scholarly journals Cultured melanotrophs of the adult rat pituitary possess a voltage-activated fast transient outward current.

1989 ◽  
Vol 411 (1) ◽  
pp. 457-468 ◽  
Author(s):  
S J Kehl
Keyword(s):  
Outward Current ◽  
Transient Outward Current ◽  
Adult Rat ◽  
Rat Pituitary ◽  
Fast Transient

Transient voltage and calcium-dependent outward currents in hippocampal CA3 pyramidal neurons

1985 ◽  
Vol 53 (4) ◽  
pp. 1038-1058 ◽  
Author(s):  
K. L. Zbicz ◽  
F. F. Weight
Keyword(s):  
Time Course ◽  
Pyramidal Neurons ◽  
Sympathetic Neurons ◽  
Outward Current ◽  
Transient Current ◽  
Transient Outward Current ◽  
Molluscan Neurons ◽  
Voltage Sensitivity ◽  
Transient Currents ◽  
Fast Transient

Membrane currents activated by step changes in membrane potential were studied in hippocampal pyramidal neurons of region CA3 using the single microelectrode voltage-clamp technique. The transient outward current activated by depolarizing steps appeared to be composed of two transient currents that could be distinguished by differences in voltage sensitivity, time course, and pharmacological sensitivity. The more slowly decaying current was activated by voltage steps positive to -60 mV and declined exponentially with a time constant between 200 and 400 ms. This current inactivated as the holding potential was made more positive over the range of -75 to -45 mV and was 50% inactivated near -60 mV. The more slowly decaying transient current was selectively blocked by 0.5 mM 4-aminopyridine (4-AP) but not by 5-10 mM tetraethylammonium (TEA) or 2-5 mM Mn2+. The second transient current had a much faster time course than the 4-AP-sensitive current, having a duration of 5-20 ms. This very fast transient current was observed during potential steps positive to -45 mV. The fast transient current was inactivated when the holding potential was made positive to -45 mV. The amplitude of the fast transient current was greatly reduced by the application of 4 mM Mn2+ or Ca2+-free artificial cerebrospinal fluid (CSF). The fast transient current appeared to be unaffected by 0.5 mM 4-AP but was greatly reduced by 10 mM TEA. These results suggest that the transient outward current observed during depolarizing steps is composed of at least two distinct transient currents. The more slowly decaying current resembles the A-current originally described in molluscan neurons (9, 32, 42) in voltage sensitivity, time course, and pharmacological sensitivity. The faster transient current resembles a fast, Ca2+-dependent transient current previously observed in bull-frog sympathetic neurons (5, 27).

Current- and Voltage-Clamp Recordings and Computer Simulations of Kenyon Cells in the Honeybee

2004 ◽  
Vol 92 (4) ◽  
pp. 2589-2603 ◽  
Author(s):  
Daniel G. Wüstenberg ◽  
Milena Boytcheva ◽  
Bernd Grünewald ◽  
John H. Byrne ◽  
Randolf Menzel ◽  
...  
Keyword(s):  
Voltage Clamp ◽  
Mushroom Body ◽  
Outward Current ◽  
Delayed Rectifier ◽  
Transient Outward Current ◽  
Insect Brain ◽  
Type Model ◽  
Kenyon Cells ◽  
Fast Transient

The mushroom body of the insect brain is an important locus for olfactory information processing and associative learning. The present study investigated the biophysical properties of Kenyon cells, which form the mushroom body. Current- and voltage-clamp analyses were performed on cultured Kenyon cells from honeybees. Current-clamp analyses indicated that Kenyon cells did not spike spontaneously in vitro. However, spikes could be elicited by current injection in approximately 85% of the cells. Of the cells that produced spikes during a 1-s depolarizing current pulse, approximately 60% exhibited repetitive spiking, whereas the remaining approximately 40% fired a single spike. Cells that spiked repetitively showed little frequency adaptation. However, spikes consistently became broader and smaller during repetitive activity. Voltage-clamp analyses characterized a fast transient Na+ current ( INa), a delayed rectifier K+ current ( IK,V), and a fast transient K+ current ( IK,A). Using the neurosimulator SNNAP, a Hodgkin–Huxley-type model was developed and used to investigate the roles of the different currents during spiking. The model led to the prediction of a slow transient outward current ( IK,ST) that was subsequently identified by reevaluating the voltage-clamp data. Simulations indicated that the primary currents that underlie spiking are INa and IK,V, whereas IK,A and IK,ST primarily determined the responsiveness of the model to stimuli such as constant or oscillatory injections of current.

