Barcelona, Spain
- Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain
| | - Cyril Goudet
- IGF, CNRS, INSERM, Univ. Montpellier, Montpellier, France
| | - Santi Nonell
- Institut Químic de Sarrià, Universitat Ramon Llull, Barcelona, Spain
| | - Ferdinando Nicoletti
- I.R.C.C.S. Neuromed, Pozzilli, Italy
- Department of Physiology and Pharmacology, University Sapienza, Rome, Italy
| | - Amadeu Llebaria
- MCS, Laboratory of Medicinal Chemistry, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain
| | - Francisco Ciruela
- Departament de Patologia i Terapèutica Experimental, Facultat de Medicina i Ciències de la Salut, IDIBELL, Universitat de Barcelona, Barcelona, Spain
- Institut de Neurociències, Universitat de Barcelona, Barcelona, Spain
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Palazzo E, Marabese I, Luongo L, Guida F, de Novellis V, Maione S. Nociception modulation by supraspinal group III metabotropic glutamate receptors. J Neurochem 2017; 141:507-519. [DOI: 10.1111/jnc.13725] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 06/15/2016] [Accepted: 06/20/2016] [Indexed: 02/02/2023]
Affiliation(s)
- Enza Palazzo
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Ida Marabese
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Livio Luongo
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Francesca Guida
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Vito de Novellis
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
| | - Sabatino Maione
- Department of Experimental Medicine; The Second University of Naples; Naples Italy
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Chen A, Hu WW, Jiang XL, Potegal M, Li H. Molecular mechanisms of group I metabotropic glutamate receptor mediated LTP and LTD in basolateral amygdala in vitro. Psychopharmacology (Berl) 2017; 234:681-694. [PMID: 28028604 DOI: 10.1007/s00213-016-4503-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 12/08/2016] [Indexed: 11/30/2022]
Abstract
The roles of group I metabotropic glutamate receptors, metabotropic glutamate receptor 1 (mGluR1) and mGluR5, in regulating synaptic plasticity and metaplasticity in the basolateral amygdala (BLA) remain unclear. The present study examined mGluR1- and mGluR5-mediated synaptic plasticity in the BLA and their respective signaling mechanisms. Bath application of the group I mGluR agonist, 3,5-dihydroxyphenylglycine (DHPG) (20 μM), directly suppressed basal fEPSPs (84.5 ± 6.3% of the baseline). The suppressive effect persisted for at least 30 min after washout; it was abolished by the mGluR1 antagonist 7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester (CPCCOEt) but was unaffected by the mGluR5 antagonist 2-methyl-6- (phenylethynyl)-pyridine (MPEP). Interestingly, application of DHPG (at both 2 and 20 μM), regardless of the presence of CPCCOEt, could transform single theta burst stimulation (TBS)-induced short-term synaptic potentiation into a long-term potentiation (LTP). Such a facilitating effect could be blocked by the mGluR5 antagonist MPEP. Blockade of phospholipase C (PLC), the downstream enzyme of group I mGluR, with U73122, prevented both mGluR1- and mGluR5-mediated effects on synaptic plasticity. Nevertheless, blockade of protein kinase C (PKC), the downstream enzyme of PLC, with chelerythrine (5 μM) only prevented the transforming effect of DHPG on TBS-induced LTP and did not affect DHPG-induced long-term depression (LTD). These results suggest that mGluR1 activation induced LTD via a PLC-dependent and PKC-independent mechanism, while the priming action of mGluR5 receptor on the BLA LTP is both PLC and PKC dependent. The BLA metaplasticity mediated by mGluR1 and mGluR5 may provide signal switching mechanisms mediating learning and memory with emotional significance.
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Affiliation(s)
- A Chen
- Department of Physiology, Fujian Medical University, Fuzhou, People's Republic of China
| | - W W Hu
- Department of Physiology, Fujian Medical University, Fuzhou, People's Republic of China
| | - X L Jiang
- Department of Psychiatry, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD, 20814-4799, USA
| | - M Potegal
- Department of Pediatrics, University of Minnesota, Minneapolis, MN, 55414, USA
| | - H Li
- Department of Psychiatry, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD, 20814-4799, USA.
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Wanasuntronwong A, Jansri U, Srikiatkhachorn A. Neural hyperactivity in the amygdala induced by chronic treatment of rats with analgesics may elucidate the mechanisms underlying psychiatric comorbidities associated with medication-overuse headache. BMC Neurosci 2017; 18:1. [PMID: 28049513 PMCID: PMC5209916 DOI: 10.1186/s12868-016-0326-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 12/17/2016] [Indexed: 01/30/2023] Open
Abstract
Background Patients with medication-overuse headache suffer not only from chronic headache, but often from psychiatric comorbidities, such as anxiety and depression. The mechanisms underlying these comorbidities are unclear, but the amygdala is likely to be involved in their pathogenesis. To investigate the mechanisms underlying the comorbidities we used elevated plus maze and open field tests to assess anxiety-like behavior in rats chronically treated with analgesics. We measured the electrical properties of neurons in the amygdala, and examined the cortical spreading depression (CSD)-evoked expression of Fos in the trigeminal nucleus caudalis (TNC) and amygdala of rats chronically treated with analgesics. CSD, an analog of aura, evokes Fos expression in the TNC of rodents suggesting trigeminal nociception, considered to be a model of migraine. Results Increased anxiety-like behavior was seen both in elevated plus maze and open field tests in a model of medication overuse produced in male rats by chronic treatment with aspirin or acetaminophen. The time spent in the open arms of the maze by aspirin- or acetaminophen-treated rats (53 ± 36.1 and 37 ± 29.5 s, respectively) was significantly shorter than that spent by saline-treated vehicle control rats (138 ± 22.6 s, P < 0.001). Chronic treatment with the analgesics increased the excitability of neurons in the central nucleus of the amygdala as indicated by their more negative threshold for action potential generation (–54.6 ± 5.01 mV for aspirin-treated, –55.2 ± 0.97 mV for acetaminophen-treated, and –31.50 ± 5.34 mV for saline-treated rats, P < 0.001). Chronic treatment with analgesics increased the CSD-evoked expression of Fos in the TNC and amygdala [18 ± 10.2 Fos-immunoreactive (IR) neurons per slide in the amygdala of rats treated with aspirin, 11 ± 5.4 IR neurons per slide in rats treated with acetaminophen, and 4 ± 3.7 IR neurons per slide in saline-treated control rats, P < 0.001]. Conclusions Chronic treatment with analgesics can increase the excitability of neurons in the amygdala, which could underlie the anxiety seen in patients with medication-overuse headache. Electronic supplementary material The online version of this article (doi:10.1186/s12868-016-0326-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Aree Wanasuntronwong
- Department of Oral Biology, Faculty of Dentistry, Mahidol University, 6 Yothi Road, Ratchathewi, Bangkok, 10400, Thailand.
