scholarly journals Nonlinear effects of hyperpolarizing shifts in activation of mutant Nav1.7 channels on resting membrane potential

2017 ◽  
Vol 117 (4) ◽  
pp. 1702-1712 ◽  
Author(s):  
Mark Estacion ◽  
Stephen G. Waxman
Keyword(s):  
Membrane Potential ◽  
Dorsal Root Ganglion ◽  
Sodium Channel ◽  
Dorsal Root ◽  
Voltage Dependence ◽  
Dorsal Root Ganglion Neurons ◽  
Resting Membrane Potential ◽  
Dynamic Clamp ◽  
Drg Neurons ◽  
Ganglion Neurons

The Nav1.7 sodium channel is preferentially expressed within dorsal root ganglion (DRG) and sympathetic ganglion neurons. Gain-of-function mutations that cause the painful disorder inherited erythromelalgia (IEM) shift channel activation in a hyperpolarizing direction. When expressed within DRG neurons, these mutations produce a depolarization of resting membrane potential (RMP). The biophysical basis for the depolarized RMP has to date not been established. To explore the effect on RMP of the shift in activation associated with a prototypical IEM mutation (L858H), we used dynamic-clamp models that represent graded shifts that fractionate the effect of the mutation on activation voltage dependence. Dynamic-clamp recording from DRG neurons using a before-and-after protocol for each cell made it possible, even in the presence of cell-to-cell variation in starting RMP, to assess the effects of these graded mutant models. Our results demonstrate a nonlinear, progressively larger effect on RMP as the shift in activation voltage dependence becomes more hyperpolarized. The observed differences in RMP were predicted by the “late” current of each mutant model. Since the depolarization of RMP imposed by IEM mutant channels is known, in itself, to produce hyperexcitability of DRG neurons, the development of pharmacological agents that normalize or partially normalize activation voltage dependence of IEM mutant channels merits further study. NEW & NOTEWORTHY Inherited erythromelalgia (IEM), the first human pain disorder linked to a sodium channel, is widely regarded as a genetic model of neuropathic pain. IEM is produced by Nav1.7 mutations that hyperpolarize activation. These mutations produce a depolarization of resting membrane potential (RMP) in dorsal root ganglion neurons. Using dynamic clamp to explore the effect on RMP of the shift in activation, we demonstrate a nonlinear effect on RMP as the shift in activation voltage dependence becomes more hyperpolarized.

Inflammatory Mediators Enhance the Excitability of Chronically Compressed Dorsal Root Ganglion Neurons

2006 ◽  
Vol 95 (4) ◽  
pp. 2098-2107 ◽  
Author(s):  
C. Ma ◽  
K. W. Greenquist ◽  
R. H. LaMotte
Keyword(s):  
Dorsal Root Ganglion ◽  
Action Potential ◽  
Inflammatory Mediators ◽  
Dorsal Root ◽  
Dorsal Root Ganglion Neurons ◽  
Resting Membrane Potential ◽  
Prostaglandin E ◽  
Drg Neurons ◽  
Neuronal Hyperexcitability ◽  
Ganglion Neurons

A laterally herniated disk, spinal stenosis, and various degenerative or traumatic diseases of the spine can sometimes lead to a chronic compression and inflammation of the dorsal root ganglion and chronic abnormal sensations including pain. After a chronic compression of the dorsal root ganglion (CCD) in rats, the somata in the dorsal root ganglion (DRG) become hyperexcitable, and some exhibit ectopic, spontaneous activity (SA). Inflammatory mediators have a potential role in modulating the excitability of DRG neurons and therefore may contribute to the neuronal hyperexcitability after CCD. In this study, an inflammatory soup (IS) consisting of bradykinin, serotonin, prostaglandin E2, and histamine (each 10−6M) was applied topically to the DRG. The responses of DRG neurons were electrophysiologically recorded extracellularly from teased dorsal root fibers or intracellularly from the somata in the intact DRG or from dissociated neurons within 30 h of culture. In all three preparations, IS remarkably increased the discharge rates of SA CCD neurons and evoked discharges in more silent-CCD than control neurons. IS slightly depolarized the resting membrane potential and decreased the current and voltage thresholds of action potential in both intact and dissociated neurons, although the magnitude of depolarization or decrease in action potential threshold was not significantly different between CCD and control. IS-evoked responses were found in a proportion of neurons in each size category including those with and without nociceptive properties. Inflammatory mediators, by increasing the excitability of DRG somata, may contribute to CCD-induced neuronal hyperexcitability and to hyperalgesia and tactile allodynia.

