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Puja G, Losi G, Rovati L, Lanza M, Caselli G, Bardoni R. Modulation of NMDA receptor activity by CR4056, an imidazoline-2 receptor ligand with analgesic properties. FRONTIERS IN PAIN RESEARCH 2022; 3:1003068. [DOI: 10.3389/fpain.2022.1003068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 08/31/2022] [Indexed: 11/13/2022] Open
Abstract
CR4056 is an imidazoline-2 receptor ligand having potent analgesic activity and synergistic effect with opioids. Very recently it has been found that CR4056 can revert the cognitive impairment in animal models of Alzheimer's disease (AD). Since several lines of evidence highlight the importance of NMDAR modulators in nociceptive signaling and in AD progression, we considered as important to investigate the effects of CR4056 on NMDAR activity. In primary culture of cortical neurons, application of NMDA and glycine elicits a current that is decreased in a dose-dependent fashion by CR4056 (IC50 5.3 ± 0.1 µM). CR4056 antagonism is reversible, not competitive and voltage-independent and it is not blocked by pertussis toxin. CR4056 interacts with the co-agonist glycine site in a competitive way, indeed high glycine concentrations diminish its effect. Fibroblasts expressing different recombinant NMDA receptors are differently modulated by CR4056: the potency and the efficacy of the compound are higher in GluN1- GluN2B than in GluN1-GluN2A containing receptors. In lamina II neurons of spinal cord slices, single stimulation of afferent fibers evokes an NMDA-mediated current that is inhibited by 10 µM CR4056. Repetitive stimulation of the dorsal root at high frequency and high intensity produces a firing activity that is significatively depressed by CR4056. Taken together, our results broad the understanding of the molecular mechanisms of CR4056 analgesic activity, involving the modulation of NMDAR activity. Therefore, we propose that the analgesic action of CR4056 and the neuroprotective effects in AD models may be mediated also by NMDAR inhibition.
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Guo X, Xue Y, Ji W, Liang J, Qingshi Z. Effects of administration of α2 adrenergic receptor agonist into psoas major muscle on inflammatory pain induced by injection of complete Freund's adjuvant in rats. Mol Pain 2022; 18:17448069221107810. [PMID: 35658695 PMCID: PMC9358342 DOI: 10.1177/17448069221107810] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
α2 adrenergic agonists are widely used in clinical anesthesia and ICU
sedation owing to their effective sedative and analgesic effects. Lumbago and
leg pain is the most common clinical pain disease. Studies have reported that
lumbago and leg pain is associated with dysregulation of paravertebral muscles,
especially psoas major muscles. In the present study, a unilateral lower
extremity chronic inflammation and pain model was established by subcutaneous
administration of low-dose complete Fredrin’s adjuvant (CFA) into the posterior
paw of rats. α2 adrenalin receptor agonist was then injected into the
psoas major muscle. Behavioral tests were conducted for 21 days. Psoas major
muscle tissue was harvested for evaluation of biochemical indexes related to
pain. The effect of α2 adrenergic receptor agonist injected into
psoas major muscle on chronic inflammatory pain of lower extremities in rats was
explored. The results showed that injection of α2 adrenergic receptor
agonist into the psoas major muscle relieved CFA-induced mechanical
hyperalgesia. Administration of α2 adrenergic receptor antagonist
yohimbine reversed the analgesic effect of α2 adrenergic receptor
agonists. Administration of dexmedetomidine into psoas major muscle
downregulated the levels of norepinephrine, interleukin-6 and tumor necrosis
factor-α in tissues. The findings of the present study show that administration
of α2 adrenoceptor agonists into the psoas major muscle relieves
chronic inflammatory pain induced by CFA. Local injection of dexmedetomidine
also exerted anti-inflammatory and anti-sympathetic effect by activating
α2-adrenoceptor in the psoas major muscle.
