Dear colleages,
I'm trying to evoke LTP in CA1 of 2-3 months old mice using a TBS protocol. Up to now, I've tried the two following ones:
a.- Bursts of 4 pulses at 100 Hz, given 10 times and interspaced 200 ms.
b.- The very same stimulation protocol but applied three times with 20s interval.
Up to now, I have just tried in controls -finding LTP in almost all of the slices-, but I am about to start doing experiments in transgenic mice and I would like to know which protocol may be better in my condition. Which are the benefits and caveats of each of these protocols? I guess the three-times stimulation protocol is stronger, but I find in most papers the authors use the one-time stimulation.
May someone contribute with some hints?
Thanks in advance;
Sergio
Dear Sergio
it depends a little on what exactly you want to investigate. Both protocols are pretty strong. They will elicit (close to) the maximum possible potentiation. The second protocol will probably be strong enough to cause L-LTP, the very long lasting (3 hours), protein synthesis dependent form of LTP. So, if you are interested in those processes, that would be the protocol to go for. However, if you have a mutant that leads you to believe the difference might not be in the protein synthesis dependent phase or in the maximum amount of potentiation, I would go for another protocol.
I would suggest to use two protocols. One using only two trains of 4 pulses at 100Hz spaced 200ms. This is the absolute minimum. It will be on the threshold of evoking potentiation. Any very subtle difference between mutant and wild-type would probably be picked with this protocol. The other I would use the more standard 4 trains of 4 pulses at 100Hz spaced 200ms. Record for 1 hour after induction, unless you are interested in the L-LTP as mentioned above.
good luck and do not hesitate to ask follow up questions
Nils
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