Differences in amygdala cell proliferation between adolescent and young adult rats.

Adolescence is characterized by changes in both behavior and neural organization. During this period, the amygdala, a structure that mediates social and emotional behaviors, is changing in terms of neural and glia density. We examined cell proliferation within the amygdala of adolescent (post natal day (PND) 31) and adult (PND 70) male Sprague-Dawley rats using BrdU (bromodeoxyuridine) to label dividing cells. BrdU-labeled cells were distributed throughout the amygdala, often found in fibers surrounding major nuclei. Using two independent cell counting strategies under light and confocal microcopy, respectively, we found significantly more labeled cells in the amygdala in adolescent compared to adult animals (239.3 ± 87.18 vs. 44.75 ± 13.68; n=4/group; p<.05). BrdU/doublecortin (DCX) positive cells constitute approximately 30% of all dividing cells in the amygdala in both adolescents and adults. These data suggest that compared to young adulthood, adolescence is a relatively active period of cell proliferation in the amygdala. Moreover, the normal decline in dividing cells with age does not preferentially affect cells co-containing DCX-immunoreactivity.