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Affiliation(s)
- Xingxing Guo
- Division of Anesthesiology,
Department of Cardiovascular Surgery, Guangdong Institute of
Cardiovascular, Guangdong Provincial People’s Hospital, Guangdong Academy
of Medical Sciences, Guangzhou, China
- Department of Anesthesiology, Guangdong Provincial People’s
Hospital, (Zhuhai Golden Bay Center Hospital), Zhuhai, China
| | - Yan Xue
- Division of Anesthesiology,
Department of Cardiovascular Surgery, Guangdong Institute of
Cardiovascular, Guangdong Provincial People’s Hospital, Guangdong Academy
of Medical Sciences, Guangzhou, China
- Department of Anesthesiology, Guangdong Provincial People’s
Hospital, Guangdong Academy of Medical Sciences, Guangzhou,
China
| | - Wenjin Ji
- Department of Anesthesiology, Guangdong Provincial People’s
Hospital, Guangdong Academy of Medical Sciences, Guangzhou,
China
| | - Jiexian Liang
- Division of Anesthesiology,
Department of Cardiovascular Surgery, Guangdong Institute of
Cardiovascular, Guangdong Provincial People’s Hospital, Guangdong Academy
of Medical Sciences, Guangzhou, China
- Department of Anesthesiology, Guangdong Provincial People’s
Hospital, (Zhuhai Golden Bay Center Hospital), Zhuhai, China
- Jiexian Liang, Division of Anesthesiology,
Department of Cardiovascular Surgery, Guangdong Institute of Cardiovascular,
Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences,
96 DongChun Road, Guangzhou, Guangdong 510080, China.
| | - Zeng Qingshi
- Department of Anesthesiology, Guangdong Provincial People’s
Hospital, (Zhuhai Golden Bay Center Hospital), Zhuhai, China
- Qingshi Zeng, Department of Anesthesiology,
Guangdong Provincial People’s Hospital Zhuhai Hospital (Zhuhai Golden Bay Center
Hospital), Zhuhai 519040, China.
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Bardoni R. Experimental Protocols and Analytical Procedures for Studying Synaptic Transmission in Rodent Spinal Cord Dorsal Horn. Curr Protoc 2022; 2:e409. [PMID: 35435326 DOI: 10.1002/cpz1.409] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Synaptic modulation and plasticity are key mechanisms underlying pain transmission in the spinal cord and supra-spinal centers. The study and understanding of these phenomena are fundamental to investigating both acute nociception and maladaptive changes occurring in chronic pain. This article describes experimental protocols and analytical methods utilized in electrophysiological studies to investigate synaptic modulation and plasticity at the first station of somatosensory processing, the spinal cord dorsal horn. Protocols useful for characterizing the nature of synaptic inputs, the site of modulation (pre- versus postsynaptic), and the presence of short-term synaptic plasticity are presented. These methods can be employed to study the physiology of acute nociception, the pathological mechanisms of persistent inflammatory and neuropathic pain, and the pharmacology of receptors and channels involved in pain transmission. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Spinal cord dissection and acute slice preparation Basic Protocol 2: Stimulation of the dorsal root and extracellular recording (compound action potentials and field potentials) Basic Protocol 3: Patch-clamp recording from dorsal horn neurons: action potential firing patterns and evoked synaptic inputs Basic Protocol 4: Analysis of parameters responsible for changes in synaptic efficacy Basic Protocol 5: Recording and analysis of currents mediated by astrocytic glutamate.
