Reduction in Potassium Currents in Identified Cutaneous Afferent Dorsal Root Ganglion Neurons After Axotomy

1999 ◽  
Vol 82 (2) ◽  
pp. 700-708 ◽  
Author(s):  
Brian Everill ◽  
Jeffery D. Kocsis
Keyword(s):  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Neuronal Excitability ◽  
Potassium Currents ◽  
Dorsal Root Ganglion Neurons ◽  
Channel Blockers ◽  
Afferent Neurons ◽  
Drg Neurons ◽  
Whole Cell Patch Clamp ◽  
Ganglion Neurons

Potassium currents have an important role in modulating neuronal excitability. We have investigated the effects of axotomy on three voltage-activated K+ currents, one sustained and two transient, in cutaneous afferent dorsal root ganglion (DRG) neurons. Fourteen to 21 days after axotomy, L4 and L5 DRG neurons were acutely dissociated and were studied 2–8 h after plating. Whole cell patch-clamp recordings were obtained from identified cutaneous afferent neurons (46–50 μm diam); K+ currents were isolated by blocking Na+ and Ca2+ currents with appropriate ion replacement and channel blockers. Separation of the current components was achieved on the basis of sensitivity to dendrotoxin or 4-aminopyridine and by the response to variation in conditioning voltage. Both control and injured neurons displayed qualitatively similar complex K+ currents composed of distinct kinetic and pharmacological components. Three distinct K+ current components, a sustained ( I K) and two transient ( I A and I D), were identified in variable proportions. However, total peak current was reduced by 52% in the axotomized cells when compared with control cells. Two current components were reduced after ligation, I Aby 60%, I K by over 65%, compared with control cells. I D appeared unaffected after acute ligation. These results indicate a large reduction in overall K+ current, resulting from reductions in I K and I A, on large cutaneous afferent neurons after nerve ligation and have implications for excitability changes of injured primary afferent neurons.

scholarly journals Orexin affects dorsal root ganglion neurons: a mechanism for regulating the spinal nociceptive processing

2008 ◽  
pp. 797-800
Author(s):  
J-A Yan ◽  
L Ge ◽  
W Huang ◽  
B Song ◽  
X-W Chen ◽  
...  
Keyword(s):  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Pain Treatment ◽  
Dorsal Root Ganglion Neurons ◽  
Drg Neurons ◽  
Orexin A ◽  
Nociceptive Transmission ◽  
Whole Cell Patch Clamp ◽  
Nociceptive Processing ◽  
Ganglion Neurons

Orexins (orexin A and B) are initially known to be a hypothalamic peptide critical for feeding and normal wakefulness. In addition, emerging evidence from behavioral tests suggests that orexins are also involved in the regulation of nociceptive processing, suggesting a novel potential therapeutic approach for pain treatment. Both spinal and supraspinal mechanisms appear to contribute to the role of orexin in nociception. In the spinal cord, dorsal root ganglion (DRG) neurons are primary afferent neurons that transmit peripheral stimuli to the pain-processing areas. Morphological results show that both orexin A and orexin1 receptor are distributed in DRG neurons. Moreover, by using whole-cell patch-clamp recordings and calcium imaging measurements we found that orexin A induced excitability and intracellular calcium concentration elevation in the isolated rat DRG neurons, which was mainly dependent on the activation of spinal orexin-1 receptor. Based on these findings, we propose a hypothesis that the direct effect of orexin A on DRG neurons would represent a possible mechanism for the orexinergic modulation of spinal nociceptive transmission.

GDNF and NGF Reverse Changes in Repriming of TTX-Sensitive Na+ Currents Following Axotomy of Dorsal Root Ganglion Neurons

2002 ◽  
Vol 88 (2) ◽  
pp. 650-658 ◽  
Author(s):  
Andreas Leffler ◽  
Theodore R. Cummins ◽  
Sulayman D. Dib-Hajj ◽  
William N. Hormuzdiar ◽  
Joel A. Black ◽  
...  
Keyword(s):  
Dorsal Root Ganglion ◽  
Sodium Channel ◽  
Sensory Neurons ◽  
Dorsal Root ◽  
Neuronal Excitability ◽  
Dorsal Root Ganglion Neurons ◽  
Current Profile ◽  
Drg Neurons ◽  
Α Subunit ◽  
Ganglion Neurons

