scholarly journals Contribution of KCNQ and TREK Channels to the Resting Membrane Potential in Sympathetic Neurons at Physiological Temperature

2020 ◽  
Vol 21 (16) ◽  
pp. 5796
Author(s):  
Paula Rivas-Ramírez ◽  
Antonio Reboreda ◽  
Lola Rueda-Ruzafa ◽  
Salvador Herrera-Pérez ◽  
Jose Antonio Lamas
Keyword(s):  
Membrane Potential ◽  
Room Temperature ◽  
Sympathetic Neurons ◽  
K Channel ◽  
Resting Membrane Potential ◽  
Physiological Temperature ◽  
M Current ◽  
Key Players ◽  
Cervical Ganglion ◽  
Ionic Mechanisms

The ionic mechanisms controlling the resting membrane potential (RMP) in superior cervical ganglion (SCG) neurons have been widely studied and the M-current (IM, KCNQ) is one of the key players. Recently, with the discovery of the presence of functional TREK-2 (TWIK-related K+ channel 2) channels in SCG neurons, another potential main contributor for setting the value of the resting membrane potential has appeared. In the present work, we quantified the contribution of TREK-2 channels to the resting membrane potential at physiological temperature and studied its role in excitability using patch-clamp techniques. In the process we have discovered that TREK-2 channels are sensitive to the classic M-current blockers linopirdine and XE991 (IC50 = 0.310 ± 0.06 µM and 0.044 ± 0.013 µM, respectively). An increase from room temperature (23 °C) to physiological temperature (37 °C) enhanced both IM and TREK-2 currents. Likewise, inhibition of IM by tetraethylammonium (TEA) and TREK-2 current by XE991 depolarized the RMP at room and physiological temperatures. Temperature rise also enhanced adaptation in SCG neurons which was reduced due to TREK-2 and IM inhibition by XE991 application. In summary, TREK-2 and M currents contribute to the resting membrane potential and excitability at room and physiological temperature in the primary culture of mouse SCG neurons.

scholarly journals PIP2 Mediated Inhibition of TREK Potassium Currents by Bradykinin in Mouse Sympathetic Neurons

2020 ◽  
Vol 21 (2) ◽  
pp. 389 ◽  
Author(s):  
Paula Rivas-Ramírez ◽  
Antonio Reboreda ◽  
Lola Rueda-Ruzafa ◽  
Salvador Herrera-Pérez ◽  
J. Antonio Lamas
Keyword(s):  
Single Channel ◽  
Sympathetic Neurons ◽  
K Channel ◽  
Muscarinic Agonists ◽  
Open Probability ◽  
M Current ◽  
Voltage Dependent ◽  
Cervical Ganglion ◽  
Patch Technique ◽  
Single Channel Currents

Bradykinin (BK), a hormone inducing pain and inflammation, is known to inhibit potassium M-currents (IM) and to increase the excitability of the superior cervical ganglion (SCG) neurons by activating the Ca2+-calmodulin pathway. M-current is also reduced by muscarinic agonists through the depletion of membrane phosphatidylinositol 4,5-biphosphate (PIP2). Similarly, the activation of muscarinic receptors inhibits the current through two-pore domain potassium channels (K2P) of the “Tandem of pore-domains in a Weakly Inward rectifying K+ channel (TWIK)-related channels” (TREK) subfamily by reducing PIP2 in mouse SCG neurons (mSCG). The aim of this work was to test and characterize the modulation of TREK channels by bradykinin. We used the perforated-patch technique to investigate riluzole (RIL) activated currents in voltage- and current-clamp experiments. RIL is a drug used in the palliative treatment of amyotrophic lateral sclerosis and, in addition to blocking voltage-dependent sodium channels, it also selectively activates the K2P channels of the TREK subfamily. A cell-attached patch-clamp was also used to investigate TREK-2 single channel currents. We report here that BK reduces spike frequency adaptation (SFA), inhibits the riluzole-activated current (IRIL), which flows mainly through TREK-2 channels, by about 45%, and reduces the open probability of identified single TREK-2 channels in cultured mSCG cells. The effect of BK on IRIL was precluded by the bradykinin receptor (B2R) antagonist HOE-140 (d-Arg-[Hyp3, Thi5, d-Tic7, Oic8]BK) but also by diC8PIP2 which prevents PIP2 depletion when phospholipase C (PLC) is activated. On the contrary, antagonizing inositol triphosphate receptors (IP3R) using 2-aminoethoxydiphenylborane (2-APB) or inhibiting protein kinase C (PKC) with bisindolylmaleimide did not affect the inhibition of IRIL by BK. In conclusion, bradykinin inhibits TREK-2 channels through the activation of B2Rs resulting in PIP2 depletion, much like we have demonstrated for muscarinic agonists. This mechanism implies that TREK channels must be relevant for the capture of information about pain and visceral inflammation.

