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Zhang Y, Zhao S, Rodriguez E, Takatoh J, Han BX, Zhou X, Wang F. Identifying local and descending inputs for primary sensory neurons. J Clin Invest 2015; 125:3782-94. [PMID: 26426077 DOI: 10.1172/jci81156] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Accepted: 07/23/2015] [Indexed: 12/25/2022] Open
Abstract
Primary pain and touch sensory neurons not only detect internal and external sensory stimuli, but also receive inputs from other neurons. However, the neuronal derived inputs for primary neurons have not been systematically identified. Using a monosynaptic rabies viruses-based transneuronal tracing method combined with sensory-specific Cre-drivers, we found that sensory neurons receive intraganglion, intraspinal, and supraspinal inputs, the latter of which are mainly derived from the rostroventral medulla (RVM). The viral-traced central neurons were largely inhibitory but also consisted of some glutamatergic neurons in the spinal cord and serotonergic neurons in the RVM. The majority of RVM-derived descending inputs were dual GABAergic and enkephalinergic (opioidergic). These inputs projected through the dorsolateral funiculus and primarily innervated layers I, II, and V of the dorsal horn, where pain-sensory afferents terminate. Silencing or activation of the dual GABA/enkephalinergic RVM neurons in adult animals substantially increased or decreased behavioral sensitivity, respectively, to heat and mechanical stimuli. These results are consistent with the fact that both GABA and enkephalin can exert presynaptic inhibition of the sensory afferents. Taken together, this work provides a systematic view of and a set of tools for examining peri- and extrasynaptic regulations of pain-afferent transmission.
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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: 53] [Impact Index Per Article: 5.9] [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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Foster E, Wildner H, Tudeau L, Haueter S, Ralvenius WT, Jegen M, Johannssen H, Hösli L, Haenraets K, Ghanem A, Conzelmann KK, Bösl M, Zeilhofer HU. Targeted ablation, silencing, and activation establish glycinergic dorsal horn neurons as key components of a spinal gate for pain and itch. Neuron 2015; 85:1289-304. [PMID: 25789756 PMCID: PMC4372258 DOI: 10.1016/j.neuron.2015.02.028] [Citation(s) in RCA: 252] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 01/26/2015] [Accepted: 02/12/2015] [Indexed: 01/28/2023]
Abstract
The gate control theory of pain proposes that inhibitory neurons of the spinal dorsal horn exert critical control over the relay of nociceptive signals to higher brain areas. Here we investigated how the glycinergic subpopulation of these neurons contributes to modality-specific pain and itch processing. We generated a GlyT2::Cre transgenic mouse line suitable for virus-mediated retrograde tracing studies and for spatially precise ablation, silencing, and activation of glycinergic neurons. We found that these neurons receive sensory input mainly from myelinated primary sensory neurons and that their local toxin-mediated ablation or silencing induces localized mechanical, heat, and cold hyperalgesia; spontaneous flinching behavior; and excessive licking and biting directed toward the corresponding skin territory. Conversely, local pharmacogenetic activation of the same neurons alleviated neuropathic hyperalgesia and chloroquine- and histamine-induced itch. These results establish glycinergic neurons of the spinal dorsal horn as key elements of an inhibitory pain and itch control circuit. Glycinergic dorsal horn neurons exert segmental control over pain and itch Their local inhibition causes hyperalgesia and signs of spontaneous discomfort Local activation reduces acute pain, neuropathic hyperalgesia, and chemical itch
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Dieb W, Alvarez P, Hafidi A. PKCγ-positive neurons gate light tactile inputs to pain pathway through pERK1/2 neuronal network in trigeminal neuropathic pain model. J Oral Facial Pain Headache 2015; 29:70-82. [PMID: 25635962 DOI: 10.11607/ofph.1353] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
AIMS To explore the possible relationship between protein kinase C gamma (PKCγ) and phosphorylated forms of extracellular signal-regulated kinases 1/2 (pERK1/2) in the rat medullary dorsal horn and the facial hypersensitivity indicative of dynamic mechanical allodynia (DMA) following chronic constriction of the infraorbital nerve (CCI-IoN). METHODS A well-established rat model of trigeminal neuropathic pain involving CCI-IoN was used. Facial mechanical hypersensitivity was tested with non-noxious dynamic mechanical stimulation (air-puff), and the medullary dorsal horn was examined immunohistochemically using PKCγ and pERK1/2 as pain markers. Statistical analysis was performed using Student t test or one-way analysis of variance (ANOVA). RESULTS Increased PKCγ and pERK1/2 expressions within the medullary dorsal horn were associated with DMA following CCI-IoN. A segmental network composed of PKCγ-positive cells located in medullary dorsal horn laminae II/III, contacting more superficially located pERK1/2-expressing cells, was identified. Ultrastructural analysis confirmed the presence of PKCγ to pERK1/2-positive cells. Moreover, intracisternal administration of the selective PKCγ inhibitor KIG31-I blocked both the DMA and pERK1/2 expression in a dose-dependent manner. Although the number of pERK1/2-positive cells was significantly elevated with air-puff stimulation, DMA rats not receiving air-puff stimulation showed significant pERK1/2 expression, suggesting they were experiencing spontaneous pain. CONCLUSION PKCγ cells in the medullary dorsal horn may be involved in DMA following CCI-IoN through the activation of pERK1/2-expressing cells, which then may relay non-nociceptive information to lamina I cells in the medullary dorsal horn.