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Affiliation(s)
- Rita Bardoni
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Via Campi, Modena, Italy
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Wang Y, Fang X, Liu C, Ma X, Song Y, Yan M. Impact of Intraoperative Infusion and Postoperative PCIA of Dexmedetomidine on Early Breastfeeding After Elective Cesarean Section: A Randomized Double-Blind Controlled Trial. DRUG DESIGN DEVELOPMENT AND THERAPY 2020; 14:1083-1093. [PMID: 32210537 PMCID: PMC7073426 DOI: 10.2147/dddt.s241153] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 02/24/2020] [Indexed: 12/13/2022]
Abstract
Objective Few studies have investigated the effects of dexmedetomidine (DEX) on breastfeeding after cesarean delivery. A randomized double-blind controlled trial was conducted to investigate whether the administration of DEX, immediately after delivery and for patient-controlled intravenous analgesia (PCIA), can be beneficial for breastfeeding. Patients and Methods One hundred sixty parturients scheduled for elective cesarean section under spinal anesthesia were randomly allocated to the DEX group (a loading dose of DEX was pumped at 0.5 μg/kg within 10 min, followed by a further infusion of DEX at 0.5 μg/kg/h until the end of the surgery and PCIA for 2 days with DEX plus sufentanil) or the standard care group (infusion saline intraoperatively, and PCIA for 2 days with sufentanil). The number of days required to switch to exclusive breastfeeding within six weeks of delivery, the time to first lactation and breast milk volume on day 1 and day 2 after delivery were recorded. Recovery quality, comfort, anxiety, depression, postoperative analgesia, and adverse reactions of parturients were also assessed. Results Compared with the standard care group, parturients in the DEX group could be converted to exclusive breastfeeding earlier (11 [14] vs 8 [10] days, log-rank P=0.025), the first lactation time was sooner (28.38 [13.82] vs 33.79 [14.85] hrs, P=0.024), and the amount of breast milk on the second day after delivery increased (P=0.012). There was no difference between the two groups in postpartum uterine contraction pain, but postpartum rest and movement VAS scores and recovery quality score in the DEX group were better than those in the standard care group (all P<0.05). Moreover, the hospital anxiety and depression scale and anxiety subscale score on the second day after delivery and the comfort score on the third day after delivery in the DEX group were significantly better than those in the standard care group (5 [5] vs 6 [8], 2 [2] vs 3 [3], 83.58 [6.75] vs 80.48 [6.58]; P=0.013, P=0.005, P=0.006, respectively). The incidence of adverse events, such as bradycardia, vomiting, hypersomnia, hypertension and hypotension, was not significantly different between the DEX and standard care groups (6.9% vs 2.7%, 5.6% vs 13.7%, 4.2% vs 0%, 5.6% vs 2.7%, 11.1% vs 8.2%; P=0.275, P=0.158, P=0.366, P=0.681, P=0.556, respectively), except more parturients experienced nausea in the standard care group than in the DEX group (28.8% vs 11.1%, P=0.012). Furthermore, there was no difference in Neonatal Behavioral Neurological Assessment scores on the first and second days after delivery between the DEX and standard care groups (38 [3] vs 37 [2], 38.5 [2] vs 38 [2]; P=0.173, P=0.312, respectively). Conclusion The application of DEX in the perioperative period of cesarean section was not only conducive to the early conversion of infant feeding to exclusive breastfeeding but could also improve the recovery quality and comfort of the parturient, optimize analgesia, shorten the time to first lactation, and increase lactation. Clinical Trials Registration NCT03805945.
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Affiliation(s)
- Yu Wang
- Department of Anesthesiology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, People's Republic of China
| | - Xiang Fang
- Department of Anesthesiology, Renmin Hospital of Wuhan University, Wuhan, Hubei, People's Republic of China
| | - Chao Liu
- Department of Anesthesiology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, People's Republic of China
| | - Xiaotong Ma
- Department of Anesthesiology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, People's Republic of China
| | - Yutong Song
- Department of Anesthesiology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, People's Republic of China
| | - Ming Yan
- Department of Anesthesiology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, People's Republic of China
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Abstract
Chronic pain is one of the most debilitating and expensive diseases, yet current therapies are often insufficient in bringing about long-term relief. Further, many treatments for chronic pain also carry significant side effects. The molecule adenosine has long been identified as a potent inhibitor of nociceptive circuits in the spinal cord; however, the widespread expression of adenosine receptors in many organ systems has limited its use as an analgesic. Recently several 5' ectonucleotidases, including tissue non-specific alkaline phosphatase (TNAP), have been characterized for their ability to generate endogenous adenosine in nociceptive circuitry of the dorsal spinal cord. These ectonucleotidases have the ability to hydrolyze the endogenous pronociceptive nucleotides like adenosine triphosphate (ATP) into the antinociceptive nucleoside adenosine. This chapter discusses the role of TNAP and other ectonucleotidases in nociceptive circuits, and their potential as future targets of new therapeutics to treat chronic pain.
