The diagram illustrates the uptake of free choline (Ch) into the nerve ending of the pre-ganglionic neurone and its acetylation by choline acetyltransferase, yielding acetylcholine (ACh).
In the terminal bouton, the newly synthesised ACh is incorporated into vesicles.
An action potential arriving at the nerve bouton triggers the exocytotic release of ACh into the synaptic cleft.
Released ACh diffuses to the post-synaptic membrane and binds to nicotinic cholinoceptors causing depolarisation. ACh is rapidly broken down by free or membrane-bound cholinesterase.
Drugs can effect ganglionic transmission in a number of ways:
- Interfere with choline uptake and limit the production of new ACh (e.g. Hemicholinium).
- Inhibit the release of ACh (e.g. Botulinum toxin).
- Block the action of ACh at the post-synaptic membrane (cholinoceptor antagonists).
- Mimic the action of ACh at the post-synaptic membrane (cholinoceptor agonists).
Note that receptors may also be present for other neuro-transmitters.
DEMO
