Ion channels are specialized proteins embedded in the membrane. The ion selectivity of the channel is a property associated with its permeation pathway, normally called the pore. The magnitude of the current across the membrane depends on the density of channels, the conductance of the open channel, and how often the channel spends in its open position or its open probability. The salient feature of channels involved in excitable membranes is that the open probability is regulated by the transmembrane voltage or membrane potential. Changes in the membrane potential can be picked up by a voltage sensor that detects the voltage and transfers its energy to the pore to control its gate[1]. Despite their differences in ion selectivity and gating capabilities, voltage-gated channels in general share a number of structural features. They have a common structure with 24 transmembrane segments and a specialized pore region. Voltage-gated Na⁺ and Ca²⁺ channels are composed of a single pore-forming polypeptide (the alpha subunit), plus various auxiliary subunits. The alpha subunits of these channels contain four repeats of a core motif, which consists of six predicted transmembrane regions, S1-S6. Voltage-activated K+ channels are tetramers, with each subunit containing a single core motif. The ion-selective pore of these channels are formed by loops between the S5 and S6 regions, often called the P-regions or P-loops; four of these loops approach close together at the axis of the pore[2].