Depolarization

For other uses, see Depolarization (disambiguation).

Neuroscience portal

In biology, depolarization is a change in a cell's membrane potential, making it more positive, or less negative. In neurons and some other cells, a large enough depolarization may result in an action potential. Hyperpolarization is the opposite of depolarization, and inhibits the rise of an action potential.

Mechanism

If, for example, a cell has a resting potential of -70mV, once the membrane potential changes to -50mV, then the cell has been depolarized. Depolarization is often caused by influx of cations, e.g. Na⁺ through Na⁺ channels, or Ca²⁺ through Ca²⁺ channels. On the other hand, efflux of K⁺ through K⁺ channels inhibits depolarization, as does influx of Cl^– (an anion) through Cl^– channels. If a cell has K⁺ or Cl^– currents at rest, then inhibition of those currents will also result in a depolarization.

Because depolarization is a change in membrane voltage, electrophysiologists measure it using current clamp techniques. In voltage clamp, the membrane currents giving rise to depolarization are either an increase in inward current, or a decrease in outward current.

Depolarization blockers

There are drugs, called depolarization blocking agents, that inhibit depolarization, e.g. by blocking the channels responsible for depolarization, or by opening K⁺ channels. Examples include the nicotinic agonists suxamethonium and decamethonium.^[1]

References

1. ^ Rang, H. P. (2003). Pharmacology. Edinburgh: Churchill Livingstone. ISBN 0-443-07145-4.  Page 149

External links

• Neuroscience - online textbook by Purves, et al.
• Basic Neurochemistry Molecular, Cellular, and Medical Aspects by Siegel, et al.