Fertilization alters the spatial distribution and the density of voltage-dependent sodium current in the egg of the ascidian Boltenia villosa

1988 ◽  
Vol 127 (2) ◽  
pp. 408-420 ◽  
Author(s):  
Rita E. Hice ◽  
William J. Moody
Keyword(s):  
Spatial Distribution ◽  
Sodium Current ◽  
Boltenia Villosa ◽  
Voltage Dependent

scholarly journals On The Mechanism of Spontaneous Impulse Generation in the Pacemaker of the Heart

1961 ◽  
Vol 45 (2) ◽  
pp. 317-330 ◽  
Author(s):  
Wolfgang Trautwein ◽  
Donald G. Kassebaum
Keyword(s):  
Sodium Current ◽  
Potassium Conductance ◽  
Rhythmic Activity ◽  
Current Strength ◽  
Heart Beat ◽  
Free Medium ◽  
Pacemaker Potential ◽  
Impulse Generation ◽  
Sodium Conductance ◽  
Voltage Dependent

Rhythmic activity in Purkinje fibers of sheep and in fibers of the rabbit sinus can be produced or enhanced when a constant depolarizing current is applied. When extracellular calcium is reduced successively, the required current strength is less, and eventually spontaneous beating occurs. These effects are believed due to an increase in steady-state sodium conductance. A significant hyperpolarization occurs in fibers of the rabbit sinus bathed in a sodium-free medium, suggesting an appreciable sodium conductance of the "resting" membrane. During diastole, there occurs a voltage-dependent and, to a smaller extent, time-dependent reduction in potassium conductance, and a pacemaker potential occurs as a result of a large resting sodium conductance. It is postulated that the mechanism underlying the spontaneous heart beat is a high resting sodium current in pacemaker tissue which acts as the generator of the heart beat when, after a regenerative repolarization, the decrease in potassium conductance during diastole reestablishes the condition of threshold.

scholarly journals Zfhx3 Transcription Factor Represses the Expression of SCN5A Gene and Decreases Sodium Current Density (INa)

2021 ◽  
Vol 22 (23) ◽  
pp. 13031
Author(s):  
Marcos Rubio-Alarcón ◽  
Anabel Cámara-Checa ◽  
María Dago ◽  
Teresa Crespo-García ◽  
Paloma Nieto-Marín ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Cardiac Tissue ◽  
Sodium Current ◽  
Na Channel ◽  
Ubiquitin Protein Ligase ◽  
Endogenous Expression ◽  
Voltage Dependent ◽  
Familial Atrial Fibrillation ◽  
Cardiac Excitability ◽  
Scn5a Gene

The ZFHX3 and SCN5A genes encode the zinc finger homeobox 3 (Zfhx3) transcription factor (TF) and the human cardiac Na+ channel (Nav1.5), respectively. The effects of Zfhx3 on the expression of the Nav1.5 channel, and in cardiac excitability, are currently unknown. Additionally, we identified three Zfhx3 variants in probands diagnosed with familial atrial fibrillation (p.M1260T) and Brugada Syndrome (p.V949I and p.Q2564R). Here, we analyzed the effects of native (WT) and mutated Zfhx3 on Na+ current (INa) recorded in HL-1 cardiomyocytes. ZFHX3 mRNA can be detected in human atrial and ventricular samples. In HL-1 cardiomyocytes, transfection of Zfhx3 strongly reduced peak INa density, while the silencing of endogenous expression augmented it (from −65.9 ± 8.9 to −104.6 ± 10.8 pA/pF; n ≥ 8, p < 0.05). Zfhx3 significantly reduced the transcriptional activity of human SCN5A, PITX2, TBX5, and NKX25 minimal promoters. Consequently, the mRNA and/or protein expression levels of Nav1.5 and Tbx5 were diminished (n ≥ 6, p < 0.05). Zfhx3 also increased the expression of Nedd4-2 ubiquitin-protein ligase, enhancing Nav1.5 proteasomal degradation. p.V949I, p.M1260T, and p.Q2564R Zfhx3 produced similar effects on INa density and time- and voltage-dependent properties in WT. WT Zfhx3 inhibits INa as a result of a direct repressor effect on the SCN5A promoter, the modulation of Tbx5 increasing on the INa, and the increased expression of Nedd4-2. We propose that this TF participates in the control of cardiac excitability in human adult cardiac tissue.

