ABSTRACT
K+ channels are the largest and most widely distributed family of ion channels. In excitable cells, their main role is to regulate membrane potential and so control cell excitability. This can be achieved by altering action potential waveform and duration (during the repolarizing phase), by altering the rate at which threshold for action potential generation is achieved (via their contribution to pacemaker potentials), or more simply by providing a tonic hyperpolarizing influence on resting membrane potential. Any external stimulus that can modulate K+ channel activity will, therefore, have a profound effect on cell function. This is particularly true for cellular functions that are dependent on Ca2+ influx through voltage-gated Ca2+ channels; by alteration of membrane potential (via modulation of K+ channel activity), the degree of Ca2+ channel activity is finely controlled, hence Ca2+-dependent functions such as contraction or exocytosis can be indirectly regulated via modulation of K+ channel activity.
