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Week 2 Flashcards

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1
Q

Why do we need to understand synaptic plasticity?

A

Get indication of underlying mechanism of learning and memory

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2
Q

What topology does glutamate receptor subunit have?

A

Tetrameric complexes with the helix region forming the pore

Pore = analogues to voltage gates ion channels

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3
Q

Once glutamates receptor have been identified on the molecular level

A

Possible to investigate where in the brain it is expressed

Investigate the different combinations to subunits that come together to form functioning ion channels

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4
Q

What are majority of AMPA receptors

A

In the CNS

Main mediators of fast, excitatory, glutamatergic transmission in the brain

Receptors that are heteromers

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5
Q

What does AMPA receptors comprise?

A

GluR2 subunits

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6
Q

AMPA receptors that have the GluR2 subunits

A

Impermeable to calcium in neurons

GluR2 subunits - form majority of these receptors in the brain

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7
Q

In the absence of GluR2

A

AMPA receptors are permeable to sodium, potassium and calcium

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8
Q

What is predominant in the forebrain?

A
  1. GluR2 and GluR1

With low levels of GluR3 and GluR4

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9
Q

What does AMPA receptors mediate at most excitatory synapse in the CNS?

A
  1. Mediate postsynaptic depolarisation as a consequence of a net influx of sodium ions
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10
Q

What are the 2 different techniques to investigate the expression of GluR1 subunits in the rat brain?

A
  1. MRNA in-situ hybridisation

2. Immunohistochemistry

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11
Q

Who was the first person to describe neurons in the brain using very primitive microscopy methods?

A
  1. Purkinje

2. See cell bodies of neurons because there was no staining techniques

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12
Q

What technique enables you to visualise the entire neurons?

A
  1. Golgi staining
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13
Q

What can antibodies be used for in the cerebellar cortex?

A
  1. Visualise the actual proteins GluR1 subunits in the dendrite in the molecular layer of cerebellar cortex
  2. Cannot see axons because the axons are not expressing the protein
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14
Q

Where doesn’t the messenger RNA go beyond?

A

The cell body

Only visualising the cells expressing the gene

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15
Q

What evidence show that kainate receptors are found?

A
  1. Pre and post synaptically in synapses in many regions of the brain
  2. Pre- and postsynaptic localisation
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16
Q

What is not uniquely associated with nervous system?

A

Ionotropic glutamate receptors

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17
Q

What structure is different from the ACH/GABA/Glycine type receptors?

A

The ionotropic glutamate receptors

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18
Q

Nicotinic ACH/GABA/Glycine family

A

Evolved completely independently from inotropic glutamate receptors as mediators or inhibitory of synaptic transmission

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19
Q

What are homologous of ACH/GABA/glycine receptors?

A

Prokaryotic

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20
Q

Where has ionotropic glutamate receptors been found?

A

Outside the animal kingdom

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21
Q

What is the most intensively studied plant species?

A

Arabidopsis

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22
Q

What is important to recognise when studying the brain?

A

Often we are dealing with genes mediating neurotransmission which have homologous in completely different organisms that doesn’t have nervous system

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23
Q

What are some examples of genes in Arabidopsis that mediate responses to light?

A
  1. Clade I - GLR1.1
  2. Clade II - GLR2.1
  3. Clade III - GLR 3.1
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24
Q

What primitive plant can fairly live in watery environment?

