Glutamate Flashcards
Amino acid neurotransmitters
- Not required in diet
- Synthesized in most cells of the body
Two functional groups of Amino acid neurotransmitters
Excitatory amino acid NT
Inhibitory amino acid NT
Excitatory amino acid NT (4)
Glutamate, Aspartate, Cysteate, Homocysteate
Inhibitory amino acid NT (4)
γ-aminobutyric acid (GABA), Glycine, Taurine,
Alanine
Excitatory amino acid neurotransmitters Aspartate Released in a
Ca2+
-dependent manner
Aspartate May not be stored in
secretory vesicles
Aspartate May be directly released from
cell cytoplasm Not considered a ‘classic’ neurotransmitter
Aspartate Acts at
glutamatergic receptors
Aspartate Physiological functions
unclear
Excitatory amino acid neurotransmitters Glutamate
Most widely used excitatory neurotransmitter
Glutamate____of all neurons, ______of all synapses are
glutamatergic
90% of all neurons, 80-90% of all synapses are
glutamatergic
Glutamate mediates fast
excitatory neurotransmission
Glutamate Mediates fast excitatory neurotransmission
Sensory, motor coordination, emotion, cognition,
memory formation and retrieval
Glutamate Proteinogenic amino acid
Abundant throughout the cell
Concentrated in presynaptic compartments
Glutamate
synthesis from
glutamine
Glutamine —glutaminase —> glutamate
In the CNS the majority
of glutamate is
recycled from
glutamine by the
enzyme glutaminase
Glutamate
transporters
Vesicular glutamate transporter (VGLUT) can be
used to identify glutamatergic neurons
VGLUTs are structurally and functionally similar to
VMAT
- VGLUT1 and 2 are expressed
on
distinct glutamatergic
populations in the CNS.
VGLUT3 is expressed in (3 neurons
)
various neurons including
GABAergic, cholinergic, and
monoaminergic neurons
suggesting possible
modulatory functions.
VGLUT2 locations
Deep cerebellar nuclei, inferior colliculus, thalamus
VGLUT 1 locations
cerebellar cortex, hippocampus, cortex
Glutamate is
metabolized to
glutamine
Glutamine
synthetase is the
enzyme responsible
for
conversion of
glutamate to
glutamine
Glutamate transporters on the
cell membrane are termed
excitatory amino acid
transporters (EAATs)
Glutamate transporters on the
cell membrane are termed
excitatory amino acid
transporters (EAATs) Non-specific for both
glutamate and aspartate
how many families are in EAAT
5
- EAAT1 and 2 are expressed on
astrocytes
EAAT3 and 4 are expressed on
neurons
EAAT5 is expressed in the
retina
- EAAT expression
compartmentalizes
glutamate
recycling
Neurons comprise only
50% of the cells in the
CNS
Glia in the CNS
Astrocytes, Oligodendrocytes
Ependymal cells
Microglia
Astrocytes
define the brain side of the BBB
- Oligodendrocytes
myelinate axons in white
matte
Ependymal cells
generate and regulate CSF
Microglia
Immune surveillance and
development
Astrocyte functions * Define the
blood brain barrier -Regulate intake of nutrients and O2
Astrocyte functions -Regulate
blood flow in the brain
Astrocyte functions Form extensive
signalling networks -Coupled with electrical synapses – Gap junctions
Astrocyte functions Regulate synaptic
functions and
contribute to plasticity
Astrocytes and cognition
- Proposed to contribute to cognitive
processes - more astrocytes increased cognition
High levels of extracellular glutamate are
toxic to neurons
Genetic knockdown of EAAT 1 and 2
(astrocytic) result in
widespread increases in
glutamate levels esp. in the striatum