M-current and its role in neuronal physiology

Published on February 28, 2011 Updated on May 1, 2020   39 min

Other Talks in the Series: Ion Channels

0:00
Hello, my name is David Brown. I'm a professor of pharmacology, Department of Neuroscience, Physiology, and Pharmacology at University College London. I'm going to talk to you about the-M current and its role in neuronal physiology.
0:14
What is the M-current? It's a species of voltage-gated potassium current. It was first seen in frog neurons, but is present in many mammalian and human peripheral and central neurons, and in the nerve fibres. It is inhibited by stimulating muscarinic acetylcholine receptors, that's how it got its name 'M', though in fact it can be inhibited by stimulating other receptors so long as they're linked to the G-protein, Gq. Channels are composed of subunits of the Kv7 family, mainly Kv7.2 and 7.3. The function is to stabilise membrane potential and to control excitability, so that when the current is inhibited, neurons are depolarised and they show an increased excitability. In this talk, I'll illustrate these points with some pictures of experimental recordings, just to give you a feel for how the current works, and how it affects nerve cell behavior.
1:09
This shows one of our original recordings of the M-current in a frog sympathetic neuron, made using a dual electro-voltage clamp. One electrode sets the voltage, and the other one monitors the membrane current. In the record on the right, the cell membrane potential is held at -60 millivolts to start with, and then it's set for one second to -30 millivolts. This generates the outward current shown by the arrow. It has two main features, firstly, it activates rather slowly over tens or hundreds of milliseconds. Secondly, it does not show the inactivation characteristic of many other voltage-gated potassium currents, as, once switched on, the current stays on for many seconds or minutes, generating a steady outward current.
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M-current and its role in neuronal physiology

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