Characterization of a fast transient outward current in neocortical neurons from epilepsy patients

2004 ◽  
Vol 75 (6) ◽  
pp. 807-816 ◽  
Author(s):  
C. Rüschenschmidt ◽  
R. Köhling ◽  
M. Schwarz ◽  
H. Straub ◽  
A. Gorji ◽  
...  
Keyword(s):  
Outward Current ◽  
Transient Outward Current ◽  
Neocortical Neurons ◽  
Fast Transient

Two electrophysiologically distinct types of cultured pacemaker cells from rabbit sinoatrial node

1986 ◽  
Vol 250 (2) ◽  
pp. H325-H329 ◽  
Author(s):  
R. D. Nathan
Keyword(s):  
Sinoatrial Node ◽  
Sodium Current ◽  
Outward Current ◽  
Slow Inward Current ◽  
Transient Outward Current ◽  
Type I ◽  
Pacemaker Cells ◽  
Inward Current ◽  
Fast Transient

Previous investigations employing multicellular nodal preparations (i.e., mixtures of dominant and subsidiary pacemaker cells) have suggested that the fast transient inward sodium current (iNa) either is not present in dominant pacemaker cells or is present but inactivated at the depolarized take-off potentials that these cells exhibit. In the present study, this question was resolved by voltage clamp analysis of single pacemaker cells isolated from the sinoatrial node and maintained in vitro for 1-3 days. Two types of cells, each with a different morphology, exhibited two modes of electrophysiological behavior. Type I cells (presumably dominant pacemakers) displayed only a tetrodotoxin (TTX)-resistant (but cadmium-sensitive) slow inward current, whereas type II cells (presumably subsidiary pacemakers) exhibited two components of inward current, a TTX-sensitive, fast transient inward current and a TTX-resistant (but cadmium-sensitive) slow inward current. Three other voltage-gated currents, 1) a slowly developing inward current activated by hyperpolarization (if, ih, delta ip), 2) a transient outward current activated by strong depolarization (ito, iA), and 3) a delayed outward current, were recorded in both types of pacemaker cells.

scholarly journals Diverse Ionic Currents and Electrical Activity of Cultured Myenteric Neurons From the Guinea Pig Proximal Colon

2000 ◽  
Vol 83 (3) ◽  
pp. 1253-1263 ◽  
Author(s):  
Fivos Vogalis ◽  
Kirk Hillsley ◽  
Terence K. Smith
Keyword(s):  
Patch Clamp ◽  
Guinea Pig ◽  
Action Potential ◽  
Action Potentials ◽  
Outward Current ◽  
Proximal Colon ◽  
Equilibrium Potential ◽  
Transient Outward Current ◽  
Myenteric Neurons ◽  
Fast Transient

The aim of this study was to perform a patch-clamp analysis of myenteric neurons from the guinea pig proximal colon. Neurons were enzymatically dispersed, cultured for 2–7 days, and recorded from using whole cell patch clamp. The majority of cells fired phasically, whereas about one-quarter of the neurons fired in a tonic manner. Neurons were divided into three types based on the currents activated. The majority of tonically firing neurons lacked an A-type current, but generated a large fast transient outward current that was associated with the rapid repolarizing phase of an action potential. The fast transient outward current was dependent on calcium entry and was blocked by tetraethylammonium. Cells that expressed both an A-type current and a fast transient outward current were mostly phasic. Depolarization of these cells to suprathreshold potentials from less than −60 mV failed to trigger action potentials, or action potentials were only triggered after a delay of >50 ms. However, depolarizations from more positive potentials triggered action potentials with minimal latency. Neurons that expressed neither the A-type current or the fast transient outward current were all phasic. Sixteen percent of neurons were similar to AH/type II neurons in that they generated a prolonged afterhyperpolarization following an action potential. The current underlying the prolonged afterhyperpolarization showed weak inward rectification and had a reversal potential near the potassium equilibrium potential. Thus cultured isolated myenteric neurons of the guinea pig proximal colon retain many of the diverse properties of intact neurons. This preparation is suitable for further biophysical and molecular characterization of channels expressed in colonic myenteric neurons.