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Shelykh TN, Plakhova VB, Podzorova SA, Bagrov AY, Krylov BV. Modulating effect of the cardiotonic steroid marinobufagenin on slow sodium channels. DOKLADY BIOLOGICAL SCIENCES : PROCEEDINGS OF THE ACADEMY OF SCIENCES OF THE USSR, BIOLOGICAL SCIENCES SECTIONS 2014; 458:278-280. [PMID: 25371252 DOI: 10.1134/s0012496614050111] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Indexed: 06/04/2023]
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Levine AJ, Hinckley CA, Hilde KL, Driscoll SP, Poon TH, Montgomery JM, Pfaff SL. Identification of a cellular node for motor control pathways. Nat Neurosci 2014; 17:586-93. [PMID: 24609464 PMCID: PMC4569558 DOI: 10.1038/nn.3675] [Citation(s) in RCA: 146] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 02/13/2014] [Indexed: 12/28/2022]
Abstract
The rich behavioral repertoire of animals is encoded in the CNS as a set of motorneuron activation patterns, also called 'motor synergies'. However, the neurons that orchestrate these motor programs as well as their cellular properties and connectivity are poorly understood. Here we identify a population of molecularly defined motor synergy encoder (MSE) neurons in the mouse spinal cord that may represent a central node in neural pathways for voluntary and reflexive movement. This population receives direct inputs from the motor cortex and sensory pathways and, in turn, has monosynaptic outputs to spinal motorneurons. Optical stimulation of MSE neurons drove reliable patterns of activity in multiple motor groups, and we found that the evoked motor patterns varied on the basis of the rostrocaudal location of the stimulated MSE. We speculate that these neurons comprise a cellular network for encoding coordinated motor output programs.
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Spicarova D, Adamek P, Kalynovska N, Mrozkova P, Palecek J. TRPV1 receptor inhibition decreases CCL2-induced hyperalgesia. Neuropharmacology 2014; 81:75-84. [PMID: 24495396 DOI: 10.1016/j.neuropharm.2014.01.041] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2013] [Revised: 01/23/2014] [Accepted: 01/24/2014] [Indexed: 01/03/2023]
Abstract
Modulation of nociceptive synaptic transmission in the spinal cord is implicated in the development and maintenance of several pathological pain states. The chemokine CCL2 (C-C motif ligand 2) was shown to be an important factor in the development of neuropathic pain after peripheral nerve injury. In our experiments we have studied the effect of CCL2 application and TRPV1 (transient receptor potential vanilloid 1) receptor activation on nociceptive signaling and the modulation of synaptic transmission. Intrathecal drug application in behavioral experiments and patch-clamp recordings of spontaneous, miniature and dorsal root stimulation-evoked excitatory postsynaptic currents (sEPSCs, mEPSCs, eEPSCs) from superficial dorsal horn neurons in acute rat spinal cord slices were used. The intrathecal application of CCL2 induced thermal hyperalgesia and mechanical allodynia, while pretreatment with the TRPV1 receptor antagonist SB366791 diminished the thermal but not the mechanical hypersensitivity. Patch-clamp experiments showed an increase of sEPSC and mEPSC (124.5 ± 12.8% and 161.2 ± 17.3%, respectively) frequency in dorsal horn neurons after acute CCL2 application. This CCL2-induced increase was prevented by SB366791 pretreatment (89.4 ± 6.0%, 107.5 ± 14.2%). CCL2 application increased the amplitude of eEPSCs (188.1 ± 32.1%); this increase was significantly lower in experiments with SB366791 pretreatment (120.8 ± 17.2%). Our results demonstrate that the activation of spinal TRPV1 receptors plays an important role in the modulation of nociceptive signaling induced by CCL2 application. The mechanisms of cooperation between the CCL2 activated receptors and TRPV1 receptors on the central branches of primary afferent fibers may be especially important during different pathological pain states and need to be further investigated.