scholarly journals Activation of Ca(2+)-dependent K+ current by acetylcholine and histamine in a human gastric epithelial cell line.

1993 ◽  
Vol 102 (4) ◽  
pp. 667-692 ◽  
Author(s):  
E Hamada ◽  
T Nakajima ◽  
S Ota ◽  
A Terano ◽  
M Omata ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Epithelial Cell ◽  
Cell Line ◽  
K Channel ◽  
Resting Membrane Potential ◽  
Induced Response ◽  
Epithelial Cell Line ◽  
Bathing Solution ◽  
Pipette Solution ◽  
K Current

The effects of acetylcholine (ACh) and histamine (His) on the membrane potential and current were examined in JR-1 cells, a mucin-producing epithelial cell line derived from human gastric signet ring cell carcinoma. The tight-seal, whole cell clamp technique was used. The resting membrane potential, the input resistance, and the capacitance of the cells were approximately -12 mV, 1.4 G ohms, and 50 pF, respectively. Under the voltage-clamp condition, no voltage-dependent currents were evoked. ACh or His added to the bathing solution hyperpolarized the membrane by activating a time- and voltage-independent K+ current. The ACh-induced hyperpolarization and K+ current persisted, while the His response desensitized quickly (< 1 min). These effects of ACh and His were mediated predominantly by m3-muscarinic and H1-His receptors, respectively. The K+ current induced by ACh and His was inhibited by charybdotoxin, suggesting that it is a Ca(2+)-activated K+ channel current (IK.Ca). The measurement of intracellular Ca2+ ([Ca2+]i) using Indo-1 revealed that both agents increased [Ca2+]i with similar time courses as they increased IK.Ca. When EGTA in the pipette solution was increased from 0.15 to 10 mM, the induction of IK.Ca by ACh and His was abolished. Thus, both ACh and His activate IK.Ca by increasing [Ca2+]i in JR-1 cells. In the Ca(2+)-free bathing solution (0.15 mM EGTA in the pipette), ACh evoked IK.Ca transiently. Addition of Ca2+ (1.8 mM) to the bath immediately restored the sustained IK.Ca. These results suggest that the ACh response is due to at least two different mechanisms; i.e., the Ca2+ release-related initial transient activation and the Ca2+ influx-related sustained activation of IK.Ca. Probably because of desensitization, the Ca2+ influx-related component of the His response could not be identified. Intracellularly applied inositol 1,4,5-trisphosphate (IP3), with and without inositol 1,3,4,5-tetrakisphosphate (IP4), mimicked the ACh response. IP4 alone did not affect the membrane current. Under the steady effect of IP3 or IP3 plus IP4, neither ACh nor His further evoked IK.Ca. Intracellular application of heparin or of the monoclonal antibody against the IP3 receptor, mAb18A10, inhibited the ACh and His responses in a concentration-dependent fashion. Neomycin, a phospholipase C (PLC) inhibitor, also inhibited the agonist-induced response in a concentration-dependent fashion. Although neither pertussis toxin (PTX) nor N-ethylmaleimide affected the ACh or His activation of IK,Ca, GDP beta S attenuated and GTP gamma S enhanced the agonist response.(ABSTRACT TRUNCATED AT 400 WORDS)

