Long-term effects of prenatal stress experiences and postnatal maternal separation on emotionality and attentional processes.

Postnatal environmental manipulations naturally occur on the background of prenatal experiences. In the laboratory rat, both pre- and postnatal environmental manipulations have been shown to alter adult behaviour. Additionally, it has been demonstrated that the consequences of postnatal manipulations can be altered by previous prenatal stress experience (PS). In the present study, we investigated long-term behavioural consequences of combined PS and postnatal experience, namely repeated maternal separation (MS). PS primarily increases emotionality and fear-related behaviour, while postnatal repeated MS has been previously reported to affect primarily attentional processes. Thus, we tested adult male and female Wistar rats on paradigms involving both emotionality and attention, namely open field, prepulse inhibition (PPI), and latent inhibition (LI) in the active avoidance and the conditioned emotional response paradigms. In line with previous reports, PS decreased open-field locomotion and impaired avoidance learning (increased emotionality), while MS enhanced LI (selective attention) and improved avoidance learning. Further, PS also increased PPI. There was little interaction between the two manipulations: The increased PPI seen after PS was normalised by MS, and the MS-induced enhancement of LI (using the active avoidance paradigm) was not evident in subjects previously subjected to PS. Taken together, these results suggest that the effects of PS and repeated MS are not synergistic in any of the investigated paradigms but can antagonise each other. Thus, in assessing the effects of postnatal manipulations, attention should be paid to the inadvertent occurrence of prenatal stress.