| | - Ukkrit Jansri
- Department of Physiology, Faculty of Medicine, Chulalongkorn University, 1874 Rama 4 Road, Pathumwan, Bangkok, 10330, Thailand.,International Medical College, King Mongkut's Institute of Technology, 1 Chalongkrung Road, Lad Krabang, Bangkok, 10520, Thailand
| | - Anan Srikiatkhachorn
- Department of Physiology, Faculty of Medicine, Chulalongkorn University, 1874 Rama 4 Road, Pathumwan, Bangkok, 10330, Thailand.,International Medical College, King Mongkut's Institute of Technology, 1 Chalongkrung Road, Lad Krabang, Bangkok, 10520, Thailand
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Schnitzer TJ, Torbey S, Herrmann K, Kaushal G, Yeasted R, Vania Apkarian A. A randomized placebo-controlled pilot study of the efficacy and safety of D-cycloserine in people with chronic back pain. Mol Pain 2016; 12:1744806916678627. [PMID: 27852965 PMCID: PMC5117251 DOI: 10.1177/1744806916678627] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 10/04/2016] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Few effective pharmacological treatment options exist for chronic back pain, the leading cause of disability in the US, and all are associated with significant adverse effects. OBJECTIVE To determine the efficacy and safety of D-cycloserine, a partial agonist to the N-methyl-D-aspartate receptor, in the treatment of chronic low back pain. METHODS A total of 41 participants with chronic back pain who met all inclusion and exclusion criteria were enrolled in a double-blind, placebo-controlled randomized pilot trial of D-cycloserine. Treatment was administered orally for six weeks at escalating daily doses of 100 mg, 200 mg, and 400 mg, each for two weeks. The primary outcome measure was back pain intensity using the Numeric Rating Scale (0-10). Secondary measures were back pain-related questionnaires: McGill Pain Questionnaire short form, painDETECT, PANAS, and BDI. The pre-specified analysis was a two-way repeated measures analysis of variance. RESULTS A treatment difference was observed between groups treated with D-cycloserine and placebo at six weeks of 1.05 ± 3.1 units on the Numeric Rating Scale, with an effect size of 0.4 and p = 0.14. This trend of better chronic back pain relief with D-cycloserine was also observed in the secondary measures. No safety issues were seen. CONCLUSION The difference in mean pain between the D-cycloserine and placebo groups did not reach statistical significance. However, a clinically meaningful effect size in the magnitude of pain relief was observed with a consistent pattern across multiple outcome measures with good safety, supporting further research into the effectiveness of D-cycloserine for chronic back pain.
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Affiliation(s)
- Thomas J Schnitzer
- Department of Physical Medicine and Rehabilitation and Division of Rheumatology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Souraya Torbey
- Department of Psychiatry, University of Virginia School of Medicine, VA, USA
| | - Kristi Herrmann
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Gagan Kaushal
- Jefferson School of Pharmacy, Thomas Jefferson University, PA, USA
| | - Renita Yeasted
- Department of Physical Medicine and Rehabilitation and Division of Rheumatology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - A Vania Apkarian
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
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74
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Cragg B, Ji G, Neugebauer V. Differential contributions of vasopressin V1A and oxytocin receptors in the amygdala to pain-related behaviors in rats. Mol Pain 2016; 12:12/0/1744806916676491. [PMID: 27837170 PMCID: PMC5117246 DOI: 10.1177/1744806916676491] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 10/03/2016] [Indexed: 12/26/2022] Open
Abstract
Neuroplastic changes in the amygdala account for emotional-affective aspects of pain and involve neuropeptides such as calcitonin gene-related peptide and corticotropin-releasing factor. Another neuropeptide system, central arginine vasopressin, has been implicated in neuropsychiatric disorders, but its role in pain-related emotional expression and neuroplasticity remains to be determined. Here, we tested the hypothesis that arginine vasopressin in the amygdala contributes to pain-related emotional-affective responses, using stereotaxic applications of arginine vasopressin and antagonists for G-protein coupled vasopressin V1A and oxytocin receptors in adult male Sprague-Dawley rats. In normal animals, arginine vasopressin increased audible and ultrasonic vocalizations and anxiety-like behavior (decreased open-arm preference in the elevated plus maze). The facilitatory effects were blocked by a selective V1A antagonist (SR 49059, Relcovaptan) but not by an oxytocin receptor antagonist (L-371,257). L-371,257 had some facilitatory effects on vocalizations. Arginine vasopressin had no effect in arthritic rats (kaolin/carrageenan knee joint pain model). SR 49059 inhibited vocalizations and anxiety-like behavior (elevated plus maze) in arthritic, but not normal, rats and conveyed anxiolytic properties to arginine vasopressin. Arginine vasopressin, SR 49059, and L-371,257 had no significant effects on spinal reflexes. We interpret the data to suggest that arginine vasopressin through V1A in the amygdala contributes to emotional-affective aspects of pain (arthritis model), whereas oxytocin receptors may mediate some inhibitory effects of the vasopressin system.
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Affiliation(s)
- Bryce Cragg
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA.,Department of Psychiatry, University of Miami Miller School of Medicine, FL, USA
| | - Guangchen Ji
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA .,Center of Excellence for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, Lubbock, TX, USA
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75
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Abstract
The anterior cingulate cortex (ACC) is activated in both acute and chronic pain. In this Review, we discuss increasing evidence from rodent studies that ACC activation contributes to chronic pain states and describe several forms of synaptic plasticity that may underlie this effect. In particular, one form of long-term potentiation (LTP) in the ACC, which is triggered by the activation of NMDA receptors and expressed by an increase in AMPA-receptor function, sustains the affective component of the pain state. Another form of LTP in the ACC, which is triggered by the activation of kainate receptors and expressed by an increase in glutamate release, may contribute to pain-related anxiety.
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76
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Vachon-Presseau E, Tétreault P, Petre B, Huang L, Berger SE, Torbey S, Baria AT, Mansour AR, Hashmi JA, Griffith JW, Comasco E, Schnitzer TJ, Baliki MN, Apkarian AV. Corticolimbic anatomical characteristics predetermine risk for chronic pain. Brain 2016; 139:1958-70. [PMID: 27190016 DOI: 10.1093/brain/aww100] [Citation(s) in RCA: 248] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 03/16/2016] [Indexed: 12/21/2022] Open
Abstract
SEE TRACEY DOI101093/BRAIN/AWW147 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Mechanisms of chronic pain remain poorly understood. We tracked brain properties in subacute back pain patients longitudinally for 3 years as they either recovered from or transitioned to chronic pain. Whole-brain comparisons indicated corticolimbic, but not pain-related circuitry, white matter connections predisposed patients to chronic pain. Intra-corticolimbic white matter connectivity analysis identified three segregated communities: dorsal medial prefrontal cortex-amygdala-accumbens, ventral medial prefrontal cortex-amygdala, and orbitofrontal cortex-amygdala-hippocampus. Higher incidence of white matter and functional connections within the dorsal medial prefrontal cortex-amygdala-accumbens circuit, as well as smaller amygdala volume, represented independent risk factors, together accounting for 60% of the variance for pain persistence. Opioid gene polymorphisms and negative mood contributed indirectly through corticolimbic anatomical factors, to risk for chronic pain. Our results imply that persistence of chronic pain is predetermined by corticolimbic neuroanatomical factors.
