Voltage-dependent Ca++ channels mediate Ca++ entry into excitable cells in response to membrane depolarization, and they are involved in a variety of Ca++-dependent processes, including muscle contraction, hormone or neurotransmitter release and gene expression. Calcium channels are highly diverse, multimeric complexes composed of an (alpha)1 subunit, an intracellular (beta) subunit, a disulfide linked (alpha)2/(delta) subunit and a transmembrane (gamma) subunit. Ca++ currents are characterized on the basis of their biophysical and pharmacologic properties and include L-, N-, T-, P-, Q-, and R- types. T-type Ca++ currents are activated and inactivated more rapidly and at more negative membrane potentials than other Ca++ current types. T-type Ca++ channels enhance odor sensitivity by lowering the threshold of spike generation in olfactory receptor cells (ORCs).