Prenatal stress alters the size of the rostral anterior commissure in rats.

In rodents and other mammals, prenatal stress disrupts both sexual differentiation and sexual behavior. The present study examined the area of the anterior division of the anterior commissure (the Aca) in coronal, thionin-stained sections of prenatally stressed (P-S), and control male and female rats. Pregnant rats were exposed to thrice-daily heat, light, and restraint stress or left undisturbed during days 15-22 of pregnancy. Adult P-S and control males and females were killed, perfused, and their brains removed. Serial coronal sections (total of approximately 200 microm) through the rostral portion of the Aca (the rAca) were taken and stained with thionin. The sections were examined and traced under x25 using computerized microscopy to obtain the area in mm2. The data revealed that control females had a larger rAca compared to control males, and that P-S males had a larger rAca compared to control males; further, control males and P-S females were not significantly different, nor were control females and P-S males. These results suggest that, in rats, the Ac may be sexually dimorphic (in a direction similar to that described in humans) and that prenatal stress an event that modifies sex-typical behavior, physiology, and neuroanatomy reverses that sex difference.