Distinct Membrane Effects of Spinal Nerve Ligation on Injured and Adjacent Dorsal Root Ganglion Neurons in Rats

2005 ◽  
Vol 103 (2) ◽  
pp. 360-376 ◽  
Author(s):  
Damir Sapunar ◽  
Marko Ljubkovic ◽  
Philipp Lirk ◽  
J Bruce McCallum ◽  
Quinn H. Hogan
Keyword(s):  
Membrane Potential ◽  
Dorsal Root Ganglion ◽  
Action Potential ◽  
Action Potential Duration ◽  
Dorsal Root ◽  
Spinal Nerve ◽  
Spinal Nerve Ligation ◽  
Dorsal Root Ganglion Neurons ◽  
Resting Membrane Potential ◽  
Ganglion Neurons

Background Painful peripheral nerve injury results in disordered sensory neuron function that contributes to the pathogenesis of neuropathic pain. However, the relative roles of neurons with transected axons versus intact adjacent neurons have not been resolved. An essential first step is identification of electrophysiologic changes in these two neuronal populations after partial nerve damage. Methods Twenty days after spinal nerve ligation (SNL), intracellular recordings were obtained from axotomized fifth lumbar (L5) dorsal root ganglion neurons and adjacent, intact L4 neurons, as well as from control neurons and others subjected to sham-SNL surgery. Results Pronounced electrophysiologic changes were seen only in L5 neurons after SNL. Both Aalpha/beta and Adelta neuron types showed increased action potential duration, decreased afterhyperpolarization amplitude and duration, and decreased current threshold for action potential initiation. Aalpha/beta neurons showed resting membrane potential depolarization, and increased repetitive firing during sustained depolarization developed in Adelta neurons. The afterhyperpolarization duration in neurons with C fibers shortened after axotomy. In contrast to the axotomized L5 neurons, neighboring L4 neurons showed no changes in action potential duration, afterhyperpolarization dimensions, or excitability after SNL. Depolarization rate (dV/dt) increased after SNL in L4 Aalpha/beta and Adelta neurons but decreased in L5 neurons. Time-dependent rectification during hyperpolarizing current injection (sag) was greater after SNL in Aalpha/beta L4 neurons compared with L5. Sham-SNL surgery produced only a decreased input resistance in Aalpha/beta neurons and a decreased conduction velocity in medium-sized cells. In the L5 ganglion after axotomy, a novel set of neurons, consisting of 24% of the myelinated population, exhibited long action potential durations despite myelinated neuron conduction velocities, particularly depolarized resting membrane potential, low depolarization rate, and absence of sag. Conclusions These findings indicate that nerve injury-induced electrical instability is restricted to axotomized neurons and is absent in adjacent intact neurons.

Effect of Intracellular Dialysis of ATP on the Hyperpolarization-Activated Cation Current in Rat Dorsal Root Ganglion Neurons

2003 ◽  
Vol 90 (4) ◽  
pp. 2115-2122 ◽  
Author(s):  
You Komagiri ◽  
Naoki Kitamura
Keyword(s):  
Dorsal Root Ganglion ◽  
Adenylate Cyclase ◽  
Voltage Clamp ◽  
Dorsal Root ◽  
Voltage Dependence ◽  
Dorsal Root Ganglion Neurons ◽  
Drg Neurons ◽  
Positive Direction ◽  
Cation Current ◽  
Ganglion Neurons

