scholarly journals Large-Conductance Calcium-Activated Potassium Channels and Voltage-Dependent Sodium Channels in Human Cementoblasts

2021 ◽  
Vol 12 ◽  
Author(s):  
Satomi Kamata ◽  
Maki Kimura ◽  
Sadao Ohyama ◽  
Shuichiro Yamashita ◽  
Yoshiyuki Shibukawa
Keyword(s):  
Alveolar Bone ◽  
Attachment Site ◽  
Ionic Currents ◽  
Ionic Channels ◽  
Patch Clamp Recording ◽  
Physiological Processes ◽  
Whole Cell Patch Clamp ◽  
Outward Currents ◽  
Voltage Dependent ◽  
Inward Currents

Cementum, which is excreted by cementoblasts, provides an attachment site for collagen fibers that connect to the alveolar bone and fix the teeth into the alveolar sockets. Transmembrane ionic signaling, associated with ionic transporters, regulate various physiological processes in a wide variety of cells. However, the properties of the signals generated by plasma membrane ionic channels in cementoblasts have not yet been described in detail. We investigated the biophysical and pharmacological properties of ion channels expressed in human cementoblast (HCEM) cell lines by measuring ionic currents using conventional whole-cell patch-clamp recording. The application of depolarizing voltage steps in 10 mV increments from a holding potential (Vh) of −70 mV evoked outwardly rectifying currents at positive potentials. When intracellular K+ was substituted with an equimolar concentration of Cs+, the outward currents almost disappeared. Using tail current analysis, the contributions of both K+ and background Na+ permeabilities were estimated for the outward currents. Extracellular application of tetraethylammonium chloride (TEA) and iberiotoxin (IbTX) reduced the densities of the outward currents significantly and reversibly, whereas apamin and TRAM-34 had no effect. When the Vh was changed to −100 mV, we observed voltage-dependent inward currents in 30% of the recorded cells. These results suggest that HCEM express TEA- and IbTX-sensitive large-conductance Ca2+-activated K+ channels and voltage-dependent Na+ channels.

Activation of subfornical organ neurons in rats through pre- and postsynaptic α-adrenoceptors

2006 ◽  
Vol 290 (6) ◽  
pp. R1646-R1653 ◽  
Author(s):  
Eiko Honda ◽  
Kentaro Ono ◽  
Shinji Kataoka ◽  
Kiyotoshi Inenaga
Keyword(s):  
Gaba Receptor ◽  
Membrane Conductance ◽  
Subfornical Organ ◽  
Patch Clamp Recording ◽  
Pcr Assay ◽  
Whole Cell Patch Clamp ◽  
Outward Currents ◽  
Current Clamp Mode ◽  
Inward Currents ◽  
Pulse Stimulation

The effects of noradrenaline (NA) and its analogs on subfornical organ (SFO) neurons in rat slice preparations were investigated by using whole cell patch-clamp recording. In the current-clamp mode, the application of NA at 10–100 μM produced membrane depolarization (63%, 17 responsive neurons/27 neurons tested) and hyperpolarization (22%, 6/27 neurons). In the voltage-clamp mode, NA application at 1–100 μM produced inward currents (69%, 42/61 neurons) and outward currents (23%, 14/61 neurons). These currents remained in the presence of TTX or both glutamate and GABA receptor antagonists. In most of the neurons (25/31 neurons) showing inward currents in the presence of NA, the membrane conductance was not changed by voltage ramps or hyperpolarizing pulse stimulation. Similar responses were obtained by the application of the α1-agonist phenylephrine. The phenylephrine-induced inward currents were inhibited by the α1-antagonist prazosin. The α2-agonist clonidine decreased the frequency of spontaneous GABAergic inhibitory postsynaptic currents (4/10 neurons). In addition, RT-PCR assay and immunohistochemical staining showed the existence of α1-adrenoceptors in the SFO. The results suggest that SFO neurons in rats are activated postsynaptically through α1-adrenoceptors and that the activation is enhanced by suppressing GABAergic inhibitory synaptic inputs through presynaptic α2-adrenoceptors.

