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Cui X, Liu J, Uniyal A, Xu Q, Zhang C, Zhu G, Yang F, Sivanesan E, Linderoth B, Raja SN, Guan Y. Enhancing spinal cord stimulation-induced pain inhibition by augmenting endogenous adenosine signalling after nerve injury in rats. Br J Anaesth 2024; 132:746-757. [PMID: 38310069 PMCID: PMC10925891 DOI: 10.1016/j.bja.2024.01.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 01/03/2024] [Accepted: 01/05/2024] [Indexed: 02/05/2024] Open
Abstract
BACKGROUND The mechanisms for spinal cord stimulation (SCS) to alleviate chronic pain are only partially known. We aimed to elucidate the roles of adenosine A1 and A3 receptors (A1R, A3R) in the inhibition of spinal nociceptive transmission by SCS, and further explored whether 2'-deoxycoformycin (dCF), an inhibitor of adenosine deaminase, can potentiate SCS-induced analgesia. METHODS We used RNAscope and immunoblotting to examine the distributions of adora1 and adora3 expression, and levels of A1R and A3R proteins in the spinal cord of rats after tibial-spared nerve injury (SNI-t). Electrophysiology recording was conducted to examine how adenosine receptor antagonists, virus-mediated adora3 knockdown, and dCF affect SCS-induced inhibition of C-fibre-evoked spinal local field potential (C-LFP). RESULTS Adora1 was predominantly expressed in neurones, whereas adora3 is highly expressed in microglial cells in the rat spinal cord. Spinal application of antagonists (100 μl) of A1R (8-cyclopentyl-1,3-dipropylxanthine [DPCPX], 50 μM) and A3R (MRS1523, 200 nM) augmented C-LFP in SNI-t rats (DPCPX: 1.39 [0.18] vs vehicle: 0.98 [0.05], P=0.046; MRS1523: 1.21 [0.07] vs vehicle: 0.91 [0.03], P=0.002). Both drugs also blocked inhibition of C-LFP by SCS. Conversely, dCF (0.1 mM) enhanced SCS-induced C-LFP inhibition (dCF: 0.60 [0.04] vs vehicle: 0.85 [0.02], P<0.001). In the behaviour study, dCF (100 nmol 15 μl-1, intrathecal) also enhanced inhibition of mechanical hypersensitivity by SCS in SNI-t rats. CONCLUSIONS Spinal A1R and A3R signalling can exert tonic suppression and also contribute to SCS-induced inhibition of spinal nociceptive transmission after nerve injury. Inhibition of adenosine deaminase may represent a novel adjuvant pharmacotherapy to enhance SCS-induced analgesia.
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Affiliation(s)
- Xiang Cui
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Jing Liu
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Ankit Uniyal
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Qian Xu
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD, USA; Howard Hughes Medical Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Chi Zhang
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Guangwu Zhu
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Fei Yang
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Eellan Sivanesan
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Bengt Linderoth
- Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden
| | - Srinivasa N Raja
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA
| | - Yun Guan
- Department of Anaesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD, USA; Department of Neurological Surgery, Johns Hopkins University, School of Medicine, Baltimore, MD, USA.
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Yang L, Liu B, Zheng S, Xu L, Yao M. Understanding the initiation, delivery and processing of bone cancer pain from the peripheral to the central nervous system. Neuropharmacology 2023; 237:109641. [PMID: 37392821 DOI: 10.1016/j.neuropharm.2023.109641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 06/01/2023] [Accepted: 06/20/2023] [Indexed: 07/03/2023]
Abstract
Bone cancer pain is a complex condition characterized by persistent, sudden, spontaneous pain accompanied by hyperalgesia that typically arises from bone metastases or primary bone tumors, causing severe discomfort and significantly diminishing cancer patients' quality of life and confidence in their ability to overcome the disease. It is widely known that peripheral nerves are responsible for detecting harmful stimuli, which are then transmitted to the brain via the spinal cord, resulting in the perception of pain. In the case of bone cancer, tumors and stromal cells within the bone marrow release various chemical signals, including inflammatory factors, colony-stimulating factors, chemokines, and hydrogen ions. Consequently, the nociceptors located at the nerve endings within the bone marrow sense these chemical signals, generating electrical signals that are then transmitted to the brain through the spinal cord. Subsequently, the brain processes these electrical signals in a complex manner to create the sensation of bone cancer pain. Numerous studies have investigated the transmission of bone cancer pain from the periphery to the spinal cord. However, the processing of pain information induced by bone cancer within the brain remains unclear. With the continuous advancements in brain science and technology, the brain mechanism of bone cancer pain would become more clearly understood. Herein, we focus on summarizing the peripheral nerve perception of the spinal cord transmission of bone cancer pain and provide a brief overview of the ongoing research regarding the brain mechanisms involved in bone cancer pain.