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Qiao GF, Qian Z, Sun HL, Xu WX, Yan ZY, Liu Y, Zhou JY, Zhang HC, Wang LJ, Pan XD, Fu Y. Remodeling of hyperpolarization-activated current, Ih, in Ah-type visceral ganglion neurons following ovariectomy in adult rats. PLoS One 2013; 8:e71184. [PMID: 23951107 PMCID: PMC3741359 DOI: 10.1371/journal.pone.0071184] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 06/27/2013] [Indexed: 12/21/2022] Open
Abstract
Hyperpolarization-activated currents (Ih) mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels modulate excitability of myelinated A− and Ah-type visceral ganglion neurons (VGN). Whether alterations in Ih underlie the previously reported reduction of excitability of myelinated Ah-type VGNs following ovariectomy (OVX) has remained unclear. Here we used the intact nodose ganglion preparation in conjunction with electrophysiological approaches to examine the role of Ih remodeling in altering Ah-type neuron excitability following ovariectomy in adult rats. Ah-type neurons were identified based on their afferent conduction velocity. Ah-type neurons in nodose ganglia from non-OVX rats exhibited a voltage ‘sag’ as well as ‘rebound’ action potentials immediately following hyperpolarizing current injections, which both were suppressed by the Ih blocker ZD7288. Repetitive spike activity induced afterhyperpolarizations lasting several hundreds of milliseconds (termed post-excitatory membrane hyperpolarizations, PEMHs), which were significantly reduced by ZD7288, suggesting that they resulted from transient deactivation of Ih during the preceding spike trains. Ovariectomy reduced whole-cell Ih density, caused a hyperpolarizing shift of the voltage-dependence of Ih activation, and slowed Ih activation. OVX-induced Ih remodeling was accompanied by a flattening of the stimulus frequency/response curve and loss of PEMHs. Also, HCN1 mRNA levels were reduced by ∼30% in nodose ganglia from OVX rats compared with their non-OVX counterparts. Acute exposure of nodose ganglia to 17beta-estradiol partly restored Ih density and accelerated Ih activation in Ah-type cells. In conclusion, Ih plays a significant role in modulating the excitability of myelinated Ah-type VGNs in adult female rats.
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Logan SM, Romero MI, Nguyen DH, Benson MD. Ephrin-B2 expression in the proprioceptive sensory system. Neurosci Lett 2013; 545:69-74. [PMID: 23623938 PMCID: PMC3867235 DOI: 10.1016/j.neulet.2013.04.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 04/04/2013] [Accepted: 04/10/2013] [Indexed: 11/17/2022]
Abstract
Recent studies have shown that ephrin-B2 on sensory afferent fibers from the dorsal root ganglia (DRG) controls transmission of pain sensation to the spinal cord. We examined ephrin-B2 expression in mouse DRG and spinal cord using an ephrin-B2/ß-galactosidase chimeric allele. We found that ephrin-B2 is expressed exclusively in proprioceptive neurons and fibers in neonates, while expression in lamina III and IV of the adult spinal cord was observed in addition to that in the deeper laminae. We confirmed that ephrin-B2 protein causes co-clustering of EphB2 and glutamate receptors in spinal cord neurons. Our data are consistent with a role for ephrin-B2 in transmission of positional information to the CNS, and thus suggest a role in synaptic plasticity of spinal cord locomotor circuits that are known to be sensitive to proprioceptive sensory input after spinal cord injury.
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Okubo M, Castro A, Guo W, Zou S, Ren K, Wei F, Keller A, Dubner R. Transition to persistent orofacial pain after nerve injury involves supraspinal serotonin mechanisms. J Neurosci 2013; 33:5152-61. [PMID: 23516281 PMCID: PMC3640487 DOI: 10.1523/jneurosci.3390-12.2013] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The orofacial region is a major focus of chronic neuropathic pain conditions characterized by primary hyperalgesia at the site of injury and secondary hyperalgesia outside the injured zone. We have used a rat model of injury to the maxillary branch (V2) of the trigeminal nerve to produce constant and long-lasting primary hyperalgesia in the V2 territory and secondary hyperalgesia in territories innervated by the mandibular branch (V3). Our findings indicate that the induction of primary and secondary hyperalgesia depended on peripheral input from the injured nerve. In contrast, the maintenance of secondary hyperalgesia depended on central mechanisms. The centralization of the secondary hyperalgesia involved descending 5-HT drive from the rostral ventromedial medulla and the contribution of 5-HT3 receptors in the trigeminal nucleus caudalis (Vc), the homolog of the spinal dorsal horn. Electrophysiological studies further indicate that after nerve injury spontaneous responses and enhanced poststimulus discharges in Vc nociresponsive neurons were time-dependent on descending 5-HT drive and peripheral input. The induction phase of secondary hyperalgesia involved central sensitization mechanisms in Vc neurons that were dependent on peripheral input, whereas the maintenance phase of secondary hyperalgesia involved central sensitization in Vc neurons conducted by a delayed descending 5-HT drive and a persistence of peripheral inputs. Our results are the first to show that the maintenance of secondary hyperalgesia and underlying central sensitization associated with persistent pain depend on a transition to supraspinal mechanisms involving the serotonin system in rostral ventromedial medulla-dorsal horn circuits.
