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Vitin AA, Egan TD. Remifentanil-induced hyperalgesia: the current state of affairs. Curr Opin Anaesthesiol 2024; 37:371-378. [PMID: 38841986 DOI: 10.1097/aco.0000000000001400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2024]
Abstract
Remifentanil-induced hyperalgesia (RIH) is a part of a general opioid-induced hyperalgesia (OIH) syndrome, seemingly resulting from abrupt cessation of continuous remifentanil infusion at rates equal or exceeding 0.3 mcg/kg/min. The intricate mechanisms of its development are still not completely understood. However, hyperactivation of the N -methyl d -aspartate receptor system, descending spinal facilitation and increased concentration of dynorphin (a κ-opioid ligand) are commonly proposed as possible mechanisms. Several ways of prevention and management have been suggested, such as slow withdrawal of remifentanil infusion, the addition of propofol, pretreatment with or concomitant administration of ketamine, buprenorphine, cyclooxygenase-2 inhibitors (NSAIDs), methadone, dexmedetomidine. In clinical and animal studies, these strategies exhibited varying success, and many are still being investigated.
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Affiliation(s)
| | - Talmage D Egan
- Department of Anesthesiology, Perioperative & Pain Medicine, Spencer Fox Eccles School of Medicine, University of Utah, Salt Lake City, Utah, USA
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2
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Dogrul BN, Machado Kopruszinski C, Dolatyari Eslami M, Watanabe M, Luo S, Moreira de Souza LH, Vizin RL, Yue X, Palmiter RD, Navratilova E, Porreca F. Descending facilitation from rostral ventromedial medulla mu opioid receptor-expressing neurons is necessary for maintenance of sensory and affective dimensions of chronic neuropathic pain. Pain 2024:00006396-990000000-00665. [PMID: 39058958 DOI: 10.1097/j.pain.0000000000003360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2024] [Accepted: 06/06/2024] [Indexed: 07/28/2024]
Abstract
ABSTRACT Pharmacological ablation of rostral ventromedial medulla (RVM) mu opioid receptor-expressing cells before peripheral nerve injury prevents the development of neuropathic pain. However, whether these neurons are required for the expression of established neuropathic pain is not known. Male Oprm1Cre heterozygous (MORCre) or wild-type (MORWT) mice received AAV8-hSyn-DIO-hM4D(Gi)-mCherry in the RVM. After partial sciatic nerve ligation (PSNL), we evaluated pain behaviors and descending control of nociception in response to acute or sustained chemogenetic inhibition of RVM-MOR cells expressing hM4D(Gi). A single systemic administration of hM4D(Gi) agonist clozapine-N-oxide (CNO) reversibly inhibited hind paw tactile allodynia and produced conditioned place preference only in MORCre mice with PSNL. Intrathecal CNO also reversibly inhibited PSNL-induced hind paw allodynia, suggesting that the spinal projections from these RVM-MOR cells are critical for manifestation of pain behaviors. Consistent with enhanced descending facilitation from RVM-MOR cells, MORCre-hM4D(Gi) mice with PSNL showed diminished descending control of nociception that was restored by systemic CNO. Sustained CNO in drinking water before PSNL prevented expression of chronic pain without affecting acute surgical pain; however, relief of chronic pain required sustained CNO treatment. Thus, in male mice, activity of spinally projecting RVM-MOR cells is required (1) for expression and manifestation of both sensory and affective dimensions of established neuropathic pain and (2) to promote descending facilitation that overcomes apparently intact descending inhibition to maintain chronic pain. Enhanced descending facilitation likely regulates the output signal from the spinal cord to the brain to shape the pain experience and may provide a mechanism for nonopioid management of pain.
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Affiliation(s)
- Bekir Nihat Dogrul
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ, United States
| | | | - Mahdi Dolatyari Eslami
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ, United States
| | - Moe Watanabe
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ, United States
| | - Shizhen Luo
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ, United States
| | | | - Robson Lilo Vizin
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ, United States
| | - Xu Yue
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ, United States
| | - Richard D Palmiter
- Department of Biochemistry, University of Washington, Seattle, WA, United States
| | - Edita Navratilova
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ, United States
| | - Frank Porreca
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, AZ, United States
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De Preter CC, Heinricher MM. The 'in's and out's' of descending pain modulation from the rostral ventromedial medulla. Trends Neurosci 2024; 47:447-460. [PMID: 38749825 PMCID: PMC11168876 DOI: 10.1016/j.tins.2024.04.006] [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: 01/24/2024] [Revised: 04/12/2024] [Accepted: 04/21/2024] [Indexed: 06/14/2024]
Abstract
The descending-pain modulating circuit controls the experience of pain by modulating transmission of sensory signals through the dorsal horn. This circuit's key output node, the rostral ventromedial medulla (RVM), integrates 'top-down' and 'bottom-up' inputs that regulate functionally defined RVM cell types, 'OFF-cells' and 'ON-cells', which respectively suppress or facilitate pain-related sensory processing. While recent advances have sought molecular definition of RVM cell types, conflicting behavioral findings highlight challenges involved in aligning functional and molecularly defined types. This review summarizes current understanding, derived primarily from rodent studies but with corroborating evidence from human imaging, of the role of RVM populations in pain modulation and persistent pain states and explores recent advances outlining inputs to, and outputs from, RVM pain-modulating neurons.
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Affiliation(s)
- Caitlynn C De Preter
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA; Department of Neurological Surgery, Oregon Health & Science University, Portland, OR 97239, USA
| | - Mary M Heinricher
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR 97239, USA; Department of Neurological Surgery, Oregon Health & Science University, Portland, OR 97239, USA.
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Lubejko ST, Livrizzi G, Buczynski SA, Patel J, Yung JC, Yaksh TL, Banghart MR. Inputs to the locus coeruleus from the periaqueductal gray and rostroventral medulla shape opioid-mediated descending pain modulation. SCIENCE ADVANCES 2024; 10:eadj9581. [PMID: 38669335 PMCID: PMC11051679 DOI: 10.1126/sciadv.adj9581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Accepted: 03/26/2024] [Indexed: 04/28/2024]
Abstract
The supraspinal descending pain modulatory system (DPMS) shapes pain perception via monoaminergic modulation of sensory information in the spinal cord. However, the role and synaptic mechanisms of descending noradrenergic signaling remain unclear. Here, we establish that noradrenergic neurons of the locus coeruleus (LC) are essential for supraspinal opioid antinociception. While much previous work has emphasized the role of descending serotonergic pathways, we find that opioid antinociception is primarily driven by excitatory output from the ventrolateral periaqueductal gray (vlPAG) to the LC. Furthermore, we identify a previously unknown opioid-sensitive inhibitory input from the rostroventromedial medulla (RVM), the suppression of which disinhibits LC neurons to drive spinal noradrenergic antinociception. We describe pain-related activity throughout this circuit and report the presence of prominent bifurcating outputs from the vlPAG to the LC and the RVM. Our findings substantially revise current models of the DPMS and establish a supraspinal antinociceptive pathway that may contribute to multiple forms of descending pain modulation.
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Affiliation(s)
- Susan T. Lubejko
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
- Neurosciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Giulia Livrizzi
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
- Biological Sciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Stanley A. Buczynski
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
- Chemistry and Biochemistry Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Janki Patel
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jean C. Yung
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Tony L. Yaksh
- Departments of Anesthesiology and Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Matthew R. Banghart
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
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Navratilova E, Qu C, Ji G, Neugebauer V, Guerrero M, Rosen H, Roberts E, Porreca F. Opposing Effects on Descending Control of Nociception by µ and κ Opioid Receptors in the Anterior Cingulate Cortex. Anesthesiology 2024; 140:272-283. [PMID: 37725756 DOI: 10.1097/aln.0000000000004773] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/21/2023]
Abstract
BACKGROUND The efficiency of descending pain modulation, commonly assessed with the conditioned pain modulation procedure, is diminished in patients with chronic pain. The authors hypothesized that the efficiency of pain modulation is controlled by cortical opioid circuits. METHODS This study evaluated the effects of µ opioid receptor activation in the anterior cingulate cortex on descending control of nociception, a preclinical correlate of conditioned pain modulation, in male Sprague-Dawley rats with spinal nerve ligation-induced chronic pain or in sham-operated controls. Additionally, the study explored the consequences of respective activation or inhibition of κ opioid receptor in the anterior cingulate cortex of naive rats or animals with neuropathic pain. Descending control of nociception was measured as the hind paw withdrawal response to noxious pressure (test stimulus) in the absence or presence of capsaicin injection in the forepaw (conditioning stimulus). RESULTS Descending control of nociception was diminished in the ipsilateral, but not contralateral, hind paw of rats with spinal nerve ligation. Bilateral administration of morphine in the anterior cingulate cortex had no effect in shams but restored diminished descending control of nociception without altering hypersensitivity in rats with neuropathic pain. Bilateral anterior cingulate cortex microinjection of κ opioid receptor antagonists, including nor-binaltorphimine and navacaprant, also re-established descending control of nociception in rats with neuropathic pain without altering hypersensitivity and with no effect in shams. Conversely, bilateral injection of a κ opioid receptor agonist, U69,593, in the anterior cingulate cortex of naive rats inhibited descending control of nociception without altering withdrawal thresholds. CONCLUSIONS Anterior cingulate cortex κ opioid receptor activation therefore diminishes descending control of nociception both in naive animals and as an adaptive response to chronic pain, likely by enhancing net descending facilitation. Descending control of nociception can be restored by activation of μ opioid receptors in the anterior cingulate cortex, but also by κ opioid receptor antagonists, providing a nonaddictive alternative to opioid analgesics. Navacaprant is now in advanced clinical trials. EDITOR’S PERSPECTIVE
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Affiliation(s)
- Edita Navratilova
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona
| | - Chaoling Qu
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona
| | - Guangchen Ji
- Department of Pharmacology and Neuroscience and Garrison Institute on Aging, Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Volker Neugebauer
- Department of Pharmacology and Neuroscience and Garrison Institute on Aging, Texas Tech University Health Sciences Center, Lubbock, Texas
| | - Miguel Guerrero
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California
| | - Hugh Rosen
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California
| | - Edward Roberts
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California
| | - Frank Porreca
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona
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Follansbee T, Le Chang H, Iodi Carstens M, Guan Y, Carstens E, Dong X. Optotagging and characterization of GABAergic rostral ventromedial medulla (RVM) neurons. Mol Pain 2024; 20:17448069241270295. [PMID: 39054310 DOI: 10.1177/17448069241270295] [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] [Indexed: 07/27/2024] Open
Abstract
The transmission of nociceptive and pruriceptive signals in the spinal cord is greatly influenced by descending modulation from brain areas such as the rostral ventromedial medulla (RVM). Within the RVM three classes of neurons have been discovered which are relevant to spinal pain modulation, the On, Off, and Neutral cells. These neurons were discovered due to their functional response to nociceptive stimulation. On cells are excited, Off cells are inhibited, and Neutral cells have no response to noxious stimulation. Since these neurons are identified by functional response characteristics it has been difficult to molecularly identify them. In the present study, we leverage our ability to perform optotagging within the RVM to determine whether RVM On, Off, and Neutral cells are GABAergic. We found that 27.27% of RVM On cells, 47.37% of RVM Off cells, and 42.6% of RVM Neutral cells were GABAergic. These results demonstrate that RVM On, Off, and Neutral cells represent a heterogeneous population of neurons and provide a reliable technique for the molecular identification of these neurons.