Ionic basis of electrical activity in cardiac tissues

1978 ◽  
Vol 234 (2) ◽  
pp. H101-H116 ◽  
Author(s):  
E. Coraboeuf
Keyword(s):  
Electrical Activity ◽  
Electrical Coupling ◽  
Ionic Currents ◽  
Ionic Channels ◽  
Cardiac Cells ◽  
Potential Range ◽  
Cardiac Tissues ◽  
Cardiac Electrical Activity ◽  
Outward Currents ◽  
Inward Currents

Cardiac electrical events are described in terms of membrane physiology. The concept that cardiac membranes possess specific ionic channels controlled by gates bearing electrical charges is discussed. When open, these channels permit ions to cross the membrane, giving rise to passive inward (depolarizing) and outward (repolarizing) currents. Two different inward and four or five different outward currents appear to be responsible for the development of cardiac electrical activity; both inward currents appear to be controlled by activation and inactivation variables, whereas outward currents are essentially controlled by activation variables and/or inward-going rectifiers. The potential range in which the different currents activate and inactivate (or are limited by inward-going rectification), and the kinetics of activation and inactivation processes explain the development of electrical activity in normal cardiac tissues and in partially depolarized fibers. In addition to passive ionic currents, electrogenic active transport participates in the development of electrical phenomena. The conductance of the membrane for potassium ions and the electrical coupling between cardiac cells depend on the intracellular concentration of calcium ions.

Ionic currents of the lateral pyloric neuron of the stomatogastric ganglion of the crab

1992 ◽  
Vol 67 (2) ◽  
pp. 318-331 ◽  
Author(s):  
J. Golowasch ◽  
E. Marder
Keyword(s):  
Ionic Currents ◽  
Stomatogastric Ganglion ◽  
Delayed Rectifier ◽  
Delayed Rectifier Current ◽  
Outward Currents ◽  
Ionic Conductances ◽  
Voltage Dependent ◽  
Inward Currents ◽  
K Current ◽  
Direct Target

1. The lateral pyloric (LP) neuron is an important component of the network that generates the pyloric rhythm of the stomatogastric ganglion (STG) and is a direct target of many modulatory inputs to the STG. Our aim in this and the subsequent two papers is to describe the conductances present in this cell and to understand the role these conductances play in shaping the activity of the neuron. 2. LP neurons were studied in two-electrode voltage clamp (TEVC) in a saline solution containing tetrodotoxin (TTX) and picrotoxin (PTX) to isolate them pharmacologically from presynaptic inputs. 3. We identified six voltage-dependent ionic conductances. These include three outward currents that resemble a delayed rectifier current, a Ca(2+)-activated K+ current and an A-current similar to those seen in many other preparations. LP neurons show three inward currents, a fast TTX-sensitive current, a hyperpolarization-activated inward current, and a Ca2+ current.

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.

Voltage-gated currents of rabbit A- and B-type horizontal cells in retinal monolayer cultures

1994 ◽  
Vol 11 (2) ◽  
pp. 369-378 ◽  
Author(s):  
Stefan Löhrke ◽  
Hans-Dieter Hofmann
Keyword(s):  
Single Channel ◽  
Ionic Currents ◽  
Calcium Currents ◽  
Horizontal Cells ◽  
Delayed Rectifier ◽  
Patch Clamp Recording ◽  
Voltage Gated ◽  
Monolayer Cultures ◽  
Inward Currents

AbstractIn monolayer cultures prepared from immature early postnatal rabbit retina, small populations of neurons can be demonstrated to differentiate into apparently mature A- and B-type horizontal cells. Using wholecell, single-channel, patch-clamp recording techniques, we have analyzed the pattern of voltage-gated conductances expressed by mammalian horizontal cells under these conditions. A total of six different voltage-dependent ionic currents were recorded. Tetrodotoxin-sensitive fast sodium inward currents (INa) were found in 81% of the A-type and 90% of the B-type cells. Inward calcium currents could be demonstrated in all cells tested after blockade of other conductances. Two types of outward potassium currents with properties of the 4–aminopyridine-sensitive transient IA and the tetraethylammonium sensitive delayed rectifier IK, respectively, could be characterized in whole-cell recordings. An inward rectifying potassium current (Ianom) typical for horizontal cells was activated in response to hyperpolarizing voltage steps. These types of currents have also been described in dissociated adult horizontal cells from lower vertebrates and cat. With single-channel recordings on inside-out patches excised from B-type cells, an additional Ca2+-dependent current (IK(Ca)) was observed which, so far, has not been described in horizontal cells developing in situ. Our results demonstrate that cultured rabbit horizontal cells express a set of voltage-gated currents which largely, but not completely, corresponds to that described in situ for horizontal cells of other species. The culture system will allow further investigation of developmental and functional aspects of mammalian horizontal cells.

