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AN4017 > L3 Synapse Formation & Elimination > Flashcards

L3 Synapse Formation & Elimination Flashcards

1
Q

Where has the bulk of study on synapse formation been done?

A

Neuromuscular synapse (much larger than central synapse - easier to manipulate)

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2
Q

What is the neurotransmitter at the NMJ?

A

ACh

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3
Q

What increase surface area for AChR clusters?

A

Post-junctional folds

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4
Q

Synapse formation requires…

A

contact, AChR clustering, weeks to mature

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5
Q

Signals for pre- and post-synaptic differentiation localised to…

A

synaptic basal lamina

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6
Q

What is the basal lamina?

A

A strong, fibrous, permeable matrix that acts primarily as a base on which cells in the body can grow (also links cells together and to underlying CT)

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7
Q

Neuromuscular transmission

A

release of ACh from nerve terminal and activation of ACh receptors in postsynaptic membrane

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8
Q

Neuromuscular synapse formation in vertebrates

A

Primitive, aneural AChR clusters prior to arrival of phrenic nerve terminals distributed in a broad region in the middle of muscle fibres. Innervation leads to appearance of large AChR clusters in the synaptic region & disappearance of primitive clusters in non-synaptic areas

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9
Q

What protein is released to initiate synapse formation once an axon has arrived at its desired location?

A

Agrin

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10
Q

What is agrin a signal for?

A

post-synaptic differentiation

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11
Q

What do anti-agrin antibodies do?

A

block AChR clustering

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12
Q

Agrin initiates…

A

AChR clustering

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13
Q

True or False: In the NMJ, agrin secreted by the neuron is trapped by the basal lamina.

A

True

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14
Q

What happens to agrin -/- mice?

A

They lack normal synapses due to a reduction in AChR clusters, and therefore die after birth due to faulty diaphragm

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15
Q

Why is there inter-axonal competition for synaptic sites during development?

A

to choose the strongest synapses that’s required to last, in many cases, a lifetime

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16
Q

__ does not lead to a net weakening of synaptic drive on target cells - the remaining input is the ‘best’

A

Synaptic elimination

17
Q

At birth, multiple axons converging at the NMJ are intermingled (inter-axonal competition). By postnatal day __ , a single axon innervates the post-synaptic site.

A

15

18
Q

__ neural activity is a feature in early brain development

A

Synchronous

19
Q

As development continues, patterns of neuronal firing of motoneurons changes from synchronous to asynchronous, which leads to __

A

inter-axonal competition and synaptic elimination

20
Q

What is the irreversible competitive AChR antagonist found in snake venom?

A

Alpha-bungarotoxin (blocks transmission through AChR clusters, thereby blocking activity in postsynaptic cell)

21
Q

What is crucial for the maintenance of synapses?

A

Post-synaptic activity

22
Q

Does asynchronous neuronal firing develop before or after synapse elimination?

A

before

23
Q

What is the Neurotrophic Factor Hypothesis?

A

Developing neurons compete with each other for a limited supply of a NTF provided by the target tissue i.e. the neuron that takes up the most BDNF, for example, survives

24
Q

The pro-form of BDNF binds…

A

p75 (low affinity receptor)

25
Q

The mature form of BDNF binds…

A

TrkB (high affinity tropomyosin-related kinase receptor)

26
Q

True or False: The pro-form of BDNF is biologically inactive

A

False - it just binds a different receptor to mBDNF

27
Q

What protein also forms a high affinity binding site with p75?

A

Sortilin

28
Q

Mature neurotrophins can stimulate __

A

neuronal survival

29
Q

Pro-neurotrophins may induce __

A

apoptosis

30
Q

Intracellular cleavage of proneurotrophins by the action of …

A

furin or proconvertase

31
Q

Extracellular cleavage of proneurotrophins by the action of …

A

matrix metalloproteinase (MMP)-7 or -9

32
Q

Morpholino knock-down endogenous TrkB shows that…

A

mBDNF plays an active role in preventing synaptic retraction of the active terminals through TrkB

AN4017 (8 decks)

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