Hormonal Signaling Actions on Kv7.1 (KCNQ1) Channels

2021 ◽  
Vol 61 (1) ◽  
pp. 381-400
Author(s):  
Emely Thompson ◽  
Jodene Eldstrom ◽  
David Fedida
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Cardiac Action Potential ◽  
Resting Membrane Potential ◽  
Voltage Gated ◽  
M Current ◽  
Kv7 Channels ◽  
Cardiac Action ◽  
Repolarization Phase ◽  
And Control

Kv7 channels (Kv7.1–7.5) are voltage-gated K+ channels that can be modulated by five β-subunits (KCNE1–5). Kv7.1-KCNE1 channels produce the slow-delayed rectifying K+ current, IKs, which is important during the repolarization phase of the cardiac action potential. Kv7.2–7.5 are predominantly neuronally expressed and constitute the muscarinic M-current and control the resting membrane potential in neurons. Kv7.1 produces drastically different currents as a result of modulation by KCNE subunits. This flexibility allows the Kv7.1 channel to have many roles depending on location and assembly partners. The pharmacological sensitivity of Kv7.1 channels differs from that of Kv7.2–7.5 and is largely dependent upon the number of β-subunits present in the channel complex. As a result, the development of pharmaceuticals targeting Kv7.1 is problematic. This review discusses the roles and the mechanisms by which different signaling pathways affect Kv7.1 and KCNE channels and could potentially provide different ways of targeting the channel.

Inward rectifier K+ channel Kir2.3 is localized at the postsynaptic membrane of excitatory synapses

2002 ◽  
Vol 282 (6) ◽  
pp. C1396-C1403 ◽  
Author(s):  
Atsushi Inanobe ◽  
Akikazu Fujita ◽  
Minoru Ito ◽  
Hitonobu Tomoike ◽  
Kiyoshi Inageda ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Granule Cells ◽  
Pdz Domain ◽  
Postsynaptic Membrane ◽  
Equilibrium Potential ◽  
K Channel ◽  
Resting Membrane Potential ◽  
Kir Channel ◽  
Anchoring Proteins

Classical inwardly rectifying K+ channels (Kir2.0) are responsible for maintaining the resting membrane potential near the K+ equilibrium potential in various cells, including neurons. Although Kir2.3 is known to be expressed abundantly in the forebrain, its precise localization has not been identified. Using an antibody specific to Kir2.3, we examined the subcellular localization of Kir2.3 in mouse brain. Kir2.3 immunoreactivity was detected in a granular pattern in restricted areas of the brain, including the olfactory bulb (OB). Immunoelectron microscopy of the OB revealed that Kir2.3 immunoreactivity was specifically clustered on the postsynaptic membrane of asymmetric synapses between granule cells and mitral/tufted cells. The immunoprecipitants for Kir2.3 obtained from brain contained PSD-95 and chapsyn-110, PDZ domain-containing anchoring proteins. In vitro binding assay further revealed that the COOH-terminal end of Kir2.3 is responsible for the association with these anchoring proteins. Therefore, the Kir channel may be involved in formation of the resting membrane potential of the spines and, thus, would affect the response of N-methyl-d-aspartic acid receptor channels at the excitatory postsynaptic membrane.

K+ channel opening mediates hyperpolarizations by nitric oxide donors and IJPs in opossum esophagus

1995 ◽  
Vol 268 (5) ◽  
pp. G831-G842 ◽  
Author(s):  
F. S. Cayabyab ◽  
E. E. Daniel
Keyword(s):  
Nitric Oxide ◽  
Soluble Guanylate Cyclase ◽  
Equilibrium Potential ◽  
K Channel ◽  
Resting Membrane Potential ◽  
Channel Blockers ◽  
No Donor ◽  
No Donors ◽  
Circular Smooth Muscle ◽  
Ionic Mechanisms

