Amino Acid Neurotransmitters
Amino acids are the most abundant neurotransmitters in the brain. Nichols
suggested: “amino acids synapses exceed those of all the other neurotransmitters
combined…amino acids are responsible for almost all the fast signalling between
neurons, leaving predominantly modulatory roles for the other transmitters.”
Glutamate is the major excitatory neurotransmitter and is distributed in all
regions of the brain. Aspartate is closely related to glutamate and the two
amino acids are often found together at axon terminals. Neurons synthesize
glutamate and aspartate and are independent of dietary supply.
Three types of receptors for glutamate have been identified: N-methyl-
D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid
(AMPA) and kainate( KA) receptors. The three chemicals that identify glutamate
receptors are also potentially neurotoxic and are routinely used in animal
experiments to investigate the harmful effects of over-stimulating glutamate
receptors. It is known that following brain injury, glutamate is released from
injured cells and extends brain damage by over exciting neurons in the
neighborhood. Neuronal death often follows overstimulation. While many chemicals
used in research block this overstimulation, none are in use medically.
Gamma amino butyric acid (GABA) is the major inhibitory neurotransmitter in
the brain, derived from glucose, which is transaminated in the Kreb’s
cycle to glutamine and then converted to GABA by the enzyme, glutamic acid
decarboxylase. The production of GABA appears to be independent of the dietary
supply of glutamine but requires dietary pyridoxine.
Glycine is an inhibitory neurotransmitter found mostly in the brain stem and
spinal cord. A major discovery that adds complexity to the already confusing
story of neurotransmitters is that glycine acts as a co-transmitter in
excitatory NMDA synapses. Nong et al stated:” Recognition that glycine
potentiates NMDAR-mediated currents as well as being a requisite co-agonist of
the NMDAR subtype of 'glutamate' receptor profoundly changed our understanding
of chemical synaptic communication in the central nervous system. The binding of
both glycine and glutamate is necessary to cause opening of the NMDAR
L-Arginine is the precursor of endogenous nitric oxide (NO), which is a
vasodilator acting via the intracellular second-messenger cGMP. In healthy
humans, L-arginine induces peripheral vasodilation and inhibits platelet
aggregation due to an increased NO production. Prostaglandin E1 (PGE1) induces
peripheral vasodilation via stimulating prostacyclin receptors.
A mixture of branch-chain amino acids, leucine, valine and isoleucine will
reduce tardive dyskinesia and movement disorder that is caused by
anti-schizophrenic drugs. Tarvil, has been marketed in the USA that delivers 6.0
grams of the 3 amino acids per packet. A dose of 6 gm three times a day has been
More about Neurotransmitters
More about amino acids
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