Prenatal stress effects over two generations in rats.

Persistent effects of stress were found in second generation rats bred from females whose own mothers had been stressed during pregnancy. The second generation rats grew more slowly, with a plateau in the growth being reached at the same age as in the controls. This resulted in adult animals of both sexes being permanently smaller than their control counterparts. When these offspring were subjected to short-term stress (one session) in adulthood, the response was not significantly different to that for the controls, indicating an intact emergency response. The male offspring from the stressed group, however, had a significantly (P less than 0.01) higher plasma progesterone concentration, and a significantly (P less than 0.01) lower testicular enzymic 3 beta-hydroxysteroid dehydrogenase activity at rest, when compared with the control offspring. The fertility of the mature female from the stressed group was not affected as a third generation of litters born did not differ from the controls. It is suggested that a changed genetic programme in the ovarian germ cells of the first generation and/or a changed uterine environment in the second generation may be implicated.