The ionic mechanisms by which nitric oxide (NO) or a related compound mediates the inhibitory junction potentials (IJPs) of the opossum esophageal circular smooth muscle were studied using microelectrodes and double sucrose gap. The NO donors, 3-morpholino-sydnonimine hydrochloride and sodium nitroprusside, induced 15- to 20-mV hyperpolarizations that reversed near the potassium equilibrium potential as did the IJPs. They inhibited the IJPs and decreased electrotonic potentials (increased conductance) even during restoration of the resting membrane potential by application of depolarizing current. Quinine was more efficacious than apamin in inhibiting the IJPs or NO donor hyperpolarizations, whereas the other K+ channel blockers tested (tetraethylammonium, charybdotoxin, 4-aminopyridine, Cs+, and glibenclamide) were without effect. Glibenclamide abolished the hyperpolarizing effects of the K+ channel opener BRL-34915. Low Cl- Krebs (isethionate substitutions) caused hyperpolarizations, increased electrotonic potentials, and reduced IJPs. The neural blockers, tetrodotoxin, omega-conotoxin GVIA, and N omega-nitro-L-arginine methyl ester, inhibited IJPs but not the responses to NO donors, indicating a postjunctional effect. Methylene blue and cystamine, soluble guanylate cyclase inhibitors, suppressed IJPs and responses to NO donors. We conclude that NO mediates esophageal IJPs, which depend on guanosine 3',5'-cyclic monophosphate elevation and activation of quinine- and apamin-sensitive K+ channels.

scholarly journals A Ba2+-Sensitive K+ Current Contributes to the Resting Membrane Potential of Neurons in Rat Suprachiasmatic Nucleus

2002 ◽  
Vol 88 (2) ◽  
pp. 869-878 ◽  
Author(s):  
Marcel de Jeu ◽  
Alwin Geurtsen ◽  
Cyriel Pennartz
Keyword(s):  
Membrane Potential ◽  
Suprachiasmatic Nucleus ◽  
Voltage Dependence ◽  
Brain Slices ◽  
Resting Potential ◽  
Resting Membrane Potential ◽  
Delayed Rectifier ◽  
Patch Clamp Technique ◽  
M Current ◽  
Whole Cell Patch Clamp

A Ba2+-sensitive K+ current was studied in neurons of the suprachiasmatic nucleus (SCN) using the whole cell patch-clamp technique in acutely prepared brain slices. This Ba2+-sensitive K+ current was found in approximately 90% of the SCN neurons and was uniformly distributed across the SCN. Current-clamp studies revealed that Ba2+ (500 μM) reversibly depolarized the membrane potential by 6.7 ± 1.3 mV ( n = 22) and concomitantly Ba2+ induced an increase in the spontaneous firing rate of 0.8 ± 0.2 Hz ( n = 12). The Ba2+-evoked depolarizations did not depend on firing activity or spike dependent synaptic transmission. No significant day/night difference in the hyperpolarizing contribution to the resting membrane potential of the present Ba2+-sensitive current was observed. Voltage-clamp experiments showed that Ba2+ (500 μM) reduced a fast-activating, voltage-dependent K+ current. This current was activated at levels below firing threshold and exhibited outward rectification. The Ba2+-sensitive K+ current was strongly reduced by tetraethylammonium (TEA; 20 and 60 mM) but was insensitive to 4-aminopyridine (4-AP; 5 mM) and quinine (100 μM). A component of Ba2+-sensitive K+ current remaining in the presence of TEA exhibited no clear voltage dependence and is less likely to contribute to the resting membrane potential. The voltage dependence, kinetics and pharmacological properties of the Ba2+- and TEA-sensitive K+ current make it unlikely that this current is a delayed rectifier, Ca2+-activated K+ current, ATP-sensitive K+ current, M-current or K+ inward rectifier. Our data are consistent with the Ba2+- and TEA-sensitive K+ current in SCN neurons being an outward rectifying K+ current of a novel identity or belonging to a known family of K+ channels with related properties. Regardless of its precise molecular identity, the current appears to exert a significant hyperpolarizing effect on the resting potential of SCN neurons.

