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L2 Neural Circuits > LTP Mechanisms > Flashcards

LTP Mechanisms Flashcards

1
Q

What is a Hebbian synapse?

A

A synapse that is strengthened by coordinated activity of the pre and postsynaptic neuron

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2
Q

Which part of the brain is involved in learning and memory?

A

Hippocampus

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3
Q

What is the circuit structure in the hippocampus? (4)

A
  • Entorhinal cortex to the dentate gyrus (perforant pathway)
  • Dentate gyrus to CA3 (mossy fibres)
  • CA3 to CA1 (Schaffer collaterals)
  • Output via the fornix and subiculum
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4
Q

What is an EPSP?

A

Excitatory Post Synaptic Potential

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5
Q

What happens when you apply a high frequency stimulus to a neuron?

A

The EPSP amplitude gets bigger and more prolonged

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6
Q

What is LTP? (2)

A
  • Long Term Potentiation
  • When synapses become stronger with frequent activation
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7
Q

How is LTP input specific?

A

The increased amplitude EPSP only occurs at the synapse that has been frequently stimulated, not all synapses that contact the neuron

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8
Q

Where does LTP usually occur?

A

CA3 to CA1 synapses in the hippocampus

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9
Q

What is LTP cooperativity? (3)

A
  • Two pathways converging on the same target are both strengthened if they fire together
  • Doesn’t require high frequency stimulation
  • May explain associative learning
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10
Q

What are the 3 types of glutamate receptors?

A
  • NMDA receptor
  • AMPA (non-NMDA) receptor
  • mGlut receptor
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11
Q

What type of synapse is between CA3 and CA1 neurons?

A

Glutamatergic

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12
Q

What type of receptor is an NMDA receptor?

A

Ion channel

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13
Q

What type of receptor is an AMPA receptor?

A

Ion channel

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14
Q

What type of receptor is an mGlut receptor?

A

Metabotropic

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15
Q

How do NMDA receptors work? (3)

A
  • Mg2+ block is removed by depolarisation
  • Glutamate binds = channel opens
  • Mostly Ca2+ and some Na+ enter the neuron through the channel
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16
Q

How do AMPA receptors work? (2)

A
  • Glutamate binds = channel opens
  • Permeable to Na+ and K+ so causes depolarisation of the neuron
17
Q

Which glutamate receptor is the main one for transmission of information?

A

AMPA receptor

18
Q

How does LTP occur? (4)

A
  • High frequency stimulation causes glutamate release which activates AMPA receptors = depolarisation
  • Depolarisation + glutamate activates NMDA receptors by removing the Mg2+ block
  • Ca2+ influx through NMDA receptors activates kinases (caMKII)
  • Phosphorylation of proteins causes increase in EPSP = LTP
19
Q

What are the 2 phases of LTP?

A

Early (induction) and late (expression)

20
Q

What changes are caused by LTP? (3)

A
  • Increase in vesicle release rate
  • Increase in number of synapses
  • Increase in number of postsynaptic receptors
21
Q

Are the biggest changes in LTP pre or postsynaptic?

A

Postsynaptic

22
Q

How is caMKII activated?

A

Binding of Ca2+/calmodulin complex

23
Q

What happens during early phase LTP? (4)

A
  • Ca2+ influx via NMDAR activates caMKII which phosphorylates downstream proteins
  • Phosphorylation increases the amplitude of AMPA currents in response to glutamate
  • Phosphorylation of AMPA receptors may increase current through individual channels
  • May involve AMPAfication
24
Q

How does CaMKII work? (3)

A
  • CaMKII contains regulatory and catalytic subunit
  • Binding of Ca2+/calmodulin causes a conformational change = active
  • CaMKII autophosphorylation which stabilises CaMKII in the active conformation so can work in the absence of Ca2+/calmodulin
25
Q

What is AMPAfication?

A

An increase in the number of AMPA receptors in the postsynaptic membrane

26
Q

What happens during late phase LTP? (5)

A
  • cAMP activates pKA which enters the nucleus
  • CREB-2 is bound to CRE sequence in DNA
  • CREB-2 substituted by CREB-1
  • CREB-1 is phosphorylated by pKA and causes transcription
  • Newly made proteins travel to the synapse
27
Q

Why does late phase LTP take longer?

A

Involves changes in gene expression and protein synthesis

28
Q

What are nootropics?

A

Drugs that enhance memory

29
Q

What is the effect of inhibiting LTP on memory formation?

A

Inhibits memory formation - LTP required for memory formation

30
Q

What experiment can be used to examine the link between LTP and memory? (2)

A
  • Morris water maze
  • Mouse swims around a pool until it finds a submerged platform, repeat the experiment, the mouse learns where the platform is hidden and finds it quicker

L2 Neural Circuits (13 decks)

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