What is the difference between a channel and a transporter?
A channel cycles between open and closed conformations. A transporter cycles between conformations in which a stable binding site is accessible on one side of the membrane.
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What are the three methods of channel gating?
Voltage, ligand binding or membrane stretch.
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What are the three classes of transporters?
Uniport, Symport and Antiport.
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What is an antiport transporter?
Two substances are transported together but in opposite directions as opposed to a symport transporter where they are transported in the same direction.
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How is glutamate converted?
Glutamate is converted to glutamine in glial cells. Neurons convert glutamine back to glutamate for location into vesicles by vesicular glutamate transporters.
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What does electrogenic mean?
Producing a change in the electrical potential of a cell.
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What are the ion movements powering glutamate uptake?
3 Na and 1 H are transported into the cell and 1 K is transported out.
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What are the ion movemensts powering GABA uptake?
2 Na and 1 Cl are transported into the cell.
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What happens when glutamate transporters are blocked with TBOA?
Prolongs the post synaptic current. Has the largest effects on CA1 pyramidal neurons during high freq stimulation and Schaeffer collateral fibres of CA3 pyramidal neurons.
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What role does GLT-1 play?
Has a critical role in LTP induction through regulation of extracellular levels of glutamate enabling NMDA receptor activation.
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What are the key features of ischemia?
Decreased cerebral blood flow, decreased ATP, increased intracellular Na, Ca, Cl, K and water, leads to neurotrasnmitter release and swelling and cell damage and death.
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Where does the calcium come from during ischemia?
Glutamate-driven influx of calcium ions involcing NMDA and AMPA receptors leads to postsynaptic cell death.
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What protects myelin against ischemic injury?
NMDA receptor inhibition.
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What underlies glutamate release during ischemia?
Glutamate release from pyramidal cells is calcium independent and is due to reversal uptake of glutamate.
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