Male rats were exposed to
prenatal (i.e. before they were born) or postnatal (after
they were born) stress, or both. The prenatally stressed
males showed low levels of male copulatory behavior and
high rates of female lordotic responding. Postnatal
stress had no effect. The modifications are attributed to
stress-mediated alterations in the ratio of adrenal to
gonadal androgens during critical stages of sexual
differentiation. Specifically, it appears that stress
causes an increase in the weak adrenal androgen,
androstendione, from the maternal fetal adrenal cortices,
or both, and a concurrent decrease in the potent gonadal
androgen, testosterone." Parental Stress Feminizes and
Demasculizes the Behavior of Males, Science, January 7,
1972 (83-84)."...The present data support the hypothesis
that exposure of pregnant rats to environmental stressors
modifies the normal process of sexual behavior
differentiation in male fetuses by decreasing functional
testosterone and elevating androstenedione levels during
prenatal development. During stress conditions plasma
testosterone emanating from the gonads decreases while
adrenal androstenedione rises. The molecular structure of
the two androgens, being very similar, it is postulated
that the two hormones compete for the same receptor
sites. Since androstenedione is a less potent androgen
than testosterone, the decrease in male copulatory
ability and increased lordotic potential seen in the
prenatally stressed animals of the present study would be
expected. The relative difference in potency between
testosterone and androstendione has been repeatedly
demonstrated. "The resulting alterations in
sexual behavior provide the basis for an effective
population control mechanism, since offspring so affected
would not possess the behavioral repertoire necessary to
contribute to population growth. Thus, the environment,
by triggering an adrenal stress response, may control the
reproductive capacity of successive generations of
differentiating fetuses and, thereby, population size. "
Abstract:
