The Role of Estrogen Receptor ß in the Dorsal Raphe Nucleus on the Expression of Female Sexual Behavior in C57BL/6J Mice.

ABSTRACT

17ß-Estradiol (E2) regulates the expression of female sexual behavior by acting through estrogen receptor (ER) α and ß. Previously, we have shown that ERß knockout female mice maintain high level of lordosis expression on the day after behavioral estrus when wild-type mice show a clear decline of the behavior, suggesting ERß may be involved in inhibitory regulation of lordosis. However, it is not identified yet in which brain region(s) ERß may mediate an inhibitory action of E2. In this study, we have focused on the dorsal raphe nucleus (DRN) that expresses ERß in higher density than ERα. We site specifically knocked down ERß in the DRN in ovariectomized mice with virally mediated RNA interference method. All mice were tested weekly for a total of 3 weeks for their lordosis expression against a stud male in two consecutive days day 1 with the hormonal condition mimicking the day of behavioral estrus, and day 2 under the hormonal condition mimicking the day after behavioral estrus. We found that the level of lordosis expression in ERß knockdown (ßERKD) mice was not different from that of control mice on day 1. However, ßERKD mice continuously showed elevated levels of lordosis behavior on day 2 tests, whereas control mice showed a clear decline of the behavior on day 2. These results suggest that the expression of ERß in the DRN may be involved in the inhibitory regulation of sexual behavior on the day after behavioral estrus in cycling female mice.