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Vierck CJ, Whitsel BL, Favorov OV, Brown AW, Tommerdahl M. Role of primary somatosensory cortex in the coding of pain. Pain 2013; 154:334-344. [PMID: 23245864 PMCID: PMC4501501 DOI: 10.1016/j.pain.2012.10.021] [Citation(s) in RCA: 148] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 09/15/2012] [Accepted: 10/29/2012] [Indexed: 02/04/2023]
Abstract
The intensity and submodality of pain are widely attributed to stimulus encoding by peripheral and subcortical spinal/trigeminal portions of the somatosensory nervous system. Consistent with this interpretation are studies of surgically anesthetized animals, demonstrating that relationships between nociceptive stimulation and activation of neurons are similar at subcortical levels of somatosensory projection and within the primary somatosensory cortex (in cytoarchitectural areas 3b and 1 of somatosensory cortex, SI). Such findings have led to characterizations of SI as a network that preserves, rather than transforms, the excitatory drive it receives from subcortical levels. Inconsistent with this perspective are images and neurophysiological recordings of SI neurons in lightly anesthetized primates. These studies demonstrate that an extreme anterior position within SI (area 3a) receives input originating predominantly from unmyelinated nociceptors, distinguishing it from posterior SI (areas 3b and 1), long recognized as receiving input predominantly from myelinated afferents, including nociceptors. Of particular importance, interactions between these subregions during maintained nociceptive stimulation are accompanied by an altered SI response to myelinated and unmyelinated nociceptors. A revised view of pain coding within SI cortex is discussed, and potentially significant clinical implications are emphasized.
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Cogli L, Progida C, Thomas CL, Spencer-Dene B, Donno C, Schiavo G, Bucci C. Charcot-Marie-Tooth type 2B disease-causing RAB7A mutant proteins show altered interaction with the neuronal intermediate filament peripherin. Acta Neuropathol 2013; 125:257-72. [PMID: 23179371 PMCID: PMC3549248 DOI: 10.1007/s00401-012-1063-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2012] [Revised: 10/29/2012] [Accepted: 10/29/2012] [Indexed: 12/13/2022]
Abstract
Charcot-Marie-Tooth type 2B (CMT2B) is a peripheral ulcero-mutilating neuropathy caused by four missense mutations in the rab7a gene. CMT2B is clinically characterized by prominent sensory loss, distal muscle weakness leading to muscle atrophy, high frequency of foot ulcers and infections that often results in toe amputations. RAB7A is a ubiquitous small GTPase, which controls transport to late endocytic compartments. Although the biochemical and functional properties of disease-causing RAB7A mutant proteins have been investigated, it is not yet clear how the disease originates. To understand how mutations in a ubiquitous protein specifically affect peripheral neurons, we performed a two-hybrid screen using a dorsal root ganglia cDNA library with the purpose of identifying RAB7A interactors specific for these cells. We identified peripherin, an intermediate filament protein expressed primarily in peripheral neurons, as a putative RAB7A interacting protein. The interaction was confirmed by co-immunoprecipitation and pull-down experiments, and established that the interaction is direct using recombinant proteins. Silencing or overexpression of wild type RAB7A changed the soluble/insoluble rate of peripherin indicating that RAB7A is important for peripherin organization and function. In addition, disease-causing RAB7A mutant proteins bind more strongly to peripherin and their expression causes a significant increase in the amount of soluble peripherin. Since peripherin plays a role not only in neurite outgrowth during development but also in axonal regeneration after injury, these data suggest that the altered interaction between disease-causing RAB7A mutants and peripherin could play an important role in CMT2B neuropathy.
