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David P Roberson,
Sagi Gudes,
Jared M Sprague,
Haley A W Patoski,
Victoria K Robson,
Felix Blasl,
Bo Duan,
Seog Bae Oh,
Bruce P Bean,
Qiufu Ma, Alexander M Binshtok,
Clifford J Woolf
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ABSTRACT: The peripheral terminals of primary sensory neurons detect histamine and non-histamine itch-provoking ligands through molecularly distinct transduction mechanisms. It remains unclear, however, whether these distinct pruritogens activate the same or different afferent fibers. Using a strategy of reversibly silencing specific subsets of murine pruritogen-sensitive sensory axons by targeted delivery of a charged sodium-channel blocker, we found that functional blockade of histamine itch did not affect the itch evoked by chloroquine or SLIGRL-NH2, and vice versa. Notably, blocking itch-generating fibers did not reduce pain-associated behavior. However, silencing TRPV1(+) or TRPA1(+) neurons allowed allyl isothiocyanate or capsaicin, respectively, to evoke itch, implying that certain peripheral afferents may normally indirectly inhibit algogens from eliciting itch. These findings support the presence of functionally distinct sets of itch-generating neurons and suggest that targeted silencing of activated sensory fibers may represent a clinically useful anti-pruritic therapeutic approach for histaminergic and non-histaminergic pruritus.
Nature Neuroscience 05/2013; · 15.53 Impact Factor
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ABSTRACT: QX-314 (N-ethyl-lidocaine) is a cationic lidocaine derivative that blocks voltage-dependent sodium channels when applied internally to axons or neuronal cell bodies. Co-application of external QX-314 together with the TRPV1 agonist capsaicin produces long-lasting sodium channel inhibition in TRPV1-expressing neurons, suggestive of QX-314 entry into the neurons. We asked whether QX-314 entry occurs directly through TRPV1 channels or through a different pathway (e.g. pannexin channels) activated downstream of TRPV1 and also whether QX-314 entry requires the phenomenon of "pore dilation" previously reported for TRPV1. With external solutions containing 10 or 20 mM QX-314 as the only cation, inward currents were activated by stimulation of both heterologously-expressed and native TRPV1 channels in rat DRG neurons. QX-314-mediated inward current did not require pore dilation, as it activated within several seconds and in parallel with Cs-mediated outward current, with a reversal potential consistent with PQX-314/PCs= 0.12. QX-314-mediated current was no different when TRPV1 channels were expressed in C6 glioma cells, which lack expression of pannexin channels. Rapid addition of QX-314 to physiological external solutions produced instant partial inhibition of inward currents carried by sodium ions, suggesting that QX-314 is a permeant blocker. Maintained co-application of QX-314 with capsaicin produced slowly-developing reduction of outward currents carried by internal Cs, consistent with intracellular accumulation of QX-314 to concentrations of 50-100 μM. We conclude that QX-314 is directly permeant in the "standard" pore formed by TRPV1 channels and does not require either pore dilation or activation of additional downstream channels for entry.
Journal of Neurophysiology 01/2013; · 3.32 Impact Factor
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Alexander M Binshtok
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ABSTRACT: Many surgical and dental procedures depend on use of local anesthetics to reversibly eliminate pain. By the blockade of voltage-gated sodium channels, local anesthetics prevent the transmission of nociceptive information. However, since all local anesthetics act non-selectively on all types of axons they also cause a loss of innocuous sensation, motor paralysis and autonomic block. Thus, approaches that produce only a selective blockade of pain fibers are of great potential clinical importance. In this chapter we will review the recent findings describing mechanisms of pain transduction and transmission and introduce novel therapeutic approaches to produce pain-selective analgesia.
