Lecture 12 - Second Messengers II Flashcards
True or False?:
CREB activation and protein synthesis can be necessary for long-term synaptic plasticity.
True
What is gCAMP6?
gCAMP6 is an expressible calcium sensor protein that combines GFP with a calcium sensing component.
What acts as a calcium sensor for presynaptic short term plasticity?
PKC
What happens if synaptotagmin-7 is knocked out in mice?
Neurons still synaptically send signals, but PPF does not occur.
How is a long-term effect induced in the A**plysia gill and syphon withdrawal reflex?
The interneuron releases transmitter which acivates Gs to produce cAMP to activate PKA. When a lot of PKA is activated for a long time, the cell will degrade the regulatory domain and just leave the catalytic domain. The isolated catalytic domain will migrate to the nucleus and phosphorylate CREB, which will cause unidentified proteins responsible for synaptic growth to be synthesized.
Where does paired-pulse depression occur?
PPD tends to occur at synapses with high release proabilities.
When does paired-pulse facilitation occur?
PPF occurs when two action potentials are fired in a row.
Why is PPD thought to occur?
PPD is thought to be due to depletion of transmitter vesicles in the pre-synaptic terminal.
Why is PPF thought to occur?
PPF is thought to be due to residual calcium remaining in the pre-synaptic terminal resulting in more neurotransmitter release.
What will occur when a cell is given a stimulus of 400 Hz for 2 seconds?
Post-Tetanic Potentiation (PTP)
Which pathway is triggered in the sensory neuron (through the interneuron) by a shock on an Aplysia’s tail? What is the short-term effect of this?
The G-protein Gs α-subunit pathway (PKA signaling) is triggered by the shock. PKA phosphorylates K+ channels (making them close) which slows down the rate of post-action potential repolarization and increasing the amount of time spent above the threshold. When above threshold, more calcium comes in (because the voltage-gated channels stay open) and more vesicles are able to fuse and release neurotransmitter. This results in more postsynaptic response and more muscle contraction.
What triggers the opening of the ryanodine channel?
The ryanodine receptor opens when the cytosolic Ca2+ concentration increases. Calcium will bind to the receptor and open it to release more calcium.
How does release probability impact the strength of a subsequent synaptic signal?
At high release probabilities, many vesicles fuse during a synaptic event, resulting in less vesicles being ready to fuse for a second close event and less neurotransmitter being released onto the postsynaptic cell (causing PPD). At low release probabilities, there are still many vesicles left over after the first synaptic event, so the higher level of calcium during the second event will result in more vesicles fusing and more neurotransmitter being released onto the postsynaptic cell (causing PPF).
True or False?:
Dunce (no phosphodiesterase which degrades cAMP) and rutabaga (no adenylyl cyclase which makes cAMP) Drosophila mutants perform worse when tested so see if they learned which smell in a T-maze will give them an electric shock.
True
True or False?:
In Aplysia, habituation is a decrease in the strength of the sensory-motor neuron synapse while sensitization is the induced increase in the stength of the same synapse.
True
How do Aplysia show habituation?
Aplysia show habituation by varying their response to touching their siphon (where they breath from). When touched once, they completely contract their gill. After being touched many times, they realize that the touch is not a threat and they do not continue to contract their gill.
Which types of short term plasticity will occur (and when) in response to the following presynaptic stimuli?
PPF followed by PPD followed by PTP.
What happens to a cell that exhibits PPD when the extracellular calcium concentration is reduced to 10% of its normal level?
The cell will experience PPF because the release probability is lowered since there is less calcium available to flow into the cell to initiate vesicle fusion.
