The emotional reactivity increase at mid-pregnancy is attenuated in female rats handled during their infancy.

In rats, while pregnancy has been reported to increase emotional reactivity, postnatal handling, consisting in a short daily maternal separation during early life, has been shown to reduce it in several behavioural tests. In the present study, we investigated the potential effects of handling in pregnant rats confronted to various stressful situations. For that purpose, groups of DA/Han female rats were tested either in the elevated plus maze test, in the probe burying test or in a cat exposure test. At the age of 10-14 weeks, control and handled females were mated. Pregnant females were isolated (day 0 of gestation) as well as some non-pregnant females (day 0 of isolation). On day 12, pregnant and non-pregnant females were subjected to one of the three emotional reactivity tests. Our results show that pregnant females (control and handled) were more reactive than non-pregnant ones in two of the three testing situations, namely the elevated plus maze and the probe burying test. In particular, pregnant females spent less time in the open arms of the elevated plus maze than their non-pregnant counterparts and their number of close sniffing towards the probe was decreased in the burying test. Comparatively, beneficial effects of postnatal handling were obvious in the three experiments, both for non-pregnant and pregnant females. We conclude (1) that pregnancy increases emotional reactivity at day 12 of pregnancy, particularly in tests involving low or mildly stressful conditions, and (2) that postnatal handling can partially reverse those effects in all three tests, even in the more stressful situation represented by the cat exposure.