International Review of Neurobiology 01/2011; 97:143-77. · 2.35 Impact Factor
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Hyun Yeong Kim,
Kihwan Kim,
Hai Ying Li,
Gehoon Chung,
Chul-Kyu Park,
Joong Soo Kim,
Sung Jun Jung,
Min Kyung Lee,
Dong Kuk Ahn,
Se Jin Hwang,
Youngnam Kang, Alexander M Binshtok,
Bruce P Bean,
Clifford J Woolf,
Seog Bae Oh
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ABSTRACT: We tested whether it is possible to selectively block pain signals in the orofacial area by delivering the permanently charged lidocaine derivative QX-314 into nociceptors via TPRV1 channels. We examined the effects of co-applied QX-314 and capsaicin on nociceptive, proprioceptive, and motor function in the rat trigeminal system. QX-314 alone failed to block voltage-gated sodium channel currents (I(Na)) and action potentials (APs) in trigeminal ganglion (TG) neurons. However, co-application of QX-314 and capsaicin blocked I(Na) and APs in TRPV1-positive TG and dental nociceptive neurons, but not in TRPV1-negative TG neurons or in small neurons from TRPV1 knock-out mice. Immunohistochemistry revealed that TRPV1 is not expressed by trigeminal motor and trigeminal mesencephalic neurons. Capsaicin had no effect on rat trigeminal motor and proprioceptive mesencephalic neurons and therefore should not allow QX-314 to enter these cells. Co-application of QX-314 and capsaicin inhibited the jaw-opening reflex evoked by noxious electrical stimulation of the tooth pulp when applied to a sensory but not a motor nerve, and produced long-lasting analgesia in the orofacial area. These data show that selective block of pain signals can be achieved by co-application of QX-314 with TRPV1 agonists. This approach has potential utility in the trigeminal system for treating dental and facial pain.
Pain 03/2010; 150(1):29-40. · 5.78 Impact Factor
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Alexander M Binshtok,
Haibin Wang,
Katharina Zimmermann,
Fumimasa Amaya,
Daniel Vardeh,
Lin Shi,
Gary J Brenner,
Ru-Rong Ji,
Bruce P Bean,
Clifford J Woolf,
Tarek A Samad
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ABSTRACT: A cardinal feature of inflammation is heightened pain sensitivity at the site of the inflamed tissue. This results from the local release by immune and injured cells of nociceptor sensitizers, including prostaglandin E(2), bradykinin, and nerve growth factor, that reduce the threshold and increase the excitability of the peripheral terminals of nociceptors so that they now respond to innocuous stimuli: the phenomenon of peripheral sensitization. We show here that the proinflammatory cytokine interleukin-1beta (IL-1beta), in addition to producing inflammation and inducing synthesis of several nociceptor sensitizers, also rapidly and directly activates nociceptors to generate action potentials and induce pain hypersensitivity. IL-1beta acts in a p38 mitogen-activated protein kinase (p38 MAP kinase)-dependent manner, to increase the excitability of nociceptors by relieving resting slow inactivation of tetrodotoxin-resistant voltage-gated sodium channels and also enhances persistent TTX-resistant current near threshold. By acting as an IL-1beta sensor, nociceptors can directly signal the presence of ongoing tissue inflammation.
Journal of Neuroscience 01/2009; 28(52):14062-73. · 7.11 Impact Factor
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ABSTRACT: Despite the clinical demand, current uses of local anesthetics do not allow selective blockade of nociceptive fibers. Regional anesthesia produces an analgesic effect accompanied with undesired side effects due to block of motor, non-nociceptive sensory and autonomic fibers. These side effects limit the clinical use of local anesthetics and affect the recovery and rehabilitation period after surgical procedures. Therefore one main goal of research in the field of regional anesthesia is selectively targeting nociceptive fibers. Recent studies describing the role of nociceptive specific sodium channels in generation and propagation of nociceptive signals make these channels ideal targets for pain selective blockade. In addition, novel methods of targeted delivery of charged local anesthetics selectively into nociceptors provide another potentially successful approach for c-fiber specific nerve block. This review summarizes currently on-going studies on several promising targets and methods to achieve pain selective anesthesia.
The Open Pain Journal 01/2009; 2:24-29.
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ABSTRACT: Transient receptor potential vanilloid 1 channels integrate nociceptive stimuli and are predominantly expressed by unmyelinated C-fiber nociceptors, but not low-threshold mechanoreceptive sensory or motor fibers. A recent report showed that the transient receptor potential vanilloid 1 channel agonist capsaicin allows a hydrophilic quaternary ammonium derivative of lidocaine, QX-314, to selectively block C fibers without motor block. The authors tested whether a similar differential block would be produced using amphipathic N-methyl amitriptyline, amitriptyline, bupivacaine, or lidocaine, either alone or together with 0.05% capsaicin, in a rat sciatic nerve block model.
Rats (n = 8/group) were anesthetized with sevoflurane, and 0.2 ml of drug was injected either alone or with capsaicin (simultaneously or 10 min later) next to the sciatic nerve in the sciatic notch. Motor function was assessed by the extensor postural thrust. Nociception was evaluated by the nocifensive withdrawal reflex and vocalization evoked by pinch of a skin fold over the lateral metatarsus (cutaneous pain) with a serrated forceps.
