Effects of prenatal exposure to diazepam on exploration behavior and learning retention in mice

Diazepam (2 mg/kg, DZP) or placebo were administered by oral gavage throughout gestation in 40 mice. The automatic hole board test for mice (Boissier and Simon) was used to measure the locomotor activity and the number of holes explored by the offspring (mean age 30.6 days). During the first test, this number represents curiosity. Its progressive decrease when the test is repeated (4 times at 1-day intervals) is a consequence of learning retention. In the first test, neither curiosity nor activity were linked with the mother's treatment or sex. During the next tests, there was no difference in locomotor activity between DZP and placebo groups. However, the DZP exposed pups explored fewer holes than controls. Although there was a tendency towards greater activity in the female group, the number of holes explored in the placebo group was significantly higher in females than in males. Paradoxically, this difference in learning memory function which exists between control males and females was not observed in the DZP group, corresponding to an impaired learning retention.