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Affiliation(s)
- Taylor Follansbee
- Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Henry Le Chang
- Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Mirela Iodi Carstens
- Department of Neurobiology, Physiology, and Behavior, University of California Davis, Davis, CA, USA
| | - Yun Guan
- Department of Neurological Surgery, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Earl Carstens
- Department of Neurobiology, Physiology, and Behavior, University of California Davis, Davis, CA, USA
| | - Xinzhong Dong
- Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD, USA
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Pearl-Dowler L, Posa L, Lopez-Canul M, Teggin A, Gobbi G. Anti-allodynic and medullary modulatory effects of a single dose of delta-9-tetrahydrocannabinol (THC) in neuropathic rats tolerant to morphine. Prog Neuropsychopharmacol Biol Psychiatry 2023; 127:110805. [PMID: 37257771 DOI: 10.1016/j.pnpbp.2023.110805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 05/24/2023] [Accepted: 05/25/2023] [Indexed: 06/02/2023]
Abstract
Neuropathic pain (NP) is often treated with opioids, the prolonged use of which causes tolerance to their analgesic effect and can potentially cause death by overdose. The phytocannabinoid delta-9-tetrahydrocannabinol (THC) may be an effective alternative analgesic to treat NP in morphine-tolerant subjects. Male Wistar rats developed NP after spared nerve injury, and were then treated with increasing doses of THC (1, 1.5, 2, 2.5, and 5 mg/kg, intraperitoneally), which reduced mechanical allodynia at the dose of 2.5 and 5 mg/kg. Another group of NP rats were treated with morphine (5 mg/kg, twice daily for 7 days, subcutaneously), until tolerance developed, and on day 8 received a single dose of THC (2.5 mg/kg), which significantly reduced mechanical allodynia. To evaluate the modulation of THC in the descending pain pathway, in vivo electrophysiological recordings of pronociceptive ON cells and antinociceptive OFF cells in the rostroventral medulla (RVM) were recorded after intra-PAG microinjection of THC (10 μg/μl). NP rats with morphine tolerance, compared to the control one, showed a tonic reduction of the spontaneous firing rate of ON cells by 44%, but the THC was able to further decrease it (a hallmark of many analgesic drugs acting at supraspinal level). On the other hand, the firing rate, of the antinociceptive OFF cells was increased after morphine tolerance by 133%, but the THC failed to further activate it. Altogether, these findings indicate that a single dose of THC produces antiallodynic effect in individuals with NP who are tolerant to morphine, acting mostly on the ON cells of the descending pain pathways, but not on OFF cells.
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Affiliation(s)
- Leora Pearl-Dowler
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada
| | - Luca Posa
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada; Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada
| | - Martha Lopez-Canul
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada
| | - Alexandra Teggin
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada
| | - Gabriella Gobbi
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada; Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada.
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8
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Yao D, Chen Y, Chen G. The role of pain modulation pathway and related brain regions in pain. Rev Neurosci 2023; 34:899-914. [PMID: 37288945 DOI: 10.1515/revneuro-2023-0037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Accepted: 05/18/2023] [Indexed: 06/09/2023]
Abstract
Pain is a multifaceted process that encompasses unpleasant sensory and emotional experiences. The essence of the pain process is aversion, or perceived negative emotion. Central sensitization plays a significant role in initiating and perpetuating of chronic pain. Melzack proposed the concept of the "pain matrix", in which brain regions associated with pain form an interconnected network, rather than being controlled by a singular brain region. This review aims to investigate distinct brain regions involved in pain and their interconnections. In addition, it also sheds light on the reciprocal connectivity between the ascending and descending pathways that participate in pain modulation. We review the involvement of various brain areas during pain and focus on understanding the connections among them, which can contribute to a better understanding of pain mechanisms and provide opportunities for further research on therapies for improved pain management.
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Affiliation(s)
- Dandan Yao
- Department of Anesthesiology, School of Medicine, Shaoxing University, Shaoxing, Zhejiang, China
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Yeru Chen
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Gang Chen
- Department of Anesthesiology, School of Medicine, Shaoxing University, Shaoxing, Zhejiang, China
- Department of Anesthesiology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310058, China
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9
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Lubejko ST, Livrizzi G, Patel J, Yung JC, Yaksh TL, Banghart MR. Inputs to the locus coeruleus from the periaqueductal gray and rostroventral medulla shape opioid-mediated descending pain modulation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.10.561768. [PMID: 37873091 PMCID: PMC10592708 DOI: 10.1101/2023.10.10.561768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
The supraspinal descending pain modulatory system (DPMS) shapes pain perception via monoaminergic modulation of sensory information in the spinal cord. However, the role and synaptic mechanisms of descending noradrenergic signaling remain unclear. Here, we establish that noradrenergic neurons of the locus coeruleus (LC) are essential for supraspinal opioid antinociception. Unexpectedly, given prior emphasis on descending serotonergic pathways, we find that opioid antinociception is primarily driven by excitatory output from the ventrolateral periaqueductal gray (vlPAG) to the LC. Furthermore, we identify a previously unknown opioid-sensitive inhibitory input from the rostroventromedial medulla (RVM), the suppression of which disinhibits LC neurons to drive spinal noradrenergic antinociception. We also report the presence of prominent bifurcating outputs from the vlPAG to the LC and the RVM. Our findings significantly revise current models of the DPMS and establish a novel supraspinal antinociceptive pathway that may contribute to multiple forms of descending pain modulation.
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Affiliation(s)
- Susan T. Lubejko
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
- Neurosciences Graduate Program, University of California San Diego, La Jolla, CA 92093, USA
| | - Giulia Livrizzi
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
- Biological Sciences Graduate Program, University of California San Diego, La Jolla, CA 92093, USA
| | - Janki Patel
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Jean C. Yung
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
| | - Tony L. Yaksh
- Departments of Anesthesiology and Pharmacology, University of California San Diego, La Jolla, CA, 92093, USA
| | - Matthew R. Banghart
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA 92093, USA
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10
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Rogness VM, Juliette J, Khasabova IA, Gupta K, Khasabov SG, Simone DA. Descending Facilitation of Nociceptive Transmission From the Rostral Ventromedial Medulla Contributes to Hyperalgesia in Mice with Sickle Cell Disease. Neuroscience 2023; 526:1-12. [PMID: 37330194 PMCID: PMC10528639 DOI: 10.1016/j.neuroscience.2023.06.007] [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: 04/25/2023] [Revised: 05/26/2023] [Accepted: 06/09/2023] [Indexed: 06/19/2023]
Abstract
Sickle cell disease (SCD) is an inherited blood disorder that is associated with acute episodic and chronic pain. Mice with SCD have robust hyperalgesia mediated, in part, by sensitization of spinal dorsal horn neurons. However, underlying mechanisms are not fully understood. Since the rostral ventromedial medulla (RVM) is a major component of descending circuitry that modulates nociceptive transmission in the spinal cord, we examined if the RVM contributes to hyperalgesia in mice with SCD. Injection of lidocaine, but not vehicle, into the RVM eliminated mechanical and heat hyperalgesia in sickle (HbSS-BERK) mice without altering mechanical and heat sensitivity in naïve C57B mice. These data indicate that the RVM contributes to the maintenance of hyperalgesia in mice with SCD. In electrophysiological studies, we determined the changes in response properties of RVM neurons that might contribute to hyperalgesia in sickle mice. Recordings were made from single ON, OFF, and Neutral cells in the RVM of sickle and control (HbAA-BERK) mice. Spontaneous activity and responses of ON, OFF and Neutral cells evoked by heat (50 °C) and mechanical (26 g) stimuli applied to the hind paw were compared between sickle and control mice. Although there were no differences in the proportions of functionally-identified neurons or spontaneous activity between sickle and control mice, evoked responses of ON cells to heat and mechanical stimuli were increased approximately 3-fold in sickle mice as compared to control mice. Thus, the RVM contributes to hyperalgesia in sickle mice via a specific ON cell-dependent descending facilitation of nociceptive transmission.
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Affiliation(s)
- Victoria M Rogness
- Department of Diagnostic & Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Joseph Juliette
- Department of Diagnostic & Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Iryna A Khasabova
- Department of Diagnostic & Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Kalpna Gupta
- Hematology/Oncology, Department of Medicine, University of California, Irvine and Southern California Institute for Research and Education, VA Medical Center, Long Beach, CA, USA
| | - Sergey G Khasabov
- Department of Diagnostic & Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Donald A Simone
- Department of Diagnostic & Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA.
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11
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Pagliusi M, Gomes FV. The Role of The Rostral Ventromedial Medulla in Stress Responses. Brain Sci 2023; 13:brainsci13050776. [PMID: 37239248 DOI: 10.3390/brainsci13050776] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 04/30/2023] [Accepted: 05/05/2023] [Indexed: 05/28/2023] Open
Abstract
The rostral ventromedial medulla (RVM) is a brainstem structure critical for the descending pain modulation system involved in both pain facilitation and inhibition through its projection to the spinal cord. Since the RVM is well connected with pain- and stress-engaged brain structures, such as the anterior cingulate cortex, nucleus accumbens, and amygdala, its involvement in stress responses has become a matter of great interest. While chronic stress has been proposed as a trigger of pain chronification and related psychiatric comorbidities due to maladaptive stress responses, acute stress triggers analgesia and other adaptative responses. Here we reviewed and highlighted the critical role of the RVM in stress responses, mainly in acute stress-induced analgesia (SIA) and chronic stress-induced hyperalgesia (SIH), providing insights into pain chronification processes and comorbidity between chronic pain and psychiatric disorders.
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Affiliation(s)
- Marco Pagliusi
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto 14015-069, SP, Brazil
| | - Felipe V Gomes
- Department of Pharmacology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto 14015-069, SP, Brazil
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12
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Jiao Y, Gao P, Dong L, Ding X, Meng Y, Qian J, Gao T, Wang R, Jiang T, Zhang Y, Kong D, Wu Y, Chen S, Xu S, Tang D, Luo P, Wu M, Meng L, Wen D, Wu C, Zhang G, Shi X, Yu W, Rong W. Molecular identification of bulbospinal ON neurons by GPER, which drives pain and morphine tolerance. J Clin Invest 2023; 133:e154588. [PMID: 36346677 PMCID: PMC9797334 DOI: 10.1172/jci154588] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 11/02/2022] [Indexed: 11/09/2022] Open
Abstract
The rostral ventromedial medulla (RVM) exerts bidirectional descending modulation of pain attributable to the activity of electrophysiologically identified pronociceptive ON and antinociceptive OFF neurons. Here, we report that GABAergic ON neurons specifically express G protein-coupled estrogen receptor (GPER). GPER+ neurons exhibited characteristic ON-like responses upon peripheral nociceptive stimulation. Optogenetic activation of GPER+ neurons facilitated, but their ablation abrogated, pain. Furthermore, activation of GPER caused depolarization of ON cells, potentiated pain, and ameliorated morphine analgesia through desensitizing μ-type opioid receptor-mediated (MOR-mediated) activation of potassium currents. In contrast, genetic ablation or pharmacological blockade of GPER attenuated pain, enhanced morphine analgesia, and delayed the development of morphine tolerance in diverse preclinical pain models. Our data strongly indicate that GPER is a marker for GABAergic ON cells and illuminate the mechanisms underlying hormonal regulation of pain and analgesia, thus highlighting GPER as a promising target for the treatment of pain and opioid tolerance.