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Affiliation(s)
- Etienne Vachon-Presseau
- 1 Department of Physiology, Feinberg School of Medicine, Northwestern University 303 E. Chicago Ave., Chicago, IL 60611, USA
| | - Pascal Tétreault
- 1 Department of Physiology, Feinberg School of Medicine, Northwestern University 303 E. Chicago Ave., Chicago, IL 60611, USA
| | - Bogdan Petre
- 1 Department of Physiology, Feinberg School of Medicine, Northwestern University 303 E. Chicago Ave., Chicago, IL 60611, USA
| | - Lejian Huang
- 1 Department of Physiology, Feinberg School of Medicine, Northwestern University 303 E. Chicago Ave., Chicago, IL 60611, USA
| | - Sara E Berger
- 1 Department of Physiology, Feinberg School of Medicine, Northwestern University 303 E. Chicago Ave., Chicago, IL 60611, USA
| | - Souraya Torbey
- 2 Department of Psychiatry and Neurobehavioral Sciences, University of Virginia , 2955 Ivy Rd, Suite 210, Charlottesville, VA 22903, USA
| | - Alexis T Baria
- 1 Department of Physiology, Feinberg School of Medicine, Northwestern University 303 E. Chicago Ave., Chicago, IL 60611, USA
| | - Ali R Mansour
- 1 Department of Physiology, Feinberg School of Medicine, Northwestern University 303 E. Chicago Ave., Chicago, IL 60611, USA
| | - Javeria A Hashmi
- 3 Department of Anesthesia, Pain Management and Perioperative Medicine Dalhousie University, Halifax, NS, Canada B3H 4R2
| | - James W Griffith
- 4 Department of Medical Social Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Erika Comasco
- 5 Department of Neuroscience, Science for Life Laboratory, Uppsala University, BMC, Pob 593, 75124, Uppsala, Sweden
| | - Thomas J Schnitzer
- 6 Northwestern University Feinberg School of Medicine, Departments of Physical Medicine and Rehabilitation and Internal Medicine/Rheumatology, 710 N. Lake Shore Drive, Room 1020, Chicago, IL 60611, USA
| | - Marwan N Baliki
- 1 Department of Physiology, Feinberg School of Medicine, Northwestern University 303 E. Chicago Ave., Chicago, IL 60611, USA 7 Rehabilitation Istitute of Chicago, 345 E Superior St, Chicago, IL 60611, USA
| | - A Vania Apkarian
- 1 Department of Physiology, Feinberg School of Medicine, Northwestern University 303 E. Chicago Ave., Chicago, IL 60611, USA
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77
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Vachon-Presseau E, Centeno MV, Ren W, Berger SE, Tétreault P, Ghantous M, Baria A, Farmer M, Baliki MN, Schnitzer TJ, Apkarian AV. The Emotional Brain as a Predictor and Amplifier of Chronic Pain. J Dent Res 2016; 95:605-12. [PMID: 26965423 DOI: 10.1177/0022034516638027] [Citation(s) in RCA: 129] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Human neuroimaging studies and complementary animal experiments now identify the gross elements of the brain involved in the chronification of pain. We briefly review these advances in relation to somatic and orofacial persistent pain conditions. First, we emphasize the importance of reverse translational research for understanding chronic pain-that is, the power of deriving hypotheses directly from human brain imaging of clinical conditions that can be invasively and mechanistically studied in animal models. We then review recent findings demonstrating the importance of the emotional brain (i.e., the corticolimbic system) in the modulation of acute pain and in the prediction and amplification of chronic pain, contrasting this evidence with recent findings regarding the role of central sensitization in pain chronification, especially for orofacial pain. We next elaborate on the corticolimbic circuitry and underlying mechanisms that determine the transition to chronic pain. Given this knowledge, we advance a new mechanistic definition of chronic pain and discuss the clinical implications of this new definition as well as novel therapeutic potentials suggested by these advances.
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Affiliation(s)
- E Vachon-Presseau
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - M V Centeno
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - W Ren
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - S E Berger
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - P Tétreault
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - M Ghantous
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - A Baria
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - M Farmer
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - M N Baliki
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - T J Schnitzer
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - A V Apkarian
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
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78
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Sugimura YK, Takahashi Y, Watabe AM, Kato F. Synaptic and network consequences of monosynaptic nociceptive inputs of parabrachial nucleus origin in the central amygdala. J Neurophysiol 2016; 115:2721-39. [PMID: 26888105 PMCID: PMC4922599 DOI: 10.1152/jn.00946.2015] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 02/15/2016] [Indexed: 01/04/2023] Open
Abstract
A large majority of neurons in the superficial layer of the dorsal horn projects to the lateral parabrachial nucleus (LPB). LPB neurons then project to the capsular part of the central amygdala (CeA; CeC), a key structure underlying the nociception-emotion link. LPB-CeC synaptic transmission is enhanced in various pain models by using electrical stimulation of putative fibers of LPB origin in brain slices. However, this approach has limitations for examining direct monosynaptic connections devoid of directly stimulating fibers from other structures and local GABAergic neurons. To overcome these limitations, we infected the LPB of rats with an adeno-associated virus vector expressing channelrhodopsin-2 and prepared coronal and horizontal brain slices containing the amygdala. We found that blue light stimulation resulted in monosynaptic excitatory postsynaptic currents (EPSCs), with very small latency fluctuations, followed by a large polysynaptic inhibitory postsynaptic current in CeC neurons, regardless of the firing pattern type. Intraplantar formalin injection at 24 h before slice preparation significantly increased EPSC amplitude in late firing-type CeC neurons. These results indicate that direct monosynaptic glutamatergic inputs from the LPB not only excite CeC neurons but also regulate CeA network signaling through robust feed-forward inhibition, which is under plastic modulation in response to persistent inflammatory pain.
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Affiliation(s)
- Yae K Sugimura
- Department of Neuroscience, The Jikei University School of Medicine, Minato, Tokyo, Japan; Center for Neuroscience of Pain, The Jikei University School of Medicine, Minato, Tokyo, Japan; Research Fellow of Japan Society for the Promotion of Science, Tokyo, Japan
| | - Yukari Takahashi
- Department of Neuroscience, The Jikei University School of Medicine, Minato, Tokyo, Japan; Center for Neuroscience of Pain, The Jikei University School of Medicine, Minato, Tokyo, Japan
| | - Ayako M Watabe
- Department of Neuroscience, The Jikei University School of Medicine, Minato, Tokyo, Japan; Center for Neuroscience of Pain, The Jikei University School of Medicine, Minato, Tokyo, Japan; Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan; and Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Fusao Kato
- Department of Neuroscience, The Jikei University School of Medicine, Minato, Tokyo, Japan; Center for Neuroscience of Pain, The Jikei University School of Medicine, Minato, Tokyo, Japan; Nagoya University Graduate School of Medicine, Nagoya, Japan
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79
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Delaney AJ, Crane JW. Presynaptic GABAB receptors reduce transmission at parabrachial synapses in the lateral central amygdala by inhibiting N-type calcium channels. Sci Rep 2016; 6:19255. [PMID: 26755335 PMCID: PMC4709695 DOI: 10.1038/srep19255] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 12/07/2015] [Indexed: 11/20/2022] Open
Abstract
The nocioceptive information carried by neurons of the pontine parabrachial nucleus to neurons of the lateral division of the central amydala (CeA-L) is thought to contribute to the affective components of pain and is required for the formation of conditioned-fear memories. Importantly, excitatory transmission between parabrachial axon terminals and CeA-L neurons can be inhibited by a number of presynaptic receptors linked to Gi/o-type G-proteins, including α2-adrenoceptors and GABAB receptors. While the intracellular signalling pathway responsible for α2-adrenoceptor inhibition of synaptic transmission at this synapse is known, the mechanism by which GABAB receptors inhibits transmission has not been determined. The present study demonstrates that activation of presynaptic GABAB receptors reduces excitatory transmission between parabrachial axon terminals and CeA-L neurons by inhibiting N-type calcium channels. While the involvement of Gβγ subunits in mediating the inhibitory effects of GABAB receptors on N-type calcium channels is unclear, this inhibition does not involve Gβγ-independent activation of pp60C-src tyrosine kinase. The results of this study further enhance our understanding of the modulation of the excitatory input from parabrachial axon terminals to CeA-L neurons and indicate that presynaptic GABAB receptors at this synapse could be valuable therapeutic targets for the treatment of fear- and pain-related disorders.