Uninjured C-type rat dorsal root ganglion (DRG) neurons predominantly express slowly inactivating TTX-resistant (TTX-R) and slowly repriming TTX-sensitive (TTX-S) Na+ currents. After peripheral axotomy, TTX-R current density is reduced and rapidly repriming TTX-S currents emerge and predominate. The change in TTX-S repriming kinetics is paralleled by an increase in the level of transcripts and protein for the Nav1.3 sodium channel α-subunit, which is known to exhibit rapid repriming. Changes in Na+current profile and kinetics in DRG neurons may substantially alter neuronal excitability and could contribute to some states of chronic pain associated with injury of sensory neurons. In the present study, we asked whether glial-derived neurotrophic factor (GDNF) and nerve growth factor (NGF), which have been shown to prevent some axotomy-induced changes such as the loss of TTX-R Na+ current expression in DRG neurons, can ameliorate the axotomy-induced change in TTX-S Na+ current repriming kinetics. We show that intrathecally administered GDNF and NGF, delivered individually, can partially reverse the effect of axotomy on the repriming kinetics of TTX-S Na+ currents. When GDNF and NGF were co-administered, the repriming kinetics were fully rescued. We observed parallel effects of GDNF and NGF on the Nav1.3 sodium channel transcript levels in axotomized DRG. Both GDNF and NGF were able to partially reverse the axotomy-induced increase in Nav1.3 mRNA, with GDNF plus NGF producing the largest effect. Our data indicate that both GDNF and NGF can partially reverse an important effect of axotomy on the electrogenic properties of sensory neurons and that their effect is additive.

Kv3 channels contribute to the delayed rectifier current in small cultured mouse dorsal root ganglion neurons

2012 ◽  
Vol 303 (4) ◽  
pp. C406-C415 ◽  
Author(s):  
Elke Bocksteins ◽  
Gerda Van de Vijver ◽  
Pierre-Paul Van Bogaert ◽  
Dirk J. Snyders
Keyword(s):  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Neuronal Excitability ◽  
Dorsal Root Ganglion Neurons ◽  
Delayed Rectifier ◽  
Drg Neurons ◽  
M Current ◽  
Delayed Rectifier Current ◽  
Mouse Dorsal Root Ganglion ◽  
Ganglion Neurons

Delayed rectifier voltage-gated K+ (KV) channels are important determinants of neuronal excitability. However, the large number of KV subunits poses a major challenge to establish the molecular composition of the native neuronal K+ currents. A large part (∼60%) of the delayed rectifier current ( IK) in small mouse dorsal root ganglion (DRG) neurons has been shown to be carried by both homotetrameric KV2.1 and heterotetrameric channels of KV2 subunits with silent KV subunits (KVS), while a contribution of KV1 channels has also been demonstrated. Because KV3 subunits also generate delayed rectifier currents, we investigated the contribution of KV3 subunits to IK in small mouse DRG neurons. After stromatoxin (ScTx) pretreatment to block the KV2-containing component, application of 1 mM TEA caused significant additional block, indicating that the ScTx-insensitive part of IK could include KV1, KV3, and/or M-current channels (KCNQ2/3). Combining ScTx and dendrotoxin confirmed a relevant contribution of KV2 and KV2/KVS, and KV1 subunits to IK in small mouse DRG neurons. After application of these toxins, a significant TEA-sensitive current (∼19% of total IK) remained with biophysical properties that corresponded to those of KV3 currents obtained in expression systems. Using RT-PCR, we detected KV3.1–3 mRNA in DRG neurons. Furthermore, Western blot and immunocytochemistry using KV3.1-specific antibodies confirmed the presence of KV3.1 in cultured DRG neurons. These biophysical, pharmacological, and molecular results demonstrate a relevant contribution (∼19%) of KV3-containing channels to IK in small mouse DRG neurons, supporting a substantial role for KV3 subunits in these neurons.

Nitric Oxide Modulates Ca2+ Channels in Dorsal Root Ganglion Neurons Innervating Rat Urinary Bladder

2001 ◽  
Vol 86 (1) ◽  
pp. 304-311 ◽  
Author(s):  
Naoki Yoshimura ◽  
Satoshi Seki ◽  
William C. de Groat
Keyword(s):  
Nitric Oxide ◽  
Urinary Bladder ◽  
Dorsal Root Ganglion ◽  
Current Density ◽  
Dorsal Root ◽  
Dorsal Root Ganglion Neurons ◽  
Afferent Neurons ◽  
Drg Neurons ◽  
No Donor ◽  
Ganglion Neurons

