Effect of diazepam and sex hormones on EEG of gonadectomized male and female rats

Waking EEG was recorded from left and right parietals in 60 adult Wistar rats gonadectomized after puberty during 5 days, 1 as baseline, 1 with vehicle and 1 with 10 mg/kg i.m. of diazepam with hormonal treatment (either testosterone propionate, 5-α-dihydrotestosterone or vehicle in males and progesterone, estradiol benzoate or vehicle in females). Quantitative EEG analysis showed that: diazepam in gonadectomized males increased absolute power of α, β1 and β2, increased interparietal correlation of A and decreased interparietal correlation of slow θ, fast θ and β1, whereas in gonadectomized females, diazepam additionally decreased slow and fast θ absolute power. EEG effects were not modified by testosterone propionate or 5-α-dihydrotestosterone treatment in males. Diazepam plus estradiol rendered the female EEG response similar to the gonadectomized or testosterone- treated males response; diazepam plus progesterone induced the same response in females as in gonadectomized females and additionally induced interparietal asymmetry and decreased interparietal correlation of all EEG bands. Present results add information on the effects of diazepam on interparietal coupling of EEG and demonstrate that the EEG response to diazepam in adult rats is sexually dimorphic and depends on sex as well as on activational effects of gonadal steroids