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Affiliation(s)
- A J Delaney
- School of Biomedical Sciences, Charles Sturt University, NSW, Australia
| | - J W Crane
- School of Biomedical Sciences, Charles Sturt University, NSW, Australia
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80
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Moriarty O, Gorman CL, McGowan F, Ford GK, Roche M, Thompson K, Dockery P, McGuire BE, Finn DP. Impaired recognition memory and cognitive flexibility in the rat L5-L6 spinal nerve ligation model of neuropathic pain. Scand J Pain 2016; 10:61-73. [PMID: 28361775 DOI: 10.1016/j.sjpain.2015.09.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 09/29/2015] [Indexed: 11/17/2022]
Abstract
BACKGROUND AND AIMS Although neuropathic pain is known to negatively affect cognition, the neural mechanisms involved are poorly understood. Chronic pain is associated with changes in synaptic plasticity in the brain which may impact on cognitive functioning. The aim of this study was to model neuropathic pain in mid-aged rats using spinal nerve ligation (SNL). Following establishment of allodynia and hyperalgesia, behaviour was assessed in a battery of cognitive tests. Expression of the presynaptic protein, synaptophysin, and its colocalisation with the vesicular GABA and glutamate transporters (vGAT and vGLUT, respectively), was investigated in the medial prefrontal cortex (mPFC) and hippocampus. METHODS Nine month old male Sprague Dawley rats underwent L5-L6 spinal nerve ligation or a sham procedure. Mechanical and cold allodynia and thermal hyperalgesia were assessed using von Frey, acetone and Hargreaves tests, respectively. Cognition was assessed in the novel-object recognition, air-puff passive avoidance and Morris water maze behavioural tasks. Immunohistochemistry was used to examine the expression of synaptophysin in the mPFC and CA1 region of the hippocampus and double labelling of synaptophysin and the vesicular transporters vGAT and vGlut was used to investigate the distribution of synaptophysin on GABAergic and glutamatergic neurons. RESULTS SNL rats displayed impaired performance in the novel-object recognition task. Passive-avoidance responding, and spatial learning and memory in the Morris water maze, were unaffected by SNL surgery. However, in the water maze reversal task, pain-related impairments were evident during training and probe trials. SNL surgery was not associated with any differences in the expression of synaptophysin or its colocalisation with vGAT or vGLUT in the mPFC or the hippocampal CA1 region. CONCLUSIONS These results suggest that the SNL model of neuropathic pain is associated with deficits in recognition memory and cognitive flexibility, but these deficits are not associated with altered synaptophysin expression or distribution in the mPFC and CA1. IMPLICATIONS Cognitive complaints are common amongst chronic pain patients. Here we modelled cognitive impairment in a well-established animal model of neuropathic pain and investigated the neural mechanisms involved. A better understanding of this phenomenon is an important prerequisite for the development of improved treatment of patients affected.
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Affiliation(s)
- Orla Moriarty
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland, Galway, Ireland
- NCBES Neuroscience Centre, National University of Ireland, Galway, Ireland
- Centre for Pain Research, National University of Ireland, Galway, Ireland
| | - Claire L Gorman
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland, Galway, Ireland
| | - Fiona McGowan
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland, Galway, Ireland
- NCBES Neuroscience Centre, National University of Ireland, Galway, Ireland
- Centre for Pain Research, National University of Ireland, Galway, Ireland
| | - Gemma K Ford
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland, Galway, Ireland
- NCBES Neuroscience Centre, National University of Ireland, Galway, Ireland
- Centre for Pain Research, National University of Ireland, Galway, Ireland
| | - Michelle Roche
- Physiology, School of Medicine, National University of Ireland, Galway, Ireland
- NCBES Neuroscience Centre, National University of Ireland, Galway, Ireland
- Centre for Pain Research, National University of Ireland, Galway, Ireland
| | - Kerry Thompson
- Anatomy, School of Medicine, National University of Ireland, Galway, Ireland
- Centre for Microscopy and Imaging, National University of Ireland, Galway, Ireland
| | - Peter Dockery
- Anatomy, School of Medicine, National University of Ireland, Galway, Ireland
- NCBES Neuroscience Centre, National University of Ireland, Galway, Ireland
- Centre for Microscopy and Imaging, National University of Ireland, Galway, Ireland
| | - Brian E McGuire
- School of Psychology, National University of Ireland, Galway, Ireland
- NCBES Neuroscience Centre, National University of Ireland, Galway, Ireland
- Centre for Pain Research, National University of Ireland, Galway, Ireland
| | - David P Finn
- Pharmacology and Therapeutics, School of Medicine, National University of Ireland, Galway, Ireland
- NCBES Neuroscience Centre, National University of Ireland, Galway, Ireland
- Centre for Pain Research, National University of Ireland, Galway, Ireland
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81
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Muley MM, Krustev E, McDougall JJ. Preclinical Assessment of Inflammatory Pain. CNS Neurosci Ther 2015; 22:88-101. [PMID: 26663896 DOI: 10.1111/cns.12486] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 10/28/2015] [Accepted: 10/29/2015] [Indexed: 12/21/2022] Open
Abstract
While acute inflammation is a natural physiological response to tissue injury or infection, chronic inflammation is maladaptive and engenders a considerable amount of adverse pain. The chemical mediators responsible for tissue inflammation act on nociceptive nerve endings to lower neuronal excitation threshold and sensitize afferent firing rate leading to the development of allodynia and hyperalgesia, respectively. Animal models have aided in our understanding of the pathophysiological mechanisms responsible for the generation of chronic inflammatory pain and allowed us to identify and validate numerous analgesic drug candidates. Here we review some of the commonly used models of skin, joint, and gut inflammatory pain along with their relative benefits and limitations. In addition, we describe and discuss several behavioral and electrophysiological approaches used to assess the inflammatory pain in these preclinical models. Despite significant advances having been made in this area, a gap still exists between fundamental research and the implementation of these findings into a clinical setting. As such we need to characterize inherent pathophysiological pathways and develop new endpoints in these animal models to improve their predictive value of human inflammatory diseases in order to design safer and more effective analgesics.
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Affiliation(s)
- Milind M Muley
- Departments of Pharmacology and Anaesthesia, Pain Management & Perioperative Medicine, Dalhousie University, Halifax, NS, Canada
| | - Eugene Krustev
- Departments of Pharmacology and Anaesthesia, Pain Management & Perioperative Medicine, Dalhousie University, Halifax, NS, Canada
| | - Jason J McDougall
- Departments of Pharmacology and Anaesthesia, Pain Management & Perioperative Medicine, Dalhousie University, Halifax, NS, Canada
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82
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Abstract
Recent neuroimaging studies suggest that the brain adapts with pain, as well as imparts risk for developing chronic pain. Within this context, we revisit the concepts for nociception, acute and chronic pain, and negative moods relative to behavior selection. We redefine nociception as the mechanism protecting the organism from injury, while acute pain as failure of avoidant behavior, and a mesolimbic threshold process that gates the transformation of nociceptive activity to conscious pain. Adaptations in this threshold process are envisioned to be critical for development of chronic pain. We deconstruct chronic pain into four distinct phases, each with specific mechanisms, and outline current state of knowledge regarding these mechanisms: the limbic brain imparting risk, and the mesolimbic learning processes reorganizing the neocortex into a chronic pain state. Moreover, pain and negative moods are envisioned as a continuum of aversive behavioral learning, which enhance survival by protecting against threats.
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Affiliation(s)
- Marwan N Baliki
- Department of Physiology, Feinberg School of Medicine, 303 East Chicago Avenue, Chicago, IL 60610, USA.
| | - A Vania Apkarian
- Department of Physiology, Feinberg School of Medicine, 303 East Chicago Avenue, Chicago, IL 60610, USA; Department of Anesthesia, Feinberg School of Medicine, 303 East Chicago Avenue, Chicago, IL 60610, USA; Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, 303 East Chicago Avenue, Chicago, IL 60610, USA.
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83
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Dexmedetomidine Dose-Dependently Attenuates Ropivacaine-Induced Seizures and Negative Emotions Via Inhibiting Phosphorylation of Amygdala Extracellular Signal-Regulated Kinase in Mice. Mol Neurobiol 2015; 53:2636-46. [PMID: 26099305 DOI: 10.1007/s12035-015-9276-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 06/01/2015] [Indexed: 02/07/2023]
Abstract
Ropivacaine (Ropi), one of the newest and safest amino amide local anesthetics, is linked to toxicity, including the potential for seizures, changes in behavior, and even cardiovascular collapse. Dexmedetomidine (Dex), an α2-adrenergic receptor agonist, has been widely used in anesthesia and critical care practice. To date, the underlying mechanisms of the effects of Dex premedication on Ropi-induced toxicity have not been clearly identified. In the current study, we investigated the effects of increasing doses of Dex premedication on 50% convulsive dose (CD50) of Ropi. With increasing doses of intraperitoneal (i.p.) Dex 10 min prior to each i.p. RopiCD50, the latency and duration of seizure activity were recorded. Open-field (OF) and elevated plus maze (EPM) test were used to measure negative behavioral emotions such as depression and anxiety. Immunohistochemistry and Western blot were utilized to investigate phosphorylation-extracellular regulated protein kinases (p-ERK) expression in the basolateral amygdala (BLA) on 2 h and in the central amygdala (CeA) on 24 h after convulsion in mice. The results of our investigation demonstrated that Dex dose-dependently increased RopiCD50, prolonged the latency and shortened the duration of each RopiCD50-induced seizure, improved the negative emotions revealed by both OF and EPM test, and inhibited p-ERK expression in the BLA and the CeA.
