Lecture 4: Synapse And Plasticity III

Question 1

3 phases of Long term potentiation (LTP)

Answer 1

IEM
1. Induction
2. Expression
3. Maintenance

Question 2

Explain induction

Answer 2

Stimulation protocols induce an increase in synapse strength

Question 3

What happens if there is no induction?

Answer 3

There will be no expression or maintenance of long term potentiation (LTP)

Question 4

What is expression?

Answer 4

It is how synapse strength is increased

Question 5

What is maintenance

Answer 5

It is how the increased synapse strength is maintained

Question 6

List the three properties of long term potentiation

Answer 6

SIA

Saturable
Input specificity
Associativity

Question 7

Explain the long term potentiation property of “saturable”

Answer 7

Stimulated synapse can only increase in strength to a maximum level.

Question 8

Explain the long term potential property of input specificity

Answer 8

Only the activated synapses are potentiated while the other synapses are not

Question 9

Explain the long term potentiation property of associativity

Answer 9

Both postsynaptic cell depolarisation and presynaptic cell stimulation are needed for glutamate release.

Postsynaptic cell depolarisation + presynaptic cell stimulation = glutamate release

Question 10

How is long term potentiation induced

Answer 10

TθP

Tetanic stimulation

Theta burst stimulation

Pairing

Question 11

What is the purpose of these induction protocols ?

Answer 11

Associativity

For induction to occur, synapses must be active at the same time the postsynaptic cell depolarises.

Question 12

Explain tetanic stimulation

Answer 12

Stimulations of high frequency in brief bursts

release large amount of glutamate (presynaptic terminal) -> stimulate AMPA receptors -> depolarisation of postsynaptic cell

Question 13

Explain pairing

Answer 13

For 1 minute, presynaptic axons are stimulated at lower frequency & (combined with) postsynaptic cell depolarisation by current injection

Question 14

Explain theta burst stimulation

Answer 14

LTP is induced at theta rhythm (6-10 oscillation)

Question 15

Why does long term potentiation (LTP) induction need both the presynaptic transmitter release and postsynaptic cell depolarisation?

Answer 15

LTP induction dependent on calcium influx through NMDA receptor

(Sufficient postsynaptic cell depolarisation - magnesium unbounds, allowing calcium to flow through)

Question 16

How is long term potentiation (LTP) blocked

Answer 16

When NMDA receptors blockers are used during LTP induction but not after

Question 17

CaMKII : calcium calmoldulin-dependent protein kinase II

1. what is it know for
2. how is it activated
3. what does it do after activation

Answer 17

1. It is known for phosphorylating many proteins which decreases further need for calcium influx
2. It is activated by calcium influx through NMDA receptors
3. It phosphorylates AMPA receptors

Question 18

True/ false : CaMKII injection into postsynaptic cell is enough to induce LTP

Answer 18

True

Question 19

Where are AMPA receptors phosphorylated?

Answer 19

CaMKII phosphorylation site

Question 20

Phosphorylation of AMPA receptors leads to

These factors also result in increased synaptic strength

Answer 20

Increase AMPAR (AMPA receptor) conductance & increase number of AMPA receptors (AMPAR)

Question 21

The two factors that increase conductance of AMPARs….

Answer 21

1. Phosphorylation of existing AMPARs that occur during LTP
2. CaMKII phosphorylation of AMPARs

Question 22

It is known that increasing the number of postsynaptic AMPARs will induce long term potentiation. How is the number of AMPARs increased?

Answer 22

By endosmose trafficking. These endosmoses contain postsynaptic AMPARs which will later be fused into the postsynaptic apparatus.

Question 23

Describe a summary of long term potentiation (LTP)

Answer 23

Stimulation -> NMDARs activation -> calcium influx -> CaMKII activation -> AMPARs phosphorylation -> Increased AMPAR conductance & AMPARs inserted into synapses -> Increased synapse strength