Potassium Channels and Their Role in Pain

This set of flashcards covers the fundamental types, structures, and physiological roles of potassium (K+) channels, with a specific focus on their involvement in pain pathways and nociception.

Ligand-gated channel

A type of channel that opens or closes in response to a specific extracellular ligand.

Signal-gated channel

A type of channel that opens or closes in response to a specific intracellular molecule.

Leakage channel

A channel that is always open and helps set the baseline membrane potential.

Voltage-gated channel

A channel that opens transiently in response to changes in membrane voltage.

Na+/K+ ATPase

Also known as the sodium pump, it maintains high $K^+$ inside the cell and high $Na^+$ outside the cell.

Electrochemical gradient

Stored energy arising from the asymmetric distribution of charges and ion concentrations across the membrane.

Resting membrane potential (RMP)

The stable voltage across the membrane when the neuron is not firing, typically $-70\,mV$.

Firing threshold

The membrane potential level, approximately $-55\,mV$, required to trigger an action potential.

2TM/P channels

A class of K+ channels characterized as inwardly rectifying, such as the bacterial channel $KcsA$.

4TM/2P channels

Also called 'leakage' channels, these consist of two repeats of 2TM/P channels and are targets for numerous anaesthetics.

6TM/P channels

The predominant class among ligand-gated and voltage-gated K+ channels.

Selective filter

An essential part of the potassium channel structure that allows only specific ions to pass through the pore.

S4 segment

The specific domain within voltage-gated channels that acts as the voltage sensor.

S6 segment

The part of the pore domain that forms the bundle crossing at the intracellular side of the potassium channel.

Kv3 channels

High voltage-activated channels primarily involved in action potential repolarization.

Kv1, Kv4, and Kv7 channels

Low voltage-activated channels that typically respond at the action potential threshold.

Delayed Rectifier

The specific activity provided by $Kv2$ channels during an action potential.

Nociception

The physiological process resulting in the perception of pain, involving transduction, transmission, and modulation.

Kv3.4 hyperphosphorylation

A process triggered by the upregulation of PKC that reduces surface expression of channels, contributing to pain.

KCNG4

The gene that encodes the voltage-gated potassium channel $Kv6.4$ subunit, which influences human labor pain.

p.Val419Met

A missense change in $Kv6.4$ caused by a rare allele that impairs the function of $Kv2.1$ heterotetramers, increasing pain tolerance.

K2P channels

Channels that provide a constant outward current to stabilize the membrane and prevent spontaneous firing.

TREK channels

A type of K2P channel that detects mechanical and thermal stimuli; loss of function leads to hyperresponsiveness.