03.01.4.2 Inhibition of Sodium Channels

A good example of how inhibiting a channel can change function is the blockage of sodium channels with local anaesthetics e.g. lignocaine. When you have tissue damage, the afferent nerves are activated and a message is sent along the afferent (sensory) nerves to the brain, which originates the feeling of pain (Figure 3.12).

Figure 3.12 Na⁺ channels and lignocaine (Copyright QUT, Sheila Doggrell)

The pain message is carried along the nerve as part of the wave form known as the action potential. The upstroke or depolarization phase of the action potential is due to sodium entering the nerve cell. Na⁺ channel blockers, like lignocaine, block the Na⁺ channels, so there are no longer action potentials, and without this messenger there is no pain.