A

Mosses

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25
What has Glutamate receptor like (GLR) family have been implicated in?
1. Defence against pathogens 2. Reproduction 3. Control of stomata aperture 4. Light signal
26
What are the GLR genes?
1. GLR1 | 2. GLR2
27
What does the GLR1 and GLR2 cause?
1. Failure of sperm cells to target the female reproductive organs
28
What do GLR genes encode?
Non-selective Ca2+ permeable channels that can regulate cytoplasmic Ca2+
29
Why has ionotropic glutamate receptors been conserved throughout plant evolution?
Mediate cell-to-cell communication during sexual reproduction
30
What fam origins of ionotropic glutamate receptors be traced back to?
Prokaryotic world
31
What disease is linked to glutamate receptors?
1. Rasmussen’s encephalitis
32
What is Rasmussen’s encephalitis?
A disease that is characterised by seizures in children (<10) Only in one half of the cortex Typically blind on one side Post mortem shows inflammation on affected side of the brain Treatment: remove the cortical brain tissue on affected side
33
What is the disease caused by?
Autoantibodies to GluR3 Antibodies to the ligand-binding domain
34
What shares similarity with bacterial GluRs (GluR0)
Ligand binding domain
35
How does Rasmussen’s encephalitis develop?
When antibodies to bacterial GluRs cross the blood brain barrier and interact with GluR3s in the brain
36
What is permeable to calcium ions?
NMDA receptors
37
What are NMDA channels blocked by?
Magnesium when the membrane potential is at resting state
38
What can magnesium ion blockade of channel achieved by?
Membrane depolarisation
39
What is NMDA receptors thought to be?
1. Ligand gated ion channel | 2. Voltage regulated channels
40
What does maximal activation of NMDA receptors require?
Presence of extracellular glycine
41
What is glycine?
Inhibitory neurotransmitter in the spinal cord Acts in its own receptors e.g. ligand gated chloride channels
42
In the brain, what does glycine act as?
Co-activator is the NMDA receptors
43
What is used to study NMDA receptors?
Patch clamping method
44
What are all 3 receptor subtypes activated by?
Glutamate
45
What is the role of NMDA?
Selective activation of only NMDA type receptors
46
What receptor is not influenced by glycine?
Kainite
47
What is glycine able to selectively potentiate?
The action of the agonist of NMDA or glutamate on NMDA type receptors
48
Properties of NMDA receptors (graph)
Measuring currents in response to a ligand at different membrane potentials
49
What does comparing the two graphs illustrate?
How magnesium is affecting the activity of channel in more negative membrane potential which is around resting potential
50
What is the discussion of the graph?
1. The contribution of magnesium ions particularly how they affect activation of receptors in the more negative membrane potential 2. The contribution of glycine ions as a terminal of the channels
51
What was the first glutamate receptor to be discovered at all?
AMPA receptors Cloning technique
52
What was the first NMDA receptor identified?
NMDAR1
53
What was first cloned and sequences in 1991?
1. NMDAR1 | 2. GRIN1
54
What was the 6 other NMDA receptor subunit identified?
``` NMDAR2A NMDAR2B NMDAR2C NMDAR2D NMDAR3A NMDAR3B ```
55
What shares sequence similarity with non-NMDA receptors suggesting common evolutionary origin?
NMDAR1 | GRIN1
56
What comes into dentate gyrus?
Perforant fibre
57
Where are granule cells located?
Dentate gyrus Project to CA3
58
Where does CA3 pyramidal cells project to?
CA1 region Form synapses there
59
Where does CA1 pyramidal cells project out to?
Hippocampus and back to the cortex
60
Who discovered LTP?
Bliss + Lomo Performed experiments on rabbits Electrophysiological experiments
61
What did Bliss and Lomo do?
Apply electrical stimulus in the presynaptic pathway and record the EPSP post-synaptically Then they did experiment where they applied high frequency stimulus in succession
62
Large magnitude post-synaptically
1. Large EPSP | 2. More glutamate released
63
Activity in a particular pathway
Strengthening of the synapse
64
What was most experiment done on LTP
Delivering presynaptic stimulus to the Schaffer collaterals (axons of the CA3 pyramidal cells) Record from CA1 pyramidal cells with electrodes
65
What are the 2 pathways?
1. Single stimuli being delivered | 2. High frequency stimulus is being delivered
66
Pathway 1
Active High frequency stimulation is delivered Potentiation Increase in magnitude of EPSP Sustained for a long time
67
What is associativity?
If you have high frequency stimulation in pathway 1 and pair it with weak stimulation of pathway 2 Strengthening of both synapses
68
What can high frequency stimulation in one pathway influence?
Adjacent synapse provided there is some activity in pathway 2 Synapse onto the same postsynaptic cell
69
What is required for LTP to occur?
Both pre- and postsynaptic activity
70
What are the molecular mechanism of LTP?
1. Excitatory synaptic transmission in the hippocampus is mediated by AMPA-type glutamate receptors 2. Single-pulse stimulus to Schaffer collaterals causes release of glutamate, triggering a AMPA-receptor-mediated EPSP in CA1 pyramidal cell 3. Pyramidal cells also express NMDA receptors but these are not activated by a single-pulse stimulus because EPSP is not sufficient to relieve them of magnesium block 4. A high-frequency stimulus to Schaffer collaterals causes release of glutamate, triggering a large AMPA -receptor mediated EPSP in CA1 pyramidal cell 5. Elevation of post-synaptic calcium is the trigger for LTP
71
How is glutamate released?
Pre-synaptically
72
What are present in the postsynaptic cell?
1. AMPA receptors | 2. NMDA receptors
73
What are critical for LTP to occur?
NMDA receptors
74
How do you block NMDA receptors?
Antagonist - AP5
75
How does post-synaptic entry of calcium ions trigger LTP?
1. Calcium activates calmodulin 2. Calcium/calmodulin (CAM) activates CAM-kinase II 3. CAM-kinase II phosphorylates AMPA receptors 4. Phosphorylation of AMPA receptors causes increased postsynaptic responsiveness to glutamate
76
What are the consequences of phosphorylation of AMPA receptors?
1. Up-regulation of AMPA receptors on the post-synaptic cells 2. Increasing the number of AMPA receptors on the post-synaptic membrane
77
More receptors post-synaptically
Much larger response to a single stimulus than you’ve done before
78
Phenomonen aspect of LTP
Increase in the number of AMPA receptors
79
What are synaptotagmin?
Proteins that are important in regulating and mediating calcium dependent neurotransmitter release presynaptically
80
Adenovirus mechanism
Knock down gene expression in particular population of neurons
81
What are required for induction of LTP?
Synaptotagmin 1 and 7 Facilitates the process by which AMPA receptors are being released onto cell surface
82
What are synaptotagmin involved in?
1. Regulating the fusion of these AMPAR receptors with cell surface
83
CA3-CA1 synapse
1. All of the changes are occurring postsynaptically | 2. It is the up-regulation of AMPA receptors as a result of NMDA receptor activation with no changes presynaptically
84
How can you achieve a decrease in synaptic strength?p
Low frequency stimulation over sustained period
85
LTP
1. LTP is induced by high frequency stimulation | 2. 100Hz stimulation for 1s
86
LTD
1. LTDis induced by low frequency stimulation | 2. 5Hz stimulation for 3 min given twice with 3 min interval
87
LTD - opposite effect
Reduction in number of AMPAR receptors on the cell surface
88
What are activated in LTD?
1. Phosphatases 2. Calcinerium PP1 3. De-phosphorylation of AMPAR 4. Reduction of cell surface targets
89
What can be changed as a mechanism of LTP?
Size of the post-synaptic density

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