Effects of perinatal diazepam administration on two sexually dimorphic nonreproductive behaviors.

The effects of prenatal and/or early postnatal diazepam (DZ) administration on open field activity and continuously reinforced lever-pressing response were studied. Rat pups of both sexes were prenatally (during the last week of pregnancy) and/or postnatally (from the day of birth to day 16) daily exposed to a 2.5 mg/kg dose of DZ. At the age of 60 days all groups were tested in the open field for 5 consecutive days and thirty days later they were studied in a continuously reinforced lever-pressing situation during four consecutive days. In the open field test, females showed greater activity than males and prenatal and/or early postnatal DZ treatments did not alter this sexual dimorphism, although all treatments decreased the open field activity in both male and female 60-day-old rats. In the Skinner box, 90-day-old males presented higher rates of lever-pressing response than females, and only the early postnatal DZ treatment was effective in altering this sexual dimorphism, by decreasing the male's but not female's rates of response. These results are discussed in regard to the possible interaction between DZ and gonadal hormones during the early sexual differentiation period.