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LTP vs LTD

Wookie koetje at boe.nl
Mon Feb 22 15:45:03 EST 1999


It seems that in the Hippocampus there are two mechanisms that can
countereffect each other.
LTP [long term potentiation] which increases synaptic strength (larger
EPSC's which leads to larger EPSP's) 
and LTD [Long Term Depression] that decreases synaptic strength.
In both mechanisms there seems to be a roll for Ca2+.
In LTP the post-synaptic [Ca2+] rises very high (up to 5 micromolar)
in LTD the post-synaptic [Ca2+] rises only slightly [lower than 1
micromolar].
So there you have it, these differences in concentration determine
what enzymes are used.
In LTP (with high concentrations Ca2+)  Protein kinases are activated
while in 
LTD (with low concentrations Ca2+) Protein phosphatases are activated.
I'm lost here , how can this be?
How can this difference in concentration alone account for the choice
of enzymes?
My guess is that there is some time dependence too.
In LTP there is a huge Calciumflux in a short period
whle in LTD there are small calcium fluxes in shorter periods.
Who knows more about the relation between Ca2+ concentration and 
the activiation of kinases/phosphatases?

Wookie





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