Abstract

Compared to non-storing juncos, cell proliferation is enhanced in chickadees. Following hippocampal injury, however, the chickadee hippocampus hasfewer new cells than juncos, possibly due to rates of cellular turnover. To examine the temporal characteristics of cell birth in fall-caught Maine chickadees, all birds received a unilateral hippocampal lesion and one injection of BrdU (mitotic label) immediately or 24 hours post-lesion. Chickadees were euthanized 2 or 168 hours post-BrdU, after which BrdU-IR cells were counted in the hippocampus and adjacent stem cell rich pSVZ. Surprisingly, the pSVZ showed no injury-induced increase in cell birth at any time. Injury-induced hippocampal cell proliferation, however, was observed 24 or more hours post-lesion. Over time, BrdU-IR cell density in both structures remained relatively constant. Therefore, speed of cellular turnover fails to explain the differences between chickadees and juncos. Additionally, the stem cell layer does not upregulate cell birth following injury, as in other species.