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Affiliation(s)
- Sarah E Street
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA,
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Sdrulla AD, Xu Q, He SQ, Tiwari V, Yang F, Zhang C, Shu B, Shechter R, Raja SN, Wang Y, Dong X, Guan Y. Electrical stimulation of low-threshold afferent fibers induces a prolonged synaptic depression in lamina II dorsal horn neurons to high-threshold afferent inputs in mice. Pain 2015; 156:1008-1017. [PMID: 25974163 PMCID: PMC4437220 DOI: 10.1097/01.j.pain.0000460353.15460.a3] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Electrical stimulation of low-threshold Aβ-fibers (Aβ-ES) is used clinically to treat neuropathic pain conditions that are refractory to pharmacotherapy. However, it is unclear how Aβ-ES modulates synaptic responses to high-threshold afferent inputs (C-, Aδ-fibers) in superficial dorsal horn. Substantia gelatinosa (SG) (lamina II) neurons are important for relaying and modulating converging spinal nociceptive inputs. We recorded C-fiber-evoked excitatory postsynaptic currents (eEPSCs) in spinal cord slices in response to paired-pulse test stimulation (500 μA, 0.1 millisecond, 400 milliseconds apart). We showed that 50-Hz and 1000-Hz, but not 4-Hz, Aβ-ES (10 μA, 0.1 millisecond, 5 minutes) induced prolonged inhibition of C-fiber eEPSCs in SG neurons in naive mice. Furthermore, 50-Hz Aβ-ES inhibited both monosynaptic and polysynaptic forms of C-fiber eEPSC in naive mice and mice that had undergone spinal nerve ligation (SNL). The paired-pulse ratio (amplitude second eEPSC/first eEPSC) increased only in naive mice after 50-Hz Aβ-ES, suggesting that Aβ-ES may inhibit SG neurons by different mechanisms under naive and nerve-injured conditions. Finally, 50-Hz Aβ-ES inhibited both glutamatergic excitatory and GABAergic inhibitory interneurons, which were identified by fluorescence in vGlut2-Td and glutamic acid decarboxylase-green fluorescent protein transgenic mice after SNL. These findings show that activities in Aβ-fibers lead to frequency-dependent depression of synaptic transmission in SG neurons in response to peripheral noxious inputs. However, 50-Hz Aβ-ES failed to induce cell-type-selective inhibition in SG neurons. The physiologic implication of this novel form of synaptic depression for pain modulation by Aβ-ES warrants further investigation.
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Affiliation(s)
- Andrei D. Sdrulla
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Qian Xu
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
- Howard Hughes Medical Institute, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Shao-Qiu He
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Vinod Tiwari
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Fei Yang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Chen Zhang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
- Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, China
| | - Bin Shu
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Ronen Shechter
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Srinivasa N. Raja
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Yun Wang
- Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, China
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
- Howard Hughes Medical Institute, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
| | - Yun Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, 21205
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7
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Lee J, Favorov OV, Tommerdahl M, Lee CJ, Whitsel BL. Attenuated Glial K(+) Clearance Contributes to Long-Term Synaptic Potentiation Via Depolarizing GABA in Dorsal Horn Neurons of Rat Spinal Cord. Exp Neurobiol 2014; 23:53-64. [PMID: 24737940 PMCID: PMC3984957 DOI: 10.5607/en.2014.23.1.53] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2014] [Revised: 03/05/2014] [Accepted: 03/05/2014] [Indexed: 11/19/2022] Open
Abstract
It has been reported that long-term enhancement of superficial dorsal horn (DHs) excitatory synaptic transmission underlies central sensitization, secondary hyperalgesia, and persistent pain. We tested whether impaired clearance of K(+) and glutamate by glia in DHs may contribute to initiation and maintenance of the CNS pain circuit and sensorimotor abnormalities. Transient exposure of the spinal cord slice to fluorocitrate (FC) is shown to be accompanied by a protracted decrease of the DHs optical response to repetitive electrical stimulation of the ipsilateral dorsal root, and by a similarly protracted increase in the postsynaptic response of the DHs like LTP. It also is shown that LTPFC does not occur in the presence of APV, and becomes progressively smaller as [K(+)]o in the perfusion solution decreased from 3.0 mM to 0.0 mM. Interestingly LTPFC is reduced by bath application of Bic. Whole-cell patch recordings were carried out to evaluate the effects of FC on the response of DHs neurons to puffer-applied GABA. The observations reveal that transient exposure to FC is reliably accompanied by a prolonged (>1 hr) depolarizing shift of the equilibrium potential for the DHs neuron transmembrane ionic currents evoked by GABA. Considered collectively, the findings demonstrate that LTPFC involves (1) elevation of [K(+)]o in the DHs, (2) NMDAR activation, and (3) conversion of the effect of GABA on DHs neurons from inhibition to excitation. It is proposed that a transient impairment of astrocyte energy production can trigger the cascade of dorsal horn mechanisms that underlies hyperalgesia and persistent pain.
