Figure 1: Cellular response to insertion and removal of a microneedle. (a) Low power view of cells labeled with BrdU in region of hippocampus and midbrain (; ); needle was inserted on the right side of brain (yellow line). BrdU injections were given on the day of lesion and subsequent two days. Image taken one week after lesion. BrdU+ cells are found along the needle track and in the subarachnoid space and vasculature on both sides of brain. Scale μm for panels (a), (b), (c), and (d). (b) Hippocampus (rostral to section in (a)) from the same animal on the unlesioned side. BrdU+ cells are seen in cortex, corpus callosum, the subarachnoid space, dentate gyrus, subgranular zone, and stratum lacunosum molecular of the hippocampus (one week after lesion). (c) Nonlesioned hippocampus opposite the lesioned hippocampus in panel (d) (2 wks after lesion). (d) Site and track of needle insertion (yellow line). Two weeks after lesion. (e) Nonlesioned hippocampus at higher power ( scale; μm for panels (e), (f), (g), and (h)). (f) Iba1+ cells in lesioned hippocampus. (g) BrdU+ cells on nonlesioned side, corresponding to panel (e). (h) BrdU+ cells on lesioned side, corresponding to panel (f).