Evidence for a Ca-activated inwardly rectifying K channel in human macrophages

1989 ◽  
Vol 257 (1) ◽  
pp. C77-C85 ◽  
Author(s):  
E. K. Gallin
Keyword(s):  
Membrane Potential ◽  
Single Channel ◽  
Reversal Potential ◽  
K Channel ◽  
Resting Membrane Potential ◽  
Base Line ◽  
Channel Activity ◽  
Human Macrophages ◽  
Excised Patches ◽  
Single Channel Currents

Cell-attached patch studies of cultured human macrophages demonstrate that exposure to ionomycin induces inward-rectifying single-channel currents that differ from the voltage-dependent 28 pS inward-rectifying K currents previously described in these cells (J. Membr. Biol. 103: 55-66, 1988). With 150 mM KCl in the electrode and NaCl Hanks' solution in the bath, the ionomycin-induced single-channel conductance for inward currents was 37 pS, and the reversal potential was 57 mV. Channel activity was often associated with a shift in the base-line current level indicating that the cell membrane potential hyperpolarized. The ability of ionomycin to induce channel activity depended on extracellular [Ca] supporting the view that the channels were gated by calcium. Ionomycin-induced channels were permeable to K, relatively impermeable to Cl or Na, exhibited bursting kinetics, and had no apparent voltage dependence. Barium (3 mM in the patch electrode) did not significantly block the ionomycin-induced channel at rest but blocked channel activity when the patch was hyperpolarized beyond the resting membrane potential. Exposure of macrophages to platelet-activating factor, which is known to increase intracellular [Ca] [( Ca]i) (J. Cell Biol. 103: 439-450, 1986), also transiently induced channel activity. In excised patches with 3 microM [Ca]i bursting inward-rectifying channels with a 41 pS conductance were noted that probably correspond to the ionomycin-induced channels present in cell-attached patches. Increasing [Ca]i from 10(-8) to 3 x 10(-6) M induced inward-rectifying channel activity in previously quiescent excised patches.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Temperature Effects on Pacemaker Generation, Membrane Potential, and Critical Firing Threshold in Aplysia Neurons

1967 ◽  
Vol 50 (6) ◽  
pp. 1469-1484 ◽  
Author(s):  
David O. Carpenter
Keyword(s):  
Membrane Potential ◽  
Effect Of Temperature ◽  
Resting Membrane Potential ◽  
Visceral Ganglion ◽  
Firing Threshold ◽  
Aplysia Neurons ◽  
Ionic Mechanisms ◽  
Pacemaker Potentials ◽  
Effects Of Temperature ◽  
Frequency Curves

Temperature increases cause a regular and reproducible increase in the frequency of generation of pacemaker potentials in most Aplysia neurons specialized for this type of activity which can only be explained as a direct stimulating effect of temperature upon the ionic mechanisms responsible for pacemaker potentials. At the same time all cells in the visceral ganglion undergo a membrane potential hyperpolarization of approximately 1–2 mv/°C warmed. In spite of the marked variation in resting membrane potential the critical firing threshold remains at a constant membrane potential level at all temperatures in the absence of accommodative changes. The temperature-frequency curves of all types of cells are interpreted as a result of the interaction between the effects of temperature on the pacemaker-generating mechanism and resting membrane potential. Previous observations on the effects of temperature on excitability of mammalian neurons suggest that other types of neurons may undergo similar marked shifts in resting membrane potential with temperature variation.

