09.03 Release

The next level at which the actions of a neurotransmitter can be modified is at the level of release. Theoretically, drugs can be used to inhibit or increase the release of neurotransmitters. A drug that inhibits the release of neurotransmitters is lignocaine. Lignocaine is a Na⁺ channel blocker. The conduction of impulses along nerves requires the opening and closing of sodium channels. Lignocaine is commonly used as a local anaesthetic, as application to afferent/sensory nerves stops the conduction of impulses that translate into the sensation of pain in the brain. Thus, prior to minor surgery, lignocaine can be used locally to dull pain.

A drug that increases the release of a neurotransmitter is amantadine. Thus, a second approach to enhancing dopaminergic neurotransmission in Parkinson’s disease, is to promote the release of endogenous dopamine. Amantadine increases the release of dopamine from the dopaminergic nerves in the brain. Amantadine is not very effective alone. It is only used alone in the early stages of Parkinson’s disease where there are still sufficient stores of endogenous dopamine to allow amantadine to release dopamine.