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FOCUS ON ION CHANNELS
Ions generally cannot move freely across cell membranes, but must enter or exit a cell through pores created by ion channels. Ion channels open and close, or gate, in response to particular stimuli, including ions, other cellular factors, changes in electrical voltage or drugs.
The concentration of specific ions in particular cells in the body is critically important to many vital physiological functions. Consequently, ion channels play a key role in a wide variety of processes in the human body, which can be broadly grouped into three categories:
- Electrical impulse generation and conduction along nerves in the central and peripheral nervous system, the heart and other organs;
- Signal transduction within and among cells, including immune system cells that, when activated, trigger an inflammatory response; and
- Fluid balance within cells and across cell membranes, including fluid balance in red blood cells, cells in the eye and other cells throughout the body
Small molecule compounds have been shown to both activate and inhibit ion channels. As a result, ion channels represent an important class of targets for pharmaceutical intervention in a broad range of disease areas. Examples of currently marketed drugs that exert their effects through ion channel modulation include calcium channel blockers, such as Norvasc and verapamil, which are used for the treatment of hypertension and various other cardiovascular disorders; sodium channel blockers, such as Lamictal, which is used for the treatment of epilepsy, and lidocaine, a local anesthetic; and potassium channel blockers, such as Glipizide, which is used in the treatment of diabetes.
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