scholarly journals Effect of FMRFamide on voltage-dependent currents in identified centrifugal neurons of the optic lobe of the cuttlefish, Sepia officinalis

2020 ◽  
Author(s):  
Abdesslam Chrachri
Keyword(s):  
Visual Processing ◽  
Calcium Current ◽  
Optic Lobe ◽  
Low Voltage ◽  
Sodium Current ◽  
Calcium Currents ◽  
Delayed Rectifier ◽  
Outward Currents ◽  
Voltage Dependent ◽  
Inward Currents

AbstractWhole-cell patch-clamp recordings from identified centrifugal neurons of the optic lobe in a slice preparation allowed the characterization of five voltage-dependent currents; two outward and three inward currents. The outward currents were; the 4-aminopyridine-sensitive transient potassium or A-current (IA), the TEA-sensitive sustained current or delayed rectifier (IK). The inward currents were; the tetrodotoxin-sensitive transient current or sodium current (INa). The second is the cobalt- and cadmium-sensitive sustained current which is enhanced by barium and blocked by the dihydropyridine antagonist, nifedipine suggesting that it could be the L-type calcium current (ICaL). Finally, another transient inward current, also carried by calcium, but unlike the L-type, this current is activated at more negative potentials and resembles the low-voltage-activated or T-type calcium current (ICaT) of other preparations.Application of the neuropeptide FMRFamide caused a significant attenuation to the peak amplitude of both sodium and sustained calcium currents without any apparent effect on the transient calcium current. Furthermore, FMRFamide also caused a reduction of both outward currents in these centrifugal neurons. The fact that FMRFamide reduced the magnitude of four of five characterized currents could suggest that this neuropeptide may act as a strong inhibitory agent on these neurons.SummaryFMRFamide modulate the ionic currents in identified centrifugal neurons in the optic lobe of cuttlefish: thus, FMRFamide could play a key role in visual processing of these animals.

Use- and Voltage-Dependent Depression by Ethmozine (Moricizine) of the Rapid Inward Sodium Current in Single Rat Ventricular Muscle Cells

1986 ◽  
Vol 8 (2) ◽  
pp. 358-366 ◽  
Author(s):  
Bernd Schubert ◽  
Steffen Hering ◽  
Rolf Bodewei ◽  
Leonid V. Rosenshtraukh ◽  
Albert Wollenberger
Keyword(s):  
Sodium Current ◽  
Muscle Cells ◽  
Ventricular Muscle ◽  
Voltage Dependent

Voltage-Dependent Effects of Volatile Anesthetics on Cardiac Sodium Current

1997 ◽  
Vol 84 (2) ◽  
pp. 285-293 ◽  
Author(s):  
Henry U. Weigt ◽  
Wai-Meng Kwok ◽  
Georg C. Rehmert ◽  
Lawrence A. Turner ◽  
Zeljko J. Bosnjak
Keyword(s):  
Sodium Current ◽  
Volatile Anesthetics ◽  
Voltage Dependent

The development of voltege-dependent ionic conductances In murine spinal cord neurones in culture

1988 ◽  
Vol 66 (10) ◽  
pp. 1328-1336 ◽  
Author(s):  
C. Krieger ◽  
T. A. Sears
Keyword(s):  
Spinal Cord ◽  
Sodium Current ◽  
Potassium Conductance ◽  
Calcium Currents ◽  
Delayed Rectifier ◽  
Patch Clamp Technique ◽  
Calcium Dependent ◽  
Ionic Conductances ◽  
Voltage Dependent