Local Excitatory Circuits in the Intermediate Gray Layer of the Superior Colliculus

1999 ◽  
Vol 81 (3) ◽  
pp. 1424-1427 ◽  
Author(s):  
Diana L. Pettit ◽  
Matthew C. Helms ◽  
Psyche Lee ◽  
George J. Augustine ◽  
William C. Hall
Keyword(s):  
Superior Colliculus ◽  
Intermediate Layer ◽  
Tree Shrew ◽  
Patch Clamp Recording ◽  
Inward Current ◽  
Whole Cell Patch Clamp ◽  
Synaptic Interactions ◽  
Layer Neuron ◽  
Inward Currents ◽  
Synaptic Responses

Local excitatory circuits in the intermediate gray layer of the superior colliculus. We have used photostimulation and whole cell patch-clamp recording techniques to examine local synaptic interactions in slices from the superior colliculus of the tree shrew. Uncaging glutamate 10–75 μm from the somata of neurons in the intermediate gray layer elicited a long-lasting inward current, due to direct activation of glutamate receptors on these neurons, and brief inward currents caused by activation of presynaptic neurons. The synaptic responses occurred as individual currents or as clusters that lasted up to several hundred milliseconds. Excitatory synaptic responses, which reversed at membrane potentials near 0 mV, could be evoked by uncaging glutamate anywhere within 75 μm of an intermediate layer neuron. Our results indicate the presence of extensive local excitatory circuits in the intermediate layer of the superior colliculus and support the hypothesis that such intrinsic circuitry contributes to the development of presaccadic command bursts.

The effects of glycine and GABA on isolated horizontal cells from the salamander retina

1991 ◽  
Vol 66 (6) ◽  
pp. 2002-2013 ◽  
Author(s):  
T. A. Gilbertson ◽  
S. Borges ◽  
M. Wilson
Keyword(s):  
Horizontal Cell ◽  
Horizontal Cells ◽  
Gamma Aminobutyric Acid ◽  
Light Responses ◽  
Whole Cell Patch Clamp ◽  
Synaptic Interactions ◽  
Outward Currents ◽  
Na Currents ◽  
Inward Currents ◽  
Kinetics Of

1. Horizontal cells, identified by their morphology, were isolated from the salamander retina and examined in whole cell patch clamp. 2. All cells showed large outward currents activating positive to about -50 mV, and a minority of cells showed fast, tetrodotoxin-suppressible Na+ currents. Slow inward currents that might shape the light responses were never observed. 3. All cells showed conductance increases to both gamma-aminobutyric acid (GABA) and glycine that were completely blocked by bicuculline and strychnine, respectively. No cross-blocking by these antagonists was observed. Partial replacements of Cl- with large, impermeant anions indicated that both GABA- and glycine-evoked currents were carried by Cl- ions. 4. Responses to both GABA and glycine desensitized strongly with time constants of approximately 2 s. 5. Responses to glutamate were not enhanced by glycine. Similarly, responses to GABA were not enhanced by glutamate. 6. GABA-mediated synaptic interactions between horizontal cells may account for the changes in the kinetics of horizontal cell light responses seen when glycine is applied to the intact retina.

Segment-specific effects of FMRFamide on membrane properties of heart interneurons in the leech

1995 ◽  
Vol 74 (4) ◽  
pp. 1485-1497 ◽  
Author(s):  
J. Schmidt ◽  
S. Gramoll ◽  
R. L. Calabrese
Keyword(s):  
Outward Current ◽  
Membrane Conductance ◽  
Membrane Properties ◽  
Inward Current ◽  
Specific Effects ◽  
Outward Currents ◽  
Voltage Dependent ◽  
Inward Currents ◽  
K Current ◽  
Conductance Increase

1. The effects of Phe-Met-Arg-Phe (FMRF)amide (10(-6) M) on membrane properties of heart interneurons in the third, fourth, and fifth segmental ganglia [HN(3), HN(4), and HN(5) cells, respectively] of the leech were studied using discontinuous current-clamp and single-electrode voltage-clamp techniques. FMRFamide was focally applied onto the soma of the cell under investigation. 2. Application of FMRFamide depolarized HN(3) and HN(4) cells by evoking an inward current. These responses were subject to pronounced desensitization. The inward currents evoked by application of FMRFamide were associated with an increase in membrane conductance and appeared to be voltage dependent. Currents were enhanced at more depolarized potentials. 3. The responsiveness of the HN(3) and HN(4) cells was not affected when the Ca2+ concentration in the bath saline was reduced from normal (1.8 mM) to 0.1 mM. The depolarizing response on application of FMRFamide was blocked when Co2+ was substituted for Ca2+. 4. HN(3) and HN(4) cells did not respond to FMRFamide application in Na(+)-free solution. Inward currents were largely reduced when bath saline with 30% of the normal Na+ concentration was used. When Li+ was substituted for Na+ in the saline, application of FMRFamide still evoked depolarizing responses in HN(3) and HN(4) cells. 5. We conclude that focal application of FMRFamide onto the somata of HN(3) and HN(4) cells evokes a voltage-dependent inward current, carried largely by Na+. 6. Focal application of FMRFamide onto somata of HN(5) cells hyperpolarized these cells by activating a voltage-dependent outward current. 7. HN(5) cells were loaded with Cl- until inhibitory postsynaptic potentials carried by Cl- reversed. Cl(-)-loaded cells still responded with a hyperpolarization when FMRFamide was applied onto their somata. Therefore the outward current evoked by FMRFamide appears to be mediated by a K+ conductance increase. 8. Application of FMRFamide onto the somata of HN(5) cells enhanced outward currents that were evoked by depolarizing voltage steps from a holding potential of -45 mV. 9. We conclude that the hyperpolarizing response of HN(5) cells to focal application of FMRFamide onto their somata is the result of an up-regulation of a voltage-dependent K+ current.