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Shypshyna MS, Veselovs'kyĭ MS. [Pre- and postsynaptic expression mechanisms of long-term depression in rats glutamatergic primary afferent synapses on dorsal horn spinal cord neurons in co-culture]. FIZIOLOHICHNYI ZHURNAL (KIEV, UKRAINE : 1994) 2013; 59:117-123. [PMID: 23713358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In co-culture of dorsal root ganglion (DRG) and dorsal horn (DH) neurons we studied the long-term depression (LTD) caused by 5 sec(-1) low-frequency stimulation (LFS) of DRG neurons. Dual whole-cell patch clamp recording in the pairs of DRG and DH neurons was used. The monosynaptic AMPA-receptor mediated eEPSC initiated in DH neurons by LFS of DRG neurons were analyzed. LFS with durations from 60 to 360 sec affected the LTD magnitude and involved the different LTD expression mechanisms. The amplitude and variability of miniature EPSC were not changed during LTD. LFS during 60 sec did not alter the eEPSC amplitudes, but significantly increased the coefficient of variation (CV; 56.8% +/- 11.5%, n = 5; P < 0.002) and the paired-pulse ratio (PPR; 37.8% +/- 11.4%, n = 5; P < 0.05), and decreased the release probability (p; 21.9% +/- 5.6%, n = 5; P < 0.05) calculated using binomial analysis. LFS for 120 sec led to LTD (eEPSC decreased to 14% +/- 3.3%, n = 13; P < 0.005); no changes in CV, PPR and p were found. LFS for 160, 200, 240 and 360 sec induced robust LTD: eEPSC decreased to 37.3 +/- 4.3 (n = 9); 48.1 +/- 3.5 (n = 7); 58.3 +/- 2.5 (n = 8) and 57.3% +/- 2.8% (n = 8), respectively; P < 0.001. LTD induced by such LFS durations was not accompanied by significant changing in PPR and p, but showed an increase in CV: 24.4 +/- 8.6 (n = 6); 35.1 +/- 11.2 (n = 6); 37.7 +/- 12.8 (n = 7), and 38.1% +/- 9.3% (n = 8), respectively. LTD magnitude was correlated with the enhancement in CV value at different LFS duration (r = 0.96). Our data suggest that the different mechanisms could be involved in LTD expression according to duration of LFS. Thus, 60 sec LFS induces presynaptic changes, but no change in eEPSC, whereas LTD elicited by 120 and 160 sec LFS affected the postsynaptic site. LTD initiated by longer LFS (200 - 360 sec) probably was caused by a silencing of functional synapses without changes in glutamate release probability.
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Zhou T, Wang J, Han CX. [Nonlinear dynamic analysis of electrical signals of wide dynamic range neurons in the spinal dorsal horn evoked by acupuncture manipulation at different frequencies]. ZHONGGUO ZHONG XI YI JIE HE ZA ZHI ZHONGGUO ZHONGXIYI JIEHE ZAZHI = CHINESE JOURNAL OF INTEGRATED TRADITIONAL AND WESTERN MEDICINE 2012; 32:1403-1406. [PMID: 23163156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
OBJECTIVE To study the encoding information of electrical signals of wide dynamic range (WDR) neurons in the spinal dorsal horn evoked by acupuncture manipulation at different frequencies using nonlinear dynamics analysis. METHODS Microelectrode extracellular recordings were used to observe the WDR neuron discharge evoked by acupuncture manipulation at Zusanli point (ST36) with different frequencies (0.5, 1, 2, and 3 Hz) in SD rats. The nonlinear dynamics analysis method was used to extract the nonlinear characteristic parameters, such as interspike interval, the Lyapunov exponent, Lempel-Ziv complexity, and the neural coding of the electrical signal evoked by acupuncture manipulations at different frequencies. RESULTS Different characteristics were manifested with acupuncture manipulations at 4 different frequencies. More than a simple linear correlation was shown between the firing rate of the WDR neurons and the frequency of the acupuncture manipulation. The electrical signals evoked by acupuncture manipulation at Zusanli point (ST36) showed distinguished chaotic features. CONCLUSIONS It is applicable and feasible to describe and summarize the rhythm of the acupuncture electrical signal using the concepts and terminology of the nonlinear dynamics. Different acupuncture manipulation methods could interfere the transmission, coding, and processing of electrical signals in the spinal dorsal horn.
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Cao DY, Ji Y, Tang B, Traub RJ. Estrogen receptor β activation is antinociceptive in a model of visceral pain in the rat. THE JOURNAL OF PAIN 2012; 13:685-94. [PMID: 22698981 DOI: 10.1016/j.jpain.2012.04.010] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 04/19/2012] [Accepted: 04/27/2012] [Indexed: 01/31/2023]
Abstract
UNLABELLED The mechanism underlying estrogen modulation of visceral pain remains unclear. Our previous studies indicate that activation of estrogen receptor α (ERα) enhances visceral pain. The purpose of the present study was to investigate the role of estrogen receptor β (ERβ) activation in spinal processing of visceral stimuli. The effects of selective ERβ agonists on the visceromotor response (VMR) and dorsal horn neuronal responses to colorectal distention (CRD) were tested in ovariectomized and intact female rats. The magnitude of the VMR to CRD was significantly attenuated by ERβ agonists diarylpropionitrile (DPN) and WAY-200070 4 hours after subcutaneous injection. Pretreatment with the estrogen receptor antagonist ICI 182,780 obscured the DPN-evoked attenuation. There was no effect of DPN on the VMR at earlier time points. Subcutaneous and spinal administration of DPN attenuated the response of visceroceptive dorsal horn neurons with a comparable time course. DPN attenuated the VMR in intact rats regardless of estrous cycle stage. The time course of effect of ERβ activation on the visceromotor response and neuronal activity is consistent with transcriptional or translational modulation of neuronal activity. PERSPECTIVE Activation of ERβ is antinociceptive in the colorectal distention model of visceral pain, which may provide a therapeutic target to manage irritable bowel syndrome in the clinic.
