In addition to the dentate gyrus of the hippocampus (DG) and the anterior portion of the subventricular zone (SVZ) , newly proliferated cells are found in other brain areas, including the amygdala--an area implicated in many physiological and behavioral functions. In our recent study in female prairie voles (Microtus ochrogaster), cells labeled by a proliferation marker, 5-bromo-2'-deoxyuridine (BrdU), were found in the amygdala, and male exposure and mating induced an enduring increase in the number of BrdU labeled cells in the amygdala. As male exposure and mating induce social attachment between female and male prairie voles, and the amygdala is important for the social attachment formation, we hypothesize that the stimuli associated with male exposure increase the number of newly proliferated cells in the amygdala, which, in turn, play a functional role in social attachment formation in female prairie voles. To test this hypothesis, we first study the effects of stimuli associated with male-exposure, such as an increased level of estrogen and mating behavior, on cell proliferation and cell death in the amygdala of female prairie voles. Thereafter, we treat animals with an anti-mitotic drug in general or site-specifically into the amygdala to examine the effects on cell proliferation and social attachment. These data will not only broaden our understanding of the functional significance of newly proliferated cells in general, but also provide valuable information regarding involvement of new cells of the amygdala in social attachment formation in particular.