Synaptic Transmission 2 Flashcards
What is synaptic plasticity?
the ability of the synapse to change its properties depending on its recent level of activity
What is thought to be the basis of learning and memory?
synaptic plasticity
Describe how to record long-term potentiation/plasticity. Which structure of the brain is involved?
- stimulate schaffer collaterals
- CA3 releases NTs
- CA1 stimulated
- record CA1 activity
(in hippocampus)
What kind of memory is the hippocampus mainly involved in?
spatial memory
What is the cellular correlate of learning and memory?
LTP
What is the specificity and associativity of LTP?
- specificity: synapse strengthened for pathways highly activated (at high frequencies)
- associativity: b/c path 2 fires with path 1, both paths’ synapses are strengthened
TRUE or FALSE: in synaptic plasticity, a larger presynaptic stimulus results in a larger post-synaptic response (in comparison to baselin)
FALSE: SMALLER stimulus results in SIMILAR response
Draw a diagram using 3 different neurons to demonstrate how synaptic strength can be increased.
slide 6
TRUE or FALSE: highly active synapse = strengthened synapse
TRUE
TRUE or FALSE: changes in the postsynaptic cell lead to a strengthened synapse
FALSE: changes in both pre and postsynaptic cells are requireD
How did Donald Hebb describe the mechanism for the strengthening of synapses?
some growth process or metabolic change takes place in one or both cells so that A’s EFFICIENCY as one of the cells firing C is increased
What are the 2 properties of LTP?
specific and associative
What is the Hebbian definition for LTP?
an enduring increase in synaptic efficacy resulting from an activity dependent (Hebbian) process
Where was LTP first discovered in the brain? Where has it been shown to exist?
hippocampus; most glutamatergic synapses in the brain
What are the 2 requirements to get a larger postsynaptic event?
- more receptors on surface
- increase conductance states of channels (more ions flow into post cell
Before tetanic stimulation, the slope of the synaptic potential is _________. After, it is ________.
low; high
How long can LTP last?
days to weeks
What are the 3 LTP phases?
- early - INDUCTION phase
- medium - EXPRESSION phase
- late - MAINTENANCE phase
In summary, what occurs during the early induction phase of LTP?
NMDA receptor activation and calcium dependence
In summary, What occurs during the medium expression phase of the LTP?
- changes to receptors and release machinery
- local protein synthesis
In summary, What occurs during the late maintenance phase of the LTP?
- genomic involvement
- translation dependent
- anatomical changes?
TRUE or FALSE: after tetanic stimulation, synaptic currents are smaller in amplitude
FALSE: larger amplitude
At what frequency should you tetanically stimulate a cell to induce LTP?
100 Hz
Describe the mechanism of the induction phase of LTP.
- NMDAR activated –> double-gated coincidence detector (ligand-dependent AND voltage-dependent…bind glu, remove Mg2+)…see notes in previous unit
- Ca2+ entry through NMDA
- increase Ca2+ intracellular triggers increase in post responsiveness: increases in post AMPAR, pre NT release, and synaptic contacts
- LTP is induced
- this INDUCES LTP
(i.e. unblock NMDA –> Ca2+ flows in –> express LTP)
The influx of which ion is necessary for LTP?
Ca2+
Which receptor is crucial for induction of LTP?
NMDA
TRUE or FALSE: blocking NMDA prevents LTP
TRUE
Describe the mechanism of the expression phase of LTP.
- Ca-MKII inserts and traffics AMPAR’s to membrane
- more AMPAR = larger synaptic response
Which enzyme is crucial for the expression phase of LTP?
Ca-MKII
TRUE or FALSE: the number of silent synapses is increased during LTP
FALSE: decreased
What is a silent synapse?
- synapse in which the postsynaptic membrane only expresses NMDA receptors
- note: NMDA receptors are not activated due to the Mg2+ block
How does LTP affect silent synapses? Describe the mechanism.
AMPARs are inserted into synapses during LTP (i.e. decrease number of silent synapses where only NMDARs are present)
TRUE or FALSE: silent synapses contain only AMPARs
FALSE: only NMDARs
What kind of stimulation is required for insertion of AMPAR into the synapse?
tetanic stimulation
At what frequency should you stimulate a cell to induce LTD? LTP?
- LTD = 1 Hz
- LTP = 100 Hz
What is long-term depression (LTD)?
smaller post-synaptic response due to removal/retrieval of receptors (AMPA)
note: LTP = larger response due to insertion of AMPAR
What is the difference between expression and maintenance phases of LTP?
- expression = local signaling and local protein synthesis
- maintenance = nuclear involvement via genomic translation
Is the cellular mechanism of LTP pre or post-synaptic?
post?
Are retrograde factors involved in LTP?
YES (ask someone to explain)
Describe the mechanism of LTD.
(opposite of LTP)
Ca2+ dependent synaptic depression
- less Ca2+ entry into cleft = oppose synaptic enhancement
- evoked by both NMDAR and V-gated Ca2+ channel activation
- include both pre and post-synaptic elements: decreases in post AMPAR, pre NT release (glu), synaptic contacts
