Glutamate

Question 1

What is glutamate?

Answer 1

Main excitatory transmitter
Simple molecule
Amino acid

Question 2

What is glutamate synthesised from?

Answer 2

Glutamine from diet

Question 3

Is too much glutamate bad?

Answer 3

Yes, it’s also a neurotoxin

Can cause neuronal damage

Question 4

What are glial cells?

Answer 4

The non-neuronal supporting cells important for brain function
Produces and stores glutamine

Question 5

Describe the synthesis and recycling of glutamate (Start at glutamine in the glial cells)

Answer 5

1) Glutamine exits the glial cell via glutamine transporters
2) Enters nerve terminal via another glutamine transporter
3) Glutamine is converted into glutamate by phosphate activated glutaminase (associated w/ mitochondria)
4) Glutamate is the packaged into vesicles (uptake via specific vesicular transporter (VgluT))
5) Released into synaptic cleft
and binds to postsynaptic receptors
6) Then has 2 fates:
Taken back up into nerve terminal via EAAT (excitatory amino acid transporter) and repackaged
OR
Taken back up into glial cells via EAAT and converted into glutamine by glutamine synthase

Question 6

What are the 2 families of glutamate receptors?

Answer 6

Ionotropic

Metabotropic

Question 7

What is the difference between ionotropic and metabotropic receptors?

Answer 7

Ionotropic receptors have ion channels

Metabotropic receptors do not have channels but are indirectly linked to them via cell signalling (often G proteins)

Question 8

Name the 3 classes of iontropic glutamate receptors

Answer 8

NMDA
AMPA
KA

Question 9

Is glutamate rigid or flexible?

Answer 9

Flexible (can rotate along 2 different axes)

Question 10

How many subunits do ionotropic glutamate receptors have?

Answer 10

4

Question 11

How many membrane segments does each subunit of ionotropic glutamate receptors have?

Answer 11

4

Question 12

Which segment of a ionotropic glutamate receptor subunit is known as the p element?

Answer 12

2

Question 13

Which class of ionotropic glut receptors can only be heteromeric?

Answer 13

NMDA

Question 14

Which is faster - AMPA or NMDA receptors?

Answer 14

AMPA

NMDA is slower due to Ca+ inflow

Question 15

Which is always permeable to Na+, K+ and Ca+ - AMPA or NMDA receptors?

Answer 15

NMDA

AMPA only if there’s no GluA2 subunit

Question 16

What co-agonist modulates NMDA receptors?

Answer 16

Glycine/serine

Question 17

NMDA receptors need what as well as glutamate (agonist) to work?

Answer 17

Depolarisation

Question 18

NMDA receptors can act as what?

Answer 18

Transmitter and voltage sensors

Question 19

What type of receptors are metabotropic glutamate receptors?

Answer 19

G protein coupled receptors

Question 20

Are mGluRs fast or slow?

Answer 20

Slow

Question 21

What effect does mGluRs have on ion channels?

Answer 21

Closes Ca+ and K+ channels

Leads to slow depolarisation

Question 22

Which receptor is linked with Ca release?

Answer 22

mGluRs

Question 23

Name the 3 presynaptic glutamate receptors

Answer 23

mGluR
NMDA
KAR

Question 24

Name the 4 postsynaptic glutamate receptors

Answer 24

AMPA
mGluR
NMDA
KAR

Question 25

How is glutamate release controlled at the presynaptic terminal?

Answer 25

Presynaptic NMDAr increases glutamate release (via increase Ca influx)
Presynaptic mGluR decreases glutamate release (via decrease Ca influx)