Abstract
We examined the sexual odor preference and opposite sex odor-induced Fos expression in forebrain regions using sexually experienced and naïve Long-Evans rats of both sexes. The sexually experienced males significantly preferred estrous female-soiled bedding over male-soiled bedding. In these animals, exposure to estrous bedding increased of Fos expression throughout the vomeronasal projection pathway (the VN pathway), i.e., posterior-dorsal medial amygdala (MePD), the bed nucleus of the stria terminalis (BNST) and the medial preoptic area (mPOA), and also in the nucleus accumbens (NAcc) core and shell. The sexually naïve males, however, did not show preference for estrous odor, and estrous odor-induced Fos expression was restricted to the peripheral portion of the VN pathway, i.e., MePD. Unlike male rats, female rats preferred male bedding over estrous bedding irrespective of the presence or absence of prior sexual experience. In both the sexually naïve and sexually experienced female rats, exposure to male bedding significantly increased Fos expression in the BNST and the MePD although Fos increment in the mPOA and the NAcc core was observed only in the sexually experienced subjects. These data suggest that mPOA, the BNST and the NAcc in male rats and the MePD and the BNST in female rats are candidate brain regions involved in the expression of preference for opposite-sex. [J Physiol Sci. 2008;58 Suppl:S93]