The effect of a nitric oxide (NO) donor on high-voltage-activated Ca2+ channel currents ( I Ca) was examined using the whole cell patch-clamp technique in L6–S1 dorsal root ganglion (DRG) neurons innervating the urinary bladder. The neurons were labeled by axonal transport of a fluorescent dye, Fast Blue, injected into the bladder wall. Approximately 70% of bladder afferent neurons exhibited tetrodotoxin (TTX)-resistant action potentials (APs), and 93% of these neurons were sensitive to capsaicin, while the remaining neurons had TTX-sensitive spikes and were insensitive to capsaicin. The peak current density of nimodipine-sensitive L-type Ca2+ channels activated by depolarizing pulses (0 mV) from a holding potential of −60 mV was greater in bladder afferent neurons with TTX-resistant APs (39.2 pA/pF) than in bladder afferent neurons with TTX-sensitive APs (28.9 pA/pF), while the current density of ω-conotoxin GVIA-sensitive N-type Ca2+channels was similar (43–45 pA/pF) in both types of neurons. In both types of neurons, the NO donor, S-nitroso- N-acetylpenicillamine (SNAP) (500 μM), reversibly reduced (23.4–26.6%) the amplitude of I Ca elicited by depolarizing pulses to 0 mV from a holding potential of −60 mV. SNAP-induced inhibition of I Ca was reduced by 90% in the presence of ω-conotoxin GVIA but was unaffected in the presence of nimodipine, indicating that NO-induced inhibition of I Ca is mainly confined to N-type Ca2+ channels. Exposure of the neurons for 30 min to 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 μM), an inhibitor of NO-stimulated guanylyl cyclase, prevented the SNAP-induced reduction in I Ca. Extracellular application of 8-bromo-cGMP (1 mM) mimicked the effects of NO donors by reducing the peak amplitude of I Ca(28.6% of reduction). Action potential configuration and firing frequency during depolarizing current pulses were not altered by the application of SNAP (500 μM) in bladder afferent neurons with TTX-resistant and -sensitive APs. These results indicate that NO acting via a cGMP signaling pathway can modulate N-type Ca2+ channels in DRG neurons innervating the urinary bladder.

scholarly journals On the inhibition of capsaicin response in dorsal root ganglion neurons by nobilamide B and analogues: a structure–activity relationship study

MedChemComm ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 1673-1678
Author(s):  
Oliver John V. Belleza ◽  
Jortan O. Tun ◽  
Gisela P. Concepcion ◽  
Aaron Joseph L. Villaraza
Keyword(s):  
Dorsal Root Ganglion ◽  
Primary Culture ◽  
Dorsal Root ◽  
Dorsal Root Ganglion Neurons ◽  
Activity Relationship ◽  
Drg Neurons ◽  
Structure Activity ◽  
Relationship Study ◽  
Trpv1 Antagonist ◽  
Ganglion Neurons

Nobilamide B, a TRPV1 antagonist, and a series of Ala-substituted analogues were synthesized and their neuroactivity was assessed in a primary culture of dorsal root ganglion (DRG) neurons.

Variation in IH, IIR, and ILEAK between acutely isolated adult rat dorsal root ganglion neurons of different size

1994 ◽  
Vol 71 (1) ◽  
pp. 271-279 ◽  
Author(s):  
R. S. Scroggs ◽  
S. M. Todorovic ◽  
E. G. Anderson ◽  
A. P. Fox
Keyword(s):  
Dorsal Root Ganglion ◽  
Action Potentials ◽  
Dorsal Root ◽  
Membrane Surface ◽  
Small Diameter ◽  
Reversal Potential ◽  
Dorsal Root Ganglion Neurons ◽  
Time Dependent ◽  
Drg Neurons ◽  
Ganglion Neurons

1. The distribution of IH, IIR, and ILEAK was studied in different diameter rat dorsal root ganglion (DRG) neuron cell bodies (neurons). DRG neurons were studied in three diameter ranges: small (19–27 microns), medium (33–37 microns), and large (44-54 microns). IH was defined as a slowly activating inward current evoked by hyperpolarizing voltage steps from a holding potential (HP) of -60 mV, and blocked by 1 mM Cs2+ but not 1 mM Ba2+. Inward rectifier current (IIR) was defined as a rapidly activating current evoked by hyperpolarizations from HP -60 mV, which rectified inwardly around the reversal potential for potassium (EK), and was completely blocked by 100 microM Ba2+. ILEAK was defined as an outward resting current at HP -60 mV, which did not rectify and was blocked by 100 microM Ba2+ but not by 2 mM Cs+. 2. IH was observed in 23 of 23 large, 11 of 12 medium, and in 9 of 20 small diameter DRG neurons tested. Peak IH normalized to membrane surface area was significantly greater in large than in medium or small diameter DRG neurons expressing IH. All neurons exhibiting IH under voltage clamp conditions had short duration action potentials and exhibited time-dependent rectification under current clamp conditions, properties similar to A-type DRG neurons. The 11 small diameter neurons not expressing IH had long duration action potentials and did not exhibit time-dependent rectification, properties similar to C-type DRG neurons. 3. IIR was detected in 18 of 22 medium diameter neurons tested.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals An integrated cell isolation and purification method for rat dorsal root ganglion neurons

