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All parts of the brain › Brain chemicals › Glutamate

Where is glutamate made in the brain?

Glutamate is the brain’s chief excitatory messenger, its accelerator: it is by far the most abundant one, at an estimated 90% of the synaptic connections in the human brain. Neurons throughout the brain make it. Lit are the main sources of its long-range signals: the pyramidal cells of the cerebral cortex and the hippocampus, and the relay neurons of the thalamus. [1][2][3]

The 3D brain needs JavaScript. The lists below still say where glutamate is made and where it is sent.

Lit: the main sources of glutamate (blue) and where they send it (orange).

Slice

Its main sources are lit in blue, where they send glutamate in orange. Drag to turn, pinch or scroll to zoom; tap a part or a “light” button to name it on its own; .

Made by neurons throughout the brain; lit: the cell groups the cited source names as its main sources. Glutamate is used by every major excitatory function in the brain, an estimated 90% of its synaptic connections, so nearly every part makes it. The lit parts are the main sources of its long-range signals: the pyramidal cells of the cortex and hippocampus and the thalamus’s relay neurons. [1][2][3] Lit in blue: the frontal lobe, parietal lobe, temporal lobe, occipital lobe, insula, thalamus and hippocampus.

Lit in orange: the caudate nucleus, putamen, spinal cord (central canal), mammillary bodies and septum (septum of telencephalon), where its fibres end. The fibres themselves are not drawn: the two colours show where the cells are and where they send glutamate, not the routes in between. [4]

Main sources: lit in blue

  • Cerebral cortex, lit as the frontal lobe, parietal lobe, temporal lobe, occipital lobe and insula: Pyramidal cells, glutamate-releasing projection neurons found mainly in layers III and V, are the majority of its neurons; the other 20–30% are interneurons. The cortex is drawn as the five lobe shells. [2][5]
  • Thalamus, lit as the thalamus: Its glutamate relay neurons pass every sense but smell on to that sense’s primary area of the cortex; all of them arise from one embryonic domain, its GABA cells from another. [3]
  • Hippocampus, lit as the hippocampus: Its pyramidal cells use glutamate; its main output runs from CA1 to the subiculum, and the best-studied form of long-term potentiation is seen at CA1’s glutamate synapses. [2][6]

Sent to: lit in orange

  • Striatum (corticostriatal and thalamostriatal): The cortex is its largest input in axon numbers: glutamate pyramidal neurons from layers II–VI, densest from layer V, ending on the spines of its spiny neurons; a second glutamate input comes from the thalamus. [7]
  • Spinal cord (corticospinal tract): Pyramidal neurons are the main cell type of the corticospinal tract, whose axons make specific connections in the spinal cord for movement. This atlas draws the cord only as its central canal, cropped just below the medulla, so that thin line is what is lit. [2]
  • Mammillary bodies (hippocampus → fornix): A major hippocampal output runs through the fornix to the mammillary body of the hypothalamus. [6]
  • Septum (hippocampus → fornix): The same fornix output reaches the lateral septal area. [6]
  • Not lit as targets: the cerebral cortex and the thalamus, which send glutamate to each other (thalamocortical relay and strong cortical feedback); both are lit in blue as sources. [3]
  • Not lit: the entorhinal cortex, where the hippocampus’s main input comes from (the perforant path) and where much of its output returns. [6]

The pathways, as the sources name them

  • Thalamocortical radiations, from the thalamus out to the cerebral cortex in all directions (the cortex is lit in blue, as a source). Each sense except smell has a thalamic nucleus that relays it to its primary cortical area: the lateral geniculate nucleus to the visual cortex, the medial geniculate nucleus to the auditory cortex. Each of those areas sends strong feedback back. [3] See What part of the brain controls vision?
  • Corticostriatal and thalamostriatal, from pyramidal neurons across much of the neocortex, and from the thalamus’s centromedian–parafascicular complex, to the striatum. Both inputs are glutamate; the striatum’s spiny neurons, which answer with GABA, open the basal ganglia loops. [7][8] See What part of the brain controls movement?
  • Corticospinal tract, from pyramidal neurons of the cortex down to the spinal cord. Normal motor control depends on these axons finding their right partners in the spinal cord. [2] See What part of the brain controls movement?
  • Hippocampus → fornix, from the hippocampus through the fornix to the mammillary body and the lateral septal area. One of its outputs; others run back to the entorhinal cortex and on to cortical areas including the prefrontal cortex. [6] See What part of the brain controls memory?

Good to know

  • Most glutamate neurons are not in the lit parts: the cerebellum’s granule cells, which use glutamate as their main transmitter, number about 50 billion, roughly three quarters of the brain’s neurons. Their signals stay inside the cerebellum, reaching the Purkinje cells through parallel fibres, so the cerebellum is not lit as a long-range source. [1][9][10]
  • Made from glutamine: neurons and nearby glial cells make it with the enzyme glutaminase, in the glutamate–glutamine cycle. Glutamate cannot cross the blood–brain barrier unaided, and a transport system keeps its level in brain fluids fairly constant. [1]
  • Four receptor families: AMPA receptors for fast excitation, within a fraction of a millisecond; NMDA receptors, which also let calcium in and so matter for learning and memory; kainate receptors; and the slower metabotropic receptors. [1] See What part of the brain is responsible for learning?
  • It is also the raw material for GABA: one enzyme step turns the brain’s main accelerator into its main brake. [11]
  • Because glutamate is in every part of the body as a building block of protein, its role as a messenger was hard to see: first suggested by T. Hayashi in 1952, it was not generally accepted until the 1970s, and almost universally by 1980. [1]

What it takes part in

Each lit with every part that takes part: What part of the brain is responsible for learning? · What part of the brain controls memory? · What part of the brain controls movement? · What part of the brain controls vision?

Its main sources, each on its own page: Cerebral cortex, Thalamus, Hippocampus.

Sources

  1. Wikipedia: Glutamate (neurotransmitter)
  2. Wikipedia: Pyramidal cell
  3. Wikipedia: Thalamus
  4. BodyParts3D 4.0 (3D model measured on this page), © DBCLS, CC BY-SA 2.1 Japan
  5. Wikipedia: Interneuron
  6. Wikipedia: Hippocampus
  7. Wikipedia: Striatum
  8. Wikipedia: Medium spiny neuron
  9. Wikipedia: Cerebellum
  10. Wikipedia: Purkinje cell
  11. Wikipedia: GABA

Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); glutamate is made by neurons all through the brain, so the lit parts are its main sources as the cited sources name them, not the only places it is made. Real brains vary.