Voltage-dependent Ca2+ channels mediate Ca2+ entry into excitable cells in response to membrane depolarization, and they are involved in a variety of Ca2+-dependent processes, including muscle contraction, hormone or neurotransmitter release and gene expression.Ca2+ currents are characterized on the basis of their biophysical and pharmacologic properties and include L-, N-, T-, P-, Q-, and R- types. L-type Ca2+ currents initiate muscle contraction, endocrine secretion, and gene transcription, and can be regulated through second-messenger activated protein phosphorylation pathways. L-type calcium channels may form macromolecular signaling complexes with G protein-coupled receptors, thereby enhancing the selectivity of regulating specific targets.