Membrane properties and electrogenesis in the distal axons of small dorsal root ganglion neurons in vitro

2012 ◽  
Vol 108 (3) ◽  
pp. 729-740 ◽  
Author(s):  
Dmytro V. Vasylyev ◽  
Stephen G. Waxman
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Dorsal Root ◽  
Small Diameter ◽  
Dorsal Root Ganglion Neurons ◽  
Membrane Properties ◽  
Resting Potential ◽  
Drg Neurons ◽  
Ganglion Neurons

Although it is generally thought that sensory transduction occurs at or close to peripheral nerve endings, with action potentials subsequently propagating along the axons of dorsal root ganglia (DRG) neurons toward the central nervous system, the small diameter of nociceptive axons and their endings have made it difficult to estimate their membrane properties and electrogenic characteristics. Even the resting potentials of nociceptive axons are unknown. In this study, we developed the capability to record directly with patch-clamp electrodes from the small-diameter distal axons of DRG neurons in vitro. We showed using current-clamp recordings that 1) these sensory axons have a resting potential of −60.2 ± 1 mV; 2) both tetrodotoxin (TTX)-sensitive (TTX-S) and TTX-resistant (TTX-R) Na+ channels are present and available for activation at resting potential, at densities that can support action potential electrogenesis in these axons; 3) TTX-sensitive channels contribute to the amplification of small depolarizations that are subthreshold with respect to the action potential in these axons; 4) TTX-R channels can support the production of action potentials in these axons; and 5) these TTX-R channels can produce repetitive firing, even at depolarized membrane potentials where TTX-S channels are inactivated. Finally, using voltage-clamp recordings with an action potential as the command, we confirmed the presence of both TTX-S and TTX-R channels, which are activated sequentially during action potential in these axons. These results provide direct evidence for the presence of TTX-S and TTX-R Na+ channels that are functionally available at resting potential and contribute to electrogenesis in small-diameter afferent axons.

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 Chronic compression of mouse dorsal root ganglion alters voltage-gated sodium and potassium currents in medium-sized dorsal root ganglion neurons

2011 ◽  
Vol 106 (6) ◽  
pp. 3067-3072 ◽  
Author(s):  
Ni Fan ◽  
David F. Donnelly ◽  
Robert H. LaMotte
Keyword(s):  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Small Diameter ◽  
Radicular Pain ◽  
Dorsal Root Ganglion Neurons ◽  
Delayed Rectifier ◽  
Drg Neurons ◽  
Voltage Dependent ◽  
Ganglion Neurons

Chronic compression (CCD) of the dorsal root ganglion (DRG) is a model of human radicular pain produced by intraforaminal stenosis and other disorders affecting the DRG, spinal nerve, or root. Previously, we examined electrophysiological changes in small-diameter lumbar level 3 (L3) and L4 DRG neurons treated with CCD; the present study extends these observations to medium-sized DRG neurons, which mediate additional sensory modalities, both nociceptive and non-nociceptive. Whole-cell patch-clamp recordings were obtained from medium-sized somata in the intact DRG in vitro. Compared with neurons from unoperated control animals, CCD neurons exhibited a decrease in the current threshold for action potential generation. In the CCD group, current densities of TTX-resistant and TTX-sensitive Na+ current were increased, whereas the density of delayed rectifier voltage-dependent K+ current was decreased. No change was observed in the transient or “A” current after CCD. We conclude that CCD in the mouse produces hyperexcitability in medium-sized DRG neurons, and the hyperexcitability is associated with an increased density of Na+ current and a decreased density of delayed rectifier voltage-dependent K+ current.

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.

scholarly journals Role of CaMK II α in the Injury of Dorsal Root Ganglion Neurons Induced by Ropivacaine Hydrochloride in the Dorsal Root Ganglion of Rats

2021 ◽  
pp. 1-7
Author(s):  
Wu Zhaoxia ◽  
Chen Meixin ◽  
Li Yiqun ◽  
Yang Shuxuan ◽  
Wen Xianjie
Keyword(s):  
Dorsal Root Ganglion ◽  
Cell Viability ◽  
Intracellular Calcium ◽  
Dorsal Root ◽  
Dorsal Root Ganglion Neurons ◽  
Drg Neurons ◽  
Apoptosis Rate ◽  
Ganglion Neurons ◽  
Ropivacaine Hydrochloride

Objective: To investigate whether CaMKⅡα participates in the dorsal root ganglion neurotoxicity induced by ropivacaine hydrochloride. Methods: DRG neurons were isolated from 1-day-old SD rats and cultured in vitro. pAd-shRNA-CaMKⅡα-DRG cells were constructed by RNA interference technique to inhibit the expression of CaMKⅡα. The experiment was divided into six groups: DRG group (DRG group), vector DRG group (vector group), pAd-shRNA- CaMKIIα-DRG group (pAd-shRNA group), DRG + ropivacaine group (DRG + R group), vector DRG + ropivacaine group (vector + R group), pAd-shRNA-CaMKII α - DRG + ropivacaine group (pAd-shRNA + R group), and the last three groups were treated with 3 mM ropivacaine hydrochloride for 4 hours. MTT assay was used to detect cell viability, flow cytometry was used to detect cell apoptosis rate, laser confocal microscopy was used to detect intracellular calcium level, and real-time PCR was used to detect the mRNA expression of CaMKⅡα, Cav3.2 and Cav3.3. Results: The cell viability of DRG+R group, vector+R group and pAd-shRNA+R group decreased significantly after 3 mM ropivacaine hydrochloride treatment for 4 h. Compared with DRG+R group, the cell viability of pAd-shRNA+R group was significantly higher. After 3 mM ropivacaine hydrochloride treatment for 4 h, the apoptosis rate of DRG + R group, vector + R group and pAd-shRNA + R group increased significantly. Compared with DRG+R group, the apoptosis rate in pAd shRNA+R group was significantly lower. After 3 mM ropivacaine hydrochloride treatment for 4 h, the intracellular calcium levels in DRG + R group, vector + R group and pAd-shRNA + R group were significantly increased, and the intracellular calcium levels in pAd-shRNA + R group were significantly lower than those in DRG + R group. The mRNA expressions of CaMKⅡα, Cav3.2 and Cav3.3 were significantly decreased in pAd- shRNA group. The mRNA expressions of CaMK Ⅱ α, Cav3.2 and Cav3.3 were up-regulated in DRG + R group, vector + R group and pAd-shRNA + R group after 3 mm ropivacaine treatment for 4 h. The mRNA expressions of CaMKⅡα, Cav3.2 and Cav3.3 in pAd-shRNA + R group were significantly lower than those in DRG + R group. Conclusion: Inhibition of CaMKⅡα expression can down regulate the expression of Cav3.2 and Cav3.3 mRNA, increase cell viability of DRG neurons, reduce the apoptosis rate, and improve the dorsal root ganglion neurotoxicity induced by ropivacaine hydrochloride.

Biophysical Properties and Responses to Neurotransmitters of Petrosal and Geniculate Ganglion Neurons Innervating the Tongue

2000 ◽  
Vol 84 (3) ◽  
pp. 1404-1413 ◽  
Author(s):  
Tomoshige Koga ◽  
Robert M. Bradley
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Membrane Properties ◽  
Patch Clamp Recording ◽  
Potential Decay ◽  
Ganglion Neurons ◽  
Fast Rise ◽  
Posterior Tongue ◽  
Passive Membrane Properties

