Perinatal delta-9-tetrahydrocannabinol exposure disrupts social and open field behavior in adult male rats

Marijuana is the most frequently used illegal drug among women of reproductive age, but little is known about the consequences of using marijuana during pregnancy. Delta-9-tetrahydrocannabinol (Δ9-THC), one of the active chemicals in marijuana, has been shown to cross the placental barrier easily. In this study, pregnant Long Evans rats were assigned to one of three treatment groups (Δ9-THC-exposed, vehicle control, and non-treated control) on day 1 of gestation. Drug exposure consisted of 2 mg/kg of natural Δ9-THC, administered twice daily by subcutaneous (s.c.) injection, from gestational day 1 through 22. Pups continued to receive drug exposure via s.c. injection from postnatal day 2 through 10. Male rats from each group were tested starting on postnatal day 90 in a battery of tests which included open field activity, active social interaction, and the forced swim test. There were no significant differences in weight gained by dams or weight of offspring when compared to controls. Δ9-THC-exposed rats showed decreased time in the inner part of the open field and an increase in investigation time in the test of social interaction compared to both control groups. There were no differences among groups in the forced swim test. Perinatal Δ9-THC exposure may result in increased susceptibility to anxious behavior and alter social functioning in adult offspring.