Postsynaptic Function Flashcards
What is the name of the post synaptic structure that excitatory synapses form on?
Dendritic spines
What is the theory of functional compartmentalisation?
Dendritic spines restrict the biochemical changes that result from calcium influx, to just one synapse. They prevent the events at one synapse from having a ‘sphere of influence’ on surrounding synapses.
Where are dendritic spines found?
On the dendrites of only excitatory post synaptic membranes.
What is the main form of glutamate?
L-glutamate
Is glutamate essential or non-essential?
It is classified as a ‘non-essential’ amino acid as it can be synthesised by the body - we don’t need to eat it.
What is VGLUT?
VGLUT is the vesicular glutamate transporter. It transports cytoplasmic glutamate into vesicles, using the proton gradient.
What are the core principles for defining a neurotransmitter?
Process for synthesis Stored in synaptic vesicles Calcium-dependent release mechanism Specific protein (receptor) targets Process for removal from synaptic cleft
How is glutamate removed from the synaptic cleft?
Glutamate transporters on both the pre and and postsynaptic terminals
Glutamate transporters on astrocytes
What is the distance of the synaptic cleft?
20nm
What determines if an AMPA receptor is permeable to calcium or not?
If there is presence of a GluA2 subunit within the AMPA receptor, it will be impermeable to calcium.
Give an example of a synthetic, selective, competitive antagonist of AMPA receptors.
NBQX
Give an selective agonist of GABA-b receptors.
R-Baclofen
Give an example of a selective, competitive antagonist of GABA-b receptors
CGP55845
Give an example of a selective NMDA antagonist
D-AP5
What is the difference between and EPSP and an action potential?
An EPSP is depolarisation of a cell caused by entry of sodium ions. EPSPs have an additive effect. If you have enough EPSPs, you may reach the action potential threshold and initiate a full action potential.
How large, roughly, is a single EPSP?
Only a few millivolts
What is the voltage threshold for the removal of the magnesium block in NMDA receptors?
-35mV
What is the difference between EPSPs from AMPA receptors and NMDA receptors?
Activation of AMPA receptors initiates a fast EPSP.
Activation of NMDA receptors initiates a slow-rising, longer laster EPSP.
How is GABA synthesised?
GABA is synthesised from Glutamate, by Glutamate Decarboxylase
What two membrane transporters remove GABA from the synaptic cleft?
GAT1 and GAT3
Why are dendritic spines not needed on the postsynaptic membrane for inhibitory neurotransmission?
Inhibitory receptors (GABA receptors) do not allow entry of calcium into the cell. Therefore they do not result in any biochemical changes - just voltage changes.
Why are IPSPs longer and biphasic, compared to EPSPs?
The initial ‘dip’ is mediated by the influx of chloride ions from the fast, ionotropic GABA-a receptor.
The second, shallower dip is mediated by efflux of potassium ions, mediated by the slower, metabotropic GABA-b receptor.
What is an autoreceptor?
A receptor for a neurotransmitter present on the presynaptic terminal
