Abstract
The posterior-dorsal medial amygdala (MePD) contains a large amount of sex steroid receptors and processes pheromonal signals. The involvement of the MePD in the expression of male-directed odor preference of female rats was investigated. In experiment 1, ovariectomized female rats were bilaterally implanted with guide cannulae aimed at the MePD. These rats were primed with estrogen benzoate (EB) and pretested for the expression of preference for air-borne odors from a sexually active male as opposed to an estrous female. Three weeks later, these subjects were retested to confirm that the odor preference was completely eliminated, and then they were implanted with either 100% crystalline estradiol (E) (High E Group) or 10% E (diluted with choresterol; Low E Group) through inner cannulae (30-gauge) 48 h prior to behavioral testing. Odor preference was restored in neither group. In High E Group, however, lordosis behavior was observed. This suggests that at least in this group the level of estrogen in the vicinity of the MePD, such as the ventromedial nucleus of hypothalamus, was high enough to induce physiological events. In experiments 2, implantations of tamoxifen (anti-estrogen) were made instead of E through inner cannulae (24-gauge) together with EB priming 48 hr prior to behavioral testing. Odor preference was not restored by these treatments although lordosis behavior was observed. Taken together, these results suggest that estrogen activation at the MePD was necessary, but not sufficient, to express male-directed odor preference of female rats. [J Physiol Sci. 2008;58 Suppl:S93]
