scholarly journals Co-Application of Eugenol and QX-314 Elicits the Prolonged Blockade of Voltage-Gated Sodium Channels in Nociceptive Trigeminal Ganglion Neurons

Biomolecules ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1513
Author(s):  
Sung-Min Hwang ◽  
Kihwan Lee ◽  
Sang-Taek Im ◽  
Eun Jin Go ◽  
Yong Ho Kim ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Trigeminal Ganglion ◽  
Transient Receptor Potential ◽  
Pain Treatment ◽  
Transient Receptor Potential Vanilloid ◽  
Dependent Manner ◽  
Noxious Heat ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Ganglion Neurons

Local anesthetics (LAs) can completely block nociception by inhibiting voltage-gated sodium channels (VGSCs), and thus, blocking action potentials (APs) within sensory neurons. As one of the several LAs, eugenol is used for dental pain treatment. It reportedly features multiple functions in regulating diverse ion channels. This study aimed to investigate the long-lasting analgesic effect of eugenol alone, as well as that of the combination of eugenol as a noxious-heat-sensitive transient receptor potential vanilloid 1 (TRPV1) channel agonist and a permanently charged sodium channel blocker (QX-314), on neuronal excitability in trigeminal ganglion (TG) neurons. Eugenol alone increased inward current in a dose-dependent manner in capsaicin-sensitive TG neurons. Eugenol also inhibited the VGSC current and AP. These effects were reversed through wash-out. The combination of eugenol and QX-314 was evaluated in the same manner. The combination completely inhibited the VGSC current and AP. However, these effects were not reversed and were continuously blocked even after wash-out. Taken together, our results suggest that, in contrast to the effect of eugenol alone, the combination of eugenol and QX-314 irreversibly and selectively blocked VGSCs in TG neurons expressing TRPV1.

scholarly journals Dexmedetomidine Inhibits Voltage-Gated Sodium Channels via α2-Adrenoceptors in Trigeminal Ganglion Neurons

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Sang-Taek Im ◽  
Youn Yi Jo ◽  
Gayoung Han ◽  
Hyun Jung Jo ◽  
Yong Ho Kim ◽  
...  
Keyword(s):  
G Protein ◽  
Sodium Channels ◽  
Trigeminal Ganglion ◽  
Trigeminal System ◽  
Voltage Gated ◽  
Analgesic Effects ◽  
Voltage Gated Sodium Channels ◽  
New Findings ◽  
Orofacial Region ◽  
Ganglion Neurons

Dexmedetomidine, an α2-adrenoceptor agonist, is widely used as a sedative and analgesic agent in a number of clinical applications. However, little is known about the mechanism by which it exerts its analgesic effects on the trigeminal system. Two types of voltage-gated sodium channels, Nav1.7 and Nav1.8, as well as α2-adrenoceptors are expressed in primary sensory neurons of the trigeminal ganglion (TG). Using whole-cell patch-clamp recordings, we investigated the effects of dexmedetomidine on voltage-gated sodium channel currents (INa) via α2-adrenoceptors in dissociated, small-sized TG neurons. Dexmedetomidine caused a concentration-dependent inhibition of INa in small-sized TG neurons. INa inhibition by dexmedetomidine was blocked by yohimbine, a competitive α2-adrenoceptor antagonist. Dexmedetomidine-induced inhibition of INa was mediated by G protein-coupled receptors (GPCRs) as this effect was blocked by intracellular perfusion with the G protein inhibitor GDPβ-S. Our results suggest that the INa inhibition in small-sized TG neurons, mediated by the activation of Gi/o protein-coupled α2-adrenoceptors, might contribute to the analgesic effects of dexmedetomidine in the trigeminal system. Therefore, these new findings highlight a potential novel target for analgesic drugs in the orofacial region.

scholarly journals Eugenol Inhibits K+ Currents in Trigeminal Ganglion Neurons

2007 ◽  
Vol 86 (9) ◽  
pp. 898-902 ◽  
Author(s):  
H.Y. Li ◽  
C.-K. Park ◽  
S.J. Jung ◽  
S.-Y. Choi ◽  
S.J. Lee ◽  
...  
Keyword(s):  
Trigeminal Ganglion ◽  
Transient Receptor Potential ◽  
Receptor Potential ◽  
Transient Receptor Potential Vanilloid ◽  
Inhibitory Effects ◽  
Independent Manner ◽  
Voltage Gated ◽  
Trigeminal Ganglion Neurons ◽  
Transient Receptor ◽  
Ganglion Neurons