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Affiliation(s)
- Yingfu Jiao
- Department of Anatomy and Physiology and
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Po Gao
- Department of Anatomy and Physiology and
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Li Dong
- Department of Anatomy and Physiology and
| | | | - Youqiang Meng
- Department of Anatomy and Physiology and
- Department of Neurosurgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Chongming Branch, Shanghai University of Medicine and Health Sciences Affiliated Chongming Hospital, Shanghai, China
| | | | - Ting Gao
- Department of Anatomy and Physiology and
| | - Ruoxi Wang
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Tao Jiang
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yunchun Zhang
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Dexu Kong
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yi Wu
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Sihan Chen
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Saihong Xu
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Dan Tang
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Ping Luo
- Department of Anatomy and Physiology and
| | - Meimei Wu
- Department of Anatomy and Physiology and
| | - Li Meng
- Department of Anatomy and Physiology and
| | - Daxiang Wen
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Changhao Wu
- School of Biosciences and Medicine, University of Surrey, Guildford, United Kingdom
| | | | - Xueyin Shi
- Department of Anesthesiology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Weifeng Yu
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Weifang Rong
- Department of Anatomy and Physiology and
- Department of Anesthesiology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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13
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Peng B, Jiao Y, Zhang Y, Li S, Chen S, Xu S, Gao P, Fan Y, Yu W. Bulbospinal nociceptive ON and OFF cells related neural circuits and transmitters. Front Pharmacol 2023; 14:1159753. [PMID: 37153792 PMCID: PMC10157642 DOI: 10.3389/fphar.2023.1159753] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 04/10/2023] [Indexed: 05/10/2023] Open
Abstract
The rostral ventromedial medulla (RVM) is a bulbospinal nuclei in the descending pain modulation system, and directly affects spinal nociceptive transmission through pronociceptive ON cells and antinociceptive OFF cells in this area. The functional status of ON and OFF neurons play a pivotal role in pain chronification. As distinct pain modulative information converges in the RVM and affects ON and OFF cell excitability, neural circuits and transmitters correlated to RVM need to be defined for an in-depth understanding of central-mediated pain sensitivity. In this review, neural circuits including the role of the periaqueductal gray, locus coeruleus, parabrachial complex, hypothalamus, amygdala input to the RVM, and RVM output to the spinal dorsal horn are discussed. Meanwhile, the role of neurotransmitters is concluded, including serotonin, opioids, amino acids, cannabinoids, TRPV1, substance P and cholecystokinin, and their dynamic impact on both ON and OFF cell activities in modulating pain transmission. Via clarifying potential specific receptors of ON and OFF cells, more targeted therapies can be raised to generate pain relief for patients who suffer from chronic pain.
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Affiliation(s)
- Bingxue Peng
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Yingfu Jiao
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Yunchun Zhang
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Shian Li
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Sihan Chen
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Saihong Xu
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Po Gao
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
| | - Yinghui Fan
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
- *Correspondence: Yinghui Fan, ; Weifeng Yu,
| | - Weifeng Yu
- Department of Anesthesiology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Anesthesiology (Shanghai Jiao Tong University), Ministry of Education, Shanghai, China
- *Correspondence: Yinghui Fan, ; Weifeng Yu,
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14
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Enhanced anxiolytic and analgesic effectiveness or a better safety profile of morphine and tramadol combination in cholestatic and addicted mice. Neuroreport 2022; 33:681-689. [DOI: 10.1097/wnr.0000000000001834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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15
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Posa L, De Gregorio D, Lopez-Canul M, He Q, Darcq E, Rullo L, Pearl-Dowler L, Luongo L, Candeletti S, Romualdi P, Kieffer BL, Gobbi G. Supraspinal melatonin MT 2 receptor agonism alleviates pain via a neural circuit that recruits mu opioid receptors. J Pineal Res 2022; 73:e12825. [PMID: 35996205 DOI: 10.1111/jpi.12825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 08/03/2022] [Accepted: 08/05/2022] [Indexed: 11/30/2022]
Abstract
Melatonin, through its G protein-coupled receptor (GPCR) (MTNR1B gene) MT2 , is implicated in analgesia, but the relationship between MT2 receptors and the opioid system remains elusive. In a model of rodent neuropathic pain (spared nerve injured [SNI]), the selective melatonin MT2 agonist UCM924 reversed the allodynia (a pain response to a non-noxious stimulus), and this effect was nullified by the pharmacological blockade or genetic inactivation of the mu opioid receptor (MOR), but not the delta opioid receptor (DOR). Indeed, SNI MOR, but not DOR knockout mice, did not respond to the antiallodynic effects of the UCM924. Similarly, the nonselective opioid antagonist naloxone and the selective MOR antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP) blocked the effects of UCM924 in SNI rats, but not the DOR antagonist naltrindole (NTI). Electrophysiological recordings in the rostral-ventromedial medulla (RVM) revealed that the typical reduction of the firing activity of pronociceptive ON-cells, and the enhancement of the firing of the antinociceptive OFF-cells, induced by the microinjection of the MT2 agonist UCM924 into the ventrolateral periaqueductal gray (vlPAG) were blocked by MOR, but not DOR, antagonism. Immunohistochemistry studies showed that MT2 receptors are expressed in both excitatory (CaMKIIα+ ) and inhibitory (GAD65+ ) neuronal cell bodies in the vlPAG (~2.16% total), but not RVM. Only 0.20% of vlPAG neurons coexpressed MOR and MT2 receptors. Finally, UCM924 treatment induced an increase in the enkephalin precursor gene (PENK) in the PAG of SNI mice. Collectively, the melatonin MT2 receptor agonism requires MORs to exert its antiallodynic effects, mostly through an interneuronal circuit involving MOR and MT2 receptors.
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Affiliation(s)
- Luca Posa
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, Quebec, Canada
- Alan Edwards Centre for Research on Pain, McGill University, Montreal, Quebec, Canada
| | - Danilo De Gregorio
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, Quebec, Canada
- Division of Neuroscience, Vita-Salute San Raffaele University, Italy, Milano
| | - Martha Lopez-Canul
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, Quebec, Canada
| | - Qianzi He
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, Quebec, Canada
| | - Emmanuel Darcq
- Department of Psychiatry, School of Medicine, Douglas Hospital Research Center, McGill University, Quebec, Montreal, Canada
| | - Laura Rullo
- Department of Pharmacy and Biotechnology (FaBiT), Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Leora Pearl-Dowler
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, Quebec, Canada
| | - Livio Luongo
- Department of Experimental Medicine, University of Campania "Luigi Vanvitelli", Naples, Italy
| | - Sanzio Candeletti
- Department of Pharmacy and Biotechnology (FaBiT), Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Patrizia Romualdi
- Department of Pharmacy and Biotechnology (FaBiT), Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Brigitte Lina Kieffer
- Department of Psychiatry, School of Medicine, Douglas Hospital Research Center, McGill University, Quebec, Montreal, Canada
| | - Gabriella Gobbi
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, Quebec, Canada
- Alan Edwards Centre for Research on Pain, McGill University, Montreal, Quebec, Canada
- McGill University, Health Center (MUHC), Montreal, Quebec, Canada
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16
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Chen Q, Heinricher MM. Shifting the Balance: How Top-Down and Bottom-Up Input Modulate Pain via the Rostral Ventromedial Medulla. FRONTIERS IN PAIN RESEARCH 2022; 3:932476. [PMID: 35836737 PMCID: PMC9274196 DOI: 10.3389/fpain.2022.932476] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 05/23/2022] [Indexed: 11/17/2022] Open
Abstract
The sensory experience of pain depends not only on the transmission of noxious information (nociception), but on the state of the body in a biological, psychological, and social milieu. A brainstem pain-modulating system with its output node in the rostral ventromedial medulla (RVM) can regulate the threshold and gain for nociceptive transmission. This review considers the current understanding of how RVM pain-modulating neurons, namely ON-cells and OFF-cells, are engaged by “top-down” cognitive and emotional factors, as well as by “bottom-up” sensory inputs, to enhance or suppress pain.
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Affiliation(s)
- Qiliang Chen
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, CA, United States
| | - Mary M. Heinricher
- Department of Neurological Surgery and Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, United States
- *Correspondence: Mary M. Heinricher
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17
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Reeves KC, Shah N, Muñoz B, Atwood BK. Opioid Receptor-Mediated Regulation of Neurotransmission in the Brain. Front Mol Neurosci 2022; 15:919773. [PMID: 35782382 PMCID: PMC9242007 DOI: 10.3389/fnmol.2022.919773] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 05/26/2022] [Indexed: 12/15/2022] Open
Abstract
Opioids mediate their effects via opioid receptors: mu, delta, and kappa. At the neuronal level, opioid receptors are generally inhibitory, presynaptically reducing neurotransmitter release and postsynaptically hyperpolarizing neurons. However, opioid receptor-mediated regulation of neuronal function and synaptic transmission is not uniform in expression pattern and mechanism across the brain. The localization of receptors within specific cell types and neurocircuits determine the effects that endogenous and exogenous opioids have on brain function. In this review we will explore the similarities and differences in opioid receptor-mediated regulation of neurotransmission across different brain regions. We discuss how future studies can consider potential cell-type, regional, and neural pathway-specific effects of opioid receptors in order to better understand how opioid receptors modulate brain function.
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Affiliation(s)
- Kaitlin C. Reeves
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
- Department of Neuroscience, Charleston Alcohol Research Center, Medical University of South Carolina, Charleston, SC, United States
| | - Nikhil Shah
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
- Medical Scientist Training Program, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Braulio Muñoz
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Brady K. Atwood
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, United States
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18
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Crawford LS, Boorman DC, Keay KA, Henderson LA. The pain conductor: brainstem modulation in acute and chronic pain. Curr Opin Support Palliat Care 2022; 16:71-77. [PMID: 35639572 DOI: 10.1097/spc.0000000000000598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW It is well established in experimental settings that brainstem circuits powerfully modulate the multidimensional experience of pain. This review summarizes current understanding of the roles of brainstem nuclei in modulating the intensity of pain, and how these circuits might be recruited therapeutically for pain relief in chronic and palliative settings. RECENT FINDINGS The development of ultra-high field magnetic resonance imaging and more robust statistical analyses has led to a more integrated understanding of brainstem function during pain. It is clear that a number of brainstem nuclei and their overlapping pathways are recruited to either enhance or inhibit incoming nociceptive signals. This review reflects on early preclinical research, which identified in detail brainstem analgesic function, putting into context contemporary investigations in humans that have identified the role of specific brainstem circuits in modulating pain, their contribution to pain chronicity, and even the alleviation of palliative comorbidities. SUMMARY The brainstem is an integral component of the circuitry underpinning pain perception. Enhanced understanding of its circuitry in experimental studies in humans has, in recent years, increased the possibility for better optimized pain-relief strategies and the identification of vulnerabilities to postsurgical pain problems. When integrated into the clinical landscape, these experimental findings of brainstem modulation of pain signalling have the potential to contribute to the optimization of pain management and patient care from acute, to chronic, to palliative states.
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Affiliation(s)
- Lewis S Crawford
- School of Medical Sciences (Neuroscience), Brain and Mind Centre, University of Sydney, NSW, Australia
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19
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Fauss GNK, Hudson KE, Grau JW. Role of Descending Serotonergic Fibers in the Development of Pathophysiology after Spinal Cord Injury (SCI): Contribution to Chronic Pain, Spasticity, and Autonomic Dysreflexia. BIOLOGY 2022; 11:234. [PMID: 35205100 PMCID: PMC8869318 DOI: 10.3390/biology11020234] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/27/2022] [Accepted: 01/29/2022] [Indexed: 12/12/2022]
Abstract
As the nervous system develops, nerve fibers from the brain form descending tracts that regulate the execution of motor behavior within the spinal cord, incoming sensory signals, and capacity to change (plasticity). How these fibers affect function depends upon the transmitter released, the receptor system engaged, and the pattern of neural innervation. The current review focuses upon the neurotransmitter serotonin (5-HT) and its capacity to dampen (inhibit) neural excitation. A brief review of key anatomical details, receptor types, and pharmacology is provided. The paper then considers how damage to descending serotonergic fibers contributes to pathophysiology after spinal cord injury (SCI). The loss of serotonergic fibers removes an inhibitory brake that enables plasticity and neural excitation. In this state, noxious stimulation can induce a form of over-excitation that sensitizes pain (nociceptive) circuits, a modification that can contribute to the development of chronic pain. Over time, the loss of serotonergic fibers allows prolonged motor drive (spasticity) to develop and removes a regulatory brake on autonomic function, which enables bouts of unregulated sympathetic activity (autonomic dysreflexia). Recent research has shown that the loss of descending serotonergic activity is accompanied by a shift in how the neurotransmitter GABA affects neural activity, reducing its inhibitory effect. Treatments that target the loss of inhibition could have therapeutic benefit.