The properties of afferent sensory neurons supplying taste receptors on the tongue were examined in vitro. Neurons in the geniculate (GG) and petrosal ganglia (PG) supplying the tongue were fluorescently labeled, acutely dissociated, and then analyzed using patch-clamp recording. Measurement of the dissociated neurons revealed that PG neurons were significantly larger than GG neurons. The active and passive membrane properties of these ganglion neurons were examined and compared with each other. There were significant differences between the properties of neurons in the PG and GG ganglia. The mean membrane time constant, spike threshold, action potential half-width, and action potential decay time of GG neurons was significantly less than those of PG neurons. Neurons in the PG had action potentials that had a fast rise and fall time (sharp action potentials) as well as action potentials with a deflection or hump on the falling phase (humped action potentials), whereas action potentials of GG neurons were all sharp. There were also significant differences in the response of PG and GG neurons to the application of acetylcholine (ACh), serotonin (5HT), substance P (SP), and GABA. Whereas PG neurons responded to ACh, 5HT, SP, and GABA, GG neurons only responded to SP and GABA. In addition, the properties of GG neurons were more homogeneous than those of the PG because all the GG neurons had sharp spikes and when responses to neurotransmitters occurred, either all or most of the neurons responded. These differences between neurons of the GG and PG may relate to the type of receptor innervated. PG ganglion neurons innervate a number of receptor types on the posterior tongue and have more heterogeneous properties, while GG neurons predominantly innervate taste buds and have more homogeneous properties.

Similar Electrophysiological Changes in Axotomized and Neighboring Intact Dorsal Root Ganglion Neurons

2003 ◽  
Vol 89 (3) ◽  
pp. 1588-1602 ◽  
Author(s):  
Chao Ma ◽  
Yousheng Shu ◽  
Zheng Zheng ◽  
Yong Chen ◽  
Hang Yao ◽  
...  
Keyword(s):  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Receptive Fields ◽  
Input Resistance ◽  
Spinal Nerve ◽  
Dorsal Root Ganglion Neurons ◽  
Drg Neurons ◽  
Ganglion Neurons

We investigated electrophysiological changes in chronically axotomized and neighboring intact dorsal root ganglion (DRG) neurons in rats after either a peripheral axotomy consisting of an L5 spinal nerve ligation (SNL) or a central axotomy produced by an L5 partial rhizotomy (PR). SNL produced lasting hyperalgesia to punctate indentation and tactile allodynia to innocuous stroking of the foot ipsilateral to the injury. PR produced ipsilateral hyperalgesia without allodynia with recovery by day 10. Intracellular recordings were obtained in vivo from the cell bodies (somata) of axotomized and intact DRG neurons, some with functionally identified peripheral receptive fields. PR produced only minor electrophysiological changes in both axotomized and intact somata in L5 DRG. In contrast, extensive changes were observed after SNL in large- and medium-sized, but not small-sized, somata of intact (L4) as well as axotomized (L5) DRG neurons. These changes included (in relation to sham values) higher input resistance, lower current and voltage thresholds, and action potentials with longer durations and slower rising and falling rates. The incidence of spontaneous activity, recorded extracellularly from dorsal root fibers in vitro, was significantly higher (in relation to sham) after SNL but not after PR, and occurred in myelinated but not unmyelinated fibers from both L4 (9.1%) and L5 (16.7%) DRGs. We hypothesize that the changes in the electrophysiological properties of axotomized and intact DRG neurons after SNL are produced by a mechanism associated with Wallerian degeneration and that the hyperexcitability of intact neurons may contribute to SNL-induced hyperalgesia and allodynia.

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.

scholarly journals Millisecond infrared laser pulses depolarize and elicit action potentials on in-vitro dorsal root ganglion neurons

2017 ◽  
Vol 8 (10) ◽  
pp. 4568 ◽  
Author(s):  
Lambert Paris ◽  
Isabelle Marc ◽  
Benoit Charlot ◽  
Michel Dumas ◽  
Jean Valmier ◽  
...  
Keyword(s):  
Dorsal Root Ganglion ◽  
Action Potentials ◽  
Dorsal Root ◽  
Laser Pulses ◽  
Infrared Laser ◽  
Dorsal Root Ganglion Neurons ◽  
Ganglion Neurons

scholarly journals Intra-articular AAV-PHP.S mediated chemogenetic targeting of knee-innervating dorsal root ganglion neurons alleviates inflammatory pain in mice