2019 ◽  
Vol 47 (7) ◽  
pp. 3253-3260
Author(s):  
Huaishuang Shen ◽  
Minfeng Gan ◽  
Huilin Yang ◽  
Jun Zou
Keyword(s):  
Neuropathic Pain ◽  
Dorsal Root Ganglion ◽  
Primary Culture ◽  
Dorsal Root ◽  
Cell Isolation ◽  
Dorsal Root Ganglion Neurons ◽  
Drg Neurons ◽  
Purification Method ◽  
Isolation And Purification ◽  
Ganglion Neurons

Objective Neurobiology studies are increasingly focused on the dorsal root ganglion (DRG), which plays an important role in neuropathic pain. Existing DRG neuron primary culture methods have considerable limitations, including challenging cell isolation and poor cell yield, which cause difficulty in signaling pathway studies. The present study aimed to establish an integrated primary culture method for DRG neurons. Methods DRGs were obtained from fetal rats by microdissection, and then dissociated with trypsin. The dissociated neurons were treated with 5-fluorouracil to promote growth of neurons from the isolated cells. Then, reverse transcription polymerase chain reaction and immunofluorescence assays were used to identify and purify DRG neurons. Results Isolated DRGs were successfully dissociated and showed robust growth as individual DRG neurons in neurobasal medium. Both mRNA and protein assays confirmed that DRG neurons expressed neurofilament-200 and neuron-specific enolase. Conclusions Highly purified, stable DRG neurons could be easily harvested and grown for extended periods by using this integrated cell isolation and purification method, which may help to elucidate the mechanisms underlying neuropathic pain.

Interaction of opioids and membrane potential to modulate Ca2+ channels in rat dorsal root ganglion neurons

1995 ◽  
Vol 73 (5) ◽  
pp. 1793-1798 ◽  
Author(s):  
M. D. Womack ◽  
E. W. McCleskey
Keyword(s):  
Dorsal Root Ganglion ◽  
Sensory Neurons ◽  
Action Potentials ◽  
Dorsal Root ◽  
Dorsal Root Ganglion Neurons ◽  
High Threshold ◽  
Partial Recovery ◽  
Drg Neurons ◽  
Ganglion Neurons ◽  
Ca2 Channels

1. Using patch-clamp methods, we show that brief prepulses to very positive voltages increase (facilitate) the amplitude of current through Ca2+ channels during a subsequent test pulse in some, but not all, dorsal root ganglion (DRG) sensory neurons. The amplitude of this facilitated current generally increases when the Ca2+ channels are inhibited by activation of the mu-opioid receptor. 2. The facilitated current is blocked by omega-conotoxin GVIA, activates in the range of high-threshold Ca2+ channels, and inactivates at relatively negative holding voltages. Thus facilitated current passes through N-type Ca2+ channels, the same channels that are inhibited by opioids and control neurotransmitter release in sensory neurons. 3. Although maximal facilitation occurs only at unphysiologically high membrane potentials (above +100 mV), some facilitation is seen after prepulses to voltages reached during action potentials. After return to the holding potential, facilitation persists for hundreds of milliseconds, considerably longer than in other neurons. Brief trains of pulses designed to mimic action potentials caused small facilitation (19% of maximal) in a fraction (8 of 24) of opioid-inhibited neurons. 4. We conclude that 1) prepulses to extremely positive voltages can cause partial recovery of Ca2+ channels inhibited by opioids; and 2) small, but detectable, facilitation is also seen after physiological stimulation in some DRG neurons. Facilitation, largely considered a biophysical epiphenomenon because of the extreme voltages used to induce it, appears to be physiologically relevant during opioid inhibition of Ca2+ channels in DRG neurons.