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Affiliation(s)
- Jaekwang Lee
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. ; WCI Center for Functional Connectomics, Institute of Science and Technology (KIST), Seoul, Korea
| | - Oleg V Favorov
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Mark Tommerdahl
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - C Justin Lee
- WCI Center for Functional Connectomics, Institute of Science and Technology (KIST), Seoul, Korea. ; KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, Korea
| | - Barry L Whitsel
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. ; Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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Mitchell K, Lebovitz EE, Keller JM, Mannes AJ, Nemenov MI, Iadarola MJ. Nociception and inflammatory hyperalgesia evaluated in rodents using infrared laser stimulation after Trpv1 gene knockout or resiniferatoxin lesion. Pain 2014; 155:733-745. [PMID: 24434730 DOI: 10.1016/j.pain.2014.01.007] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 12/19/2013] [Accepted: 01/10/2014] [Indexed: 01/23/2023]
Abstract
TRPV1 is expressed in a subpopulation of myelinated Aδ and unmyelinated C-fibers. TRPV1+ fibers are essential for the transmission of nociceptive thermal stimuli and for the establishment and maintenance of inflammatory hyperalgesia. We have previously shown that high-power, short-duration pulses from an infrared diode laser are capable of predominantly activating cutaneous TRPV1+ Aδ-fibers. Here we show that stimulating either subtype of TRPV1+ fiber in the paw during carrageenan-induced inflammation or following hind-paw incision elicits pronounced hyperalgesic responses, including prolonged paw guarding. The ultrapotent TRPV1 agonist resiniferatoxin (RTX) dose-dependently deactivates TRPV1+ fibers and blocks thermal nociceptive responses in baseline or inflamed conditions. Injecting sufficient doses of RTX peripherally renders animals unresponsive to laser stimulation even at the point of acute thermal skin damage. In contrast, Trpv1-/- mice, which are generally unresponsive to noxious thermal stimuli at lower power settings, exhibit withdrawal responses and inflammation-induced sensitization using high-power, short duration Aδ stimuli. In rats, systemic morphine suppresses paw withdrawal, inflammatory guarding, and hyperalgesia in a dose-dependent fashion using the same Aδ stimuli. The qualitative intensity of Aδ responses, the leftward shift of the stimulus-response curve, the increased guarding behaviors during carrageenan inflammation or after incision, and the reduction of Aδ responses with morphine suggest multiple roles for TRPV1+ Aδ fibers in nociceptive processes and their modulation of pathological pain conditions.
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Affiliation(s)
- Kendall Mitchell
- Department of Perioperative Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, USA Department of Anesthesia, Stanford University, Palo Alto, CA, USA Lasmed LLC, Mountain View, CA, USA Neurobiology and Pain Therapeutics Section, Laboratory of Sensory Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
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Funai Y, Pickering AE, Uta D, Nishikawa K, Mori T, Asada A, Imoto K, Furue H. Systemic dexmedetomidine augments inhibitory synaptic transmission in the superficial dorsal horn through activation of descending noradrenergic control: an in vivo patch-clamp analysis of analgesic mechanisms. Pain 2013; 155:617-628. [PMID: 24355412 DOI: 10.1016/j.pain.2013.12.018] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 11/26/2013] [Accepted: 12/10/2013] [Indexed: 12/19/2022]
Abstract
α2-Adrenoceptors are widely distributed throughout the central nervous system (CNS) and the systemic administration of α2-agonists such as dexmedetomidine produces clinically useful, centrally mediated sedation and analgesia; however, these same actions also limit the utility of these agents (ie, unwanted sedative actions). Despite a wealth of data on cellular and synaptic actions of α2-agonists in vitro, it is not known which neuronal circuits are modulated in vivo to produce the analgesic effect. To address this issue, we made in vivo recordings of membrane currents and synaptic activities in superficial spinal dorsal horn neurons and examined their responses to systemic dexmedetomidine. We found that dexmedetomidine at doses that produce analgesia (<10 μg/kg) enhanced inhibitory postsynaptic transmission within the superficial dorsal horn without altering excitatory synaptic transmission or evoking direct postsynaptic membrane currents. In contrast, higher doses of dexmedetomidine (>10 μg/kg) induced outward currents by a direct postsynaptic action. The dexmedetomidine-mediated inhibitory postsynaptic current facilitation was not mimicked by spinal application of dexmedetomidine and was absent in spinalized rats, suggesting that it acts at a supraspinal site. Furthermore, it was inhibited by spinal application of the α1-antagonist prazosin. In the brainstem, low doses of systemic dexmedetomidine produced an excitation of locus coeruleus neurons. These results suggest that systemic α2-adrenoceptor stimulation may facilitate inhibitory synaptic responses in the superficial dorsal horn to produce analgesia mediated by activation of the pontospinal noradrenergic inhibitory system. This novel mechanism may provide new targets for intervention, perhaps allowing analgesic actions to be dissociated from excessive sedation.
