Lecture 13 - Synaptic Plasticity I Flashcards
What does glutamate uncaging causing LTP indicate about the nature of LTP?
Since glutamate uncaging activates postsynaptic glutamate receptors without the involvement of the presynaptic cell, uncaging causing LTP indicates that LTP is a postsynaptic phenomenon.
True or False?:
LTP requires a rise in postsynaptic potassium.
False
LTP requires a rise in postsynaptic calcium.
What happens to an inactive synapse when another synapse on the same postsynaptic cell is given a strong stimulation (tetanus)? What is this trait called?
The inactive synapse is not strengthened. This is called specificity. The strengthening of the stimulated synapse is specific to just that synapse.
True or False?:
Weak but prolong stimuli can cause heterosynaptic LTD.
False
Weak but prolong stimuli can cause homosynaptic LTD.
What happens to long-LTP (L-LTP) if protein synthesis is inhibited? Does the same happen for LTP?
If protein synthesis is blocked, L-LTP will degrade over time (relative to a control) because there will not be enough protein available to enlarge the spine and add more AMPARs. This does not happen for LTP because it isn’t as long and uses proteins already present in the cell.
What happens to a synapse when it is weakly stimulated at the same time that another synapse on the same postsynaptic cell is given a strong stimulation (tetanus)? What is this trait called?
The weakly stimulated synapse will be strengthened. This is called associativity. Since the inputs are activated together, they will both strengthen.
LTP and LTD are both dependent on an influx of Ca2+. Why does calcium trigger protein phosphatases in LTD to reduce the amount of AMPARs while it triggers CaMKII in LTP to increase the amount of AMPARs?
Protein phosphatases have a high calcium affinity and protein kinases (CaMKII) have a low calcium affinity. When there is a low amount of calcium, more is bound by the high affinity phosphatases than the low affinity kinases. When there is a high amount of calcium, the low affinity kinases are able to bind at a rate higher than that of the phosphatases. As such, LTD facilitates a low intracellular calcium concentration while LTP facilitates a high intracellular calcium concentration.
True or False?:
The pairing of pre-synaptic activity with direct post-synaptic depolarization will induce LTP.
True
What happens when you stimulate the Schaffer Collateral-CA1 synapse after tetanus relative to before tetanus? What is this called?
After tetanus, it becomes more depolarized than before tetanus. This is called long-term potentiation.
What is the most studied synapse in the brain? Why?
CA3(/Schaffer Collaterals) to CA1 (in the Hippocampus)
It is one of the most studied because of its accessibility, but mostly because it is thought to be a key structure for memory.
What are the distinct temporal phases of LTP?
- Insertion of more AMPARs
- Local synthesis of dendritic mRNAs
- CREB dependent transcription
- Growth of spines
True or False?:
LPT occurs at synapses on spines.
True
What did Hebb postulate?
“When an axon of cell A… excite[s] cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells so that A’s efficiency as one of the cells firing B is increased.”
(Neurons that fire together wire together.)
What did Stent’s extension of Hebb’s Postulate state?
“Neural connections weaken when they are inactive at the same time that the postsynaptic neuron is active or will weaken if they are active but consitently fail to cause the cell to fire an action potential.”
What happens when you shine UV light on caged glutamate?
Glutamate separates from the rest of the cage.
What happens to long-term potentiation if NMDARs are blocked?
LTP will not occur. The initial spike seen in the graph on the right is due to PTP.
What changes to the long-term change to synaptic strength when the amount of NMDA receptor activation increases?
LTD will occur at low NMDA activation, but as you increase it, LTP will occur.
What happens to LTP when CaMKII autophosphorylation is blocked?
There is a brief increase but it is not long-lasting.
What do motor learning and novel sensory experiences lead to in mice?
Motor learning and novel sensory experiences promote rapid dendritic spine formation.
What are the two types of long-term depression? How does each happen?
Heterosynaptic - Synapse is weakened because it is inactive when the neuron is active.
Homosynaptic - Synapse is weakened because it is active but fails to cause the cell to fire an action potential.
What is the benefit of using 2-photon excitation microscopy instead of 1-photon excitation microscopy?
2-photon results in fluorescens from the focal spot only while 1-photon will have fluorescence in out of focus planes.
What are the characteristics of long-term potentiation that are expected for memory?
- Persistence - Is maintained for a long time following a rapid induction.
- Input Specificity - Induced only at appropriately stimulated synapses, and not neighbouring unstimulated synapses.
- Associativity - Inputs activated together will strengthen.
How does botox inhibit LTP?
Botox interferes with vesicle fusing by damaging the SNARE proteins. The AMPARs that are moved to the synaptic membrane to cause LTP are stored on vesicles. As such, botox inhibits more AMPARs from being added to the synapse.
True or False?:
L-LTP requires CREB activation and dendritic protein synthesis.
True