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84
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Sato M, Ito M, Nagase M, Sugimura YK, Takahashi Y, Watabe AM, Kato F. The lateral parabrachial nucleus is actively involved in the acquisition of fear memory in mice. Mol Brain 2015; 8:22. [PMID: 25888401 PMCID: PMC4377188 DOI: 10.1186/s13041-015-0108-z] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 03/05/2015] [Indexed: 12/31/2022] Open
Abstract
Background Pavlovian fear conditioning is a form of learning accomplished by associating a conditioned stimulus (CS) and an unconditioned stimulus (US). While CS–US associations are generally thought to occur in the amygdala, the pathway mediating US signal processing has only been partially identified. The external part of the pontine lateral parabrachial nucleus (elPB) is well situated for providing US nociceptive information to the central amygdala (CeA), which was recently revealed to play a primary role in fear acquisition. Therefore, we manipulated the elPB activity to examine its role in the regulation of fear learning. Results First, we transiently inactivate the elPB during the acquisition of fear memory. Mice received bilateral elPB injections of the GABAA agonist muscimol (MUS) or phosphate-buffered saline (drug control), with bilateral misplacement of MUS defined as a placement control group. After the injection, mice were conditioned with a pure tone and foot-shock. On a memory retrieval test on day 2, the freezing ratio was significantly lower in the MUS group compared with that in the drug control or placement control groups. A second retrieval test using a pip tone on day 4 following de novo training on day 3, resulted in significant freezing with no group differences, indicating integrity of fear learning and a temporary limited effect of MUS. Next, we examined whether selectively activating the elPB-CeC pathway is sufficient to induce fear learning when paired with CS. Mice with channelrhodopsin2 (ChR2) expressed in the elPB received a pure tone (CS) in association with optical stimulation in the CeA (CS-LED paired group). On the retrieval test, CS-LED paired mice exhibited significantly higher freezing ratios evoked by CS presentation compared with both control mice receiving optical stimulation immediately after being placed in the shock chamber and exposed to the CS much later (immediate shock group) and those expressing only GFP (GFP control group). These results suggest that selective stimulation of the elPB-CeC pathway substitutes for the US to induce fear learning. Conclusions The elPB activity is necessary and sufficient to trigger fear learning, likely as a part of the pathway transmitting aversive signals to the CeA.
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Affiliation(s)
- Masaru Sato
- Department of Neuroscience, Jikei University School of Medicine, Tokyo, 105-8461, Japan. .,Department of Anesthesiology, Jikei University School of Medicine, Tokyo, 105-8461, Japan.
| | - Mariko Ito
- Department of Neuroscience, Jikei University School of Medicine, Tokyo, 105-8461, Japan. .,Department of Anesthesiology, Jikei University School of Medicine, Tokyo, 105-8461, Japan.
| | - Masashi Nagase
- Department of Neuroscience, Jikei University School of Medicine, Tokyo, 105-8461, Japan.
| | - Yae K Sugimura
- Department of Neuroscience, Jikei University School of Medicine, Tokyo, 105-8461, Japan.
| | - Yukari Takahashi
- Department of Neuroscience, Jikei University School of Medicine, Tokyo, 105-8461, Japan.
| | - Ayako M Watabe
- Department of Neuroscience, Jikei University School of Medicine, Tokyo, 105-8461, Japan. .,Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Saitama, 332-0012, Japan. .,Nagoya University Graduate School of Medicine, Nagoya, 466-8550, Japan.
| | - Fusao Kato
- Department of Neuroscience, Jikei University School of Medicine, Tokyo, 105-8461, Japan. .,Nagoya University Graduate School of Medicine, Nagoya, 466-8550, Japan.
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85
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Lu HC, Chang WJ, Kuan YH, Huang ACW, Shyu BC. A [14C]iodoantipyrine study of inter-regional correlations of neural substrates following central post-stroke pain in rats. Mol Pain 2015; 11:9. [PMID: 25889278 PMCID: PMC4358859 DOI: 10.1186/s12990-015-0006-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 02/17/2015] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Central pain syndrome is characterized by a combination of abnormal pain sensations, and pain medications often provide little or no relief. Accumulating animal and clinical studies have shown that impairments of the spinothalamic tract (STT) and thalamocingulate pathway causes somatosensory dysfunction in central post-stroke pain (CPSP), but the involvement of other neuronal circuitries in CPSP has not yet been systematically examined. The aim of the present study was to evaluate changes in brain activity and neuronal circuitry using [(14)C]iodoantipyrine (IAP) in an animal model of CPSP. RESULTS Rats were subjected to lateral thalamic hemorrhage to investigate the characteristics of CPSP. Thermal and mechanical hyperalgesia developed in rats that were subjected to thalamic hemorrhagic lesion. The medial prefrontal cortex (mPFC), anterior cingulate cortex (ACC), striatum, thalamus, hypothalamus, and amygdala were more active in the CPSP group compared with rats that were not subjected to lateral thalamic hemorrhage. The inter-regional correlation analysis showed that regional cerebral blood flow in the mPFC was highly correlated with the amygdala in the right brain, and the right brain showed complex connections among subregions of the ACC. Rats with CPSP exhibited strong activation of the thalamocingulate and mPFC-amygdala pathways. CONCLUSIONS These results corroborate previous findings that the STT and thalamocingulate pathway are involved in the pathophysiological mechanisms of CPSP symptoms. The mPFC, amygdala, and periaqueductal gray emerged as having important correlations in pain processing in CPSP. The present data provide a basis for a neural correlation hypothesis of CPSP, with implications for CPSP treatment.
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Affiliation(s)
- Hsiang-Chin Lu
- Institute of Biomedical Sciences, Academia Sinica, Taipei, 11529, Taiwan.
| | - Wei-Jen Chang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, 11529, Taiwan.
| | - Yung-Hui Kuan
- Institute of Biomedical Sciences, Academia Sinica, Taipei, 11529, Taiwan.
| | | | - Bai Chuang Shyu
- Institute of Biomedical Sciences, Academia Sinica, Taipei, 11529, Taiwan.
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86
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Kolber BJ. mGluRs Head to Toe in Pain. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 131:281-324. [DOI: 10.1016/bs.pmbts.2014.12.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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87
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Abstract
A limbic brain area, the amygdala plays a key role in emotional responses and affective states and disorders such as learned fear, anxiety, and depression. The amygdala has also emerged as an important brain center for the emotional-affective dimension of pain and for pain modulation. Hyperactivity in the laterocapsular division of the central nucleus of the amygdala (CeLC, also termed the "nociceptive amygdala") accounts for pain-related emotional responses and anxiety-like behavior. Abnormally enhanced output from the CeLC is the consequence of an imbalance between excitatory and inhibitory mechanisms. Impaired inhibitory control mediated by a cluster of GABAergic interneurons in the intercalated cell masses (ITC) allows the development of glutamate- and neuropeptide-driven synaptic plasticity of excitatory inputs from the brainstem (parabrachial area) and from the lateral-basolateral amygdala network (LA-BLA, site of integration of polymodal sensory information). BLA hyperactivity also generates abnormally enhanced feedforward inhibition of principal cells in the medial prefrontal cortex (mPFC), a limbic cortical area that is strongly interconnected with the amygdala. Pain-related mPFC deactivation results in cognitive deficits and failure to engage cortically driven ITC-mediated inhibitory control of amygdala processing. Impaired cortical control allows the uncontrolled persistence of amygdala pain mechanisms.
