Neurotransmitter Systems II: GABA And Glycine

Question 1

What does GABA stand for?

Answer 1

Gamma-aminobutyric acid

Question 2

What is GABA?

Answer 2

Major inhibitory neurotransmitter in the CNS

Question 3

What is the main precursor to GABA?

Answer 3

Glucose

Question 4

How does glucose turn into GABA?

Answer 4

Glucose -> glutamate, which then is turned into GABA by glutamate decarboxylase with the cofactor pyridoxal phosphatase

Question 5

What shaped vesicles is glutamate stored in?

Answer 5

Round

Question 6

What shaped vesicles is GABA stored in

Answer 6

Oval

Question 7

How is GABA retaken up?

Answer 7

High affinity sodium dependant GABA transporters GAT-1 on neurons and GAT-3 on glial cells

Question 8

What are the steps in GABA degredation (no enzymes)?

Answer 8

GABA -> succinic semialdehyde -> succinic acid

Question 9

What enzyme catalyses GABA -> succinic semialdehyde?

Answer 9

GABA Transaminase (GABA-T)

Question 10

What enzyme catalyses succinic semialdehyde -> succinic acid?

Answer 10

Succinic semialdehyde dehydrogenase (SSADH)

Question 11

What type of receptors are GABAa receptors?

Answer 11

Ionotropic

Question 12

What type of receptors are GABAb receptors?

Answer 12

Metabotropic

Question 13

What happens upon GABA binding to GABAa receptor?

Answer 13

Channel opens and allows the influx of chloride ions

Question 14

What are the possible GABAa receptor subunits?

Answer 14

6 alpha, 3 beta, 3 gamma, delta, epsilon, pi and theta

Question 15

What is the most common GABAa configuration?

Answer 15

2 alpha, 2 beta and a gamma

Question 16

Why are GABAa receptors a key drug target?

Answer 16

Multiple binding sites

Question 17

Where do agonists/ antagonists bind on GABAa receptors?

Answer 17

Between the alpha and beta subunits

Question 18

Where does benzodiazepine bind on GABAa receptors?

Answer 18

Between alpha and gamma subunits

Question 19

Where do channel blockers bind on GABAa receptors?

Answer 19

Blocks the ion pore (non-competitive antagonist)

Question 20

How do channel modulators work on GABAa receptors?

Answer 20

Increase the opening

Question 21

What is an example of a GABAa channel blocker?

Answer 21

Picrotoxin

Question 22

Where do allosteric modulators bind on GABAa receptors?

Answer 22

The receptor

Question 23

Give an example of a GABAa allosteric modulator

Answer 23

Barbituates

Question 24

What are the heteromers of the GABAb receptor?

Answer 24

GABAb1 and GABAb2

Question 25

How does the GABAb receptor work?

Answer 25

Binding stimulates the Gi/O pathway

Question 26

What does activation of the Gi/O pathway cause?

Answer 26

Activates adenylyl cyclase to reduce cAMP levels, which activates potassium channels, causing an effluent

Question 27

What are the two ways in which hyperpolarisation can happen?

Answer 27

Influx of calcium or efflux of potassium

Question 28

How much of the brains volume does the cerebellum account for?

Answer 28

10%

Question 29

What is the function of the cerebellum?

Answer 29

Helps the motor cortex to procure precise and coordinated movements- detects the differences in motor error between an intended movement and the actual movement

Question 30

What are purkinje cells?

Answer 30

A class of GABAergic neurons that comprise the principle projection neurons of the cerebellar cortex

Question 31

What do the purkinje cells dendritic trees receive?

Answer 31

Convergent input from cells in the molecular layer

Question 32

What do the purkinje cells dendritic trees send out?

Answer 32

GABAergic projections to Deep cerebellar neurons

Question 33

What does the GABAergic projection to the deep cerebellar neurons generate?

Answer 33

An error connection signal that can modify movements

Question 34

What do GABA projections in the cerebellum provide the basis for?

Answer 34

Real time control of precise and synchronous movement

Question 35

What two things work together to control the brains overall level of excitation?

Answer 35

GABA and glutamate

Question 36

What is epilepsy?

Answer 36

Brain disorder characterised by periodic and unpredictable seizures mediated by the rhythmic firing of large groups of neurons

Question 37

How do epilepsy drugs work?

Answer 37

Increase inhibition by increasing GABA

Question 38

What is glycine?

Answer 38

Major inhibitory neurotransmitter in the CNS

Question 39

Where is glycine most commonly found?

Answer 39

In the ventral ramus Which is the location for spinal interneuron terminals

Question 40

What is the precursor to glycine?

Answer 40

Serine

Question 41

What catalyses serine -> glycine?

Answer 41

Serine hydroxymethyltransferase

Question 42

Where is glycine synthesised?

Answer 42

Nerve terminals

Question 43

What class of enzymes causes the reuptake of glycine?

Answer 43

GlyT 1 and 2

Question 44

What enzyme is glycine -> serine catalysed by?

Answer 44

Serine hydroxymethyl

Question 45

What type of receptor does glycine bind to?

Answer 45

Ligand gated ion channel

Question 46

What happens when glycine binds to its receptor?

Answer 46

Allows chloride ions into the neuron, leading to hyperpolarisation

Question 47

What different subtypes of the glycine receptor are there?

Answer 47

4 alpha, one beta

Question 48

What are the most common glycine LGIC configurations?

Answer 48

3 alpha, 2 beta or 4 alpha, 1 beta

Question 49

What potently blocks glycine receptors?

Answer 49

Plant alkaloid strychnine

Question 50

What is hyperekplexia?

Answer 50

A rare disorder characterised by hypertonic and increased muscle tone

Question 51

What can hyperekplexia lead to?

Answer 51

Neuronal hyperexcitability and hypertonic and an exaggerated startle response

Question 52

Why do the fainting goats faint?

Answer 52

Decreased muscle chloride conductance, which can be caused by glycine receptor mutations