Evidence of a relationship between aversive learning and hippocampal interleukin 1 beta levels in neonatal handled rats

Abstract

The Neonatal Handling (NH) model presents a “blunted” corticosterone response to stress as well as an enhancement in contextual fear tasks. So the aim of this work was to examine a possible relationship between diminished imunosuppression over Interleukin 1 beta (IL-1) hippocampal levels and enhancement in aversive learning. To achieve that, we subjected male handled Wistar rats 30-35 and 90 days old to an inhibitory avoidance task, comparing the avoidance scores with respective hippocampal IL-1 levels at different time points. We found that handled adult animals learned the aversive task concomitantly with higher levels of hippocampal interleukin 1 beta 2h after footshock, while control animals showed diminished aversive learning and lower IL-1 beta levels at the same time. In the other hand, both handled and non-handled juvenile rats learned the aversive task, with no signal of immunosuppressant efect over interleukin 1 beta. However, basal levels of IL-1 beta were different between handled and non-handled animals in both ages, pointing a novel neuroimmunomodulation involvement to the NH model.