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McCoy ES, Taylor-Blake B, Zylka MJ. CGRPα-expressing sensory neurons respond to stimuli that evoke sensations of pain and itch. PLoS One 2012; 7:e36355. [PMID: 22563493 PMCID: PMC3341357 DOI: 10.1371/journal.pone.0036355] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2012] [Accepted: 04/02/2012] [Indexed: 01/09/2023] Open
Abstract
Calcitonin gene-related peptide (CGRPα, encoded by Calca) is a classic marker of nociceptive dorsal root ganglia (DRG) neurons. Despite years of research, it is unclear what stimuli these neurons detect in vitro or in vivo. To facilitate functional studies of these neurons, we genetically targeted an axonal tracer (farnesylated enhanced green fluorescent protein; GFP) and a LoxP-stopped cell ablation construct (human diphtheria toxin receptor; DTR) to the Calca locus. In culture, 10–50% (depending on ligand) of all CGRPα-GFP-positive (+) neurons responded to capsaicin, mustard oil, menthol, acidic pH, ATP, and pruritogens (histamine and chloroquine), suggesting a role for peptidergic neurons in detecting noxious stimuli and itch. In contrast, few (2.2±1.3%) CGRPα-GFP+ neurons responded to the TRPM8-selective cooling agent icilin. In adult mice, CGRPα-GFP+ cell bodies were located in the DRG, spinal cord (motor neurons and dorsal horn neurons), brain and thyroid—reproducibly marking all cell types known to express Calca. Half of all CGRPα-GFP+ DRG neurons expressed TRPV1, ∼25% expressed neurofilament-200, <10% contained nonpeptidergic markers (IB4 and Prostatic acid phosphatase) and almost none (<1%) expressed TRPM8. CGRPα-GFP+ neurons innervated the dorsal spinal cord and innervated cutaneous and visceral tissues. This included nerve endings in the epidermis and on guard hairs. Our study provides direct evidence that CGRPα+ DRG neurons respond to agonists that evoke pain and itch and constitute a sensory circuit that is largely distinct from nonpeptidergic circuits and TRPM8+/cool temperature circuits. In future studies, it should be possible to conditionally ablate CGRPα-expressing neurons to evaluate sensory and non-sensory functions for these neurons.
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Aicher SA, Hermes SM, Whittier KL, Hegarty DM. Descending projections from the rostral ventromedial medulla (RVM) to trigeminal and spinal dorsal horns are morphologically and neurochemically distinct. J Chem Neuroanat 2012; 43:103-11. [PMID: 22119519 PMCID: PMC3319838 DOI: 10.1016/j.jchemneu.2011.11.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Revised: 11/08/2011] [Accepted: 11/09/2011] [Indexed: 01/16/2023]
Abstract
Neurons in the rostral ventromedial medulla (RVM) are thought to modulate nociceptive transmission via projections to spinal and trigeminal dorsal horns. The cellular substrate for this descending modulation has been studied with regard to projections to spinal dorsal horn, but studies of the projections to trigeminal dorsal horn have been less complete. In this study, we combined anterograde tracing from RVM with immunocytochemical detection of the GABAergic synthetic enzyme, GAD67, to determine if the RVM sends inhibitory projections to trigeminal dorsal horn. We also examined the neuronal targets of this projection using immunocytochemical detection of NeuN. Finally, we used electron microscopy to verify cellular targets. We compared projections to both trigeminal and spinal dorsal horns. We found that RVM projections to both trigeminal and spinal dorsal horn were directed to postsynaptic profiles in the dorsal horn, including somata and dendrites, and not to primary afferent terminals. We found that RVM projections to spinal dorsal horn were more likely to contact neuronal somata and were more likely to contain GAD67 than projections from RVM to trigeminal dorsal horn. These findings suggest that RVM neurons send predominantly GABAergic projections to spinal dorsal horn and provide direct input to postsynaptic neurons such as interneurons or ascending projection neurons. The RVM projection to trigeminal dorsal horn is more heavily targeted to dendrites and is only modestly GABAergic in nature. These anatomical features may underlie differences between trigeminal and spinal dorsal horns with regard to the degree of inhibition or facilitation evoked by RVM stimulation.