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Affiliation(s)
- Lei Yang
- Department of Anesthesia and Pain Medicine, Affiliated Hospital of Jiaxing University, No. 1882 Zhong-Huan-Nan Road, Jiaxing, 314001, China
| | - Beibei Liu
- Department of Anesthesia and Pain Medicine, Affiliated Hospital of Jiaxing University, No. 1882 Zhong-Huan-Nan Road, Jiaxing, 314001, China
| | - Shang Zheng
- Department of Anesthesia and Pain Medicine, Affiliated Hospital of Jiaxing University, No. 1882 Zhong-Huan-Nan Road, Jiaxing, 314001, China
| | - Longsheng Xu
- Department of Anesthesia and Pain Medicine, Affiliated Hospital of Jiaxing University, No. 1882 Zhong-Huan-Nan Road, Jiaxing, 314001, China.
| | - Ming Yao
- Department of Anesthesia and Pain Medicine, Affiliated Hospital of Jiaxing University, No. 1882 Zhong-Huan-Nan Road, Jiaxing, 314001, China.
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Morales-Medina JC, Pugliese N, Di Cerbo A, Zizzadoro C, Iannitti T. Evidence for Endogenous Opioid Dependence Related to Latent Sensitization in a Rat Model of Chronic Inflammatory Pain. Int J Mol Sci 2023; 24:ijms24032812. [PMID: 36769126 PMCID: PMC9917357 DOI: 10.3390/ijms24032812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 01/25/2023] [Accepted: 01/30/2023] [Indexed: 02/05/2023] Open
Abstract
Studies performed in a mouse model of chronic inflammatory pain induced by intraplantar injection of complete Freund's adjuvant (CFA) have shown that constitutive activation of the endogenous opioid signaling, besides serving as a mechanism of endogenous analgesia that tonically represses pain sensitization, also generates a state of endogenous opioid dependence. Since species-related differences concerning pain biology and addictive behaviors occur between mice and rats, the present study explored whether the coexistence of endogenous opioid analgesia and endogenous opioid dependence also characterizes a homologous rat model. To this aim, CFA-injured Wistar rats were treated with either 3 mg/kg or 10 mg/kg of the opioid receptor inverse agonist naltrexone (NTX) during the pain remission phase and monitored for 60 min for possible withdrawal behaviors. At 3 mg/kg, NTX, besides inducing the reinstatement of mechanical allodynia, also caused a distinct appearance of ptosis, with slight but nonsignificant changes to the occurrence of teeth chatters and rearing. On the other hand, 10 mg/kg of NTX failed to unmask pain sensitization and induced significantly lower levels of ptosis than 3 mg/kg. Such an NTX-related response pattern observed in the rat CFA model seems to differ substantially from the pattern previously described in the mouse CFA model. This supports the knowledge that mice and rats are not identical in terms of pharmacological response and stresses the importance of choosing the appropriate species for preclinical pain research purposes depending on the scientific question being asked.
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Affiliation(s)
- Julio César Morales-Medina
- Centro de Investigación en Reproducción Animal, CINVESTAV-Universidad Autónoma de Tlaxcala, AP 62, Tlaxcala 90000, Mexico
| | - Nicola Pugliese
- Department of Veterinary Medicine, University of Bari, 70010 Valenzano, Italy
| | - Alessandro Di Cerbo
- School of Biosciences and Veterinary Medicine, University of Camerino, 62024 Matelica, Italy
- Correspondence: (A.D.C.); (C.Z.)
| | - Claudia Zizzadoro
- Department of Veterinary Medicine, University of Bari, 70010 Valenzano, Italy
- Correspondence: (A.D.C.); (C.Z.)
