Proteasome inhibition after intrahippocampal injection of LPS induced the formation of aggresome-like structures in hippocampal neurons. (A) Upper: immunofluorescence analysis of the cellular distribution of ubiquitinated proteins in hippocampal slices from rats treated with saline, saline + LPS, saline + LT and LPS + LT. Images correspond to animals sacrificed 48 hours after the last injection. Lower: higher magnification corresponding to neurons from the stratum pyramidale taken from images showed above. Nuclei were counterstained with DAPI. Note the presence of large aggresome-like structures (arrowheads) only in the LPS + LT-injected rats. Bar scale: 75 μm for upper images and 10 μm for lower images. (B) Similar as in A but images correspond to aged rat hippocampus injected with LT alone. DAPI: 4′-6-diamidino-2-phenylindole; LPS: lipopolysaccharide; LT: lactacystin; sp: stratum pyramidale.