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Affiliation(s)
| | | | - James W. Grau
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, TX 77843, USA; (G.N.K.F.); (K.E.H.)
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20
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Oliva V, Hartley-Davies R, Moran R, Pickering AE, Brooks JC. Simultaneous brain, brainstem and spinal cord pharmacological-fMRI reveals involvement of an endogenous opioid network in attentional analgesia. eLife 2022; 11:71877. [PMID: 35080494 PMCID: PMC8843089 DOI: 10.7554/elife.71877] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 01/25/2022] [Indexed: 11/13/2022] Open
Abstract
Pain perception is decreased by shifting attentional focus away from a threatening event. This attentional analgesia engages parallel descending control pathways from anterior cingulate (ACC) to locus coeruleus, and ACC to periaqueductal grey (PAG) – rostral ventromedial medulla (RVM), indicating possible roles for noradrenergic or opioidergic neuromodulators. To determine which pathway modulates nociceptive activity in humans, we used simultaneous whole brain-spinal cord pharmacological-fMRI (N = 39) across three sessions. Noxious thermal forearm stimulation generated somatotopic-activation of dorsal horn (DH) whose activity correlated with pain report and mirrored attentional pain modulation. Activity in an adjacent cluster reported the interaction between task and noxious stimulus. Effective connectivity analysis revealed that ACC interacts with PAG and RVM to modulate spinal cord activity. Blocking endogenous opioids with Naltrexone impairs attentional analgesia and disrupts RVM-spinal and ACC-PAG connectivity. Noradrenergic augmentation with Reboxetine did not alter attentional analgesia. Cognitive pain modulation involves opioidergic ACC-PAG-RVM descending control which suppresses spinal nociceptive activity.
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Affiliation(s)
- Valeria Oliva
- Department of Anesthesiology, University of California, San Diego, La Jolla, United States
| | - Ron Hartley-Davies
- School of Psychological Science, University of Bristol, Bristol, United Kingdom
| | - Rosalyn Moran
- Department of Neuroimaging, King's College London, London, United Kingdom
| | - Anthony E Pickering
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
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21
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Lubejko ST, Graham RD, Livrizzi G, Schaefer R, Banghart MR, Creed MC. The role of endogenous opioid neuropeptides in neurostimulation-driven analgesia. Front Syst Neurosci 2022; 16:1044686. [PMID: 36591324 PMCID: PMC9794630 DOI: 10.3389/fnsys.2022.1044686] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 11/18/2022] [Indexed: 12/15/2022] Open
Abstract
Due to the prevalence of chronic pain worldwide, there is an urgent need to improve pain management strategies. While opioid drugs have long been used to treat chronic pain, their use is severely limited by adverse effects and abuse liability. Neurostimulation techniques have emerged as a promising option for chronic pain that is refractory to other treatments. While different neurostimulation strategies have been applied to many neural structures implicated in pain processing, there is variability in efficacy between patients, underscoring the need to optimize neurostimulation techniques for use in pain management. This optimization requires a deeper understanding of the mechanisms underlying neurostimulation-induced pain relief. Here, we discuss the most commonly used neurostimulation techniques for treating chronic pain. We present evidence that neurostimulation-induced analgesia is in part driven by the release of endogenous opioids and that this endogenous opioid release is a common endpoint between different methods of neurostimulation. Finally, we introduce technological and clinical innovations that are being explored to optimize neurostimulation techniques for the treatment of pain, including multidisciplinary efforts between neuroscience research and clinical treatment that may refine the efficacy of neurostimulation based on its underlying mechanisms.
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Affiliation(s)
- Susan T. Lubejko
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA, United States
| | - Robert D. Graham
- Department of Anesthesiology, Pain Center, School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
| | - Giulia Livrizzi
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA, United States
| | - Robert Schaefer
- Department of Anesthesiology, Pain Center, School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
| | - Matthew R. Banghart
- Department of Neurobiology, School of Biological Sciences, University of California, San Diego, La Jolla, CA, United States
- *Correspondence: Matthew R. Banghart,
| | - Meaghan C. Creed
- Department of Anesthesiology, Pain Center, School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
- Department of Neuroscience, Washington University in St. Louis, St. Louis, MO, United States
- Department of Psychiatry, Washington University in St. Louis, St. Louis, MO, United States
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, United States
- Meaghan C. Creed,
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22
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Abstract
Managing chronic pain remains a major unmet clinical challenge. Patients can be treated with a range of interventions, but pharmacotherapy is the most common. These include opioids, antidepressants, calcium channel modulators, sodium channel blockers, and nonsteroidal anti-inflammatory drugs. Many of these drugs target a particular mechanism; however, chronic pain in many diseases is multifactorial and induces plasticity throughout the sensory neuroaxis. Furthermore, comorbidities such as depression, anxiety, and sleep disturbances worsen quality of life. Given the complexity of mechanisms and symptoms in patients, it is unsurprising that many fail to achieve adequate pain relief from a single agent. The efforts to develop novel drug classes with better efficacy have not always proved successful; a multimodal or combination approach to analgesia is an important strategy in pain control. Many patients frequently take more than one medication, but high-quality evidence to support various combinations is often sparse. Ideally, combining drugs would produce synergistic action to maximize analgesia and reduce side effects, although sub-additive and additive analgesia is still advantageous if additive side-effects can be avoided. In this review, we discuss pain mechanisms, drug actions, and the rationale for mechanism-led treatment selection.Abbreviations: COX - cyclooxygenase, CGRP - calcitonin gene-related peptide, CPM - conditioned pain modulation, NGF - nerve growth factor, NNT - number needed to treat, NMDA - N-methyl-d-aspartate, NSAID - nonsteroidal anti-inflammatory drugs, TCA - tricyclic antidepressant, SNRI - serotonin-noradrenaline reuptake inhibitor, QST - quantitative sensory testing.
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Affiliation(s)
- Ryan Patel
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, UK
| | - Anthony H Dickenson
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London, UK
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23
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Rossi GC, Bodnar RJ. Interactive Mechanisms of Supraspinal Sites of Opioid Analgesic Action: A Festschrift to Dr. Gavril W. Pasternak. Cell Mol Neurobiol 2021; 41:863-897. [PMID: 32970288 DOI: 10.1007/s10571-020-00961-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 09/03/2020] [Indexed: 12/30/2022]
Abstract
Almost a half century of research has elaborated the discoveries of the central mechanisms governing the analgesic responses of opiates, including their receptors, endogenous peptides, genes and their putative spinal and supraspinal sites of action. One of the central tenets of "gate-control theories of pain" was the activation of descending supraspinal sites by opiate drugs and opioid peptides thereby controlling further noxious input. This review in the Special Issue dedicated to the research of Dr. Gavril Pasternak indicates his contributions to the understanding of supraspinal mediation of opioid analgesic action within the context of the large body of work over this period. This review will examine (a) the relevant supraspinal sites mediating opioid analgesia, (b) the opioid receptor subtypes and opioid peptides involved, (c) supraspinal site analgesic interactions and their underlying neurophysiology, (d) molecular (particularly AS) tools identifying opioid receptor actions, and (e) relevant physiological variables affecting site-specific opioid analgesia. This review will build on classic initial studies, specify the contributions that Gavril Pasternak and his colleagues did in this specific area, and follow through with studies up to the present.
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Affiliation(s)
- Grace C Rossi
- Department of Psychology, C.W. Post College, Long Island University, Post Campus, Brookville, NY, USA.
| | - Richard J Bodnar
- Department of Psychology, Queens College of the City University of New York, Flushing, NY, USA
- CUNY Neuroscience Collaborative, Graduate Center, CUNY, New York, NY, USA
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24
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Neural Plasticity in the Brain during Neuropathic Pain. Biomedicines 2021; 9:biomedicines9060624. [PMID: 34072638 PMCID: PMC8228570 DOI: 10.3390/biomedicines9060624] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 05/27/2021] [Accepted: 05/28/2021] [Indexed: 01/02/2023] Open
Abstract
Neuropathic pain is an intractable chronic pain, caused by damage to the somatosensory nervous system. To date, treatment for neuropathic pain has limited effects. For the development of efficient therapeutic methods, it is essential to fully understand the pathological mechanisms of neuropathic pain. Besides abnormal sensitization in the periphery and spinal cord, accumulating evidence suggests that neural plasticity in the brain is also critical for the development and maintenance of this pain. Recent technological advances in the measurement and manipulation of neuronal activity allow us to understand maladaptive plastic changes in the brain during neuropathic pain more precisely and modulate brain activity to reverse pain states at the preclinical and clinical levels. In this review paper, we discuss the current understanding of pathological neural plasticity in the four pain-related brain areas: the primary somatosensory cortex, the anterior cingulate cortex, the periaqueductal gray, and the basal ganglia. We also discuss potential treatments for neuropathic pain based on the modulation of neural plasticity in these brain areas.
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25
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Khan F, Mehan A. Addressing opioid tolerance and opioid-induced hypersensitivity: Recent developments and future therapeutic strategies. Pharmacol Res Perspect 2021; 9:e00789. [PMID: 34096178 PMCID: PMC8181203 DOI: 10.1002/prp2.789] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 04/07/2021] [Indexed: 01/07/2023] Open
Abstract
Opioids are a commonly prescribed and efficacious medication for the treatment of chronic pain but major side effects such as addiction, respiratory depression, analgesic tolerance, and paradoxical pain hypersensitivity make them inadequate and unsafe for patients requiring long-term pain management. This review summarizes recent advances in our understanding of the outcomes of chronic opioid administration to lay the foundation for the development of novel pharmacological strategies that attenuate opioid tolerance and hypersensitivity; the two main physiological mechanisms underlying the inadequacies of current therapeutic strategies. We also explore mechanistic similarities between the development of neuropathic pain states, opioid tolerance, and hypersensitivity which may explain opioids' lack of efficacy in certain patients. The findings challenge the current direction of analgesic research in developing non-opioid alternatives and we suggest that improving opioids, rather than replacing them, will be a fruitful avenue for future research.
