Excitatory Amino Acid Neurotransmitters

Excitatory amino acid neurotransmitters examples (3)

Glutamate, aspartate, homocysteic acid

what do excitatory amino acid neurotransmitters do

Produce an excitatory response in neurons

• i.e., the neuron is more likely to send an action potential

Most important NT for normal brain function

Glutamate (Nearly all excitatory neurons in CNS are glutamatergic)(but remember glutamate are present in all cells!)

Glutamate is synthesised from ______ by what enzyme

Glutamate is synthesised from glutamine by glutaminase

Glutamate that has been released is taken up by what

astrocytes

When glutamate is taken up by astrocytes, it is converted to what by what enzyme

it is converted back to glutamine by glutamine synthetase

Antagonists of the NMDA receptor

D-AP5

MK801

Mg²⁺

Significance of AMPA receptors & NMDA receptors being on the same membrane generally

The opening of NMDA receptor is reliant on the AMPA receptor

How is the NMDA receptor reliant on the AMPA receptor

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Link between excitatory amino acid receptors & stroke

It is usually excitatory amino acid receptors that cause the damage associated with strokes

How do excitatory amino acid receptors cause the damage associated with strokes

With the ischemia that comes with the block in blood supply, there is excessive Glu release → causes over-stimulation of NMDA receptors → Excess Ca2+ influx into postsynaptic neurons → Leading to excitotoxic cell death (excitotoxicity)

Explain how the bold part works: With the ischemia that comes with the block in blood supply, there is excessive Glu release → causes over-stimulation of NMDA receptors → Excess Ca2+ influx into postsynaptic neurons → Leading to excitotoxic cell death (excitotoxicity)

Large influx of Ca2+…

• Can activate proteases (calpains), phospholipases, nitric oxide synthase (NOS), nucleases etc. → Leads to very rapid cell death by necrosis

• Is spotted & gathered into mitochondria resulting in swelling and eventual rupture of mitochondria → Leads to delayed cell death

NMDA-R antagonists _____ and _____ provide protection in models of ischemia

NMDA-R antagonists D-AP5 and MK801 provide protection in models of ischemia

Take a moment to compartmentalise :)

Give an example of an inhibitory amino acid neurotransmitter

GABA

What do inhibitory amino acid neurotransmitters do

They cause an influx of negatively charged ions such as Cl-

Inside of cell becomes more negative

Hyperpolarisation of post-synaptic cell making it less likely to initiate an action potential

What is the main inhibitory NT in the brain

γ-aminobutyric acid (GABA)

Approx ___% of synapses in brain uses GABA

Approx 33% of synapses in brain uses GABA

Presence of ____ indicates a GABAergic neuron

Presence of GAD indicates a GABAergic neuron

slide 69 diagram

True/False GABA receptors can be Ionotropic & Metabotropic

True

Ionotropic: GABA_A and GABA_C

Metabotropic: GABA_B

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How does Presynaptic inhibition work

Inhibitory NT binds to receptors on the presynaptic cell → 

Reduction in depolarisation of the presynaptic nerve terminal → Less Ca2+ influx → Less excitatory NT release

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What are Biogenic amines

Bioactive amine neurotransmitters

What do Biogenic amines do

Implicated in wide range of behaviours

E.g., movement, reward, addiction, depression, sleep

What do Biogenic amines all have in common

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catecholamine neurotransmitters are all derived from what

They are all derived from tyrosine

Explain the pathway from tyrosine to catecholamine

neurotransmitters such as epinephrine

Tyrosine → DOPA → Dopamine → Norepinephrine → Epinephrine

The rate limiting step in the formation of catecholamine neurotransmitters is controlled by what enzyme

Tyrosine hydroxylase

Where is Tyrosine hydroxylase found

Only found in sympathetic neurons and adrenal chromaffin cells

If a cell has tyrosine hydroxylase, it is known as a what

catecholaminergic cell

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What are some treatments for Parkinson’s disease

Written in red