Effects of maternal stress during pregnancy on forced swimming test behavior of the offspring.

It has been reported that gonadal steroids modulate brain and behavioral sex differentiation during development. Prenatal maternal restraint also alters development by affecting gonadal steroid levels in the fetus. Prenatal maternal restraint of animals decreases sex differences for sexual behavior, locomotion, aggression, etc. In recent work on animal models, we reported that, like humans, laboratory rats show sex differences in depression. From the present study, performed on Sprague-Dawley rats, we conclude that: 1) there are sex differences for depression in two different animal models (swimming-induced immobility and natatory tests); 2) there are also sex differences in open-field behavior; 3) prenatal maternal restraint decreases sex differences for depression but does not affect sex differences in open-field behavior; 4) prenatal maternal restraint affects female but not male behavior in the two depression tests used. These results suggest that: 1) sex differences reported in animal models of depression are under the control of gonadal steroids during prenatal brain development; 2) stress during early phases of development increases the risk for depression in adulthood.