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Affiliation(s)
- Yusuke Funai
- Department of Information Physiology, National Institutes for Physiological Sciences, Okazaki, Japan Department of Anesthesiology, Osaka City University Graduate School of Medicine, Osaka, Japan School of Physiology and Pharmacology, University of Bristol, Bristol, UK School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Japan
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Buesa I, Urrutia A, Bilbao J, Aguilera L, Zimmermann M, Azkue JJ. Morphine-induced depression of spinal excitation is not altered following acute disruption of GABAA or GABAB receptor activity. Eur J Pain 2012; 12:677-85. [DOI: 10.1016/j.ejpain.2007.10.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Ishii H, Kohno T, Yamakura T, Ikoma M, Baba H. Action of dexmedetomidine on the substantia gelatinosa neurons of the rat spinal cord. Eur J Neurosci 2008; 27:3182-90. [PMID: 18554299 PMCID: PMC2658019 DOI: 10.1111/j.1460-9568.2008.06260.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Dexmedetomidine is a highly specific, potent and selective alpha(2)-adrenoceptor agonist. Although intrathecal and epidural administration of dexmedetomidine has been found to produce analgesia, whether this analgesia results from an effect on spinal cord substantia gelatinosa (SG) neurons remains unclear. Here, we investigated the effects of dexmedetomidine on postsynaptic transmission in SG neurons of rat spinal cord slices using the whole-cell patch-clamp technique. In 92% of the SG neurons examined (n = 84), bath-applied dexmedetomidine induced outward currents at -70 mV in a concentration-dependent manner, with the value of effective concentration producing a half-maximal response (0.62 microM). The outward currents induced by dexmedetomidine were suppressed by the alpha(2)-adrenoceptor antagonist yohimbine, but not by prazosin, an alpha(1)-, alpha(2B)- and alpha(2C)-adrenoceptor antagonist. Moreover, the dexmedetomidine-induced currents were partially suppressed by the alpha(2C)-adrenoceptor antagonist JP-1302, while simultaneous application of JP-1302 and the alpha(2A)-adrenoceptor antagonist BRL44408 abolished the current completely. The action of dexmedetomidine was mimicked by the alpha(2A)-adrenoceptor agonist oxymetazoline. Plots of the current-voltage relationship revealed a reversal potential at around -86 mV. Dexmedetomidine-induced currents were blocked by the addition of GDP-beta-S [guanosine-5'-O-(2-thiodiphosphate)] or Cs+ to the pipette solution. These findings suggest that dexmedetomidine hyperpolarizes the membrane potentials of SG neurons by G-protein-mediated activation of K+ channels through alpha(2A)- and alpha(2C)-adrenoceptors. This action of dexmedetomidine might contribute, at least in part, to its antinociceptive action in the spinal cord.
