High Conductance Calcium-Activated Potassium Channels

Potassium channels represent a vast and diverse family of ion channel proteins which are found in many different types of tissues [1, 2]. These channels modulate the electrical excitability of certain cells, such as those derived from neuronal, endocrine and muscle sources. They also control the resting plasma membrane potential of a large variety of cells, regardless of whether the cells display electrically excitable or nonexcitable properties. K+ channels are routinely categorized according to their biophysical and pharmacological properties. However, these proteins may also be sub-divided into two major classifications depending on whether they are activated by changes in membrane potential (voltage-sensitive channels), or by an interaction with small molecule modulators (ligand-gated channels). Unfortunately, when compared with other types of ion channels, such as with the members of the voltage-gated Na+ and Ca2+ channel families [3], the biochemistry and molecular pharmacology of K+ channels is still rather undeveloped.