Eugenol, a natural capsaicin congener, is widely used in dentistry. Eugenol inhibits voltage-activated Na+ and Ca2+ channels in a transient receptor potential vanilloid 1 (TRPV1)-independent manner. We hypothesized that eugenol also inhibits voltage-gated K+ currents, and investigated this in rat trigeminal ganglion neurons and in a heterologous system using whole-cell patch clamping. Eugenol inhibited voltage-gated K+ currents, and the inhibitory effects of eugenol were observed in both capsaicin-sensitive and capsaicin-insensitive neurons. Pre-treatment with capsazepine, a well-known antagonist of TRPV1, failed to block the inhibitory effects of eugenol on K+ currents, suggesting no involvement of TRPV1. Eugenol inhibited human Kv1.5 currents stably expressed in Ltk− cells, where TRPV1 is not endogenously expressed. We conclude that eugenol inhibits voltage-gated K+ currents in a TRPV1-independent manner. The inhibition of voltage-gated K+ currents is likely to contribute to the irritable action of eugenol. Abbreviations: human Kv1.5 channel, hKv1.5; transient receptor potential vanilloid 1, TRPV1.

Effects of WIN55,212-2 on voltage-gated sodium channels in trigeminal ganglion neurons of rats

2008 ◽  
Vol 30 (1) ◽  
pp. 85-91 ◽  
Author(s):  
Hui Fu ◽  
Jian Min Xiao ◽  
Xue Hong Cao ◽  
Zhang Yin Ming ◽  
Lie Ju Liu
Keyword(s):  
Sodium Channels ◽  
Trigeminal Ganglion ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Trigeminal Ganglion Neurons ◽  
Ganglion Neurons

Capsaicin Inhibits Activation of Voltage-Gated Sodium Currents in Capsaicin-Sensitive Trigeminal Ganglion Neurons

2001 ◽  
Vol 85 (2) ◽  
pp. 745-758 ◽  
Author(s):  
L. Liu ◽  
M. Oortgiesen ◽  
L. Li ◽  
S. A. Simon
Keyword(s):  
Trigeminal Ganglion ◽  
Second Messengers ◽  
Receptor Activation ◽  
Hot Pepper ◽  
Capsaicin Receptor ◽  
Voltage Gated ◽  
Analgesic Effects ◽  
Voltage Gated Sodium Channels ◽  
Camp Generation ◽  
Ganglion Neurons

Capsaicin, the pungent ingredient in hot pepper, activates nociceptors to produce pain and inflammation. However, repeated exposures of capsaicin will cause desensitization to nociceptive stimuli. In cultured trigeminal ganglion (TG) neurons, we investigated mechanisms underlying capsaicin-mediated inhibition of action potentials (APs) and modulation of voltage-gated sodium channels (VGSCs). Capsaicin (1 μM) inhibited APs and VGSCs only in capsaicin-sensitive neurons. Repeated applications of capsaicin produced depolarizing potentials but failed to evoke APs. The capsaicin-induced inhibition of VGSCs was prevented by preexposing the capsaicin receptor antagonist, capsazepine (CPZ). The magnitude of the capsaicin-induced inhibition of VGSCs was dose dependent, having a K 1/2 = 0.45 μM. The magnitude of the inhibition of VGSCs was proportional to the capsaicin induced current (for – I CAP < 0.2 nA). Capsaicin inhibited activation of VGSCs without changing the voltage dependence of activation or markedly changing channel inactivation and use-dependent block. To explore the changes leading to this inhibition, it was found that capsaicin increased cAMP with a K 1/2 = 0.18 μM. At 1 μM capsaicin, this cAMP generation was inhibited 64% by10 μM CPZ, suggesting that activation of capsaicin receptors increased cAMP. The addition of 100 μM CPT-cAMP increased the capsaicin-activated currents but inhibited the VGSCs in both capsaicin-sensitive and -insensitive neurons. In summary, the inhibitory effects of capsaicin on VGSCs and the generation of APs are mediated by activation of capsaicin receptors. The capsaicin-induced activation of second messengers, such as cAMP, play a part in this modulation. These data distinguish two pathways by which neuronal sensitivity can be diminished by capsaicin: by modulation of the capsaicin receptor sensitivity, since the block of VGSCs is proportional to the magnitude of the capsaicin-evoked currents, and by modulation of VGSCs through second messengers elevated by capsaicin receptor activation. These mechanisms are likely to be important in understanding the analgesic effects of capsaicin.