GABA-Induced Cl− Current in Cultured Embryonic Human Dorsal Root Ganglion Neurons

1999 ◽  
Vol 82 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Alexander Y. Valeyev ◽  
John C. Hackman ◽  
Alice M. Holohean ◽  
Patrick M. Wood ◽  
Jennifer L. Katz ◽  
...  
Keyword(s):  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Single Channel ◽  
Dorsal Root Ganglion Neurons ◽  
Hill Coefficient ◽  
Equilibrium Potential ◽  
Single Channels ◽  
Drg Neurons ◽  
Whole Cell ◽  
Ganglion Neurons

γ-Aminobutyric acid (GABA)-activated channels in embryonic (5–8 wk old) human dorsal root ganglion (DRG) neurons in dissociated culture were characterized by whole cell and single-channel techniques. All DRG neurons when held at negative holding membrane potentials displayed inward current to micromolar concentrations of GABA applied by pressure pulses from closely positioned micropipettes. The current was directly proportional to the concentration of GABA (EC50, 111 μM; Hill coefficient, 1.7). DRG neurons also responded to micromolar concentrations of pentobarbital and alphaxalone but not to cis-4-aminocrotonic acid (CACA), glycine, or taurine. Baclofen (100 μM) affected neither the holding currents nor K+ conductance (when patch pipettes were filled with 130 mM KCl) caused by depolarizing pulses. Whole cell GABA-currents were blocked by bicuculline, picrotoxin, and t-butylbicyclophosphorothionate (TBPS; all at 100 μM). The reversal potential of whole cell GABA-currents was close to the theoretical Cl− equilibrium potential, shifting with changes in intracellular Cl− concentration in a manner expected for Cl−-selective channels. The whole cell I-V curve for GABA-induced currents demonstrated slight outward rectification with nearly symmetrical outside and inside Cl− concentrations. Spectral analysis of GABA-induced membrane current fluctuations showed that the kinetic components were best fitted by a triple Lorentzian function. The apparent elementary conductance for GABA-activated Cl− channels determined from the power spectra was 22.6 pS. Single-channel recordings from cell-attached patches with pipettes containing 10 μM GABA indicated that GABA-activated channels have a main and a subconductance level with values of 30 and 19 pS, respectively. Mean open and closed times of the channel were characterized by two or three exponential decay functions, suggesting two or three open channel states and two closed states. Single channels showed a lack of rectification. The actions of GABA on cultured human embryonic DRG neurons are mediated through the activation of GABAA receptors with properties corresponding to those found in the CNS of human and other mammalian species but differing from those of cultured human adult DRG neurons.

scholarly journals Systematic Administration of B Vitamins Alleviates Diabetic Pain and Inhibits Associated Expression of P2X3 and TRPV1 in Dorsal Root Ganglion Neurons and Proinflammatory Cytokines in Spinal Cord in Rats

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Duan-Duan He ◽  
Yu Gao ◽  
Shan Wang ◽  
Zhong Xie ◽  
Xue-Jun Song
Keyword(s):  
Spinal Cord ◽  
Blood Glucose ◽  
Dorsal Root Ganglion ◽  
Proinflammatory Cytokines ◽  
Dorsal Root ◽  
B Vitamins ◽  
Dorsal Root Ganglion Neurons ◽  
Drg Neurons ◽  
B Vitamin ◽  
Ganglion Neurons

Background. Treatment of diabetic neuropathic pain (DNP) continues to be a major challenge, and underlying mechanisms of DNP remain elusive. We investigated treatment effects of B vitamins on DPN- and DNP-associated alterations of neurochemical signaling in the nociceptive dorsal root ganglion (DRG) neurons and the spinal cord in rats. Methods. DNP was produced in male, adult, Sprague Dawley rats by single i.p. streptozotocin (STZ). Western blot analysis and immunohistochemistry were used to analyze protein expressions in DRG and ELISA to measure the proinflammatory cytokines in the spinal cord. Behaviorally expressed DNP was determined by measuring the sensitivity of hindpaw skin to mechanical and thermal stimulation. Results. There were 87.5% (77/88) rats which developed high blood glucose within 1-2 weeks following STZ injection. Of which, 70.13% (n = 54/77) animals exhibited DNP manifested as mechanical allodynia and/or thermal hyperalgesia. Intraperitoneal administration of vitamins B1/B6/B12 (100/100/2 mg/kg, one or multiple doses) significantly attenuated DNP without affecting the blood glucose. Expressions of P2X3 and TRPV1 in CGRP-positive and IB4-positive DRG neurons as well as the interleukin-1β, tumor necrosis factor-α, and nerve growth factor in the lumbar spinal cord were greatly increased in DNP rats. Such DNP-associated neurochemical alterations were also greatly suppressed by the B-vitamin treatment. Conclusions. B-vitamin treatment can greatly suppress chronic DNP and DNP-associated increased activities of P2X3 and TRPV1 in DRG and the spinal proinflammatory cytokines, which may contribute to the pathogenesis of DNP. Systematic administration of B vitamins can be a strategy for DNP management in clinic.

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