N-Methyl amitriptyline, amitriptyline, bupivacaine, or lidocaine, followed by injection of capsaicin 10 min later, each elicited a predominantly nociceptive-specific blockade. In comparison, simultaneous application of each local anesthetic with capsaicin did not elicit a clinically significant differential block, with the exception of N-methyl amitriptyline.
Both tertiary amine local anesthetics and their quaternary ammonium derivatives can elicit a predominantly sensory/nociceptor selective block when followed by injection of capsaicin. The combined application of transient receptor potential vanilloid 1 channel agonists and various local anesthetics or their quaternary ammonium derivatives is an appealing strategy to achieve a long-lasting differential block in regional analgesia.
Anesthesiology 12/2008; 109(5):872-8. · 5.36 Impact Factor
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ABSTRACT: Most local anaesthetics used clinically are relatively hydrophobic molecules that gain access to their blocking site on the sodium channel by diffusing into or through the cell membrane. These anaesthetics block sodium channels and thereby the excitability of all neurons, not just sensory neurons. We tested the possibility of selectively blocking the excitability of primary sensory nociceptor (pain-sensing) neurons by introducing the charged, membrane-impermeant lidocaine derivative QX-314 through the pore of the noxious-heat-sensitive TRPV1 channel. Here we show that charged sodium-channel blockers can be targeted into nociceptors by the application of TRPV1 agonists to produce a pain-specific local anaesthesia. QX-314 applied externally had no effect on the activity of sodium channels in small sensory neurons when applied alone, but when applied in the presence of the TRPV1 agonist capsaicin, QX-314 blocked sodium channels and inhibited excitability. Inhibition by co-applied QX-314 and capsaicin was restricted to neurons expressing TRPV1. Injection of QX-314 together with capsaicin into rat hindpaws produced a long-lasting (more than 2 h) increase in mechanical and thermal nociceptive thresholds. Long-lasting decreases in pain sensitivity were also seen with regional injection of QX-314 and capsaicin near the sciatic nerve; however, in contrast to the effect of lidocaine, the application of QX-314 and capsaicin together was not accompanied by motor or tactile deficits.
Nature 11/2007; 449(7162):607-10. · 36.28 Impact Factor
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Doo Yeon Kim,
Bryce W. Carey,
Haibin Wang,
Laura A. M. Ingano, Alexander M. Binshtok,
Mary H. Wertz,
Warren H. Pettingell,
Ping He,
Virginia M.-Y. Lee,
Clifford J. Woolf,
Dora M. Kovacs
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ABSTRACT: BACE1 activity is significantly increased in the brains of Alzheimer's disease patients, potentially contributing to neurodegeneration. The voltage-gated sodium channel (Nav1) 2-subunit (2), a type I membrane protein that covalently binds to Nav1 -subunits, is a substrate for BACE1 and -secretase. Here, we find that BACE1–-secretase cleavages release the intracellular domain of 2, which increases mRNA and protein levels of the pore-forming Nav1.1 -subunit in neuroblastoma cells. Similarly, endogenous 2 processing and Nav1.1 protein levels are elevated in brains of BACE1-transgenic mice and Alzheimer's disease patients with high BACE1 levels. However, Nav1.1 is retained inside the cells and cell surface expression of the Nav1 -subunits and sodium current densities are markedly reduced in both neuroblastoma cells and adult hippocampal neurons from BACE1-transgenic mice. BACE1, by cleaving 2, thus regulates Nav1 -subunit levels and controls cell-surface sodium current densities. BACE1 inhibitors may normalize membrane excitability in Alzheimer's disease patients with elevated BACE1 activity.