Developmental differences in Ca2+-activated K+ channel activity in ovine basilar artery

2003 ◽  
Vol 285 (2) ◽  
pp. H701-H709 ◽  
Author(s):  
Mike T. Lin ◽  
David A. Hessinger ◽  
William J. Pearce ◽  
Lawrence D. Longo
Keyword(s):  
Membrane Potential ◽  
Cerebral Arteries ◽  
Outward Current ◽  
K Channel ◽  
Resting Membrane Potential ◽  
Channel Activity ◽  
Open Probability ◽  
Fetal Sheep ◽  
Voltage Gated ◽  
Maximal Activation

A primary determinant of vascular smooth muscle (VSM) tone and contractility is the resting membrane potential, which, in turn, is influenced heavily by K+ channel activity. Previous studies from our laboratory and others have demonstrated differences in the contractility of cerebral arteries from near-term fetal and adult animals. To test the hypothesis that these contractility differences result from maturational changes in voltage-gated K+ channel function, we compared this function in VSM myocytes from adult and fetal sheep cerebral arteries. The primary current-carrying, voltage-gated K+ channels in VSM myocytes are the large conductance Ca2+-activated K+ channels (BKCa) and voltage-activated K+ (KV) channels. We observed that at voltage-clamped membrane potentials of +60 mV in perforated whole cell studies, the normalized outward current densities in fetal myocytes were >30% higher than in those of the adult ( P < 0.05) and that these were predominately due to iberiotoxin-sensitive currents from BKCa channels. Excised, insideout membrane patches revealed nearly identical unitary conductances and Hill coefficients for BKCa channels. The plot of log intracellular [Ca2+] ([Ca2+]i) versus voltage for half-maximal activation ( V½) yielded linear and parallel relationships, and the change in V½ for a 10-fold change in [Ca2+] was also similar. Channel activity increased e-fold for a 19 ± 2-mV depolarization for adult myocytes and for an 18 ± 1-mV depolarization for fetal myocytes ( P > 0.05). However, the relationship between BKCa open probability and membrane potential had a relative leftward shift for the fetal compared with adult myocytes at different [Ca2+]i. The [Ca2+] for half-maximal activation (i.e., the calcium set points) at 0 mV were 8.8 and 4.7 μM for adult and fetal myocytes, respectively. Thus the increased BKCa current density in fetal myocytes appears to result from a lower calcium set point.

scholarly journals Ethanol Elevates Excitability of Superior Cervical Ganglion Neurons by Inhibiting Kv7 Channels in a Cell Type-Specific and PI(4,5)P2-Dependent Manner

2019 ◽  
Vol 20 (18) ◽  
pp. 4419 ◽  
Author(s):  
Kwon-Woo Kim ◽  
Keetae Kim ◽  
Hyosang Lee ◽  
Byung-Chang Suh
Keyword(s):  
Membrane Potential ◽  
Superior Cervical Ganglion ◽  
Neuronal Excitability ◽  
Sympathetic Neurons ◽  
Expression System ◽  
Dependent Manner ◽  
Cellular Targets ◽  
Kv7 Channels ◽  
Cervical Ganglion ◽  
Ganglion Neurons

Alcohol causes diverse acute and chronic symptoms that often lead to critical health problems. Exposure to ethanol alters the activities of sympathetic neurons that control the muscles, eyes, and blood vessels in the brain. Although recent studies have revealed the cellular targets of ethanol, such as ion channels, the molecular mechanism by which alcohol modulates the excitability of sympathetic neurons has not been determined. Here, we demonstrated that ethanol increased the discharge of membrane potentials in sympathetic neurons by inhibiting the M-type or Kv7 channel consisting of the Kv7.2/7.3 subunits, which were involved in determining the membrane potential and excitability of neurons. Three types of sympathetic neurons, classified by their threshold of activation and firing patterns, displayed distinct sensitivities to ethanol, which were negatively correlated with the size of the Kv7 current that differs depending on the type of neuron. Using a heterologous expression system, we further revealed that the inhibitory effects of ethanol on Kv7.2/7.3 currents were facilitated or diminished by adjusting the amount of plasma membrane phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). These results suggested that ethanol and PI(4,5)P2 modulated gating of the Kv7 channel in superior cervical ganglion neurons in an antagonistic manner, leading to regulation of the membrane potential and neuronal excitability, as well as the physiological functions mediated by sympathetic neurons.

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