Hi Jan Homolak ,

That is a very interesting question! Although I have done research on PAL using shuttle box with different methods, I have nor even thought about the possibility of longest PAL acquisition and retrieval of shock memory!

If we do not consider habituation which typically we do not use shock, I have seen younger rats to retrieve shock memory (I'd better call it avoidance memory) even after a month (lapse of no shock)! Though as you said it depends on age and current, I think retrieval of avoidance memory could be dependent even more on the duration (of training and test sessions) as well as the range of repeats or number of shocks they receive. I think that repetitive shocks with lower mA would be more effective in consolidation of passive memory rather than the magnitude or the current of the shock per se.

Please check our paper and its methodology on PAL if you would like:

Article Chronic ghrelin administration restores hippocampal long‐ter...

Dear Jan, Izquierdo's group has shown that one-trial passive avoidance memory, under certain conditions (exposure to a novel environment 1h before the retention test) was still present in rats even 19 months after the training session.

Article Exposure to novelty enhances retrieval of very remote memory in rats

https://www.sciencedirect.com/topics/medicine-and-dentistry/passive-avoidance

Older rats do not forget passive avoidance. However, how many years do you keep your animals in the laboratory? I went to Israel to look at aggressive poultry but I learned that some animals we eat:)