IHC analysis of Cav1.2 in human hippocampus tissues.
 Courtesy of Dr. Turksen, Ottawa Hospital Research Institute, Canada.

Ion channels are integral membrane proteins that help establish and control
 the small voltage gradient across the plasma membrane of living cells 
by allowing the flow of ions down their electrochemical gradient  (1). 
They are present in the membranes that surround all biological cells 
because their main function is to regulate the flow of ions across this 
membrane.  Whereas some ion channels permit the passage of ions based on
 charge, others conduct based on an ionic species, such as sodium or 
potassium.  Furthermore, in some ion channels, the passage is governed 
by a gate which is controlled by chemical or electrical signals, 
temperature, or mechanical forces.

There are a few main classifications of gated ion channels.  There are voltage- gated ion 
channels, ligand- gated, other gating systems and finally those that are
 classified differently, having more exotic characteristics.  The first 
are voltage- gated ion channels which open and close in response to 
membrane potential.  These are then separated into sodium, calcium, 
potassium, proton, transient receptor, and cyclic nucleotide-gated 
channels; each of which is responsible for a unique role.  Ligand-gated 
ion channels are also known as ionotropic receptors, and they open in 
response to specific ligand molecules binding to the extracellular 
domain of the receptor protein.  The other gated classifications include
 activation and inactivation by second messengers, inward-rectifier 
potassium channels, calcium-activated potassium channels, 
two-pore-domain potassium channels, light-gated channels, 
mechano-sensitive ion channels and cyclic nucleotide-gated channels.  
Finally, the other classifications are based on less normal 
characteristics such as two-pore channels, and transient receptor 
potential channels (2).

Specifically, Cav1.2 is a cardiac L-type calcium channel, and is important for excitation 
and contraction of the heart (3).  It may be associated with a variant of Long QT syndrome 
called Timothy's syndrome (4, 5) and also with Brugada syndrome.  Some 
references also suggest it is related to bipolar disease as well (5).

 1. Hille B. (2001) Ion Channels of Excitable Membranes, 3rd Ed., Sinauer Associated Inc.:Sunderland, MA USA.
 2. www.iochannels.org
 3. Splawski I., et al. (2004) Cell. 119 (1): 19-31.
 4. Krey J.F., and Dolmetsch R. (2009) Biophysical. 96 (3): 221a-222a.
 5. Crotti L., Celano G., Dagradi F. and Schwartz P.J. (2008) Orphanet J Rare Disease 3:18.