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Affiliation(s)
- Volker Neugebauer
- Department of Pharmacology and Neuroscience, Center for Translational Neuroscience and Therapeutics, Texas Tech University Health Sciences Center, 3601 4th Street, Lubbock, TX, 79430-6592, USA,
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88
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Min MY, Yang HW, Yen CT, Chen CC, Cheng SJ. ERK, synaptic plasticity and acid-induced-muscle pain. Commun Integr Biol 2014. [DOI: 10.4161/cib.15694] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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89
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Jiang H, Fang D, Kong LY, Jin ZR, Cai J, Kang XJ, Wan Y, Xing GG. Sensitization of neurons in the central nucleus of the amygdala via the decreased GABAergic inhibition contributes to the development of neuropathic pain-related anxiety-like behaviors in rats. Mol Brain 2014; 7:72. [PMID: 25277376 PMCID: PMC4201706 DOI: 10.1186/s13041-014-0072-z] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 09/18/2014] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Despite high prevalence of anxiety accompanying with chronic pain, the mechanisms underlying pain-related anxiety are largely unknown. With its well-documented role in pain and emotion processing, the amygdala may act as a key player in pathogenesis of neuropathic pain-related anxiety. Pain-related plasticity and sensitization of CeA (central nucleus of the amygdala) neurons have been shown in several models of chronic pain. In addition, firing pattern of neurons with spike output can powerfully affect functional output of the brain nucleus, and GABAergic neurons are crucial in the modulation of neuronal excitability. In this study, we first investigated whether pain-related plasticity (e.g. alteration of neuronal firing patterns) and sensitization of CeA neurons contribute to nerve injury-evoked anxiety in neuropathic rats. Furthermore, we explored whether GABAergic disinhibition is responsible for regulating firing patterns and intrinsic excitabilities of CeA neurons as well as for pain-related anxiety in neuropathic rats. RESULTS We discovered that spinal nerve ligation (SNL) produced neuropathic pain-related anxiety-like behaviors in rats, which could be specifically inhibited by intra-CeA administration of anti-anxiety drug diazepam. Moreover, we found potentiated plasticity and sensitization of CeA neurons in SNL-induced anxiety rats, of which including: 1) increased burst firing pattern and early-adapting firing pattern; 2) increased spike frequency and intrinsic excitability; 3) increased amplitude of both after-depolarized-potential (ADP) and sub-threshold membrane potential oscillation. In addition, we observed a remarkable reduction of GABAergic inhibition in CeA neurons in SNL-induced anxiety rats, which was proved to be important for altered firing patterns and hyperexcitability of CeA neurons, thereby greatly contributing to the development of neuropathic pain-related anxiety. Accordantly, activation of GABAergic inhibition by intra-CeA administration of muscimol, a selective GABAA receptors agonist, could inhibit SNL-induced anxiety-like behaviors in neuropathic rats. By contrast, suppression of GABAergic inhibition by intra-CeA administration of bicuculline, a selective GABAA receptors antagonist, produced anxiety-like behavior in normal rats. CONCLUSIONS This study suggests that reduction of GABAergic inhibition may be responsible for potentiated plasticity and sensitization of CeA neurons, which likely underlie the enhanced output of amygdala and neuropathic pain-related anxiety in SNL rats.
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Affiliation(s)
- Hong Jiang
- Neuroscience Research Institute, Peking University, 38 Xue-Yuan Road, Beijing, 100191, P.R. China.
| | - Dong Fang
- Neuroscience Research Institute, Peking University, 38 Xue-Yuan Road, Beijing, 100191, P.R. China.
| | - Ling-Yu Kong
- Neuroscience Research Institute, Peking University, 38 Xue-Yuan Road, Beijing, 100191, P.R. China.
| | - Zi-Run Jin
- Neuroscience Research Institute, Peking University, 38 Xue-Yuan Road, Beijing, 100191, P.R. China.
| | - Jie Cai
- Neuroscience Research Institute, Peking University, 38 Xue-Yuan Road, Beijing, 100191, P.R. China.
| | - Xue-Jing Kang
- Neuroscience Research Institute, Peking University, 38 Xue-Yuan Road, Beijing, 100191, P.R. China.
| | - You Wan
- Department of Neurobiology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, P.R. China. .,Key Laboratory for Neuroscience, Ministry of Education and Ministry of Health, Beijing, 100191, P.R. China.
| | - Guo-Gang Xing
- Neuroscience Research Institute, Peking University, 38 Xue-Yuan Road, Beijing, 100191, P.R. China. .,Department of Neurobiology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, 100191, P.R. China. .,Key Laboratory for Neuroscience, Ministry of Education and Ministry of Health, Beijing, 100191, P.R. China.
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90
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Palazzo E, Marabese I, de Novellis V, Rossi F, Maione S. Supraspinal metabotropic glutamate receptors: a target for pain relief and beyond. Eur J Neurosci 2014; 39:444-54. [PMID: 24494684 DOI: 10.1111/ejn.12398] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 09/20/2013] [Accepted: 09/23/2013] [Indexed: 01/09/2023]
Abstract
Glutamate is the main excitatory neurotransmitter in the central nervous system, controlling the majority of synapses. Apart from neurodegenerative diseases, growing evidence suggests that glutamate is involved in psychiatric and neurological disorders, including pain. Glutamate signaling is mediated via ionotropic glutamate receptors (iGluRs) and metabotropic glutamate receptors (mGluRs). So far, drugs acting via modulation of glutamatergic system are few in number, and all are associated with iGluRs and important side effects. The glutamatergic system may be finely modulated by mGluRs. Signaling via these receptors is slower and longer-lasting, and permits fine-tuning of glutamate transmission. There have been eight mGluRs cloned to date (mGluR1-mGluR8), and these are further divided into three groups on the basis of sequence homology, pharmacological profile, and second messenger signaling. The pattern of expression of mGluRs along the pain neuraxis makes them suitable substrates for the design of novel analgesics. This review will focus on the supraspinal mGluRs, whose pharmacological manipulation generates a variety of effects, which depend on the synaptic location, the cell type on which they are located, and the expression in particular pain modulation areas, such as the periaqueductal gray, which plays a major role in the descending modulation of pain, and the central nucleus of the amygdala, which is an important center for the processing of emotional information associated with pain. A particular emphasis will also be given to the novel selective mGluR subtype ligands, as well as positive and negative allosteric modulators, which have permitted discrimination of the individual roles of the different mGluR subtypes, and subtle modulation of central nervous system functioning and related disorders.
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Affiliation(s)
- Enza Palazzo
- Department of Anaesthesiology, Surgery and Emergency, The Second University of Naples, Piazza Luigi Miraglia 2, 80138, Naples, Italy
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91
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Pollema-Mays SL, Centeno MV, Apkarian AV, Martina M. Expression of DNA methyltransferases in adult dorsal root ganglia is cell-type specific and up regulated in a rodent model of neuropathic pain. Front Cell Neurosci 2014; 8:217. [PMID: 25152711 PMCID: PMC4126486 DOI: 10.3389/fncel.2014.00217] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2014] [Accepted: 07/17/2014] [Indexed: 11/13/2022] Open
Abstract
Neuropathic pain is associated with hyperexcitability and intrinsic firing of dorsal root ganglia (DRG) neurons. These phenotypical changes can be long lasting, potentially spanning the entire life of animal models, and depend on altered expression of numerous proteins, including many ion channels. Yet, how DRGs maintain long-term changes in protein expression in neuropathic conditions remains unclear. DNA methylation is a well-known mechanism of epigenetic control of gene expression and is achieved by the action of three enzymes: DNA methyltransferase (DNMT) 1, 3a, and 3b, which have been studied primarily during development. We first performed immunohistochemical analysis to assess whether these enzymes are expressed in adult rat DRGs (L4–5) and found that DNMT1 is expressed in both glia and neurons, DNMT3a is preferentially expressed in glia and DNMT3b is preferentially expressed in neurons. A rat model of neuropathic pain was then used to determine whether nerve injury may induce epigenetic changes in DRGs at multiple time points after pain onset. Real-time RT PCR analysis revealed robust and time-dependent changes in DNMT transcript expression in ipsilateral DRGs from spared nerve injury (SNI) but not sham rats. Interestingly, DNMT3b transcript showed a robust upregulation that appeared already 1 week after surgery and persisted at 4 weeks (our endpoint); in contrast, DNMT1 and DNMT3a transcripts showed only moderate upregulation that was transient and did not appear until the second week. We suggest that DNMT regulation in adult DRGs may be a contributor to the pain phenotype and merits further study.
