A comparison of behavioural effects of prenatally administered oxazepam in mice exposed to open-fields in the laboratory and the real world.

Prenatal benzodiazepine exposure has been reported to result in abnormal neurobehavioural development in laboratory animals but little is known about the behavioural relevance of this effect ina naturalistic environment. In this study, outbred CD-1 male mice were prenatally exposed to oxazepam (15 mg/kg per os, twice daily) on days 12-16 of fetal life and fostered at birth to untreated dams. At adulthood, each mouse was fitted with a radio collar and its first reactions assessed. Three hours later, behavioural and exploratory activities were recorded in a laboratory open field, and 24 h later in a natural setting. Immediate reactions to the radio collar were higher in the oxazepam-treated mice than in controls consisting of more attempts to remove it and an increase of push-digging. The attempts to remove the collar were still evident in oxazepam treated mice tested in the laboratory open-field 3 h later. Moreover, oxazepam increased the frequency of grooming and reduced walking in both the laboratory and the natural settings. In the natural settings running was increased during the initial 30-min test, while a pronounced level of grooming and a lower frequency of eating were observed 140 min after release. Frequency of sniffing, grooming, and rearing behaviours were higher in the laboratory test when compared to the natural settings. On the other hand, prolonged bouts of sniffing were recorded in the natural environment. These findings permit separation of robust drug effects (increased grooming, reduced walking) from situation-dependent effects, the natural environment revealing, in addition, more subtle effects.