2020 ◽  
Author(s):  
Sampurna Chakrabarti ◽  
Luke A. Pattison ◽  
Balint Doleschall ◽  
Rebecca H. Rickman ◽  
Helen Blake ◽  
...  
Keyword(s):  
Dorsal Root Ganglion ◽  
Knee Joint ◽  
Joint Pain ◽  
Dorsal Root ◽  
Dorsal Root Ganglion Neurons ◽  
Drg Neurons ◽  
Neuron Excitability ◽  
Ganglion Neurons

AbstractObjectiveJoint pain is the major clinical symptom of arthritis that affects millions of people. Controlling the excitability of knee-innervating dorsal root ganglion (DRG) neurons (knee neurons) could potentially provide pain relief. Therefore, our objective was to evaluate whether the newly engineered adeno-associated virus (AAV) serotype, AAV-PHP.S, can deliver functional artificial receptors to control knee neuron excitability following intra-articular knee injection.MethodsAAV-PHP.S virus packaged with dTomato fluorescent protein and either excitatory (Gq) or inhibitory (Gi) designer receptors activated by designer drugs (DREADDs) was injected into the knee joint of adult mice. Labelling of DRG neurons by AAV-PHP.S from the knee was evaluated using immunohistochemistry. Functionality of Gq- and Gi-DREADDs was evaluated using whole-cell patch clamp electrophysiology on acutely cultured DRG neurons. Pain behavior in mice was assessed using a digging assay, dynamic weight bearing and rotarod, before and after intra-peritoneal administration of the DREADD activator, Compound 21.ResultsWe show that AAV-PHP.S can deliver functional genes into the DRG neurons when injected into the knee joint in a similar manner to the well-established retrograde tracer, fast blue. Short-term activation of AAV-PHP.S delivered Gq-DREADD increases excitability of knee neurons in vitro, without inducing overt pain in mice when activated in vivo. By contrast, in vivo Gi-DREADD activation alleviated complete Freund’s adjuvant mediated knee inflammation-induced deficits in digging behavior, with a concomitant decrease in knee neuron excitability observed in vitro.ConclusionsWe describe an AAV-mediated chemogenetic approach to specifically control joint pain, which may be utilized in translational arthritic pain research.

Calcium currents and transmitter output in cultured spinal cord and dorsal root ganglion neurons

1986 ◽  
Vol 56 (5) ◽  
pp. 1257-1267 ◽  
Author(s):  
M. Jia ◽  
P. G. Nelson
Keyword(s):  
Spinal Cord ◽  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Calcium Currents ◽  
Dorsal Root Ganglion Neurons ◽  
Ion Concentration ◽  
Drg Neurons ◽  
Voltage Dependent ◽  
Ganglion Neurons

The effects of repetitive activation upon voltage-dependent calcium currents (ICa) and transmitter release were studied in dissociated cell cultures of fetal mouse spinal cord and dorsal root ganglion. Sodium and potassium currents were suppressed with tetrodotoxin (TTX) and tetraethylammonium (TEA) ions, 4-aminopyridine (4-AP), and cesium sulfate. Calcium currents were compared under voltage clamp before and after a series of depolarizing clamp pulses in spinal cord (SC) and dorsal root ganglion (DRG) neurons. Repetitive activation resulted in an exponential decline in ICa, with the decrease in ICa being much more marked in DRG compared with SC neurons. Both voltage-dependent inactivation and inactivation related to the intracellular movement of Ca2+ appeared to be involved in the decrement in ICa with repetitive activation. A decrease in transmitter output occurred with repetitive activation in DRG neurons but not in SC neurons (either excitatory or inhibitory). DRG neuron synaptic boutons had fewer mitochondria than did the boutons of either excitatory or inhibitory of SC neurons. The decrement in both ICa and synaptic transmitter output in DRG neurons could last for prolonged periods (at least minutes) following repetitive activation. We hypothesize that this vulnerability of DRG neurons to repetitive activation may be related, at least in part, to a relative incapacity to maintain a low intracellular calcium ion concentration [Ca]i during periods of increased calcium ingress associated with excitation. Such an incapacity to buffer [Ca]i may be one mechanism leading to the inactive synapses seen in some studies in vitro and in vivo of synaptic transmission.

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