Effects of prenatal testosterone treatment on sex differences in the EEG activity of the rat.

Pregnant rats were injected either with 2 mg of testosterone propionate or with vehicle on days 14 to 19 of gestation. Ano-genital distance (AGD) and body weight (b.wt.) of the offspring were measured at 10, 20, 30, 45, 60, 75 and 90 days of age. Between 98 and 104 days of age the EEG activity was monopollarly recorded with electrodes implanted in the left and right parietal cortex. Males showed higher interhemispheric correlation than females in delta, theta, alpha] and the total band. Delta relative power (RP) was lower and theta RP was higher in males than in females. These sex differences were eliminated with the prenatal testosterone treatment (PTT), which exerted a masculinizing effect on females. Absolute power (AP) did not show sex differences, but PTT produced an increase in the AP of all bands, except for beta2, regardless of sex. PTT increased the AGD at all ages, except 90 days. This increase was significant only in females at 10, 30, 45, 60 and 75 days of age. PTT increased the b.wt. at all ages, regardless of sex. These data indicate that the organizational action of sex hormones during the prenatal period plays an important role in the establishment of EEG sex differences in the rat.