Decreased Allopregnanolone Induced by Hormonal Contraceptives Is Associated with a Reduction in Social Behavior and Sexual Motivation in Female Rats

Chronic treatment with the hormonal contraceptives ethinylestradiol and levonorgestrel (EE/LNG) was found to decrease brain concentrations of the neurosteroid allopregnanolone in female rats, leading to reduced social behavior and sexual motivation. The study involved female rats treated with EE/LNG for four weeks, after which their social and sexual behaviors were assessed. The treatment significantly decreased dominance and agonistic behaviors, increased social inactivity, and eliminated proceptive behaviors, although receptivity remained unchanged. Progesterone administration restored proceptivity and increased allopregnanolone levels, while finasteride, a 5alpha-reductase inhibitor, reduced these effects. These findings suggested that the reduction in allopregnanolone due to EE/LNG treatment might explain some side effects observed in women using hormonal contraceptives.