Testosterone enhancement during pregnancy influences the 2D:4D ratio and open field motor activity of rat siblings in adulthood.

In humans, the relationship between the prenatal testosterone exposure and the ratio of the second and the fourth digits (2D:4D) has been extensively studied. Surprisingly, data on this relationship have thus far been lacking in experimental animals such as rats. We studied the effect of maternal testosterone enhancement during pregnancy on the digit ratio and open field activity of adult progeny in Wistar rats. Elevated levels of maternal testosterone resulted in lower 2D:4D ratios and an elongated 4D on the left and right forepaws in both males and females. We found no sex difference in 2D:4D in control animals. In the open field test, control females were more active than control males and testosterone females, while the activity of testosterone females did not differ from that of control males. We found a positive correlation between motor activity and the right forepaw 2D:4D ratio of control males and females. Prenatal exposure to testosterone resulted in the disappearance of this correlation in both males and females. Our results show that elevated levels of testosterone during the prenatal period can influence forepaw 4D length, 2D:4D ratio, and open field motor activity of rats, and that these variables are positively correlated. Thus, this approach represents a noninvasive and robust method for evaluating the effects of prenatal testosterone enhancement on anatomical and physiological parameters.