| | - Tommaso Iannitti
- Section of Experimental Medicine, Department of Medical Sciences, University of Ferrara, Via Fossato di Mortara 70, 44121 Ferrara, Italy
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Kim MS, Kim BY, Saghetlians A, Zhang X, Okida T, Kim SY. Anti-nociceptive effects of dual neuropeptide antagonist therapy in mouse model of neuropathic and inflammatory pain. Korean J Pain 2022; 35:173-182. [PMID: 35354680 PMCID: PMC8977203 DOI: 10.3344/kjp.2022.35.2.173] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 03/10/2022] [Accepted: 03/10/2022] [Indexed: 11/05/2022] Open
Abstract
Background Neurokinin-1 (NK1) and calcitonin gene-related peptide (CGRP) play a vital role in pain pathogenesis, and these proteins' antagonists have attracted attention as promising pharmaceutical candidates. The authors investigated the antinociceptive effect of co-administration of the CGRP antagonist and an NK1 antagonist on pain models compared to conventional single regimens. Methods C57Bl/6J mice underwent sciatic nerve ligation for the neuropathic pain model and were injected with 4% formalin into the hind paw for the inflammatory pain model. Each model was divided into four groups: vehicle, NK1 antagonist, CGRP antagonist, and combination treatment groups. The NK1 antagonist aprepitant (BIBN4096, 1 mg/kg) or the CGRP antagonist olcegepant (MK-0869, 10 mg/kg) was injected intraperitoneally. Mechanical allodynia, thermal hypersensitivity, and anxiety-related behaviors were assessed using the von Frey, hot plate, and elevated plus-maze tests. The flinching and licking responses were also evaluated after formalin injection. Results Co-administration of aprepitant and olcegepant more significantly alleviated pain behaviors than administration of single agents or vehicle, increasing the mechanical threshold and improving the response latency. Anxiety-related behaviors were also markedly improved after dual treatment compared with either naive mice or the neuropathic pain model in the dual treatment group. Flinching frequency and licking response after formalin injection decreased significantly in the dual treatment group. Isobolographic analysis showed a meaningful additive effect between the two compounds. Conclusions A combination pharmacological therapy comprised of multiple neuropeptide antagonists could be a more effective therapeutic strategy for alleviating neuropathic or inflammatory pain.
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Affiliation(s)
- Min Su Kim
- Department of Rehabilitation Medicine, Wonkwang University College of Medicine, Iksan, Korea
| | - Bo Yeon Kim
- Department of Rehabilitation Medicine, Wonkwang University College of Medicine, Iksan, Korea.,Salk Institute for Biological Studies, La Jolla, CA, USA
| | | | - Xiang Zhang
- Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Takuya Okida
- Salk Institute for Biological Studies, La Jolla, CA, USA
| | - So Yeon Kim
- Department of Rehabilitation Medicine, Wonkwang University College of Medicine, Iksan, Korea.,Salk Institute for Biological Studies, La Jolla, CA, USA
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Boakye PA, Tang SJ, Smith PA. Mediators of Neuropathic Pain; Focus on Spinal Microglia, CSF-1, BDNF, CCL21, TNF-α, Wnt Ligands, and Interleukin 1β. FRONTIERS IN PAIN RESEARCH 2022; 2:698157. [PMID: 35295524 PMCID: PMC8915739 DOI: 10.3389/fpain.2021.698157] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 07/14/2021] [Indexed: 01/04/2023] Open
Abstract
Intractable neuropathic pain is a frequent consequence of nerve injury or disease. When peripheral nerves are injured, damaged axons undergo Wallerian degeneration. Schwann cells, mast cells, fibroblasts, keratinocytes and epithelial cells are activated leading to the generation of an “inflammatory soup” containing cytokines, chemokines and growth factors. These primary mediators sensitize sensory nerve endings, attract macrophages, neutrophils and lymphocytes, alter gene expression, promote post-translational modification of proteins, and alter ion channel function in primary afferent neurons. This leads to increased excitability and spontaneous activity and the generation of secondary mediators including colony stimulating factor 1 (CSF-1), chemokine C-C motif ligand 21 (CCL-21), Wnt3a, and Wnt5a. Release of these mediators from primary afferent neurons alters the properties of spinal microglial cells causing them to release tertiary mediators, in many situations via ATP-dependent mechanisms. Tertiary mediators such as BDNF, tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and other Wnt ligands facilitate the generation and transmission of nociceptive information by increasing excitatory glutamatergic transmission and attenuating inhibitory GABA and glycinergic transmission in the spinal dorsal horn. This review focusses on activation of microglia by secondary mediators, release of tertiary mediators from microglia and a description of their actions in the spinal dorsal horn. Attention is drawn to the substantial differences in the precise roles of various mediators in males compared to females. At least 25 different mediators have been identified but the similarity of their actions at sensory nerve endings, in the dorsal root ganglia and in the spinal cord means there is considerable redundancy in the available mechanisms. Despite this, behavioral studies show that interruption of the actions of any single mediator can relieve signs of pain in experimental animals. We draw attention this paradox. It is difficult to explain how inactivation of one mediator can relieve pain when so many parallel pathways are available.
