Voltage-gated calcium channels (VGCCs), also known as voltage-dependent calcium channels (VDCCs), are a group of voltage-gated ion channels found in the membrane of excitable cells (e.g. muscle, glial cells, neurons) which are permeable to calcium ion Ca. Since these channels are slightly permeable to sodium ions, they are also called Ca–Na channels, but their permeability to calcium is about 1000-fold greater than to sodium under normal physiological conditions.
At physiologic or resting membrane potential, VGCCs are normally closed. They are activated (i.e.: opened) at depolarized membrane potentials and this is the source of the "voltage-gated" epithet. The concentration of calcium (Ca ions) is normally several thousand times higher outside the cell than inside. Activation of particular VGCCs allows a Ca influx into the cell, which, depending on the cell type, results in activation of calcium-sensitive potassium channels, muscular contraction, excitation of neurons, up-regulation of gene expression, or release of hormones or neurotransmitters.