Modulation of the transient outward current in adult rat ventricular myocytes by polyunsaturated fatty acids

1998 ◽  
Vol 274 (2) ◽  
pp. H571-H579 ◽  
Author(s):  
K. Y. Bogdanov ◽  
H. A. Spurgeon ◽  
T. M. Vinogradova ◽  
E. G. Lakatta
Keyword(s):  
Fatty Acids ◽  
Polyunsaturated Fatty Acids ◽  
Ventricular Myocytes ◽  
Outward Current ◽  
Transient Outward Current ◽  
Patch Clamp Technique ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Low Concentrations ◽  
High Concentrations

With the whole cell patch-clamp technique, we studied the effects of the n-3 and n-6 polyunsaturated fatty acids (PUFAs), linoleic (C18:2n-6), eicosapentaenoic (C20:4n-3), docosahexaenoic (C22:5n-3), and arachidonic (AA; C20:4n-6) acids, on K+ currents in rat ventricular myocytes. At low concentrations (5–10 μM) all PUFAs except AA inhibited, by ∼40%, the transient outward current ( I to) without affecting other K+ currents and markedly prolonged the action potential (AP). AA inhibited I to but also augmented a sustained depolarization-induced outward K+ current ( I sus); the latter effect did not occur in the presence of 4-aminopyridine or with eicosatetraynoic acid, a nonmetabolizable analog of AA. Higher concentrations of PUFAs (20–50 μM) further inhibited I to and also inhibited I sus. Thus, at high concentrations, PUFAs have a nonspecific effect on several K+ channels; at low concentrations, PUFAs preferentially inhibit I to and prolong the AP.

A fast transient outward current in cultured cells from human pulmonary artery smooth muscle

1995 ◽  
Vol 268 (6) ◽  
pp. H2358-H2365 ◽  
Author(s):  
A. F. James ◽  
T. Okada ◽  
M. Horie
Keyword(s):  
Smooth Muscle ◽  
Pulmonary Artery ◽  
Outward Current ◽  
Transient Outward Current ◽  
Pipette Solution ◽  
Dependent Inactivation ◽  
Voltage Dependent ◽  
Pulmonary Artery Smooth Muscle ◽  
Fast Transient ◽  
Human Pulmonary Artery

A voltage-dependent transient outward current (I(to)) was observed in cells cultured from human pulmonary artery smooth muscle when K+, but not Cs+, was the dominant cation in the pipette solution. In 30% of cells investigated using the Cs+ pipette solution, a tetrodotoxin-sensitive inward current (I(in)) dependent on extracellular Na+ was evoked from depolarizations positive to -30 mV.Iin showed voltage-dependent inactivation with a membrane potential at 50% of the evoked current (V50%) of -75.53 +/- 0.81 mV and slope factor potential (Vs) of -10.73 +/- 0.01 mV. In the presence of 1 microM tetrodotoxin, I(to) was rapidly evoked by depolarizations positive to -40 mV and decayed with a single exponential time course (tau = 9.9 +/- 1.1 ms, pulse potential = +50 mV). I(to) also showed voltage-dependent inactivation with a V50% of -70.9 +/- 2.63 mV and Vs of -7.7 +/- 0.03 mV. I(to) was inhibited concentration dependently by the K+ channel blocker, 4-aminopyridine (4-AP), with a concentration of 4-AP at which I(to) was reduced to 50% of control of 36.5 +/- 2.8 microM. These cells possess voltage-dependent currents characteristic of the K(+)-selective fast transient outward and Na(+)-selective inward currents of smooth muscle cells.

A fast transient outward current in layer II/III neurons of rat perirhinal cortex

2007 ◽  
Vol 455 (3) ◽  
pp. 515-525 ◽  
Author(s):  
G. R. Biella ◽  
P. Spaiardi ◽  
R. Jimenez-Moreno ◽  
J. Magistretti ◽  
V. Taglietti ◽  
...  
Keyword(s):  
Outward Current ◽  
Perirhinal Cortex ◽  
Transient Outward Current ◽  
Fast Transient
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