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Affiliation(s)
- Hideaki Ishii
- Division of Anesthesiology, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi, Niigata 951-8510, Japan
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12
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Buesa I, Ortiz V, Aguilera L, Torre F, Zimmermann M, Azkue JJ. Disinhibition of spinal responses to primary afferent input by antagonism at GABA receptors in urethane-anaesthetised rats is dependent on NMDA and metabotropic glutamate receptors. Neuropharmacology 2006; 50:585-94. [PMID: 16412481 DOI: 10.1016/j.neuropharm.2005.11.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2005] [Revised: 08/18/2005] [Accepted: 11/09/2005] [Indexed: 11/21/2022]
Abstract
Disruption of spinal GABAergic circuits, which regulate the conveyance of sensory information to spinal cord neurones from the primary afferent system, leads to miscoding of afferent input and often results in hyperresponsiveness states. In the present work, extracellular field potentials elicited by electrical peripheral nerve activation were recorded in the urethane-anaesthetised rat following spinal administration of GABA(A) or GABA(B) receptor-antagonists, and the involvement of glutamate receptors of the NMDA and metabotropic types in changes induced by altered GABAergic function was examined by pre-treating the spinal dorsal horn with appropriate antagonist drugs. Spinal administration of the GABA(A) receptor antagonist bicuculline (BIC) dose-dependently augmented poly- but not monosynaptic field potentials elicited by activation of A fibres or potentials elicited by activation of C fibres, whereas application of the GABA(B) receptor antagonist CGP35348 significantly increased the amplitudes of C- but not A fibre-evoked potentials. BIC-induced augmentation was blocked by pre-treatment with the NMDA receptor antagonist D-(-)-2-amino-5-phosphonopentanoic acid (D-AP5) or the group I or II metabotropic glutamate receptor (mGluR)-antagonists (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA) or (2S)-alpha-ethylglutamic acid (EGLU), respectively, but not by the group III mGluR-antagonist (RS)-alpha-methylserine-O-phosphate (MSOP). Augmentation of spinal field potentials induced by CGP35348 was prevented by pre-treatment with D-AP5 but not with mGluR-antagonists. The present findings provide novel evidence that disparate synaptic mechanisms subserved by metabotropic and NMDA glutamate receptors may be involved in spinal hyperresponsiveness states secondary to decreased GABA(A) or GABA(B) receptor activity.
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Affiliation(s)
- Itsaso Buesa
- Department of Neurosciences, School of Medicine and Dentistry, Basque Country University, Barrio Sarriena s/n, 48940 Leioa, Spain
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Lee J, Tommerdahl M, Favorov OV, Whitsel BL. Optically Recorded Response of the Superficial Dorsal Horn: Dissociation From Neuronal Activity, Sensitivity to Formalin-Evoked Skin Nociceptor Activation. J Neurophysiol 2005; 94:852-64. [PMID: 15744009 DOI: 10.1152/jn.00976.2004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In rat spinal cord, slice repetitive electrical stimulation of the dorsal root at an intensity that activates C-fibers evokes a slow-to-develop and prolonged (30–50 s) change in light transmittance (OISDR) in the superficial part of the ipsilateral dorsal horn (DHs). Inhibition of astrocyte metabolism [by bath-applied 400 μM fluoroacetate and 200 μM glutamine (FAc + Gln)] or interference with glial and neuronal K+ transport [by 100 μM 4-aminopyridine (4-AP)] leads to dissociation of the OISDR and the postsynaptic DHs response to a single-pulse, constant-current dorsal root stimulus (P-PSPDR). The OISDR decreases under FAc+Gln, whereas the P-PSPDR remains unaltered; under 4-AP, the P-PSPDR increases, but the OISDR decreases. In contrast, both the OISDR and P-PSPDR increase when K+o is elevated to 8 mM. These observations from slices from normal subjects are interpreted to indicate that the OISDR mainly reflects cell volume and light scattering changes associated with DHs astrocyte uptake of K+ and glutamate (GLU). In slices from subjects that received an intracutaneous injection of formalin 3–5 days earlier, both the OISDR and the response of the DHs ipsilateral to the injection site to 100-ms local application (via puffer pipette) of 15 mM K+ or 100 μM GLU were profoundly reduced, and the normally exquisite sensitivity of the DHs to elevated K+o is decreased. Considered collectively, the observations raise the possibility that impaired regulation of DHs K+o and GLUo may contribute to initiation and maintenance of the CNS pain circuit and sensorimotor abnormalities that develop following intracutaneous formalin injection.
