Evidence for the presence of two types of potassium channels in the rat optic nerve

doi:10.1016/0006-8993(88)90959-6

Brain Research

Volume 447, Issue 1, 26 April 1988, Pages 1-9

https://doi.org/10.1016/0006-8993(88)90959-6 Get rights and content

Abstract

Single axon and whole nerve recording techniques were used to study the effects of 4-aminopyridine (4-AP) and tetraethylammonium (TEA) on action potential waveform and firing characteristics of rat optic nerve. 4-AP led to action potential broadening and a pronounced afterhyperpolarization (AHP) several hundreds of milliseconds in duration. In addition, some fibers showed repetitive firing and a prolonged depolarization immediately following the spike. Whole nerve sucrose gap recordings obtained in the presence of 4-AP showed action potential broadening followed by a postspike positivity indicative of intracellular hyperpolarization. The time course of the postspike positivity was similar to that of the AHP seen in single fiber recordings. TEA alone had little effect on action potential waveform, but reversibly blocked the 4-AP-induced postspike positivity. These findings indicate the presence of two pharmacologically distinct potassium channels on myelinated axons of the rat optic nerve, one sensitive to 4-AP and the other to TEA. These channels appear to have different functional roles, the 4-AP-sensitive channel participating in action potential repolarization, and the TEA-sensitive channel modulating repetitive firing patterns.

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Research reportEvidence for the presence of two types of potassium channels in the rat optic nerve

Abstract

Biophys. J.

Dev. Brain Res.

Neurosci. Lett.

Brain Research

Dev. Brain Res.

Exp. Neurol.

Brain Research

M-currents and other potassium currents in bullfrog sympathetic neurones

J. Physiol. (London)

Voltage-dependent currents of vertebrate neurons and their role in membrane excitability

Adv. Neurol.

Function and distribution of three types of rectifying channel in rat spinal root myelinated axons

J. Physiol. (London)

Application of the sucrose-gap method to determine the ionic basis of the membrane potential of smooth muscle

J. Physiol. (London)

The effects of 4-aminopyridine and tetraethylammonium ions on normal and demyelinated mammalian nerve fibers

J. Physiol. (London)

Potential clamp analysis of membrane currents in rat myelinated nerve fibers

J. Physiol. (London)

Electrical properties of isolated demyelinated rat nerve fibres

Acta Physiol. Scand.

Potassium channels in nodal and internodal axonal membranes of mammalian myelinated fibres

Nature (London)

Evidence for the presence of potassium channels in the paranodal region of acutely demyelinated mammalian single nerve fibres

J. Physiol. (London)

Evidence for the presence of potassium channels in the internode of frog myelinated nerve fibres

J. Physiol. (London)

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

A quantitative description of membrane currents in rabbit myelinated nerve

J. Physiol. (London)

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Research report
Evidence for the presence of two types of potassium channels in the rat optic nerve