Accumulation of ubiquitinated proteins induced by LPS injection. (A) Ubiquitinated proteins, predominantly those of high molecular weight, accumulated in young rat hippocampi after LPS injection. Shown is a representative western blot experiment corresponding to saline- and LPS-injected animals sacrificed at indicated times. Each line corresponds to four animals pooled and the experiment was repeated at least three times with similar results. (B) Densitometric quantification of western blot experiments (n = 3). The full line, without the inclusion of the free ubiquitin, was considered for the analysis. (C) Cellular distribution of ubiquitinated proteins in the CA3 region of saline (upper) and 3 days after LPS injection (middle). Most of the immunostaining was observed in the stratum pyramidale, where the somata of principal neurons are located as revealed by the intense immunostaining of the neuronal marker NeuN (lower). Nuclei were counterstained with DAPI. *P <0.05 significant difference with respect to saline-injected animals. DAPI: 4′-6-diamidino-2-phenylindole; LPS: lipopolysaccharide; NeuN: neuronal nuclei; sp: stratum pyramidale. Scale bar: 75 μm.