The development of voltage-dependent ionic conductances of foetal mouse spinal cord neurones was examined using the whole-cell patch-clamp technique on neurones cultured from embryos aged 10–12 days (E10–E12) which were studied between the first day in vitro (V1) to V10. A delayed rectifier potassium conductance (IK) and a leak conductance were observed in neurones of E10.V1, E11, V1, and E12, V1 as well as in neurones cultured for longer periods. A rapidly activating and inactivating potassium conductance (IA) was seen in neurones from E11, V2 and E12, V1 and at longer times in vitro. A tetrodotoxin (TTX) sensitive sodium-dependent inward current was observed in neurones of E11 and E12 from V1 onwards. Calcium-dependent conductances were not detectable in these neurones unless the external calcium concentration was raised 10- to 20-foid and potassium conductances were blocked. Under these conditions calcium currents could be observed as early as E11, V3 and E12, V2 and at subsequent times in vitro. The pattern of development of voltage-dependent ionic conductances in murine spinal neurones is such that initially leak and potassium currents are present followed by sodium current and subsequently calcium current.

Identification of sodium channel subtypes induced in cultured retinal pigment epithelium cells

1995 ◽  
Vol 12 (5) ◽  
pp. 1001-1005 ◽  
Author(s):  
Heather Dawes ◽  
Gail Mandel ◽  
Gary Matthews
Keyword(s):  
Retinal Pigment Epithelium ◽  
Sodium Channel ◽  
Sodium Current ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Rpe Cells ◽  
Voltage Dependent ◽  
Dissociated Cell Culture ◽  
Epithelium Cells ◽  
Neuronal Type

AbstractRecent electrophysiological experiments have shown that retinal pigment epithelium (RPE) cells begin to produce neuronal-type voltage-dependent sodium currents when placed in dissociated cell culture. In this study, the sodium channel types induced in cultured rat RPE cells were identified. Sodium channel mRNAs encoding two distinct alpha subunits were detected in the cultured RPE cells, brain type II/IIA, and a novel rat mRNA which we have termed RET1. These two sodium channel types may correspond to the TTX-sensitive and TTX-insensitive components of sodium current reported previously in cultured rat RPE cells.

scholarly journals Monoterpenoid Terpinen-4-ol Exhibits Anticonvulsant Activity in Behavioural and Electrophysiological Studies

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Franklin F. F. Nóbrega ◽  
Mirian G. S. S. Salvadori ◽  
Cintia J. Masson ◽  
Carlos F. Mello ◽  
Tiago S. Nascimento ◽  
...  
Keyword(s):  
Neuronal Excitability ◽  
Sodium Current ◽  
Anticonvulsant Effect ◽  
Aromatic Plants ◽  
Gabaergic Neurotransmission ◽  
Benzodiazepine Binding ◽  
Voltage Dependent ◽  
Electrophysiological Studies ◽  
Anticonvulsant Effects

Terpinen-4-ol (4TRP) is a monoterpenoid alcoholic component of essential oils obtained from several aromatic plants. We investigated the psychopharmacological and electrophysiological activities of 4TRP in male Swiss mice and Wistar rats. 4TRP was administered intraperitoneally (i.p.) at doses of 25 to 200 mg/kg and intracerebroventricularly (i.c.v.) at concentrations of 10, 20, and 40 ng/2 μL. For in vitro experiments, 4TRP concentrations were 0.1 mM and 1.0 mM. 4TRP (i.p.) inhibited pentylenetetrazol- (PTZ-) induced seizures, indicating anticonvulsant effects. Electroencephalographic recordings showed that 4TRP (i.c.v.) protected against PTZ-induced seizures, corroborating the behavioural results. To determine whether 4TRP exerts anticonvulsant effects via regulation of GABAergic neurotransmission, we measured convulsions induced by 3-mercapto-propionic acid (3-MP). The obtained results showed involvement of the GABAergic system in the anticonvulsant action exerted by 4TRP, but flumazenil, a selective antagonist of the benzodiazepine site of theGABAAreceptor, did not reverse the anticonvulsant effect, demonstrating that 4TRP does not bind to the benzodiazepine-binding site. Furthermore, 4TRP decreased the sodium current through voltage-dependent sodium channels, and thus its anticonvulsant effect may be related to changes in neuronal excitability because of modulation of these channels.

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