GABA and Glycine

Question 1

Glutamate decarboxylase (GAD)

Answer 1

The enzyme that mediates the conversion of glutamate to GABA

Question 2

GABA reuptake transporter (GAT)

Answer 2

The transporter responsible for sequestering GABA into the presynaptic bouton from the cytosol

Question 3

GABA transaminase

Answer 3

The enzyme that breaks down GABA in the synaptic cleft

Question 4

Glycine reuptake transporter (GlyT)

Answer 4

The transporter responsible for sequestering glycine into the presynaptic bouton from the cytosol

Question 5

Glycine decarboxylase

Answer 5

The enzyme that breaks down Glycine in the synaptic cleft

Question 6

Panspermia

Answer 6

The theory that the universe contains the materials for the ‘building blocks’ of life

Question 7

GABA receptor - structure

Answer 7

Six 𝝰 subtypes (𝝰1–6)
Three 𝝱 subtypes (𝝱1-3)
Three 𝝲 subtypes (𝝲1-3)
Also, δ ε π θ subunits
2α 2β γ most common configuration

Question 8

The binding site for GABA receptor

Answer 8

• Agonists/antagonists e.g. GABA
• Benzodiazepine binding site
• Channel blockers e.g. picrotoxin
• Channel modulators e.g. GA
• Allosteric modulators e.g. barbiturates

Question 9

Cerebellum function

Answer 9

• 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

Question 10

GABA and Purkinje

Answer 10

• 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

Question 11

GABA and glutamate

Answer 11

• GABA and glutamate are the major neurotransmitters in the brain – both work together to control the brain’s overall level of excitation.

Question 12

Epilepsy and GABA neurotransmission

Answer 12

Epilepsy is a brain disorder characterised by periodic and unpredictable seizures mediated by the rhythmic firing of large groups of neurons.

Question 13

Anxiety and GABA neurotransmission

Answer 13

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

Question 14

Glycine receptor

Answer 14

Four α subtypes (α1 – α4)
One β subtype
3α12β or 4α1β most common configuration
Agonist/antagonist binding sites unclear –
although plant alkaloid strychnine potently
blocks glycine receptors

Question 15

Hyperekplexia and glycine neurotransmission

Answer 15

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)

Question 16

What is the role of glycine in hyperekplexia?

Answer 16

• 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