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Affiliation(s)
- Jaekwang Lee
- Department of Cell and Molecular Physiology, University of North Carolina, Chapel Hill, North Carolina 27599-7545, USA
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Tanaka H, Kakizaki H, Shibata T, Ameda K, Koyanagi T. Effects of a selective metabotropic glutamate receptor agonist on the micturition reflex pathway in urethane-anesthetized rats. Neurourol Urodyn 2003; 22:611-6. [PMID: 12951674 DOI: 10.1002/nau.10138] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
AIMS To determine a possible role of metabotropic glutamate receptors in the spinobulbospinal micturition reflex pathway in the rat. MATERIALS AND METHODS A selective metabotropic glutamate receptor agonist, trans-(+/-)-1-amino1,3-cyclopentanedicarboxylic acid (trans-ACPD) was administered to the lumbosacral spinal cord via an intrathecal catheter in urethane anesthetized rats. Amplitude of reflex bladder contractions evoked by bladder distension under isovolumetric condition as well as amplitude of bladder contractions elicited by electrical stimulation of the pontine micturition center (PMC) were examined before and after administration of trans-ACPD. The effect of trans-ACPD on the urethral activity during isovolumetric bladder contractions was also examined by monitoring urethral perfusion pressure and electromyography of the external urethral sphincter (EUS-EMG). RESULTS Trans-ACPD (3-10 microg) completely inhibited reflex bladder contractions evoked by bladder distension and the duration of inhibition was dose dependent (3 microg: 11.4 +/- 2.8 min, 5 microg: 13.2 +/- 1.3 min, 10 microg: 36.2 +/- 2.4 min). The mean amplitude of bladder contractions evoked by electrical stimulation of the PMC was reduced to 12.6 +/- 2.3% of control by 10 microg of trans-ACPD. In addition, bursting activity of EUS-EMG and corresponding high frequency oscillations of urethral pressure during isovolumetric bladder contractions were completely abolished by 10 microg of trans-ACPD. CONCLUSIONS These results indicate that intrathecal administration of a selective metabotropic glutamate receptor agonist to the lumbosacral spinal cord has an inhibitory effect on the spinobulbospinal micturition reflex pathway in urethane-anesthetized rats. This pharmacological action is attributed at least to the inhibitory effect on the descending pathway from the PMC to the lumbosacral spinal cord.
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Affiliation(s)
- Hiroshi Tanaka
- The Department of Urology, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
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Sandkühler J, Benrath J, Brechtel C, Ruscheweyh R, Heinke B. Synaptic mechanisms of hyperalgesia. PROGRESS IN BRAIN RESEARCH 2001; 129:81-100. [PMID: 11098683 DOI: 10.1016/s0079-6123(00)29007-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Affiliation(s)
- J Sandkühler
- Institut für Physiologie und Pathophysiologie, Universität Heidelberg, Germany.
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Ruscheweyh R, Sandkühler J. Bidirectional actions of nociceptin/orphanin FQ on A delta-fibre-evoked responses in rat superficial spinal dorsal horn in vitro. Neuroscience 2001; 107:275-81. [PMID: 11731101 DOI: 10.1016/s0306-4522(01)00354-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The present study investigated the modulatory actions of nociceptin/orphanin FQ on excitatory glutamatergic transmission in spinal dorsal horn. In transverse spinal cord slices with an attached dorsal root, mono- and polysynaptic A delta-fibre-evoked extracellular field potentials were recorded from superficial dorsal horn. Nociceptin/orphanin FQ showed bidirectional effects on monosynaptic transmission with a potentiation at lower concentrations (100-300 nM) and a dose-dependent depression at higher concentrations (1-3 microM). The polysynaptic field potential was dose-dependently depressed by nociceptin/orphanin FQ (100 nM-3 microM). None of the actions of nociceptin/orphanin FQ was reversed by the non-specific opioid receptor antagonist naloxone, the N-methyl-D-aspartate receptor antagonist D-2-amino-5-phosphonovaleric acid or the peptide nocistatin. The bidirectional actions of nociceptin/orphanin FQ on the monosynaptic field potential may provide an in vitro model for the bidirectional actions of nociceptin/orphanin FQ in behavioural studies showing hyperalgesia at low doses of intrathecal nociceptin/orphanin FQ and analgesia at higher doses.
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Affiliation(s)
- R Ruscheweyh
- Institute of Physiology and Pathophysiology, University of Heidelberg, Im Neuenheimer Feld 326, D-69120 Heidelberg, Germany
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