Estradiol (E(2)) modulates affective and socio-sexual behavior of female rodents. E(2)'s functional effects may involve actions through alpha and beta isoforms of estrogen receptor (ERs). The importance of E(2)'s actions at these isoforms for anxiety (open field, elevated plus maze), depression (forced swim test), and sexual behavior (lordosis) was investigated using an antisense oligonucleotide (AS-ODN) strategy. If ERbeta is required for anti-anxiety and antidepressant-like effects, and ERalpha is required for sexual receptivity, of E(2), then intracerebroventricular administration of AS-ODNs against these ERs should attenuate these effects and reduce immunoreactivity of ERs in brain regions that mediate these behaviors, such as the hippocampus and ventral medial hypothalamus (VMH). Ovariectomized rats were primed with 17beta-E(2) (10 microg) 48 h before testing (hour 0). At hours 0, 24, and 47.5, rats were infused with saline vehicle, scrambled control AS-ODNs, or AS-ODNs targeted against ERalpha and/or ERbeta, and were tested at hour 48. Rats infused with ERbeta AS-ODNs, alone, or with ERalpha AS-ODNs had significantly decreased open field central entries, decreased plus maze open arm time and entries, increased time spent immobile, and decreased time spent swimming in the forced swim test, and decreased ERbeta immunoreactivity in the brain than did rats administered ERalpha AS-ODNs, vehicle, or scrambled AS-ODNs. Rats that were administered ERalpha AS-ODNs, alone, or with ERbeta AS-ODNs had significantly decreased lordosis and decreased ERalpha immunoreactivity in the brain compared to rats administered ERbeta AS-ODNs, vehicle, or scrambled AS-ODNs. Thus, ERbeta and ERalpha may be required for E(2)'s modulation of affective and sexual behavior, respectively.