The mechanism of the effect of intracellular ATP on the hyperpolarization-activated non-selective cation current ( Ih) in rat dorsal root ganglion neurons was investigated using a whole cell voltage-clamp technique. Under voltage-clamp conditions, Ih was activated by hyperpolarizing pulses raised to a voltage of between –70 and –130 mV. The activation curve of Ih in rat dorsal root ganglion (DRG) neurons shifted by about 15 mV in the positive direction with an intracellular solution containing 1 mM cAMP. When ATP (2 mM) was applied intracellularly, the half-maximal activation voltage ( Vhalf) of Ih shifted from –97.4 ± 1.9 to –86.8 ± 1.6 mV, resulting in an increase in the current amplitude of Ih by the pulse to between –80 and –90 mV. In the presence of an adenylate cyclase inhibitor, SQ-22536 (100 μM), the intracellular dialysis of ATP also produced a shift in the voltage-dependence of Ih in rat DRG neurons, indicating that the effect of ATP was not caused by cAMP converted by adenylate cyclase. Intracellular dialysis of a nonhydrolysable ATP analog, AMP-PNP or ATP-γ-S, also produced a positive shift in the voltage-dependence of Ih activation, suggesting that the effect of ATP results from its direct action on the channel protein. These results indicate that cytosolic ATP directly regulates the voltage dependence of Ih activation as an intracellular modulating factor.

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.

Axotomy- and Autotomy-Induced Changes in the Excitability of Rat Dorsal Root Ganglion Neurons

2001 ◽  
Vol 85 (2) ◽  
pp. 630-643 ◽  
Author(s):  
Fuad A. Abdulla ◽  
Peter A. Smith
Keyword(s):  
Sciatic Nerve ◽  
Dorsal Root Ganglion ◽  
Spontaneous Activity ◽  
Dorsal Root ◽  
Sensory Nerves ◽  
Dorsal Root Ganglion Neurons ◽  
Small Cells ◽  
Resting Membrane Potential ◽  
Ganglion Neurons ◽  
Induced Changes

The spontaneous, ectopic activity in sensory nerves that is induced by peripheral nerve injury is thought to contribute to the generation of “neuropathic” pain in humans. To examine the cellular mechanisms that underlie this activity, neurons in rat L4–L5 dorsal root ganglion (DRG) were first grouped as “large,” “medium,” or “small” on the basis of their size (input capacitance) and action potential (AP) shape. A fourth group of cells that exhibited a pronounced afterdepolarization (ADP) were defined as AD-cells. Whole cell recording was used to compare the properties of control neurons with those dissociated from rats in which the sciatic nerve had been sectioned (“axotomy” group) and with neurons from rats that exhibited self-mutilatory behavior in response to sciatic nerve section (“autotomy” group). Increases in excitability in all types of DRG neuron were seen within 2–7 wk of axotomy. Resting membrane potential (RMP) and the amplitude and duration of the afterhyperpolarization (AHP) that followed the AP were unaffected. Effects of axotomy were greatest in the small, putative nociceptive cells and least in the large cells. Moderate changes were seen in the medium and AD-cells. Compared to control neurons, axotomized neurons exhibited a higher frequency of evoked AP discharge in response to 500-ms depolarizing current injections; i.e., “gain” was increased and accommodation was decreased. The minimum current required to discharge an AP (rheobase) was reduced. There were significant increases in spike width in small cells and significant increases in spike height in small, medium, and AD-cells. The electrophysiological changes promoted by axotomy were intensified in animals that exhibited autotomy; spike height, and spike width were significantly greater than control for all cell types. Under our experimental conditions, spontaneous activity was never encountered in neurons dissociated from animals that exhibited autotomy. Thus changes in the electrical properties of cell bodies alone may not entirely account for injury-induced spontaneous activity in sensory nerves. The onset of autotomy coincided with alterations in the excitability of large, putative nonnociceptive, neurons. Thus large cells from the autotomy group were muchmore excitable than those from the axotomy group, whereas small cells from the autotomy group were only slightly more excitable. This is consistent with the hypothesis that the onset of autotomy is associated with changes in the properties of myelinated fibers. Changes in Ca2+ and K+ channel conductances that contribute to axotomy- and autotomy-induced changes in excitability are addressed in the accompanying paper.

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.

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