MODULATING M POTASSIUM CHANNELS
Potassium channels have an important role in regulating the excitability of neurons, which in turn regulate many potassium channels by neurotransmitters. One of the first transmitter-regulated channel to be identified was the M channel (its activity was inhibited through stimulation of muscarinic acetylcholine receptors: M = muscarinic).
M channels are low-threshold K+ channels that were originally identified in the early 1980s in the frog and rat sympathetic neurons, and now are known to be composed of subunits of the Kv7 (KCNQ) K+ channel family. They function as brakes on repetitive action potentials discharges regulating the excitability of various central and peripheral neurons.
Potassium current through M channels is inhibited by stimulating specific receptors, which ligandi are common neurotransmitters or peptides. Until recently the link between the receptors and the M channels has remained elusive, Patrick Delmas & David A. Brown (Pathways Modulating KCNQ/M (Kv7) Potassium Channels. Nature Reviews Neuroscience 6, 850-862, 2005) summarize recent developments that have begun to clarify this link and discuss their implications for physiology and medicine.