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Affiliation(s)
- Sarah L Pollema-Mays
- Department of Physiology, Northwestern University Feinberg School of Medicine Chicago, IL, USA
| | - Maria V Centeno
- Department of Physiology, Northwestern University Feinberg School of Medicine Chicago, IL, USA
| | - A V Apkarian
- Department of Physiology, Northwestern University Feinberg School of Medicine Chicago, IL, USA
| | - Marco Martina
- Department of Physiology, Northwestern University Feinberg School of Medicine Chicago, IL, USA
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92
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Parabrachial nucleus (PBn) pituitary adenylate cyclase activating polypeptide (PACAP) signaling in the amygdala: implication for the sensory and behavioral effects of pain. Neuropharmacology 2014; 86:38-48. [PMID: 24998751 DOI: 10.1016/j.neuropharm.2014.06.022] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 06/17/2014] [Accepted: 06/19/2014] [Indexed: 11/22/2022]
Abstract
The intricate relationships that associate pain, stress responses and emotional behavior have been well established. Acute stressful situations can decrease nociceptive sensations and conversely, chronic pain can enhance other pain experiences and heighten the emotional and behavioral consequences of stress. Accordingly, chronic pain is comorbid with a number of behavioral disorders including depression, anxiety abnormalities and associated stress-related disorders including post traumatic stress disorder (PTSD). The central nucleus of the amygdala (CeA) represents a convergence of pathways for pain, stress and emotion, and we have identified pituitary adenylate cyclase activating polypeptide (PACAP) immunoreactivity in fiber elements in the lateral capsular division of the CeA (CeLC). The PACAP staining patterns colocalized in part with those for calcitonin gene related peptide (CGRP); anterograde fiber tracing and excitotoxic lesion studies demonstrated that the CeLC PACAP/CGRP immunoreactivities represented sensory fiber projections from the lateral parabrachial nucleus (LPBn) along the spino-parabrachioamygdaloid tract. The same PBn PACAP/CGRP fiber system also projected to the BNST. As in the BNST, CeA PACAP signaling increased anxiety-like behaviors accompanied by weight loss and decreased feeding. But in addition to heightened anxiety-like responses, CeA PACAP signaling also altered nociception as reflected by decreased latency and threshold responses in thermal and mechanical sensitivity tests, respectively. From PACAP expression in major pain pathways, the current observations are novel and suggest that CeA PACAP nociceptive signaling and resulting neuroplasticity via the spino-parabrachioamygdaloid tract may represent mechanisms that associate chronic pain with sensory hypersensitivity, fear memory consolidation and severe behavioral disorders.
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93
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Luo C, Kuner T, Kuner R. Synaptic plasticity in pathological pain. Trends Neurosci 2014; 37:343-55. [DOI: 10.1016/j.tins.2014.04.002] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 03/31/2014] [Accepted: 04/09/2014] [Indexed: 02/06/2023]
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94
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Medina G, Ji G, Grégoire S, Neugebauer V. Nasal application of neuropeptide S inhibits arthritis pain-related behaviors through an action in the amygdala. Mol Pain 2014; 10:32. [PMID: 24884567 PMCID: PMC4046088 DOI: 10.1186/1744-8069-10-32] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 05/22/2014] [Indexed: 11/10/2022] Open
Abstract
Recently discovered neuropeptide S (NPS) has anxiolytic and pain-inhibiting effects in rodents. We showed previously that NPS increases synaptic inhibition of amygdala output to inhibit pain behaviors. The amygdala plays a key role in emotional-affective aspects of pain. Of clinical significance is that NPS can be applied nasally to exert anxiolytic effects in rodents. This study tested the novel hypothesis that nasal application of NPS can inhibit pain-related behaviors in an arthritis model through NPS receptors (NPSR) in the amygdala. Behaviors and electrophysiological activity of amygdala neurons were measured in adult male Sprague Dawley rats. Nasal application of NPS, but not saline, inhibited audible and ultrasonic vocalizations and had anxiolytic-like effects in the elevated plus-maze test in arthritic rats (kaolin/carrageenan knee joint arthritis model) but had no effect in normal rats. Stereotaxic application of a selective non-peptide NPSR antagonist (SHA68) into the amygdala by microdialysis reversed the inhibitory effects of NPS. NPS had no effect on hindlimb withdrawal thresholds. We showed previously that intra-amygdala application of an NPSR antagonist alone had no effect. Nasal application of NPS or stereotaxic application of NPS into the amygdala by microdialysis inhibited background and evoked activity of amygdala neurons in arthritic, but not normal, anesthetized rats. The inhibitory effect was blocked by a selective NPSR antagonist ([D-Cys(tBu)5]NPS). In conclusion, nasal application of NPS can inhibit emotional-affective, but not sensory, pain-related behaviors through an action in the amygdala. The beneficial effects of non-invasive NPS application may suggest translational potential.
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Affiliation(s)
- Georgina Medina
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch at Galveston, 301 Univ. Blvd. RT1069, Galveston, TX 77555-1069, USA
| | - Guangchen Ji
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch at Galveston, 301 Univ. Blvd. RT1069, Galveston, TX 77555-1069, USA
| | - Stéphanie Grégoire
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch at Galveston, 301 Univ. Blvd. RT1069, Galveston, TX 77555-1069, USA
| | - Volker Neugebauer
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch at Galveston, 301 Univ. Blvd. RT1069, Galveston, TX 77555-1069, USA
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95
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Lu YC, Chen YZ, Wei YY, He XT, Li X, Hu W, Yanagawa Y, Wang W, Wu SX, Dong YL. Neurochemical properties of the synapses between the parabrachial nucleus-derived CGRP-positive axonal terminals and the GABAergic neurons in the lateral capsular division of central nucleus of amygdala. Mol Neurobiol 2014; 51:105-18. [PMID: 24794145 DOI: 10.1007/s12035-014-8713-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 04/09/2014] [Indexed: 11/28/2022]
Abstract
The lateral capsular division of central nucleus of amygdala (CeC) contains neurons using γ-amino butyric acid (GABA) as the predominant neurotransmitter and expresses abundant calcitonin gene-related peptide (CGRP)-positive terminals. However, the relationship between them has not been revealed yet. Using GAD67-green fluorescent protein (GFP) knock-in mouse, we investigated the neurochemical features of synapses between CGRP-positive terminals and GABAergic neurons within CeC and the potential involvement of CGRP1 receptor by combining fluorescent in situ hybridization for CGRP1 receptor mRNA with immunofluorescent histochemistry for GFP and CGRP. The ultrastructures of these synapses were investigated with pre-embedding electron microscopy for GFP and CGRP. We found that some GABAergic neurons in the CeC received parabrachial nucleus (PBN) derived CGRP innervations and some of these GABAergic neurons can be activated by subcutaneous injection of formalin. Moreover, more than 90 % GABAergic neurons innervated by CGRP-positive terminal also express CGRP1 receptor mRNA. The CGRP-positive fibers made symmetric synapses onto the GABAergic somata, and asymmetric synapses onto the GABA-LI dendritic shafts and spines. This study provides direct ultrastructural evidences for the synaptic contacts between CGRP-positive terminals and GABAergic neurons within the CeC, which may underlie the pain-related neural pathway from PBN to CeC and be involved in the chronic pain modulation.
