The role of sex steroids in forming anxiety states in female mice.

Natural fluctuations in sex hormones during the ovarian cycle have enormous influences on ongoing psychological status in the female body. We report here studies of the effects of exogenous sex steroids on anxiety levels in female mice, as evaluated in the elevated cross maze test. Female NMRI mice were subjected to bilateral oophorectomy and one week later received s.c. injections of solvent (sesame oil, controls) or estradiol benzoate for 7 days, either alone or with an additional dose of progesterone on day 7. Elevated maze tests performed 6 h later showed that animals given progesterone had the highest levels of anxiety and the highest levels of grooming reactions as compared with the other groups. Immunohistochemical analysis of the distribution of progesterone receptors in different parts of the brain demonstrated significant increases in the numbers of immunopositive cells after injections of estradiol benzoate alone, with further increases after progesterone injections. Thus, the data obtained here suggest that the genomic effects of sex steroids are important, as they appear to be involved in non-sexual forms of behavior, particularly the level of anxiety.