Ethanol inhibits voltage-gated sodium channels in cultured superior cervical ganglion neurons

Neuroreport ◽  
2008 ◽  
Vol 19 (18) ◽  
pp. 1773-1776 ◽  
Author(s):  
Zheman Xiao ◽  
Zuneng Lu ◽  
Zhongchun Liu ◽  
Wanhong Liu ◽  
Lijun Li ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Superior Cervical Ganglion ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Cervical Ganglion ◽  
Ganglion Neurons

scholarly journals Block of Voltage-Gated Sodium Channels by Atomoxetine in a State- and Use-dependent Manner

2021 ◽  
Vol 12 ◽  
Author(s):  
Karl Josef Föhr ◽  
Ariadni Nastos ◽  
Michael Fauler ◽  
Thomas Zimmer ◽  
Bettina Jungwirth ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Heart Muscle ◽  
Brain Regions ◽  
Clinical Effects ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Human Embryonic Kidney Cells ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Slow Kinetics

Atomoxetine, a neuroactive drug, is approved for the treatment of attention-deficit/hyperactivity disorder (ADHD). It is primarily known as a high affinity blocker of the noradrenaline transporter, whereby its application leads to an increased level of the corresponding neurotransmitter in different brain regions. However, the concentrations used to obtain clinical effects are much higher than those which are required to block the transporter system. Thus, off-target effects are likely to occur. In this way, we previously identified atomoxetine as blocker of NMDA receptors. As many psychotropic drugs give rise to sudden death of cardiac origin, we now tested the hypothesis whether atomoxetine also interacts with voltage-gated sodium channels of heart muscle type in clinically relevant concentrations. Electrophysiological experiments were performed by means of the patch-clamp technique at human heart muscle sodium channels (hNav1.5) heterogeneously expressed in human embryonic kidney cells. Atomoxetine inhibited sodium channels in a state- and use-dependent manner. Atomoxetine had only a weak affinity for the resting state of the hNav1.5 (Kr: ∼ 120 µM). The efficacy of atomoxetine strongly increased with membrane depolarization, indicating that the inactivated state is an important target. A hallmark of this drug was its slow interaction. By use of different experimental settings, we concluded that the interaction occurs with the slow inactivated state as well as by slow kinetics with the fast-inactivated state. Half-maximal effective concentrations (2–3 µM) were well within the concentration range found in plasma of treated patients. Atomoxetine also interacted with the open channel. However, the interaction was not fast enough to accelerate the time constant of fast inactivation. Nevertheless, when using the inactivation-deficient hNav1.5_I408W_L409C_A410W mutant, we found that the persistent late current was blocked half maximal at about 3 µM atomoxetine. The interaction most probably occurred via the local anesthetic binding site. Atomoxetine inhibited sodium channels at a similar concentration as it is used for the treatment of ADHD. Due to its slow interaction and by inhibiting the late current, it potentially exerts antiarrhythmic properties.

Abstract 326: TRPV2 Regulates Cardiomyocyte Function via Altering Ca 2+ Cycling

2012 ◽  
Vol 111 (suppl_1) ◽  
Author(s):  
Xiaoqian Gao ◽  
Sheryl Koch ◽  
Min Jiang ◽  
Nathan Robbins ◽  
Wenfeng Cai ◽  
...  
Keyword(s):  
Transient Receptor Potential ◽  
Ventricular Myocytes ◽  
Receptor Potential ◽  
Ruthenium Red ◽  
Transient Receptor Potential Vanilloid ◽  
Dependent Manner ◽  
Noxious Heat ◽  
Cardiac Tissues ◽  
Membrane Stretching ◽  
Transient Receptor

TRPV2 is a member of transient receptor potential vanilloid (TRPV) family. As a Ca 2+ channel, it can detect various stimuli such as noxious heat (>52°C), membrane stretching, as well as a number of exogenous chemicals, including probenecid, 2-aminoethoxydiphenyl borate, and lysophospholipids. TRPV2 has been found in many tissue types, including neuron and kidney, but the function of TRPV2 in the heart is poorly understood. Here we show TRPV2 is involved in the Ca 2+ cycling process and then regulates the function of the cardiomyocyte. We identified the mRNA expression of TRPV2 in the cardiac tissues of mice using real-time PCR. By performing echocardiography we found that administration of probenecid, a selective TRPV2 agonist, increased cardiac ejection fraction in mice. This positive inotropic effect of probenecid was also shown in Langendorff perfused mice hearts as increased peak +dP/dt. In isolated ventricular myocytes, we found that probenecid significantly increased myocyte fractional shortening in a dose-dependent manner, which was fully blocked by ruthenium red, a non-selective TRPV2 blocker. We also performed fluorescent studies to examine myocyte Ca 2+ cycling. We found that probenecid significantly increased Ca 2+ transient and resting-state Ca 2+ sparks and this effect was eliminated by ruthenium red. When Ca 2+ storage in sarcoplasmic reticulum (SR) was depleted with caffeine, and SR Ca 2+ reuptake was blocked by thapsigargin at the same time, probenecid did not show any effects in either Ca 2+ transient or Ca 2+ sparks. Our patch clamp experiments indicate that probenecid treatment does not trigger any significant transmembrane Ca 2+ influx. These results point to the important role of TRPV2 in regulating SR Ca 2+ release. In conclusion, TRPV2 activation may contribute to increased SR Ca 2+ release, leading to the enhancement of myocyte contractility. Thus, TRPV2 plays a potentially important role in controlling the cellular function of heart.

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