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Affiliation(s)
- Faris Khan
- School of Clinical MedicineUniversity of CambridgeCambridgeUK
| | - Aman Mehan
- School of Clinical MedicineUniversity of CambridgeCambridgeUK
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Regular physical activity reduces the percentage of spinally projecting neurons that express mu-opioid receptors from the rostral ventromedial medulla in mice. Pain Rep 2020; 5:e857. [PMID: 33294758 PMCID: PMC7717783 DOI: 10.1097/pr9.0000000000000857] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 08/13/2020] [Accepted: 08/24/2020] [Indexed: 01/02/2023] Open
Abstract
Introduction Regular physical activity/exercise is an effective nonpharmacological treatment for individuals with chronic pain. Central inhibitory mechanisms, involving serotonin and opioids, are critical to analgesia produced by regular physical activity. The rostral ventromedial medulla (RVM) sends projections to the spinal cord to inhibit or facilitate nociceptive neurons and plays a key role in exercise-induced analgesia. Objective The goal of these studies was to examine if regular physical activity modifies RVM-spinal cord circuitry. Methods Male and female mice received Fluoro-Gold placed on the spinal cord to identify spinally projecting neurons from the RVM and the nucleus raphe obscurus/nucleus raphe pallidus, dermorphin-488 into caudal medulla to identify mu-opioid receptors, and were immunohistochemically stained for either phosphorylated-N-methyl-d-aspartate subunit NR1 (p-NR1) to identify excitatory neurons or tryptophan hydroxylase (TPH) to identify serotonin neurons. The percentage of dermorphin-488-positive cells that stained for p-NR1 (or TPH), and the percentage of dermorphin-488-positive cells that stained for p-NR1 (or TPH) and Fluoro-Gold was calculated. Physically active animals were provided running wheels in their cages for 8 weeks and compared to sedentary animals without running wheels. Animals with chronic muscle pain, induced by 2 intramuscular injections of pH 4.0, were compared to sham controls (pH 7.2). Results Physically active animals had less mu-opioid-expressing neurons projecting to the spinal cord when compared to sedentary animals in the RVM, but not the nucleus raphe obscurus/nucleus raphe pallidus. No changes were observed for TPH. Conclusions These data suggest that regular exercise alters central facilitation so that there is less descending facilitation to result in a net increase in inhibition.
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Palazzo E, Boccella S, Marabese I, Pierretti G, Guida F, Maione S. The Cold Case of Metabotropic Glutamate Receptor 6: Unjust Detention in the Retina? Curr Neuropharmacol 2020; 18:120-125. [PMID: 31573889 PMCID: PMC7324884 DOI: 10.2174/1570159x17666191001141849] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 08/20/2019] [Accepted: 09/29/2019] [Indexed: 02/03/2023] Open
Abstract
It is a common opinion that metabotropic glutamate receptor subtype 6 (mGluR6) is expressed exclusively in the retina, and in particular in the dendrites of ON-bipolar cells. Glutamate released in darkness from photoreceptors activates mGluR6, which is negatively associated with a membrane non-selective cation channel, the transient receptor potential melanoma-related 1, TRPM1, resulting in cell hyperpolarization. The evidence that mGluR6 is expressed not only in the retina but also in other tissues and cell populations has accumulated over time. The expression of mGluR6 has been identified in microglia, bone marrow stromal and prostate cancer cells, B lymphocytes, melanocytes and keratinocytes and non-neural tissues such as testis, kidney, cornea, conjunctiva, and eyelid. The receptor also appears to be expressed in brain areas, such as the hypothalamus, cortex, hippocampus, nucleus of tractus solitarius, superior colliculus, axons of the corpus callosum and accessory olfactory bulb. The pharmacological activation of mGluR6 in the hippocampus produced an anxiolytic-like effect and in the periaqueductal gray analgesic potential. This review aims to collect all the evidence on the expression and functioning of mGluR6 outside the retina that has been accumulated over the years for a broader view of the potential of the receptor whose retinal confinement appears understimated.
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Affiliation(s)
- E Palazzo
- Department of Experimental Medicine, Pharmacology Division, University of Campania "L. Vanvitelli", Naples, Italy
| | - S Boccella
- Department of Experimental Medicine, Pharmacology Division, University of Campania "L. Vanvitelli", Naples, Italy
| | - I Marabese
- Department of Experimental Medicine, Pharmacology Division, University of Campania "L. Vanvitelli", Naples, Italy
| | - G Pierretti
- Department of Plastic Surgery, University of Campania "L. Vanvitelli", Naples, Italy
| | - F Guida
- Department of Experimental Medicine, Pharmacology Division, University of Campania "L. Vanvitelli", Naples, Italy
| | - S Maione
- Department of Experimental Medicine, Pharmacology Division, University of Campania "L. Vanvitelli", Naples, Italy
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Posa L, Lopez-Canul M, Rullo L, De Gregorio D, Dominguez-Lopez S, Kaba Aboud M, Caputi FF, Candeletti S, Romualdi P, Gobbi G. Nociceptive responses in melatonin MT 2 receptor knockout mice compared to MT 1 and double MT 1 /MT 2 receptor knockout mice. J Pineal Res 2020; 69:e12671. [PMID: 32430930 DOI: 10.1111/jpi.12671] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Revised: 04/21/2020] [Accepted: 05/13/2020] [Indexed: 12/28/2022]
Abstract
Melatonin, a neurohormone that binds to two G protein-coupled receptors MT1 and MT2, is involved in pain regulation, but the distinct role of each receptor has yet to be defined. We characterized the nociceptive responses of mice with genetic inactivation of melatonin MT1 (MT1 -/- ), or MT2 (MT2 -/- ), or both MT1 /MT2 (MT1 -/- /MT2 -/- ) receptors in the hot plate test (HPT), and the formalin test (FT). In HPT and FT, MT1 -/- display no differences compared to their wild-type littermates (CTL), whereas both MT2 -/- and MT1 -/- /MT2 -/- mice showed a reduced thermal sensitivity and a decreased tonic nocifensive behavior during phase 2 of the FT in the light phase. The MT2 partial agonist UCM924 induced an antinociceptive effect in MT1 -/- but not in MT2 -/- and MT1 -/- /MT2 -/- mice. Also, the competitive opioid antagonist naloxone had no effects in CTL, whereas it induced a decrease of nociceptive thresholds in MT2 -/- mice. Our results show that the genetic inactivation of melatonin MT2 , but not MT1 receptors, produces a distinct effect on nociceptive threshold, suggesting that the melatonin MT2 receptor subtype is selectively involved in the regulation of pain responses.
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Affiliation(s)
- Luca Posa
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada
- Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada
| | - Martha Lopez-Canul
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada
| | - Laura Rullo
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Danilo De Gregorio
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada
| | - Sergio Dominguez-Lopez
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada
| | - Matthew Kaba Aboud
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada
| | - Francesca Felicia Caputi
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Sanzio Candeletti
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Patrizia Romualdi
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Gabriella Gobbi
- Neurobiological Psychiatry Unit, Department of Psychiatry, McGill University Health Center, McGill University, Montreal, QC, Canada
- Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada
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Viisanen H, Lilius TO, Sagalajev B, Rauhala P, Kalso E, Pertovaara A. Neurophysiological response properties of medullary pain-control neurons following chronic treatment with morphine or oxycodone: modulation by acute ketamine. J Neurophysiol 2020; 124:790-801. [DOI: 10.1152/jn.00343.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Morphine and oxycodone are two clinically used strong opioids. Chronic treatment with oxycodone as well as morphine can lead to analgesic tolerance and paradoxical hyperalgesia. Here we show that an N-methyl-d-aspartate receptor-dependent pronociceptive change in discharge properties of rostroventromedial medullary neurons controlling spinal nociception has an important role in antinociceptive tolerance to morphine but not oxycodone. Interestingly, chronic oxycodone did not induce pronociceptive changes in the rostroventromedial medulla.
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Affiliation(s)
- Hanna Viisanen
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Department of Physiology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Tuomas O. Lilius
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Department of Clinical Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Boriss Sagalajev
- Department of Physiology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Pekka Rauhala
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Eija Kalso
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Department of Anaesthesiology, Intensive Care Medicine and Pain Medicine, Helsinki University Hospital and University of Helsinki, Helsinki, Finland
- SleepWell Research Programme, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Antti Pertovaara
- Department of Physiology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
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Aloyouny AY, Bepari A, Rahman I. Evaluating the Role of CXCR3 in Pain Modulation: A Literature Review. J Pain Res 2020; 13:1987-2001. [PMID: 32821152 PMCID: PMC7418155 DOI: 10.2147/jpr.s254276] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 07/17/2020] [Indexed: 01/01/2023] Open
Abstract
CXCR3 is a well-known receptor involved in immune cell recruitment and inflammation. Pathological inflammation leads to pain stimulation and hence nociception. Therefore, we decided to review the recent research on CXCR3 to identify its precise role in the modulation of pain in a variety of clinical conditions targeting various regions of the body. Studies were selected from PubMed Medline, which relate CXCR3 to the progression of diseases with either bone cancer pain, neuropathic pain, cystitis pain, osteoarthritis and rheumatoid arthritis pain, dental pain, in particular, periodontitis and pulpitis. In all the diseases studied, a high prevalence of CXCR3 and/or its ligand were identified where CXCR3 is a key player in the pathophysiological process of many inflammatory conditions. CXCR3 and its ligands, particularly CXCL10, modulate nociception via actions in the dorsal root ganglia and dorsal horn of the spinal cord, in cases of bone cancer pain, neuropathic, and joint pain. However, with the other studied disease, no direct link to pain has been made, although it contributes to the pathological progression of the diseases and hence would be a causal factor for the pain. Furthermore, CXCR3 appears to play a role in desensitizing the opioid receptor in the descending modulatory pathway within the brain stem as well as modulating opioid-induced hyperalgesia in the dorsal horn of the spinal cord. Further research is required for understanding the exact mechanisms of CXCR3 in pain modulation centrally and peripherally. A greater understanding of the immunological activities and pharmacological consequence of CXCR3 and its ligands could help in the discovery of newer drugs for modulating pain arising from pathogenic or inflammatory sources. Given the significance of the CXCR3 for nociception, its utilization may prove to be beneficial as a target for analgesia.
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Affiliation(s)
- Ashwag Yagoub Aloyouny
- College of Dentistry, Princess Nourah bint Abdulrahman University, Riyadh, Kingdom of Saudi Arabia
| | - Asmatanzeem Bepari
- College of Medicine, Princess Nourah bint Abdulrahman University, Riyadh, Kingdom of Saudi Arabia
| | - Ishrat Rahman
- College of Dentistry, Princess Nourah bint Abdulrahman University, Riyadh, Kingdom of Saudi Arabia
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Abstract
While the acute sensation of pain is protective, signaling the presence of actual or potential bodily harm, its persistence is unpleasant. When pain becomes chronic, it has limited evolutionarily advantage. Despite the differing nature of acute and chronic pain, a common theme is that sufferers seek pain relief. The possibility to medicate pain types as varied as a toothache or postsurgical pain reflects the diverse range of mechanism(s) by which pain-relieving "analgesic" therapies may reduce, eliminate, or prevent pain. Systemic application of an analgesic able to cross the blood-brain barrier can result in pain modulation via interaction with targets at different sites in the central nervous system. A so-called supraspinal mechanism of action indicates manipulation of a brain-defined circuitry. Pre-clinical studies demonstrate that, according to the brain circuitry targeted, varying therapeutic pain-relieving effects may be observed that relate to an impact on, for example, sensory and/or affective qualities of pain. In many cases, this translates to the clinic. Regardless of the brain circuitry manipulated, modulation of brain processing often directly impacts multiple aspects of nociceptive transmission, including spinal neuronal signaling. Consideration of supraspinal mechanisms of analgesia and ensuing pain relief must take into account nonbrain-mediated effects; therefore, in this review, the supraspinally mediated analgesic actions of opioidergic, anti-convulsant, and anti-depressant drugs are discussed. The persistence of poor treatment outcomes and/or side effect profiles of currently used analgesics highlight the need for the development of novel therapeutics or more precise use of available agents. Fully uncovering the complex biology of nociception, as well as currently used analgesic mechanism(s) and site(s) of action, will expedite this process.