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Affiliation(s)
- Ya-Cheng Lu
- Department of Anatomy, Histology and Embryology and K.K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, 710032, People's Republic of China
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96
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Liu MG, Chen J. Preclinical research on pain comorbidity with affective disorders and cognitive deficits: Challenges and perspectives. Prog Neurobiol 2014; 116:13-32. [DOI: 10.1016/j.pneurobio.2014.01.003] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 12/31/2013] [Accepted: 01/02/2014] [Indexed: 12/12/2022]
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97
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Ji G, Neugebauer V. CB1 augments mGluR5 function in medial prefrontal cortical neurons to inhibit amygdala hyperactivity in an arthritis pain model. Eur J Neurosci 2014; 39:455-66. [PMID: 24494685 PMCID: PMC4288820 DOI: 10.1111/ejn.12432] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 10/17/2013] [Accepted: 10/25/2013] [Indexed: 12/29/2022]
Abstract
The medial prefrontal cortex (mPFC) serves executive control functions and forms direct connections with subcortical areas such as the amygdala. Our previous work showed abnormal inhibition of mPFC pyramidal cells and hyperactivity of amygdala output neurons in an arthritis pain model. To restore mPFC activity and hence control pain-related amygdala hyperactivity this study focused on CB1 and mGluR5 receptors, which are important modulators of cortical functions. Extracellular single-unit recordings of infralimbic mPFC pyramidal cells and of amygdala output neurons in the laterocapsular division of the central nucleus (CeLC) were made in anesthetised adult male rats. mPFC neurons were classified as 'excited' or 'inhibited' based on their response to brief innocuous and noxious test stimuli. After arthritis pain induction, background activity and evoked responses of excited neurons and background activity and inhibition of inhibited neurons decreased. Stereotaxic application of an mGluR5-positive allosteric modulator (N-cyclobutyl-6-((3-fluorophenyl)ethynyl) nicotinamide hydrochloride, VU0360172) into the mPFC increased background and evoked activity of excited, but not inhibited, mPFC neurons under normal conditions but not in arthritis. A selective CB1 receptor agonist (arachidonyl-2-chloroethylamide) alone had no effect but restored the facilitatory effects of VU0360172 in the pain model. Coactivation of CB1 and mGluR5 in the mPFC inhibited the pain-related activity increase of CeLC neurons but had no effect under normal conditions. The data suggest that excited mPFC neurons are inversely linked to amygdala output (CeLC) and that CB1 can increase mGluR5 function in this subset of mPFC neurons to engage cortical control of abnormally enhanced amygdala output in pain.
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Affiliation(s)
- Guangchen Ji
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX, 77555-1069, USA
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98
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Liu MG, Zhuo M. Loss of long-term depression in the insular cortex after tail amputation in adult mice. Mol Pain 2014; 10:1. [PMID: 24398034 PMCID: PMC3912895 DOI: 10.1186/1744-8069-10-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Accepted: 12/30/2013] [Indexed: 01/01/2023] Open
Abstract
The insular cortex (IC) is an important forebrain structure involved in pain perception and taste memory formation. Using a 64-channel multi-electrode array system, we recently identified and characterized two major forms of synaptic plasticity in the adult mouse IC: long-term potentiation (LTP) and long-term depression (LTD). In this study, we investigate injury-related metaplastic changes in insular synaptic plasticity after distal tail amputation. We found that tail amputation in adult mice produced a selective loss of low frequency stimulation-induced LTD in the IC, without affecting (RS)-3,5-dihydroxyphenylglycine (DHPG)-evoked LTD. The impaired insular LTD could be pharmacologically rescued by priming the IC slices with a lower dose of DHPG application, a form of metaplasticity which involves activation of protein kinase C but not protein kinase A or calcium/calmodulin-dependent protein kinase II. These findings provide important insights into the synaptic mechanisms of cortical changes after peripheral amputation and suggest that restoration of insular LTD may represent a novel therapeutic strategy against the synaptic dysfunctions underlying the pathophysiology of phantom pain.
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Affiliation(s)
| | - Min Zhuo
- Center for Neuron and Disease, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an 710049, China.
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99
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Apkarian AV, Neugebauer V, Koob G, Edwards S, Levine JD, Ferrari L, Egli M, Regunathan S. Neural mechanisms of pain and alcohol dependence. Pharmacol Biochem Behav 2013; 112:34-41. [PMID: 24095683 DOI: 10.1016/j.pbb.2013.09.008] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 09/06/2013] [Accepted: 09/17/2013] [Indexed: 01/09/2023]
Abstract
An association between chronic pain conditions and alcohol dependence has been revealed in numerous studies with episodes of alcohol abuse antedating chronic pain in some people and alcohol dependence emerging after the onset of chronic pain in others. Alcohol dependence and chronic pain share common neural circuits giving rise to the possibility that chronic pain states could significantly affect alcohol use patterns and that alcohol dependence could influence pain sensitivity. The reward and emotional pathways that regulate drug/alcohol addiction also mediate chronic pain. For example, pain-evoked activation of brain learning and brain reward circuitry may modulate cortical processing of pain and central sensitization mediated by mesocorticolimbic circuitry. Imbalance and reorganization of amygdala-mPFC interactions may not only be important for persistent pain, but also for disorders characterized by the abnormal persistence of emotional-affective states such as drug and alcohol addiction. Further studies are necessary to understand how these neural circuits are regulated in comorbid conditions of alcoholism and chronic pain. In addition, long term alcohol use could induce pain symptoms and may exacerbate chronic pain arising from other sources. While prior studies have established a role of neuroendocrine stress axis mediators in alcohol abuse and neurotoxic effects, these studies have not explored the distinction between the individual impact of alcohol and stress hormones. Future studies should explore the mechanisms mediating the contribution of alcohol and stress axis hormones on pain, an important question in our understanding of the neurobiology of alcohol abuse and chronic pain.
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Affiliation(s)
- A Vania Apkarian
- Department of Neuroscience, Northwestern University Med School, Chicago, IL, USA
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Ren W, Kiritoshi T, Grégoire S, Ji G, Guerrini R, Calo G, Neugebauer V. Neuropeptide S: a novel regulator of pain-related amygdala plasticity and behaviors. J Neurophysiol 2013; 110:1765-81. [PMID: 23883857 PMCID: PMC3798934 DOI: 10.1152/jn.00874.2012] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 07/18/2013] [Indexed: 12/12/2022] Open
Abstract
Amygdala plasticity is an important contributor to the emotional-affective dimension of pain. Recently discovered neuropeptide S (NPS) has anxiolytic properties through actions in the amygdala. Behavioral data also suggest antinociceptive effects of centrally acting NPS, but site and mechanism of action remain to be determined. This is the first electrophysiological analysis of pain-related NPS effects in the brain. We combined whole cell patch-clamp recordings in brain slices and behavioral assays to test the hypothesis that NPS activates synaptic inhibition of amygdala output to suppress pain behavior in an arthritis pain model. Recordings of neurons in the laterocapsular division of the central nucleus (CeLC), which serves pain-related amygdala output functions, show that NPS inhibited the enhanced excitatory drive [monosynaptic excitatory postsynaptic currents (EPSCs)] from the basolateral amygdala (BLA) in the pain state. As shown by miniature EPSC analysis, the inhibitory effect of NPS did not involve direct postsynaptic action on CeLC neurons but rather a presynaptic, action potential-dependent network mechanism. Indeed, NPS increased external capsule (EC)-driven synaptic inhibition of CeLC neurons through PKA-dependent facilitatory postsynaptic action on a cluster of inhibitory intercalated (ITC) cells. NPS had no effect on BLA neurons. High-frequency stimulation (HFS) of excitatory EC inputs to ITC cells also inhibited synaptic activation of CeLC neurons, providing further evidence that ITC activation can control amygdala output. The cellular mechanisms by which EC-driven synaptic inhibition controls CeLC output remain to be determined. Administration of NPS into ITC, but not CeLC, also inhibited vocalizations and anxiety-like behavior in arthritic rats. A selective NPS receptor antagonist ([d-Cys(tBu)(5)]NPS) blocked electrophysiological and behavioral effects of NPS. Thus NPS is a novel tool to control amygdala output and pain-related affective behaviors through a direct action on inhibitory ITC cells.
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Affiliation(s)
- Wenjie Ren
- Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, Texas
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