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Glutamate is synthesized in the central nervous system from glutamine as part of the glutamate–glutamine cycle by the enzyme glutaminase. This can occur in the presynaptic neuron or in neighboring glial cells. Glutamate itself serves as metabolic precursor for the neurotransmitter GABA, via the action of the enzyme glutamate decarboxylase.
Glutamate (the conjugate base of glutamic acid) is abundant in the human body, but particularly in the nervous system and especially prominent in the human brain where it is the body's most prominent neurotransmitter, the brain's main excitatory neurotransmitter, and also the precursor for GABA, the brain's main inhibitory neurotransmitter. [2]
In biochemistry, the glutamate–glutamine cycle is a cyclic metabolic pathway which maintains an adequate supply of the neurotransmitter glutamate in the central nervous system. [1] Neurons are unable to synthesize either the excitatory neurotransmitter glutamate , or the inhibitory GABA from glucose .
Therefore, the effects of a neurotransmitter system depend on the connections of the neurons that use the transmitter, and the chemical properties of the receptors. Glutamate is used at the great majority of fast excitatory synapses in the brain and spinal cord.
Glutamate is the most abundant excitatory neurotransmitter in the vertebrate nervous system. [23] At chemical synapses, glutamate is stored in vesicles. Nerve impulses trigger the release of glutamate from the presynaptic cell. Glutamate acts on ionotropic and metabotropic (G-protein coupled) receptors. [23]
NMDA receptors are a crucial part of the development of the central nervous system. The processes of learning, memory, and neuroplasticity rely on the mechanism of NMDA receptors. NMDA receptors are glutamate-gated cation channels that allow for an increase of calcium permeability.
Excitatory synapses have a fundamental role in information processing within the brain and throughout the peripheral nervous system. Usually situated on dendritic spines, or neuronal membrane protrusions on which glutamate receptors and postsynaptic density components are concentrated, excitatory synapses aid in the electrical transmission of ...
Glutamate is a prime example of an excitotoxin in the brain, and it is also the major excitatory neurotransmitter in the central nervous system of mammals. [14] During normal conditions, glutamate concentration can be increased up to 1mM in the synaptic cleft, which is rapidly decreased in the lapse of milliseconds. [15]