Hemicholinium-3 (HC3), also known as hemicholine, is a
drug which blocks the
reuptake
Reuptake is the reabsorption of a neurotransmitter by a neurotransmitter transporter located along the plasma membrane of an axon terminal (i.e., the Synapse, pre-synaptic neuron at a synapse) or glial cell after it has performed its function of ...
of
choline Choline is an essential nutrient for humans and many other animals. Choline occurs as a cation that forms various salts (X− in the depicted formula is an undefined counteranion). Humans are capable of some ''de novo synthesis'' of choline but r ...
by the high-affinity
choline transporter (ChT; encoded in humans by the gene ''SLC5A7'') at the
presynapse. The reuptake of choline is the
rate-limiting step
In chemical kinetics, the overall rate of a reaction is often approximately determined by the slowest step, known as the rate-determining step (RDS or RD-step or r/d step) or rate-limiting step. For a given reaction mechanism, the prediction of th ...
in the synthesis of
acetylcholine; hence, hemicholinium-3 decreases the synthesis of acetylcholine. It is therefore classified as an
indirect acetylcholine antagonist.
Acetylcholine is synthesized from choline and a donated
acetyl group from
acetyl-CoA, by the action of
choline acetyltransferase (ChAT). Thus, decreasing the amount of choline available to a neuron will decrease the amount of acetylcholine produced. Neurons affected by hemicholinium-3 must rely on the transport of choline from the
soma
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(cell body), rather than relying on reuptake of choline from the synaptic cleft.
Toxicity
Hemicholinium-3 is highly toxic because it interferes with cholinergic neurotransmission. The LD50 of hemicholinium-3 for mice is about 35 μg.
See also
*
Triethylcholine
Triethylcholine is a drug which mimics choline, and causes failure of cholinergic transmission by interfering with synthesis of acetylcholine in nerve endings.
Effects
Triethylcholine produces a slowly developing neuromuscular weakness ...
*
Vesamicol
References
{{Acetylcholine metabolism and transport modulators
Lactols
Phenylmorpholines
Quaternary ammonium compounds
Acetylcholine synthesis inhibitors
Biphenyls