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Furutani K, Kohno T. [Local anesthetics inhibit NMDA-mediated glutamatergic transmission in spinal dorsal horn neurons]. MASUI. THE JAPANESE JOURNAL OF ANESTHESIOLOGY 2011; 60 Suppl:S151-S158. [PMID: 22458033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
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Qi J, Zhang H, Guo J, Yang L, Wang W, Chen T, Li H, Wu SX, Li YQ. Synaptic connections of the neurokinin 1 receptor-like immunoreactive neurons in the rat medullary dorsal horn. PLoS One 2011; 6:e23275. [PMID: 21858052 PMCID: PMC3157358 DOI: 10.1371/journal.pone.0023275] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Accepted: 07/10/2011] [Indexed: 01/17/2023] Open
Abstract
The synaptic connections between neurokinin 1 (NK1) receptor-like immunoreactive (LI) neurons and γ-aminobutyric acid (GABA)-, glycine (Gly)-, serotonin (5-HT)- or dopamine-β-hydroxylase (DBH, a specific marker for norepinephrinergic neuronal structures)-LI axon terminals in the rat medullary dorsal horn (MDH) were examined under electron microscope by using a pre-embedding immunohistochemical double-staining technique. NK1 receptor-LI neurons were observed principally in laminae I and III, only a few of them were found in lamina II of the MDH. GABA-, Gly-, 5-HT-, or DBH-LI axon terminals were densely encountered in laminae I and II, and sparsely in lamina III of the MDH. Some of these GABA-, Gly-, 5-HT-, or DBH-LI axon terminals were observed to make principally symmetric synapses with NK1 receptor-LI neuronal cell bodies and dendritic processes in laminae I, II and III of the MDH. The present results suggest that neurons expressing NK1 receptor within the MDH might be modulated by GABAergic and glycinergic inhibitory intrinsic neurons located in the MDH and 5-HT- or norepinephrine (NE)-containing descending fibers originated from structures in the brainstem.
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Robbins MT, Deberry J, Randich A, Ness TJ. Footshock stress differentially affects responses of two subpopulations of spinal dorsal horn neurons to urinary bladder distension in rats. Brain Res 2011; 1386:118-26. [PMID: 21376017 PMCID: PMC3086680 DOI: 10.1016/j.brainres.2011.02.081] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Revised: 02/23/2011] [Accepted: 02/24/2011] [Indexed: 11/23/2022]
Abstract
This investigation examined the effect of footshock on responses of 283 spinal dorsal horn neurons (DHNs) to urinary bladder distension (UBD). Female rats were treated with seven daily sessions of footshock (chronic footshock, CFS), six accommodation sessions followed by one exposure to footshock (acute footshock, AFS) or handled similarly without receiving any footshock (no footshock, NFS). After the final footshock or NFS session, rats were anesthetized, a laminectomy performed and extracellular single-unit recordings of L6-S1 DHNs obtained in intact or spinalized preparations. Neurons were classified as Type I-inhibited by heterotopic noxious conditioning stimuli (HNCS) or as Type II-not inhibited by HNCS-and characterized for spontaneous activity and for neuronal discharges evoked by graded UBD. A differential effect of footshock-induced stress was noted on neuronal subgroups. In intact preparations, Type I neurons were less responsive to UBD after either chronic or acute stress, while Type II neurons demonstrated significantly augmented responses to UBD. This enhanced neuronal responsiveness to UBD was present in spinalized preparations following exposure to CFS but not AFS. Type I neurons were still less responsive to stress in spinalized preparations following CFS and AFS. This study provides further evidence that (1) at least two populations of spinal neurons exist which encode for visceral stimuli and are likely to have distinct roles in visceral nociception, and that (2) the chronic stress-induced enhancement of DHN responses to UBD involves changes at the spinal level while the acute stress effects are dependent on a supraspinal substrate.
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Liu J, Chen SS, Dan QQ, Rong R, Zhou X, Zhang LF, Wang TH. Crucial roles of NGF in dorsal horn plasticity in partially deafferentated cats. Growth Factors 2011; 29:49-56. [PMID: 21291350 DOI: 10.3109/08977194.2010.549129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Though exogenous nerve growth factor (NGF) has been implicated in spinal cord plasticity, whether endogenous NGF plays a crucial role has not been established in vivo. This study investigated first the role of endogenous NGF in spinal dorsal horn (DH) plasticity following removal of L1-L5 and L7-S2 dorsal root ganglions (DRGs) in cats. Co-culture of chick embryo DRG with DH condition media, protein band fishing by cells as well as western blot showed that NGF could promote neurite growth in vitro. Immunohistochemistry and in situ hybridization technique revealed an increase in the NGF and NGF mRNA immunoreactive cells in the DH after partial deafferentation. Lastly, after blocking with NGF antibody, choleragen subunit B horseradish peroxidase (CB-HRP) tracing showed a reduction in the neuronal sprouting observed in the DH. Our results demonstrated that in the cat, endogenous NGF plays a crucial role in DH plasticity after partial deafferentation.