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Affiliation(s)
- K Bannister
- Department of Pharmacology and Therapeutics, Institute of Psychiatry, Psychology and Neuroscience, Wolfson CARD, Guy's Campus, King's College London, London, SE1 1UL, UK.
| | - A H Dickenson
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, UK
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32
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Early exposure to environmental enrichment protects male rats against neuropathic pain development after nerve injury. Exp Neurol 2020; 332:113390. [PMID: 32598929 DOI: 10.1016/j.expneurol.2020.113390] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 06/17/2020] [Accepted: 06/24/2020] [Indexed: 12/30/2022]
Abstract
Because environmental elements modify chronic pain development and endogenous mechanisms of pain control are still a great therapeutic source, we investigated the effects of an early exposure to environmental enrichment (EE) in a translational model of neuropathic pain. Young male rats born and bred in an enriched environment, which did not count on running wheel, underwent chronic constriction injury (CCI) of sciatic nerve. EE abolished neuropathic pain behavior 14 days after CCI. Opioid receptors' antagonism reversed EE-analgesic effect. β-endorphin and met-enkephalin serum levels were increased only in EE-CCI group. Blockade of glucocorticoid receptors did not alter EE-analgesic effect, although corticosterone circulating levels were increased in EE animals. In the spinal cord, EE controlled CCI-induced serotonin increase. In DRG, EE blunted the expression of ATF-3 after CCI. Surprisingly, EE-CCI group showed a remarkable preservation of sciatic nerve fibers compared to NE-CCI group. This work demonstrated global effects induced by an EE protocol that explain, in part, the protective role of EE upon chronic noxious stimulation, reinforcing the importance of endogenous mechanisms in the prevention of chronic pain development.
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Bagley EE, Ingram SL. Endogenous opioid peptides in the descending pain modulatory circuit. Neuropharmacology 2020; 173:108131. [PMID: 32422213 DOI: 10.1016/j.neuropharm.2020.108131] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 05/01/2020] [Accepted: 05/04/2020] [Indexed: 02/07/2023]
Abstract
The opioid epidemic has led to a serious examination of the use of opioids for the treatment of pain. Opioid drugs are effective due to the expression of opioid receptors throughout the body. These receptors respond to endogenous opioid peptides that are expressed as polypeptide hormones that are processed by proteolytic cleavage. Endogenous opioids are expressed throughout the peripheral and central nervous system and regulate many different neuronal circuits and functions. One of the key functions of endogenous opioid peptides is to modulate our responses to pain. This review will focus on the descending pain modulatory circuit which consists of the ventrolateral periaqueductal gray (PAG) projections to the rostral ventromedial medulla (RVM). RVM projections modulate incoming nociceptive afferents at the level of the spinal cord. Stimulation within either the PAG or RVM results in analgesia and this circuit has been studied in detail in terms of the actions of exogenous opioids, such as morphine and fentanyl. Further emphasis on understanding the complex regulation of endogenous opioids will help to make rational decisions with regard to the use of opioids for pain. We also include a discussion of the actions of endogenous opioids in the amygdala, an upstream brain structure that has reciprocal connections to the PAG that contribute to the brain's response to pain.
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Affiliation(s)
- Elena E Bagley
- Discipline of Pharmacology and Charles Perkins Centre, University of Sydney, NSW, 2006, Australia
| | - Susan L Ingram
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, 97239, USA.
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Bouchet CA, Ingram SL. Cannabinoids in the descending pain modulatory circuit: Role in inflammation. Pharmacol Ther 2020; 209:107495. [PMID: 32004514 PMCID: PMC7183429 DOI: 10.1016/j.pharmthera.2020.107495] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 01/17/2020] [Indexed: 01/09/2023]
Abstract
The legalization of cannabis in some states has intensified interest in the potential for cannabis and its constituents to lead to novel therapeutics for pain. Our understanding of the cellular mechanisms underlying cannabinoid actions in the brain have lagged behind opioids; however, the current opioid epidemic has also increased attention on the use of cannabinoids as alternatives to opioids for pain, especially chronic pain that requires long-term use. Endogenous cannabinoids are lipid signaling molecules that have complex roles in modulating neuronal function throughout the brain. In this review, we discuss cannabinoid functions in the descending pain modulatory pathway, a brain circuit that integrates cognitive and emotional processing of pain to modulate incoming sensory inputs. In addition, we highlight areas where further studies are necessary to understand cannabinoid regulation of descending pain modulation.
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Affiliation(s)
- Courtney A Bouchet
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR 97239, United States of America
| | - Susan L Ingram
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR 97239, United States of America.
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35
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Hosseini M, Parviz M, Shabanzadeh AP, Zamani E, Mohseni-Moghaddam P, Gholami L, Mehrabadi S. The inhibiting role of periaqueductal gray metabotropic glutamate receptor subtype 8 in a rat model of central neuropathic pain. Neurol Res 2020; 42:515-521. [DOI: 10.1080/01616412.2020.1747730] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Marjan Hosseini
- Department of Physiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Mohsen Parviz
- Department of Physiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Alireza P. Shabanzadeh
- Department of Physiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Elham Zamani
- Department of Physiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | | | - Leila Gholami
- Department of Physiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Shima Mehrabadi
- Department of Physiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
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Lv Q, Wu F, Gan X, Yang X, Zhou L, Chen J, He Y, Zhang R, Zhu B, Liu L. The Involvement of Descending Pain Inhibitory System in Electroacupuncture-Induced Analgesia. Front Integr Neurosci 2019; 13:38. [PMID: 31496944 PMCID: PMC6712431 DOI: 10.3389/fnint.2019.00038] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 07/30/2019] [Indexed: 12/12/2022] Open
Abstract
Chronic pain is a major health problem, which can impair quality of life and reduce productivity. Electroacupuncture (EA), a modality of medicine based on the theories of Traditional Chinese Medicine (TCM), presents great therapeutic effects on chronic pain. Its clinical application has gained increasing popularity, and in parallel, more research has been performed on the mechanisms of EA-induced analgesia. The past decades have seen enormous advances both in neuronal circuitry of needle-insertion and in its molecular mechanism. EA may block pain by activating the descending pain inhibitory system, which originates in the brainstem and terminates at the spinal cord. This review article synthesizes corresponding studies to elucidate how EA alleviate pain via the mediation of this descending system. Much emphasis has been put on the implication of descending serotonergic and noradrenergic pathways in the process of pain modulation. Also, other important transmitters and supraspinal regions related to analgesic effects of EA have been demonstrated. Finally, it should be noticed that there exist some shortcomings involved in the animal experimental designed for EA, which account for conflicting results obtained by different studies.
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Affiliation(s)
- Qiuyi Lv
- School of Acupuncture-Moxibustion and Tuina, Beijing University of Chinese Medicine, Beijing, China
| | - Fengzhi Wu
- Journal Center of Beijing University of Chinese Medicine, Beijing University of Chinese Medicine, Beijing, China
| | - Xiulun Gan
- School of Traditional Chinese Medicine, Beijing University of Chinese Medicine, Beijing, China
| | - Xueqin Yang
- School of Traditional Chinese Medicine, Beijing University of Chinese Medicine, Beijing, China
| | - Ling Zhou
- School of Acupuncture-Moxibustion and Tuina, Beijing University of Chinese Medicine, Beijing, China
| | - Jie Chen
- School of Acupuncture-Moxibustion and Tuina, Beijing University of Chinese Medicine, Beijing, China
| | - Yinjia He
- School of Acupuncture-Moxibustion and Tuina, Beijing University of Chinese Medicine, Beijing, China
| | - Rong Zhang
- School of Acupuncture-Moxibustion and Tuina, Beijing University of Chinese Medicine, Beijing, China
| | - Bixiu Zhu
- Department of Nephrology, Beijing University of Chinese Medicine Third Affiliated Hospital, Beijing, China
| | - Lanying Liu
- Department of Nephrology, Beijing University of Chinese Medicine Third Affiliated Hospital, Beijing, China
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Morphine effects within the rodent anterior cingulate cortex and rostral ventromedial medulla reveal separable modulation of affective and sensory qualities of acute or chronic pain. Pain 2019; 159:2512-2521. [PMID: 30086115 DOI: 10.1097/j.pain.0000000000001355] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Modulation of pain may result from engagement of opioid receptors in multiple brain regions. Whether sensory and affective qualities of pain are differentially affected by brain opioid receptor circuits remains unclear. We previously reported that opioid actions within the rostral anterior cingulate cortex (ACC) produce selective modulation of affective qualities of neuropathic pain in rodents, but whether such effects may occur in other areas of the ACC is not known. Here, morphine was microinjected into 3 regions of the ACC or into the rostral ventromedial medulla (RVM), and pain behaviors in naive, sham, or spinal nerve ligated (SNL) rats were evaluated. In naive animals, the tail-flick response was inhibited by RVM, but not ACC, morphine. Anterior cingulate cortex morphine did not affect tactile allodynia (the von Frey test) or mechanical (Randall-Selitto) or thermal (Hargreaves) hyperalgesia in spinal nerve ligated rats. In contrary, RVM morphine reduced tactile allodynia and produced both antihyperalgesic and analgesic effects against mechanical and thermal stimuli as well as conditioned place preference selectively in nerve-injured rats. Within the RVM, opioids inhibit nociceptive transmission reflected in both withdrawal thresholds and affective pain behaviors. Activation of mu opioid receptors within specific rostral ACC circuits, however, selectively modulates affective dimensions of ongoing pain without altering withdrawal behaviors. These data suggest that RVM and ACC opioid circuits differentially modulate sensory and affective qualities of pain, allowing for optimal behaviors that promote escape and survival. Targeting specific ACC opioid circuits may allow for treatment of chronic pain while preserving the physiological function of acute pain.
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Abstract
Chronic pain is a frequent condition that affects an estimated 20% of people worldwide, accounting for 15%-20% of doctors' appointments (Treede et al., 2015). It lacks the acute warning function of physiologic nociception, and instead involves the activation of multiple neurophysiologic mechanisms in the somatosensory system, a complex neuronal network under the control of powerful autoregulatory loops and able to undergo rapid neuroplastic alteration (Verdu et al., 2008). There is a growing body of research suggesting that some such pathways are shared by major psychologic disorders such as depression and anxiety, opening new avenues in co-treatment strategies. In particular, besides anticonvulsants, which are today used as analgesics, other psychopharmaceuticals, such as the tricyclic antidepressants, are displaying efficacy in the treatment of neuropathic and nociceptive chronic pain. The state of the art regarding the mechanisms of nociception and the pharmacology of both the neurotransmitters involved and the wide range of psychoactive compounds that may be useful in the treatment of chronic pain are discussed.
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Bravo L, Llorca-Torralba M, Berrocoso E, Micó JA. Monoamines as Drug Targets in Chronic Pain: Focusing on Neuropathic Pain. Front Neurosci 2019; 13:1268. [PMID: 31942167 PMCID: PMC6951279 DOI: 10.3389/fnins.2019.01268] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 11/08/2019] [Indexed: 12/11/2022] Open
Abstract
Monoamines are involved in regulating the endogenous pain system and indeed, peripheral and central monoaminergic dysfunction has been demonstrated in certain types of pain, particularly in neuropathic pain. Accordingly, drugs that modulate the monaminergic system and that were originally designed to treat depression are now considered to be first line treatments for certain types of neuropathic pain (e.g., serotonin and noradrenaline (and also dopamine) reuptake inhibitors). The analgesia induced by these drugs seems to be mediated by inhibiting the reuptake of these monoamines, thereby reinforcing the descending inhibitory pain pathways. Hence, it is of particular interest to study the monoaminergic mechanisms involved in the development and maintenance of chronic pain. Other analgesic drugs may also be used in combination with monoamines to facilitate descending pain inhibition (e.g., gabapentinoids and opioids) and such combinations are often also used to alleviate certain types of chronic pain. By contrast, while NSAIDs are thought to influence the monoaminergic system, they just produce consistent analgesia in inflammatory pain. Thus, in this review we will provide preclinical and clinical evidence of the role of monoamines in the modulation of chronic pain, reviewing how this system is implicated in the analgesic mechanism of action of antidepressants, gabapentinoids, atypical opioids, NSAIDs and histaminergic drugs.