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Affiliation(s)
- Paul A Boakye
- Department of Anesthesiology, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, United States
| | - Shao-Jun Tang
- Department of Anesthesiology, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, United States
| | - Peter A Smith
- Neuroscience and Mental Health Institute and Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
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Skin co-delivery of contact sensitizers and neurokinin-1 receptor antagonists integrated in microneedle arrays suppresses allergic contact dermatitis. J Allergy Clin Immunol 2022; 150:114-130. [DOI: 10.1016/j.jaci.2021.12.794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2021] [Revised: 11/03/2021] [Accepted: 12/03/2021] [Indexed: 11/18/2022]
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Gerum M, Simonin F. Behavioral characterization, potential clinical relevance and mechanisms of latent pain sensitization. Pharmacol Ther 2021; 233:108032. [PMID: 34763010 DOI: 10.1016/j.pharmthera.2021.108032] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 10/22/2021] [Accepted: 11/03/2021] [Indexed: 10/19/2022]
Abstract
Chronic pain is a debilitating disorder that can occur as painful episodes that alternates with bouts of remission and occurs despite healing of the primary insult. Those episodes are often triggered by stressful events. In the last decades, a similar situation has been evidenced in a wide variety of rodent models (including inflammatory pain, neuropathy and opioid-induced hyperalgesia) where animals develop a chronic latent hyperalgesia that silently persists after behavioral signs of pain resolution. This state, referred as latent pain sensitization, is due to the compensatory activation of antinociceptive systems, such as the opioid system or NPY and its receptors. A transitory phase of hyperalgesia can then be reinstated by pharmacological or genetic blockade of these antinociceptive systems or by submitting animals to acute stress. Those observations reveal that there is a constant endogenous analgesia responsible for chronic pain inhibition that might paradoxically contribute to maintain this maladaptive state and could then participate to the transition from acute to chronic pain. Thus, demonstration of the existence of this phenomenon in humans and a better understanding of the mechanisms by which latent pain sensitization develops and maintains over long periods of time will be of particular interest to help identifying new therapeutic strategies and targets for chronic pain treatment. The present review aims to recapitulate behavioral expression, potential clinical relevance, cellular mechanisms and intracellular signaling pathways involved so far in latent pain sensitization.
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Affiliation(s)
- Manon Gerum
- Biotechnologie et Signalisation Cellulaire, UMR7242 CNRS, Université de Strasbourg, Institut du Médicament de Strasbourg, Illkirch-Graffenstaden, France
| | - Frédéric Simonin
- Biotechnologie et Signalisation Cellulaire, UMR7242 CNRS, Université de Strasbourg, Institut du Médicament de Strasbourg, Illkirch-Graffenstaden, France.
