GABA + Glycine Flashcards

1
Q

What is GABA?

A

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system (CNS).

Approximately one third of synapses utilise GABA as their neurotransmitter

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2
Q

How is GABA synthesised and stored?

A

On image

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3
Q

How is GABA reuptake and degraded?

A

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4
Q

What are the 2 types of receptors GABA binds to?

A

Ionotropic and metabotropic receptors

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5
Q

What are the specific GABA receptors?

A

GABAa and GABAb

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6
Q

Describe the structure of a GABAa receptor

What structure does it have?

What are the binding sites?

A

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7
Q

Describe the structure of a GABAb receptor

A

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8
Q

What does GABA cause?

A

Inhibitory neurotransmitters (e.g. GABA) can cause neuronal membrane hyperpolarisation – displacement of a membrane potential towards a more negative value.

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9
Q

What is the cerebellum and what is its function?

A
The cerebellum
The cerebellum (or “little brain”) is a prominent hindbrain structure – it accounts for approximately 10% of the human brains volume.

Cerebellum function?
• The cerebellum does not initiate movement but detects differences in “motor error” between an intended movement and the actual movement
• Aids the motor cortex to produces precise and co-ordinated movement

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10
Q

Is the function of the cerebellum conserved?

A
  • It has been shown that, for example, the cerebellum is important in synchronisation of movement with musical rhythm
  • This may be widespread across the animal kingdom…
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11
Q

Describe the projections from the cerebellum

A

Purkinje cells are are a class of GABAergic neurons that comprise the principle projection neurons of the cerebellar cortex.

  • Purkinje cells have elaborate dendritic trees that receive convergent input from cells in the molecular layer
  • Purkinje cells send GABAergic projections to deep cerebellar neurons
  • Purkinje cell output to the deep cerebellar neurons generates an error connection signal that can modify movements
  • This provides the basis for real-time control of precise and synchronous movement
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12
Q

How is glutamate converted to GABA?

A

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13
Q

What is epilepsy and what does to much excitation cause?

A

Epilepsy is a brain disorder characterised by periodic and unpredictable seizures mediated by the rhythmic firing of large groups of neurons.
Too much excitation? -> increase inhibition*Other anti-epileptics directly decrease excitation

On table

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14
Q

What is anxiety?

A

Anxiety can be defined as a feeling of unease (e.g. worry or fear), which can range from mild to severe.

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15
Q

What are anxiety disorders and anxioytics?

A

(e.g. benzodiazepines – GABAA receptor)

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16
Q

What is glycine?

A

Glycine is the second major inhibitory neurotransmitter in the central nervous system (CNS).

  • Glycine was first identified in the spinal cord and brainstem in 1965
  • In the 1967, glycine was shown to inhibit action potential firing in spinal neurons
  • Glycine most commonly found as an inhibitory neurotransmitter in the ventral horn, the location for spinal interneuron terminals
  • However, our understanding of the glycine receptor is lagging behind the GABA receptors – in part due to limited allosteric modulators of the receptor
17
Q

How is glycine synthesised and stored?

A

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Synthesised in the nerve terminals
Transported into vesicles by vesicular inhibitory amino acid transporters (VIAAT)

18
Q

How is glycine reuptaken and degraded?

A

On image

19
Q

Describe the structure of the glycine receptor

A

On image

20
Q

Describe Hyperekplexia and glycine neurotransmission

A

Hyperekplexia is a rare disorder characterised by hypertonia (increased muscle tone) and an exaggerated startle response.
• Symptoms can manifest in relation to unexpected stimuli (e.g. loud noises)
What is the role of glycine?
• Gene mutations (e.g. glycine receptors, glycine transporters) can disrupt normal glycinergic neurotransmission
• Can lead to neuronal hyperexcitability (by impairing glycinergic inhibition)
• Leads to hypertonia and exaggerated startle response

21
Q

Startle (or myotonic, fainting) goats…

A
  • In startle goats, there is a decreased muscle chloride conductance – can be caused by glycine receptor mutations
  • As the goats mature, GABAA receptors are upregulated to compensate