Nature Cell Biology 06/2007; 9(7):755-764. · 19.49 Impact Factor
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Irmgard Tegeder,
Michael Costigan,
Robert S Griffin,
Andrea Abele,
Inna Belfer,
Helmut Schmidt,
Corina Ehnert,
Jemiel Nejim,
Claudiu Marian,
Joachim Scholz, [......],
Swetha Sama,
Steven J Atlas,
William A Carlezon,
Aram Parsegian,
Jörn Lötsch,
Roger B Fillingim,
William Maixner,
Gerd Geisslinger,
Mitchell B Max,
Clifford J Woolf
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ABSTRACT: We report that GTP cyclohydrolase (GCH1), the rate-limiting enzyme for tetrahydrobiopterin (BH4) synthesis, is a key modulator of peripheral neuropathic and inflammatory pain. BH4 is an essential cofactor for catecholamine, serotonin and nitric oxide production. After axonal injury, concentrations of BH4 rose in primary sensory neurons, owing to upregulation of GCH1. After peripheral inflammation, BH4 also increased in dorsal root ganglia (DRGs), owing to enhanced GCH1 enzyme activity. Inhibiting this de novo BH4 synthesis in rats attenuated neuropathic and inflammatory pain and prevented nerve injury-evoked excess nitric oxide production in the DRG, whereas administering BH4 intrathecally exacerbated pain. In humans, a haplotype of the GCH1 gene (population frequency 15.4%) was significantly associated with less pain following diskectomy for persistent radicular low back pain. Healthy individuals homozygous for this haplotype exhibited reduced experimental pain sensitivity, and forskolin-stimulated immortalized leukocytes from haplotype carriers upregulated GCH1 less than did controls. BH4 is therefore an intrinsic regulator of pain sensitivity and chronicity, and the GTP cyclohydrolase haplotype is a marker for these traits.
Nature Medicine 12/2006; 12(11):1269-77. · 22.46 Impact Factor
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Irmgard Tegeder,
Michael Costigan,
Robert S Griffin,
Andrea Abele,
Inna Belfer,
Helmut Schmidt,
Corina Ehnert,
Jemiel Nejim,
Claudiu Marian,
Joachim Scholz, [......],
Swetha Sama,
Steven J Atlas,
William A Carlezon,
Aram Parsegian,
J|[ouml]|rn L|[ouml]|tsch,
Roger B Fillingim,
William Maixner,
Gerd Geisslinger,
Mitchell B Max,
Clifford J Woolf
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[hide abstract]
ABSTRACT: We report that GTP cyclohydrolase (GCH1), the rate-limiting enzyme for tetrahydrobiopterin (BH4) synthesis, is a key modulator of peripheral neuropathic and inflammatory pain. BH4 is an essential cofactor for catecholamine, serotonin and nitric oxide production. After axonal injury, concentrations of BH4 rose in primary sensory neurons, owing to upregulation of GCH1. After peripheral inflammation, BH4 also increased in dorsal root ganglia (DRGs), owing to enhanced GCH1 enzyme activity. Inhibiting this de novo BH4 synthesis in rats attenuated neuropathic and inflammatory pain and prevented nerve injury–evoked excess nitric oxide production in the DRG, whereas administering BH4 intrathecally exacerbated pain. In humans, a haplotype of the GCH1 gene (population frequency 15.4%) was significantly associated with less pain following diskectomy for persistent radicular low back pain. Healthy individuals homozygous for this haplotype exhibited reduced experimental pain sensitivity, and forskolin-stimulated immortalized leukocytes from haplotype carriers upregulated GCH1 less than did controls. BH4 is therefore an intrinsic regulator of pain sensitivity and chronicity, and the GTP cyclohydrolase haplotype is a marker for these traits.
Nature Medicine. 10/2006; 12(11):1269-1277.
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ABSTRACT: In layer 4 of the somatosensory cortex, the glutamatergic synapses that interconnect spiny stellate (SpS) neurons, which are the major targets of thalamocortical input, differ from most other neocortical excitatory synapses in that they have an extremely large NMDA receptor (NMDAR)-mediated component that is relatively insensitive to voltage-dependent Mg2+ blockade. We now report that this unique feature of the NMDA response reflects the distinctive subunit composition of the underlying receptors. We studied NMDAR-mediated miniature EPSCs (mEPSCs) and NMDA channel currents in tangential brain slices of mouse barrel cortex, which exclusively contain layer 4. NMDAR-mediated mEPSCs in SpS neurons were prominent at negative membrane potentials, and NMDA channels in outside-out patches excised from the somata of the same neurons had relatively low conductance and reduced susceptibility to Mg2+ block. These are characteristic features of heteromeric NMDAR assemblies that contain the NR2C subunit. Some patches also contained NMDA channels with higher conductance and a greater sensitivity to Mg2+. In the neocortex of transgenic mice in which a beta-galactosidase (lacZ) indicator gene was controlled by the NR2C promoter, the lacZ indicator was densely expressed in layer 4. In current-clamp recordings, blockade of NMDARs caused hyperpolarization and an increase in apparent input resistance. Our data demonstrate that the SpS neurons of layer 4 functionally express NR2C subunits; this is the likely explanation for their ability to generate large NMDAR-mediated EPSPs that are effective at resting potential, without previous depolarization.
Journal of Neuroscience 02/2006; 26(2):708-15. · 7.11 Impact Factor