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Inyang KE, George SR, Laumet G. The µ-δ opioid heteromer masks latent pain sensitization in neuropathic and inflammatory pain in male and female mice. Brain Res 2021; 1756:147298. [PMID: 33516809 DOI: 10.1016/j.brainres.2021.147298] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 01/07/2021] [Accepted: 01/11/2021] [Indexed: 01/16/2023]
Abstract
The episodic nature of chronic pain can be studied in the rodent model of latent pain sensitization. After remission, central sensitization is opposed by activation of opioid receptors. At the behavioral level, latent pain sensitization is unmasked when pain hypersensitivity is reinstated by opioid receptor (OR) antagonism. Previous studies have focused on inflammatory pain and male rodents. Whether latent pain sensitization occurs in models of chemotherapy-induced neuropathic pain in female and male mice is unknown. The first aim of this study was to investigate whether μ- and δ-OR suppress latent pain sensitization in our model of chemotherapy-induced neuropathic pain in both sexes. Mounting evidence suggests that μ-and δ-ORs form a heteromer and that the heteromer modulates pain sensitivity. Potential implications of the μ-δ OR heteromer in latent pain sensitization have not been fully explored due to a lack of tools to effectively modulate the heteromer. To specifically target the μ-δ OR heteromer, we used a specific interfering peptide blocking the heteromerization. The second aim of this study was to investigate whether disruption of the μ-δOR heteromer, after remission, reinstates pain hypersensitivity. After remission from cisplatin-induced neuropathic pain, antagonism of µ-OR and δOR reinstates pain hypersensitivity in both sexes. After remission from cisplatin-induced neuropathic pain and postoperative pain, disruption of the μ-δOR heteromer reinstates pain hypersensitivity in both sexes. Taken together our findings suggest that the μ-δOR heteromer plays a crucial role in remission in various pain models and may represent a novel therapeutic target to prevent the relapse to pain and the transition to chronic pain.
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Affiliation(s)
| | - Susan R George
- Department of Medicine and Pharmacology, University of Toronto, Toronto, Ontario, Canada
| | - Geoffroy Laumet
- Department of Physiology, Michigan State University, East Lansing, MI, USA.
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Chen W, McRoberts JA, Ennes HS, Marvizon JC. cAMP signaling through protein kinase A and Epac2 induces substance P release in the rat spinal cord. Neuropharmacology 2021; 189:108533. [PMID: 33744339 DOI: 10.1016/j.neuropharm.2021.108533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 03/01/2021] [Accepted: 03/11/2021] [Indexed: 11/18/2022]
Abstract
Using neurokinin 1 receptor (NK1R) internalization to measure of substance P release in rat spinal cord slices, we found that it was induced by the adenylyl cyclase (AC) activator forskolin, by the protein kinase A (PKA) activators 6-Bnz-cAMP and 8-Br-cAMP, and by the activator of exchange protein activated by cAMP (Epac) 8-pCPT-2-O-Me-cAMP (CPTOMe-cAMP). Conversely, AC and PKA inhibitors decreased substance P release induced by electrical stimulation of the dorsal root. Therefore, the cAMP signaling pathway mediates substance P release in the dorsal horn. The effects of forskolin and 6-Bnz-cAMP were not additive with NMDA-induced substance P release and were decreased by the NMDA receptor blocker MK-801. In cultured dorsal horn neurons, forskolin increased NMDA-induced Ca2+ entry and the phosphorylation of the NR1 and NR2B subunits of the NMDA receptor. Therefore, cAMP-induced substance P release is mediated by the activating phosphorylation by PKA of NMDA receptors. Voltage-gated Ca2+ channels, but not by TRPV1 or TRPA1, also contributed to cAMP-induced substance P release. Activation of PKA was required for the effects of forskolin and the three cAMP analogs. Epac2 contributed to the effects of forskolin and CPTOMe-cAMP, signaling through a Raf - mitogen-activated protein kinase pathway to activate Ca2+ channels. Epac1 inhibitors induced NK1R internalization independently of substance P release. In rats with latent sensitization to pain, the effect of 6-Bnz-cAMP was unchanged, whereas the effect of forskolin was decreased due to the loss of the stimulatory effect of Epac2. Hence, substance P release induced by cAMP decreases during pain hypersensitivity.
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Affiliation(s)
- Wenling Chen
- Vatche and Tamar Manoukian Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA, 90095, USA; Veteran Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, 90073, USA
| | - James A McRoberts
- Vatche and Tamar Manoukian Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Helena S Ennes
- Vatche and Tamar Manoukian Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Juan Carlos Marvizon
- Vatche and Tamar Manoukian Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA, 90095, USA; Veteran Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, 90073, USA.
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