scholarly journals Voltage-dependent conductances in Limulus ventral photoreceptors.

1982 ◽  
Vol 79 (2) ◽  
pp. 187-209 ◽  
Author(s):  
J E Lisman ◽  
G L Fain ◽  
P M O'Day
Keyword(s):  
Outward Current ◽  
Delayed Rectifier ◽  
Molluscan Neurons ◽  
Inward Current ◽  
Transient Component ◽  
Outward Currents ◽  
Voltage Dependent ◽  
Inward Currents ◽  
K Current ◽  
A Current

The voltage-dependent conductances of Limulus ventral photoreceptors have been investigated using a voltage-clamp technique. Depolarization in the dark induces inward and outward currents. The inward current is reduced by removing Na+ or Ca2+ and is abolished by removing both ions. These results suggest that both Na+ and Ca2+ carry voltage-dependent inward current. Inward current is insensitive to tetrodotoxin but is blocked by external Ni2+. The outward current has a large transient component that is followed by a smaller maintained component. Intracellular tetraethylammonium preferentially reduces the maintained component, and extracellular 4-amino pyridine preferentially reduces the transient component. Neither component is strongly affected by removal of extracellular Ca2+ or by intracellular injection of EGTA. It is concluded that the photoreceptors contain at least three separate voltage-dependent conductances: 1) a conductance giving rise to inward currents; 2) a delayed rectifier giving rise to maintained outward K+ current; and 3) a rapidly inactivating K+ conductance similar to the A current of molluscan neurons.

Serotonergic modulation of neuronal activity in rat midbrain periaqueductal gray

2013 ◽  
Vol 109 (11) ◽  
pp. 2712-2719 ◽  
Author(s):  
Hyo-Jin Jeong ◽  
Karen Lam ◽  
Vanessa A. Mitchell ◽  
Christopher W. Vaughan
Keyword(s):  
Brain Slices ◽  
Periaqueductal Gray ◽  
Membrane Excitability ◽  
Inhibitory Effects ◽  
Whole Cell Patch Clamp ◽  
Outward Currents ◽  
Selective Ligands ◽  
Inward Currents ◽  
Subtype Selective ◽  
Serotonergic Modulation

Serotonin (5-HT) modulates pain and anxiety from within the midbrain periaqueductal gray (PAG). In the present study, the effects of 5-HT- and 5-HT1/2 subtype-selective ligands on rat PAG neurons were examined using whole cell patch-clamp recordings in brain slices. In voltage clamp, 5-HT produced outward and inward currents in distinct subpopulations of neurons that varied throughout different subregions of the PAG. The 5-HT1A agonist R(+)-8-OH-DPAT (1 μM) produced outward currents in subpopulations of PAG neurons. By contrast, sumatriptan (1 μM) and other 5-HT1B, -D, and -F subtype agonists had little or no postsynaptic activity. The 5-HT2A/C agonists DOI (3 μM) and TCB-2 (1 μM) produced inward currents in subpopulations of PAG neurons, and DOI enhanced evoked inhibitory postsynaptic currents via a presynaptic mechanism. In current clamp, both R(+)-8-OH-DPAT and sumatriptan produced an excitatory increase in evoked mixed postsynaptic potentials (PSPs). In addition, R(+)-8-OH-DPAT, but not sumatriptan, directly hyperpolarized PAG neurons. By contrast, the 5-HT2 agonist DOI depolarized subpopulations of neurons and produced an inhibitory decrease in evoked mixed PSPs. These findings indicate that 5-HT1A and 5-HT1B/D ligands have partly overlapping inhibitory effects on membrane excitability and synaptic transmission within the PAG, which are functionally opposed by 5-HT2A/C actions in specific PAG subregions.

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