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Affiliation(s)
- Lidia Bravo
- Neuropsychopharmacology and Psychobiology Research Group, Department of Neuroscience, University of Cádiz, Cádiz, Spain
- Instituto de Investigación e Innovación Biomédica de Cádiz, INiBICA, Hospital Universitario Puerta del Mar, Cádiz, Spain
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
| | - Meritxell Llorca-Torralba
- Neuropsychopharmacology and Psychobiology Research Group, Department of Neuroscience, University of Cádiz, Cádiz, Spain
- Instituto de Investigación e Innovación Biomédica de Cádiz, INiBICA, Hospital Universitario Puerta del Mar, Cádiz, Spain
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
| | - Esther Berrocoso
- Instituto de Investigación e Innovación Biomédica de Cádiz, INiBICA, Hospital Universitario Puerta del Mar, Cádiz, Spain
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
- Neuropsychopharmacology and Psychobiology Research Group, Department of Psychology, University of Cádiz, Cádiz, Spain
| | - Juan Antonio Micó
- Neuropsychopharmacology and Psychobiology Research Group, Department of Neuroscience, University of Cádiz, Cádiz, Spain
- Instituto de Investigación e Innovación Biomédica de Cádiz, INiBICA, Hospital Universitario Puerta del Mar, Cádiz, Spain
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
- *Correspondence: Juan Antonio Micó,
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Follansbee T, Akiyama T, Fujii M, Davoodi A, Nagamine M, Iodi Carstens M, Carstens E. Effects of pruritogens and algogens on rostral ventromedial medullary ON and OFF cells. J Neurophysiol 2018; 120:2156-2163. [PMID: 29947594 PMCID: PMC6295534 DOI: 10.1152/jn.00208.2018] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 06/03/2018] [Accepted: 06/03/2018] [Indexed: 11/22/2022] Open
Abstract
Rostroventromedial medulla (RVM) ON and OFF cells are thought to facilitate and inhibit spinal nociceptive transmission, respectively. However, it is unknown how ON and OFF cells respond to pruritic stimuli or how they contribute to descending modulation of spinal itch signaling. In pentobarbital sodium-anesthetized mice, single-unit recordings were made in RVM from ON and OFF cells identified by their respective increase or decrease in firing that occurred just before nocifensive hindlimb withdrawal elicited by paw pinch. Of RVM ON cells, 75% (21/28) were excited by intradermal histamine, 50% (10/20) by intradermal chloroquine, and 75% (27/36) by intradermal capsaicin. Most chemically responsive units also responded to a scratch stimulus applied to the injected hindpaw. Few ON cells responded to intradermal injection of vehicle (saline: 5/32; Tween 2/17) but still responded to scratching. For OFF cells, intradermal histamine and scratching inhibited 32% (6/19) with no effect of histamine in the remainder. Intradermal chloroquine inhibited 44% (4/9) and intradermal capsaicin inhibited 61% (11/18) of OFF cells. Few OFF cells were affected by vehicles (Tween: 1 inhibited, 7 unaffected; saline: 3 excited, 1 inhibited, 8 unaffected). Both ON and OFF cells that responded to one chemical usually also responded to others, whereas units unresponsive to the first-tested chemical tended not to respond to others. These results indicate that ascending pruriceptive signals activate RVM ON cells and inhibit RVM OFF cells. These effects are considered to facilitate and disinhibit spinal pain transmission, respectively. It is currently not clear if spinal itch transmission is similarly modulated. NEW & NOTEWORTHY The rostroventromedial medulla (RVM) contains ON and OFF cells that are, respectively, excited and inhibited by noxious stimuli and have descending projections that facilitate and inhibit spinal nociceptive transmission. Most RVM ON cells were excited, and OFF cells inhibited, by intradermal injection of the pruritogens histamine and chloroquine, as well as the algogen capsaicin. These results indicate that itchy stimuli activate RVM neurons that presumably give rise to descending modulation of spinal itch transmission.
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Affiliation(s)
- T. Follansbee
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
- Center for Neuroscience, University of California, Davis, California
| | - T. Akiyama
- Department of Dermatology and Cutaneous Surgery, University of Miami School of Medicine, Miami, Florida
| | - M. Fujii
- Department of Pharmacology, Kyoto Pharmaceutical University, Kyoto, Japan
| | - A. Davoodi
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
| | - M. Nagamine
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
| | - M. Iodi Carstens
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
| | - E. Carstens
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, California
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Coleshill MJ, Sharpe L, Colloca L, Zachariae R, Colagiuri B. Placebo and Active Treatment Additivity in Placebo Analgesia: Research to Date and Future Directions. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2018; 139:407-441. [PMID: 30146056 PMCID: PMC6179351 DOI: 10.1016/bs.irn.2018.07.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Placebo analgesia is a robust experimental and clinical phenomenon. While our understanding of the mechanisms of placebo analgesia has developed rapidly, some central questions remain unanswered. Among the important questions is how placebo analgesia interacts with active analgesic effects. It is an assumption underlying double-blind randomized placebo-controlled trials (RCTs) that the true effect of a treatment can be determined by examining the effect of the active treatment arm and subtracting the response in the placebo group ("the assumption of additivity"). However, despite the importance of this assumption for the interpretation of RCTs, it has rarely been formally examined. This article reviews the assumption of additivity in placebo analgesia by examining studies employing factorial designs manipulating both the receipt of an active analgesic and instructions about the treatment being delivered. In reviewing the literature, we identified seven studies that allowed a test of additivity. Of these, four found evidence against additivity, while the remaining three studies found results consistent with additivity. While the limited available data are somewhat mixed, the evidence suggests that at least under some conditions the assumption of additivity does not hold in placebo analgesia. The concordance between mechanisms of the active analgesic and placebo analgesia may influence whether additivity occurs or not. However, more research using factorial designs is needed to disentangle the relationship between placebo analgesia and the active effect of analgesic treatments.
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Affiliation(s)
- Matthew J Coleshill
- School of Psychology, University of Sydney, Sydney, NSW, Australia; St Vincent's Clinical School, St Vincent's Hospital, University of New South Wales, Sydney, NSW, Australia; Department of Clinical Pharmacology and Toxicology, St Vincent's Hospital, Sydney, NSW, Australia.
| | - Louise Sharpe
- School of Psychology, University of Sydney, Sydney, NSW, Australia
| | - Luana Colloca
- Center to Advance Chronic Pain Research, University of Maryland, Baltimore, MD, United States; School of Nursing, University of Maryland, Baltimore, MD, United States; School of Medicine, University of Maryland, Baltimore, MD, United States
| | - Robert Zachariae
- Aarhus University Hospital and Department of Psychology and Behavioural Science, Aarhus University, Aarhus, Denmark
| | - Ben Colagiuri
- School of Psychology, University of Sydney, Sydney, NSW, Australia
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Salas R, Ramirez K, Tortorici V, Vanegas H, Vazquez E. Functional relationship between brainstem putative pain-facilitating neurons and spinal nociceptfive neurons during development of inflammation in rats. Brain Res 2018; 1686:55-64. [DOI: 10.1016/j.brainres.2018.02.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 12/12/2017] [Accepted: 02/17/2018] [Indexed: 10/18/2022]
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Schafer SM, Geuter S, Wager TD. Mechanisms of placebo analgesia: A dual-process model informed by insights from cross-species comparisons. Prog Neurobiol 2018; 160:101-122. [PMID: 29108801 PMCID: PMC5747994 DOI: 10.1016/j.pneurobio.2017.10.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 10/24/2017] [Accepted: 10/28/2017] [Indexed: 12/19/2022]
Abstract
Placebo treatments are pharmacologically inert, but are known to alleviate symptoms across a variety of clinical conditions. Associative learning and cognitive expectations both play important roles in placebo responses, however we are just beginning to understand how interactions between these processes lead to powerful effects. Here, we review the psychological principles underlying placebo effects and our current understanding of their brain bases, focusing on studies demonstrating both the importance of cognitive expectations and those that demonstrate expectancy-independent associative learning. To account for both forms of placebo analgesia, we propose a dual-process model in which flexible, contextually driven cognitive schemas and attributions guide associative learning processes that produce stable, long-term placebo effects. According to this model, the placebo-induction paradigms with the most powerful effects are those that combine reinforcement (e.g., the experience of reduced pain after placebo treatment) with suggestions and context cues that disambiguate learning by attributing perceived benefit to the placebo. Using this model as a conceptual scaffold, we review and compare neurobiological systems identified in both human studies of placebo analgesia and behavioral pain modulation in rodents. We identify substantial overlap between the circuits involved in human placebo analgesia and those that mediate multiple forms of context-based modulation of pain behavior in rodents, including forebrain-brainstem pathways and opioid and cannabinoid systems in particular. This overlap suggests that placebo effects are part of a set of adaptive mechanisms for shaping nociceptive signaling based on its information value and anticipated optimal response in a given behavioral context.
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Affiliation(s)
- Scott M Schafer
- Department of Psychology and Neuroscience, University of Colorado, 345 UCB, Boulder, CO 80309, USA
| | - Stephan Geuter
- Department of Psychology and Neuroscience, University of Colorado, 345 UCB, Boulder, CO 80309, USA; Institute of Cognitive Science, University of Colorado Boulder, 344 UCB, Boulder, CO 80309, USA; Department of Biostatistics, Johns Hopkins University, 615 N Wolfe St, Baltimore, MD 21205, USA
| | - Tor D Wager
- Department of Psychology and Neuroscience, University of Colorado, 345 UCB, Boulder, CO 80309, USA; Institute of Cognitive Science, University of Colorado Boulder, 344 UCB, Boulder, CO 80309, USA.
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44
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McGovern AE, Ajayi IE, Farrell MJ, Mazzone SB. A neuroanatomical framework for the central modulation of respiratory sensory processing and cough by the periaqueductal grey. J Thorac Dis 2017; 9:4098-4107. [PMID: 29268420 DOI: 10.21037/jtd.2017.08.119] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Sensory information arising from the airways is processed in a distributed brain network that encodes for the discriminative and affective components of the resultant sensations. These higher brain networks in turn regulate descending motor control circuits that can both promote or suppress behavioural responses. Here we explore the existence of possible descending neural control pathways that regulate airway afferent processing in the brainstem, analogous to the endogenous descending analgesia system described for noxious somatosensation processing and placebo analgesia. A key component of this circuitry is the midbrain periaqueductal grey, a region of the brainstem recently highlighted for its altered activity in patients with chronic cough. Understanding the nature and plasticity of descending neural control may help identify novel central therapeutic targets to alleviate the neuronal hypersensitivity underpinning many symptoms of respiratory disease.
