Acetylcholine

Acetylcholine

IUPAC name 2-Acetoxy-N,N,N-trimethylethanaminiumAbbreviation ACh

Sources motor neurons, parasympathetic nervous system, brain

Targets skeletal muscles, brain, many other organsReceptors nicotinic, muscarinicAgonists nicotine, muscarine, cholinesterase inhibitors

Antagonists tubocurarine, atropinePrecursor choline, acetyl-CoA

Synthesizing enzyme choline acetyltransferase

Metabolizing enzyme acetylcholinesterase

Acetylcholine• Acetylcholine is an organic chemical that

functions in the brain and body of many type of animals, as a

• Neurotransmitter- a chemical released by nerve cells to send signals to other cells.

• Also used as a neurotransmitter in the autonomic nervous system.

• Its name is derived from its chemical structure: it is ester acetic acid and choline.

Function Of Ach• Acetylcholine has functions both in the peripheral

nervous system and CNS.• In the peripheral nervous system, Ach activates

muscles, and is a major neurotransmitter in the ANS.

• In the CNS, cholinergic projections from the basal forebrain to the cerebral cortex and hippocampus support the congnitive functions of those target areas.

Synthesis Of Acetylcholine

Synthesis• Acetylcholine is synthesized from its two immediate precursors,

choline and acetyl coenzyme A• The synthesis reaction is a single step catalyzed by the enzyme ChAT Choline+Acetyl coenzyme A Acetylcoline+Coenzyme A ⇌• Choline present in tissues has two origins :

exogenous, in food( folic acid, vitamin B12) and endogenous , by biosynthesis from glycine.

• Acetylcholinesterase (ACHE), Also known as AChE OR acetylhydrolase , is the primary cholinesterase in the body, it is an enzyme that catalyzes the breakdown of acetylcholine and some other choline esters that function as neurotransmitter.

Distribution Of Ach Tissue distribution of acetylcholine is very broad ,it is present:• In the central nervous system: brain , spinal cord ,

nerve• In the vegetative nervous system: in sympathetic

and parasympathetic ganglia and in parasympathetic terminations.

• In presynaptic termination of neuromuscular junctions.

Release OF Ach• In presynaptic termination, acetylcholine is

contained in vesicles.• Nervous impulse, i.e. action potential, induces

migration of vesicles towards the membrane and releases of acetylcholine into the synaptic cleft

• The stimulation of pre synaptic muscarinic receptors inhibits acetylcholine release and , conversely, their inhibition increases it.

• Botulinum toxins is an inhibitor of the acetylcholine releases.

Storage Of Acetylcholine• After its synthesis, acetylcholine is packaged into

vesicles.• Ach is transported from the cytoplasm into

individual vesicles by means of a carrier protein on the vesicle membrane called vesicular Ach transport (VACHT)

• VAchT is an antiporter that couples an influx of ACH with an efflux of protein(H).

• Once packaged in a vesicles, acetylcholine is stored at the nerve ending until an action potential arrives and allows for its release into the synaptic cleft.