Figure 6. Lack of microglial activation following siRNA infusion.

α-Synuclein siRNA was unilaterally infused through a cannula positioned approximately 1 mm dorsal to the substantia nigra. Representative midbrain sections were immunostained for microglial cells using an antibody against ionizing calcium-binding adaptor molecule 1 (Iba-1, brown) and counterstained with cresyl violet (purple). Images are from the right (untreated, A and C) and left (siRNA-infused, B and D) substantia nigra. At higher magnification (C and D), Iba-1-positive cells with morphological features of resting microglia are shown close to dopaminergic neurons containing neuromelanin (black granules). The arrows indicate one of these neurons in each panel. Scale bars = 20 µm (A and B) and 10 µm (C and D). (E) The number of Iba-1-immunoreactive cells was counted in the right (R) and left (L) substantia nigra. Data are shown as mean ± SEM. (F) A representative section from the left midbrain shows Iba-1 immunoreactivity close to the tip of the infusion cannula (arrow) but not within the nearby parenchyma. This robust immunoreactivity was observed within cells with morphological characteristics of activated microglia (inset). Scale bars = 250 µm (panel F) and 10 µm (inset).