>As always a nice body of work. I was wondering whether the effects you observed were specific to challenge during the preweanling stage or whether similar long term effects would occur if post-weaned animals were challenged with a similar regimen of LPS and tested after an identical period of time had elapsed? You may not have tested this, but I think it's important to determine whether the long term effects on behavioral and neuroendocrine responses are dependent on a certain state of immunological maturity and/or neural-immune interactivity specific to the preweanling stage. There is also the possibility that maternal factors vis-a-vis a "sick" pup may influence the long term outcome.
Thanks. In reply, we have not performed the experiments exposing the neonates to LPS outside of the first two weeks of life. However, Tilders has exposed adult Lewis rats to LPS and weeks later found that they remain resistant to EAE. Not sure what the mechanisms are -- may be changes in hypothalamic peptidergic regulation contributing or something more subtle in the immune/neuroendcrine interface.
As to maternal behavior, to date our analyses show now significant differences between dam's behavior for endo and sal pups (i.e. grooming bouts, time on/off nest, frequency of leaving the nest). We thought we might see something -- but alas did not. However, this does make it interesting from a developmental perspective and the importance of immune environment in steering development.