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Affiliation(s)
- Alice E McGovern
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville VIC 3010, Australia
| | - Itopa E Ajayi
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville VIC 3010, Australia
| | - Michael J Farrell
- Monash Biomedicine Discovery Institute and Department of Medical Imaging and Radiation Sciences, Monash University, Clayton VIC 3800, Australia
| | - Stuart B Mazzone
- Department of Anatomy and Neuroscience, The University of Melbourne, Parkville VIC 3010, Australia
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45
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Lima LV, DeSantana JM, Rasmussen LA, Sluka KA. Short-duration physical activity prevents the development of activity-induced hyperalgesia through opioid and serotoninergic mechanisms. Pain 2017; 158:1697-1710. [PMID: 28621702 PMCID: PMC5561491 DOI: 10.1097/j.pain.0000000000000967] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Regular physical activity prevents the development of chronic muscle pain through the modulation of central mechanisms that involve rostral ventromedial medulla (RVM). We tested if pharmacological blockade or genetic deletion of mu-opioid receptors in physically active mice modulates excitatory and inhibitory systems in the RVM in an activity-induced hyperalgesia model. We examined response frequency to mechanical stimulation of the paw, muscle withdrawal thresholds, and expression of phosphorylation of the NR1 subunit of the N-methyl-D-aspartate receptor (p-NR1) and serotonin transporter (SERT) in the RVM. Mice that had performed 5 days of voluntary wheel running prior to the induction of the model were compared with sedentary mice. Sedentary mice showed significant increases in mechanical paw withdrawal frequency and a reduction in muscle withdrawal threshold; wheel running prevented the increase in paw withdrawal frequency. Naloxone-treated and MOR mice had increases in withdrawal frequency that were significantly greater than that in physically active control mice and similar to sedentary mice. Immunohistochemistry in the RVM showed increases in p-NR1 and SERT expression in sedentary mice 24 hours after the induction of the model. Wheel running prevented the increase in SERT, but not p-NR1. Physically active, naloxone-treated, and MOR mice showed significant increases in SERT immunoreactivity when compared with wild-type physically active control mice. Blockade of SERT in the RVM in sedentary mice reversed the activity-induced hyperalgesia of the paw and muscle. These results suggest that analgesia induced by 5 days of wheel running is mediated by mu-opioid receptors through the modulation of SERT, but not p-NR1, in RVM.
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MESH Headings
- Animals
- Disease Models, Animal
- Female
- Gene Expression Regulation/physiology
- Hyperalgesia/etiology
- Hyperalgesia/prevention & control
- Male
- Medulla Oblongata/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Nerve Tissue Proteins/metabolism
- Pain Measurement
- Pain Threshold/physiology
- Physical Conditioning, Animal/methods
- Physical Stimulation/adverse effects
- Receptors, N-Methyl-D-Aspartate/metabolism
- Receptors, Opioid, mu/genetics
- Receptors, Opioid, mu/metabolism
- Serotonin Plasma Membrane Transport Proteins/metabolism
- Statistics, Nonparametric
- Time Factors
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Affiliation(s)
- Lucas V Lima
- Department of Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, IA, USA
- Graduate Program in Health Sciences, Federal University of Sergipe, Aracaju/Se, Brazil
| | - Josimari M DeSantana
- Graduate Program in Health Sciences, Federal University of Sergipe, Aracaju/Se, Brazil
- Department of Physical Therapy, Federal University of Sergipe, Aracaju/Se, Brazil
| | - Lynn A Rasmussen
- Department of Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, IA, USA
| | - Kathleen A Sluka
- Department of Physical Therapy and Rehabilitation Science, University of Iowa, Iowa City, IA, USA
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46
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Weinbroum AA. Postoperative hyperalgesia—A clinically applicable narrative review. Pharmacol Res 2017; 120:188-205. [DOI: 10.1016/j.phrs.2017.02.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 02/08/2017] [Accepted: 02/08/2017] [Indexed: 02/08/2023]
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El Bitar N, Pollin B, Karroum E, Pincedé I, Le Bars D. Entanglement between thermoregulation and nociception in the rat: the case of morphine. J Neurophysiol 2016; 116:2473-2496. [PMID: 27605533 PMCID: PMC5133307 DOI: 10.1152/jn.00482.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 09/03/2016] [Indexed: 11/22/2022] Open
Abstract
In thermoneutral conditions, rats display cyclic variations of the vasomotion of the tail and paws, the most widely used target organs in current acute or chronic animal models of pain. Systemic morphine elicits their vasoconstriction followed by hyperthermia in a naloxone-reversible and dose-dependent fashion. The dose-response curves were steep with ED50 in the 0.5-1 mg/kg range. Given the pivotal functional role of the rostral ventromedial medulla (RVM) in nociception and the rostral medullary raphe (rMR) in thermoregulation, two largely overlapping brain regions, the RVM/rMR was blocked by muscimol: it suppressed the effects of morphine. "On-" and "off-" neurons recorded in the RVM/rMR are activated and inhibited by thermal nociceptive stimuli, respectively. They are also implicated in regulating the cyclic variations of the vasomotion of the tail and paws seen in thermoneutral conditions. Morphine elicited abrupt inhibition and activation of the firing of on- and off-cells recorded in the RVM/rMR. By using a model that takes into account the power of the radiant heat source, initial skin temperature, core body temperature, and peripheral nerve conduction distance, one can argue that the morphine-induced increase of reaction time is mainly related to the morphine-induced vasoconstriction. This statement was confirmed by analyzing in psychophysical terms the tail-flick response to random variations of noxious radiant heat. Although the increase of a reaction time to radiant heat is generally interpreted in terms of analgesia, the present data question the validity of using such an approach to build a pain index.
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Affiliation(s)
- Nabil El Bitar
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Bernard Pollin
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Elias Karroum
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Ivanne Pincedé
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Daniel Le Bars
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
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Alterations in the rostral ventromedial medulla after the selective ablation of μ-opioid receptor expressing neurons. Pain 2016; 157:166-173. [PMID: 26335909 DOI: 10.1097/j.pain.0000000000000344] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The rostral ventromedial medulla (RVM) exerts both inhibitory and excitatory controls over nociceptive neurons in the spinal cord and medullary dorsal horn. Selective ablation of mu-opioid receptor (MOR)-expressing neurons in the RVM using saporin conjugated to the MOR agonist dermorphin-saporin (derm-sap) attenuates stress and injury-induced behavioral hypersensitivity, yet the effect of RVM derm-sap on the functional integrity of the descending inhibitory system and the properties of RVM neurons remain unknown. Three classes of RVM neurons (on-cells, off-cells, and neutral cells) have been described with distinct responses to noxious stimuli and MOR agonists. Using single unit recording in lightly anesthetized rats, RVM neurons were characterized after microinjections of derm-sap or saporin. Derm-sap treatment resulted in a reduction in on-cells and off-cells when compared to saporin controls (P < 0.05). The number of neutral cells remained unchanged. After derm-sap treatment, RVM microinjections of the glutamate receptor agonist homocysteic acid increased tail-flick latencies, whereas the MOR agonist DAMGO had no effect. Furthermore, electrical stimulation of the periaqueductal gray produced analgesia in both derm-sap and saporin controls with similar thresholds. Microinjection of kynurenic acid, a glutamate receptor antagonist, into the RVM disrupted periaqueductal gray stimulation-produced analgesia in both saporin-treated and derm-sap-treated rats. These results indicate that MOR-expressing neurons in the RVM are not required for analgesia produced by either direct or indirect activation of neurons in the RVM.
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49
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Salas R, Ramirez K, Vanegas H, Vazquez E. Activity correlations between on-like and off-like cells of the rostral ventromedial medulla and simultaneously recorded wide-dynamic-range neurons of the spinal dorsal horn in rats. Brain Res 2016; 1652:103-110. [PMID: 27720764 DOI: 10.1016/j.brainres.2016.10.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 09/27/2016] [Accepted: 10/01/2016] [Indexed: 12/27/2022]
Abstract
Considerable evidence supports the notion that on- and off-cells of the rostral ventromedial medulla (RVM) facilitate and depress, respectively, spinal nociceptive transmission. This notion stems from a covariation of on- or off-cell activities and spinal nocifensive reflexes. Such covariation could theoretically be due to their independently responding to a common source, or to an RVM-derived modulation of ventral horn neurons. Here, we tested whether on- and off-cells indeed modulate spinal nociceptive neurons. In deeply anesthetized rats, unitary recordings were simultaneously made from an RVM on-like or off-like cell and a spinal nociceptive neuron that shared a receptive field (RF) at a hind paw. Action potential firing in RVM/spinal neuron pairs was highly correlated, positively for on-like cells and negatively for off-like cells, both during ongoing activity and during application of calibrated noxious pressure to the RF. Microinjection of morphine into RVM induced a correlated decrease in on-like cell/spinal neuron ongoing activity and response to noxious stimulation. RVM morphine induced changes in off-like cell activity that were not correlated with spinal neuronal activity. These results suggest that on-cells exert a positive modulation upon spinal nociceptive neurons, upstream to ventral horn circuits and plausibly at the origin of nociceptive information that eventually reaches the cerebral cortex. On-cells may in this manner contribute to inflammation- and neuropathy-induced increases in withdrawal reflexes. Most significantly, on-cell modulation of nociceptive neurons may be a key factor in clinical pain conditions such as hyperalgesia and allodynia.
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Affiliation(s)
- Rafael Salas
- Catedra de Fisiologia, Escuela de Bioanalisis, Facultad de Medicina, Universidad Central de Venezuela, Apartado 9995, Caracas 1050, Venezuela.
| | - Karla Ramirez
- Laboratorio de Neurofisiologia, Centro de Biofisica y Bioquimica, Instituto Venezolano de Investigaciones Cientificas (IVIC), Apartado 20632, Caracas 1020-A, Venezuela.
| | - Horacio Vanegas
- Laboratorio de Neurofisiologia, Centro de Biofisica y Bioquimica, Instituto Venezolano de Investigaciones Cientificas (IVIC), Apartado 20632, Caracas 1020-A, Venezuela.
| | - Enrique Vazquez
- Laboratorio de Neurofisiologia, Centro de Biofisica y Bioquimica, Instituto Venezolano de Investigaciones Cientificas (IVIC), Apartado 20632, Caracas 1020-A, Venezuela.
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50
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Hitomi S, Kross K, Kurose M, Porreca F, Meng ID. Activation of dura-sensitive trigeminal neurons and increased c-Fos protein induced by morphine withdrawal in the rostral ventromedial medulla. Cephalalgia 2016; 37:407-417. [DOI: 10.1177/0333102416648655] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Aims Overuse of medications used to treat migraine headache can increase the frequency of headaches. Sudden abstinence from migraine medication can also lead to a period of withdrawal-induced headaches. The aim of this study was to examine the effect of morphine withdrawal localized to the rostral ventromedial medulla (RVM) on the activity of dura-sensitive spinal trigeminal nucleus caudalis (Vc) neurons. Methods Rats were implanted with either morphine or placebo pellets for six to seven days before the microinjection of naloxone methiodide or phosphate-buffered saline into the RVM in urethane-anesthetized animals. Dura-sensitive neurons were recorded in the Vc and the production of c-Fos-like immunoreactivity was quantified. Results In chronic morphine-treated animals, naloxone methiodide microinjections produced a significant increase both in ongoing and facial heat-evoked activity and an increase in Fos-positive neurons in the Vc and in the nucleus reticularis dorsalis, a brainstem region involved in diffuse noxious inhibitory controls. Conclusions These results indicate that activation of pronociceptive neurons in the RVM under conditions of morphine withdrawal can increase the activity of neurons that transmit headache pain. Modulation of the subnucleus reticularis dorsalis by the RVM may explain the attenuation of conditioned pain modulation in patients with chronic headache.
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Affiliation(s)
- Suzuro Hitomi
- Division of Physiology, Kyushu Dental University, Japan
| | - Konrad Kross
- Center for Excellence in the Neurosciences, University of New England, USA
| | - Masayuki Kurose
- Division of Oral Physiology, Department of Oral Biological Sciences, Niigata University, Graduate School of Medical and Dental Sciences, Japan
| | - Frank Porreca
- Department of Pharmacology, College of Medicine, University of Arizona, Health Sciences Center, USA
| | - Ian D Meng
- Center for Excellence in the Neurosciences, University of New England, USA
- Department of Biomedical Sciences, College of Osteopathic Medicine, University of New England, USA
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