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Kawamata M. [Mechanisms of postoperative pain]. MASUI. THE JAPANESE JOURNAL OF ANESTHESIOLOGY 2010; 59 Suppl:S166-S172. [PMID: 21702103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
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Biggs JE, Lu VB, Stebbing MJ, Balasubramanyan S, Smith PA. Is BDNF sufficient for information transfer between microglia and dorsal horn neurons during the onset of central sensitization? Mol Pain 2010; 6:44. [PMID: 20653959 PMCID: PMC2918544 DOI: 10.1186/1744-8069-6-44] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Accepted: 07/23/2010] [Indexed: 12/12/2022] Open
Abstract
Peripheral nerve injury activates spinal microglia. This leads to enduring changes in the properties of dorsal horn neurons that initiate central sensitization and the onset of neuropathic pain. Although a variety of neuropeptides, cytokines, chemokines and neurotransmitters have been implicated at various points in this process, it is possible that much of the information transfer between activated microglia and neurons, at least in this context, may be explicable in terms of the actions of brain derived neurotrophic factor (BDNF). Microglial-derived BDNF mediates central sensitization in lamina I by attenuating inhibitory synaptic transmission. This involves an alteration in the chloride equilibrium potential as a result of down regulation of the potassium-chloride exporter, KCC2. In lamina II, BDNF duplicates many aspects of the effects of chronic constriction injury (CCI) of the sciatic nerve on excitatory transmission. It mediates an increase in synaptic drive to putative excitatory neurons whilst reducing that to inhibitory neurons. CCI produces a specific pattern of changes in excitatory synaptic transmission to tonic, delay, phasic, transient and irregular neurons. A very similar 'injury footprint' is seen following long-term exposure to BDNF. This review presents new information on the action of BDNF and CCI on lamina II neurons, including the similarity of their actions on the kinetics and distributions of subpopulations of miniature excitatory postsynaptic currents (mEPSC). These findings raise the possibility that BDNF functions as a final common path for a convergence of perturbations that culminate in the generation of neuropathic pain.
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Leem JW, Kim HK, Hulsebosch CE, Gwak YS. Ionotropic glutamate receptors contribute to maintained neuronal hyperexcitability following spinal cord injury in rats. Exp Neurol 2010; 224:321-4. [PMID: 20211179 PMCID: PMC3008557 DOI: 10.1016/j.expneurol.2010.02.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Revised: 02/04/2010] [Accepted: 02/20/2010] [Indexed: 10/19/2022]
Abstract
In this study, we examined whether topical treatment of glutamate receptor antagonists attenuate hyperexcitability of lumbar spinal dorsal horn neurons following low thoracic hemisection spinal cord injury in rats. Four weeks after spinal hemisection, neuronal activity in response to mechanical stimuli applied on the peripheral receptive field was significantly increased in three different phenotypes of lumbar spinal dorsal horn neurons: wide dynamic range (WDR), low threshold (LT) and high threshold (HT). Topical application of MK-801 (NMDA receptor antagonist, 50 microg) significantly attenuated the activity of WDR, but not LT and HT neurons; whereas, NBQX (AMPA receptor antagonist, 0.5 and 1 microg) significantly attenuated neuronal activity in all three phenotypes of neurons (*p<0.05). However, MCPG (group I/II metabotropic glutamate receptor antagonist, 100 microg) had no effect. The present study, in the context of previous work, suggests that ionotropic glutamate receptor activation play critical roles in the maintenance of neuronal hyperexcitability and neuropathic "below-level" pain behavior following spinal hemisection injury.
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Joseph DJ, Choudhury P, MacDermott AB. An in vitro assay system for studying synapse formation between nociceptive dorsal root ganglion and dorsal horn neurons. J Neurosci Methods 2010; 189:197-204. [PMID: 20385165 PMCID: PMC2880384 DOI: 10.1016/j.jneumeth.2010.04.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Revised: 03/25/2010] [Accepted: 04/05/2010] [Indexed: 01/23/2023]
Abstract
Synapses between nociceptive dorsal root ganglion (DRG) neurons and spinal cord dorsal horn neurons represent the first loci for transmission of painful stimuli. Our knowledge of the molecular organization and development of these synapses is sparse due, partly, to a lack of a reliable model system that reconstitutes synaptogenesis between these two neuronal populations. To address this issue, we have established an in vitro assay system consisting of separately purified DRG neurons and dorsal horn neurons on astrocyte microislands. Using immunocytochemistry, we have found that 97%, 93%, 98%, 96%, and 94% of DRG neurons on these microislands express markers often associated with nociceptive neurons including Substance P, TRPV1, calcitonin-gene related peptide (CGRP), TrKA, and peripherin, respectively. Triple labeling with these nociceptive-like markers, synaptic vesicle marker Vglut2 and using MAP2 as a dendritic marker revealed the presence of nociceptive-like markers at synaptic terminals. Using this immunocytochemical approach, we counted contact points as overlapping MAP2/Vglut2 puncta and showed that they increased with time in culture. Single and dual patch-clamp recordings showed that overlapping Vglut2/MAP2 puncta observed after a few days in culture are likely to be functional synapses between DRG and dorsal horn neurons in our in vitro assay system. Taken together, these data suggest our co-culture microisland model system consists of mostly nociceptive-like DRG neurons that express presynaptic markers and form functional synapses with their dorsal horn partners. Thus, this model system may have direct application for studies on factors regulating development of nociceptive DRG/dorsal horn synapses.
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