111.4 Saturday, Jan. 7 Effects of corticosterone and dehydroepiandrosterone on adult neuroplasticity in songbirds WADA, H; NEWMAN, AEM; HALL, Z; SOMA, KK; MACDOUGALL-SHACKLETON, SA*; Univ Western Ontario; Univ Guelph; Univ Western Ontario; Univ British Columbia; Univ Western Ontario email@example.com
Chronically elevated glucocorticoids can impair brain development and reduce adult neurogenesis. In songbirds, the brain region HVC, which is critical for song learning and production, is particularly sensitive to glucocorticoids. For example, stressors during development impair HVC growth. In addition, in adult nonbreeding song sparrows,corticosterone (CORT) treatment reduces HVC size, the number of neurons in HVC, and the number of newly incorporated BrdU-labeled cells in HVC. Interestingly, these effects of CORT on HVC were prevented by co-administration of dehydroepiandrosterone (DHEA). CORT did not reduce BrdU-labeled cell number in the telencephalon outside of HVC, or along the mitotic subventricular zone. Here, we tested whether CORT reduced neuron migration to HVC by immunolabeling tissue for doublecortin (DCX), a microtubule-associated protein expressed in migrating neurons. CORT treatment significantly reduced the numbers of DCX-labeled cells and fibres in HVC. However, DHEA treatment did not significantly increase DCX-labeled cells or fibres in HVC. These data suggest that the neurodegenerative effects of CORT on HVC are mediated by disrupting neuron migration, but that the neuroprotective effects of DHEA occur through other processes such as reducing apoptosis and/or promoting neuron survival.