Acetylcholine is synthesized by the choline acetyltransferase enzyme from AcetylCoA and recycled choline. Acetylcholine is then stored in the axon for release. There are 4 different acetylcholine receptors subtypes identified. Nicotinic receptors and three diverse muscarinic receptors. (Although only the two muscarinic receptors thought to be present in the brain are shown in the graphic).
Acetylcholine is rapidly metabolized by acetylcholinesterase in the synapse. The choline product is then transported back into the presynaptic cell for synthesis into acetylcholine. Alterations in acetylcholine neurotransmission are associated with Alzheimer’s and Parkinson's disease. Thus, most pharmacological therapy aimed at these disorders attempts to either enhance or reduce acetylcholine's effects in different areas of the brain.
Acetylcholine transporter reuptake is the most efficient mechanism for clearing the synapse of released acetylcholine.
Extra info: Unfortunately, there is no reuptake transporter the acetylcholine neurotransmitter. However, there is a transporter for the choline that results from acetylcholinesterase metabolism.
Which of the following is true regarding nicotinic receptors?
Extra info: Ligand gated ion-channels (such as nicotinic receptors) are less responsive to receptor regulation and as such are said to lack “plasticity”. A is wrong because nicotine does cross the BBB. C is wrong because ion-channels respond quicker to an agonist than G-protein receptors. D is wrong because acetylcholine is the primary agonist.
The nicotinic receptor is a ligand-gated chloride ion channel.
Extra info: Close It is ligand gated SODIUM ion channel.
The choline by product is transported back into the presynaptic neuron for synthesis into acetylcholine.