Anxiety levels and neurosteroid synthesis in the brains of prenatally stressed male rats.

This report presents studies of the effects of immobilization stress applied to pregnant female rats during the last third of pregnancy on anxiety levels and neurosteroid synthesis in brain structures of adult offspring. Neurosteroid synthesis was assessed in terms of changes in the activity of 5alpha-reductase, the enzyme which converts progesterone into active metabolites. Prenatal stress results in a significant decrease in the level of anxiety and an increase in movement activity among adult males. Stressed rats showed increases in progesterone-5alpha-reductase activity in the hypothalamus, hippocampus, and frontal cortex. These results provide evidence that changes in the behavior of adult male rats due to stress in the prenatal period of development may be due to the formation of active progesterone metabolites in the brain.