The effect of phloretin on single potassium channels in myelinated nerve

1992 ◽  
Vol 21 (2) ◽  
Author(s):  
J. Klusemann ◽  
H. Meves
Keyword(s):  
Potassium Channels ◽  
Myelinated Nerve

scholarly journals The Inner Quaternary Ammonium Ion Receptor in Potassium Channels of the Node of Ranvier

1972 ◽  
Vol 59 (4) ◽  
pp. 388-400 ◽  
Author(s):  
Clay M. Armstrong ◽  
Bertil Hille
Keyword(s):  
Potassium Channels ◽  
Quaternary Ammonium ◽  
Node Of Ranvier ◽  
Nerve Fibers ◽  
Ammonium Ion ◽  
Ammonium Ions ◽  
Myelinated Nerve ◽  
Quaternary Ammonium Ions ◽  
Activation Gate ◽  
Almost All

Quaternary ammonium ions were applied to the inside of single myelinated nerve fibers by diffusion from a cut end. The resulting block of potassium channels in the node of Ranvier was studied under voltage-clamp conditions. The results agree in almost all respects with similar studies by Armstrong of squid giant axons. With tetraethylammonium ion (TEA), pentyltriethylammonium ion (C5), or nonyltriethylammonium ion (C9) inside the node, potassium current during a depolarization begins to rise at the normal rate, reaches a peak, and then falls again. This unusual inactivation is more complete with C9 than with TEA. Larger depolarizations give more block. Thus the block of potassium channels grows with time and voltage during a depolarization. The block reverses with repolarization, but for C9 full reversal takes seconds at -75 mv. The reversal is faster in 120 mM KCl Ringer's and slower during a hyperpolarization to -125 mv. All of these effects contrast with the time and voltage-independent block of potassium, channels seen with external quaternary ammonium ions on the node of Ranvier. External TEA, C5, and C9 block without inactivation. The external quaternary ammonium ion receptor appears to be distinct from the inner one. Apparently the inner quaternary ammonium ion receptor can be reached only when the activation gate for potassium channels is open. We suggest that the inner receptor lies within the channel and that the channel is a pore with its activation gate near the axoplasmic end.

scholarly journals Charges and Potentials at the Nerve Surface

1968 ◽  
Vol 51 (2) ◽  
pp. 221-236 ◽  
Author(s):  
Bertil Hille
Keyword(s):  
Potassium Channels ◽  
Sodium Channels ◽  
Voltage Dependence ◽  
Divalent Cations ◽  
Fold Increase ◽  
Nerve Fibers ◽  
Hydrogen Ions ◽  
Acidic Group ◽  
Myelinated Nerve ◽  
Bathing Medium

The voltage dependence of the voltage clamp responses of myelinated nerve fibers depends on the concentration of divalent cations and of hydrogen ions in the bathing medium. In general, increases of the [Ca], [Ni], or [H] increase the depolarization needed to elicit a given response of the nerve. An e-fold increase of the [Ca] produces the following shifts of the voltage dependence of the parameters in the Hodgkin-Huxley model: m∞, 8.7 mv; h∞, 6.5 mv; τn, 0.0 mv. The same increase of the [H], if done below pH 5.5, produces the following shifts: m∞, 13.5 mv; h∞, 13.5 mv; τn, 13.5 mv; and if done above pH 5.5: m∞, 1.3 mv; h∞, 1.3 mv; τn, 4.0 mv. The voltage shifts are proportional to the logarithm of the concentration of the divalent ions and of the hydrogen ion. The observed voltage shifts are interpreted as evidence for negative fixed charges near the sodium and potassium channels. The charged groups are assumed to comprise several types, of varying affinity for divalent and hydrogen ions. The charges near the sodium channels differ from those near the potassium channels. As the pH is lowered below pH 6, the maximum sodium conductance decreases quickly and reversibly in a manner that suggests that the protonation of an acidic group with a pKa of 5.2 blocks individual sodium channels.

Sodium and potassium channels in regenerating and developing mammalian myelinated nerves

1982 ◽  
Vol 215 (1200) ◽  
pp. 273-287 ◽  
Keyword(s):  
Potassium Channels ◽  
Action Potential ◽  
Sodium Channels ◽  
Unit Length ◽  
Nerve Fibres ◽  
Myelinated Nerve ◽  
Complementary Distribution ◽  
Myelinated Nerves ◽  
Sodium And Potassium ◽  
Regenerating Nerve

A study has been made of how the normal complementary distribution of sodium and potassium channels in mammalian myelinated nerve fibres (all the sodium channels being in the node with all the potassium channels in the internode) is altered in regenerating and in developing rabbit sciatic nerves. In regenerating nerve fibres, where a marked increase in the number of nodes per unit length occurs, there is a corresponding increase in the sodium channel content (determined from the maximum saturable binding of labelled saxitoxin), consistent with the idea that the number of sodium channels per node remains roughly constant. The use of 4-aminopyridine, which by blocking potassium channels prolongs the action potential, has shown that both in regenerating nerve fibres and in developing nerve fibres potassium currents contribute to the mammalian action potential. In both cases, with the passage of time, the sensitivity to 4-aminopyridine progressively decreases.

Quinidine blocking of sodium and potassium channels in myelinated nerve fibers

1983 ◽  
Vol 14 (3) ◽  
pp. 244-250
Author(s):  
S. V. Revenko ◽  
B. I. Khodorov ◽  
L. M. Shapovalova
Keyword(s):  
Potassium Channels ◽  
Nerve Fibers ◽  
Myelinated Nerve ◽  
Myelinated Nerve Fibers ◽  
Sodium And Potassium

On the physiological role of internodal potassium channels and the security of conduction in myelinated nerve fibres

1984 ◽  
Vol 220 (1221) ◽  
pp. 415-422 ◽  
Keyword(s):  
Electrical Properties ◽  
Potassium Channels ◽  
Theoretical Analysis ◽  
Physiological Role ◽  
Resting Potential ◽  
Nerve Fibres ◽  
Myelinated Nerve ◽  
Voltage Dependent ◽  
Passive Electrical Properties

A theoretical analysis of the passive electrical properties of normal myelinated nerve suggests that the function of the voltage-dependent potassium channels in the internodal axolemma under the myelin sheath is to permit the generation of an internodal resting potential. Calculation shows that if this internodal potential were not present, the nodal potential would be reduced (by electrotonic short-circuiting) thus impairing the security of conduction. This impairment is particularly pronounced with smaller diameter fibres.

The effects of oxaliplatin, an anticancer drug, on potassium channels of the peripheral myelinated nerve fibres of the adult rat

2008 ◽  
Vol 29 (6) ◽  
pp. 1100-1106 ◽  
Author(s):  
Alexia Kagiava ◽  
Anastasia Tsingotjidou ◽  
Christos Emmanouilides ◽  
George Theophilidis
Keyword(s):  
Potassium Channels ◽  
Anticancer Drug ◽  
Nerve Fibres ◽  
Myelinated Nerve ◽  
Adult Rat
Sign in / Sign up

Export Citation Format

Share Document