Medial Amygdala Involvement in Discrimination of Same-Species and Closely-Related-Species Male Stimuli in Estrous Female Mesocricetus Hamsters

Efficient discrimination between individuals of closely related species is important to maximize reproductive potential. Some studies using males as subjects have indicated that the medial amygdala (MeA) is involved in discrimination between odors of conspecific females and females from distantly related species. The authors investigated the involvement of the MeA in discrimination by females between odors of conspecific males and odors of males of a closely related species. The authors exposed estrous or diestrous female hamsters (Mesocricetus auratus) to saline, conspecific male odors, or heterospecific (M. brandti) male odors and quantified the expression of c-fos-related antigens in the anterior and posterior MeA. They found that estrous (but not diestrous) females investigated conspecific male odors longer than heterospecific male odors. Neural activity in both the anterior and the posterior MeA was higher in estrous than in diestrous females. In the anterior MeA, there were no significant differences in response to odors of conspecific and heterospecific males. In the posterior MeA, however, neural activity was higher when estrous females were exposed to conspecific odors than when they were exposed to heterospecific odors. No such difference was observed in diestrous females.