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LTP and post-tetanic potentiation

Bill Skaggs skaggs at bns.pitt.edu
Tue Apr 13 07:49:30 EST 1999


On 2 Mar 1999 17:07:14 GMT, Sturla Molden <stumol at stud.ntnu.no> wrote:
>
> I have a technical question regarding LTP and PTP:
> If LTP is induced massively in a brain slice (until
> saturation level), will that also occlude new PTP
> in the slice? Or, rephrased, do LTP and PTP have
> some common expression mechnisms? I would be very happy
> if anyone could direct me to recent litterature on the
> matter.

Grushnik wrote in message <37090de3.25058581 at news.ox.ac.uk>...
>
> I'm not too sure about this, but I thought PTP was an artefact of the
> electrical stimulation of the presynaptic cell. (ie. after a tetanus,
> there is an accumulation of calcium (or whatever signal)
> intracellularly and so less is needed if the cell is stimulated
> again).
> Perhaps what you mean is STP. In which case I can't help you since I
> don't know much about it either. I don't think much is known about it,
> although I do recall being told by my tutor or someone that they
> probably share some common elements.

"Richard Goodwin" <libiengoodwin at mindspring.com> writes:
> 
> Some of my colleagues might have papers that are of interest to you- check
> out Hrabetova and Sacktor.  If you have really saturated LTP, I don't think
> you can get further potentiation (may instead get a spreading depression)
> but if you induce LTD (reversal) you should then be able to potentiate.
> Also may want to look at Nicoll.  By the way are you using hippocampal
> slices?


LTP, even at saturation levels, does not occlude PTP.  PTP is a
short-lasting presynaptic effect, whose mechanism is independent of
LTP.  I don't have a specific reference for this, but it can be seen
in any number of LTP papers.  When a tetanic stimulus is delivered, it
typically gives rise to a large increase in response, which decays
within a few minutes.  This is PTP.  When LTP is evoked, the decay is
to a level that is elevated above the original baseline; but even if
there is no long-lasting potentiation, the short-lasting PTP is still
there.  

To go back to the original question, one cannot say with any certainty
that there is NO interaction between LTP and PTP, but it is certainly
true that PTP often occurs even when LTP does not.

	-- Bill



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