Figure 1.

Proinflammatory cytokine expression and neurodegeneration after intracerebral sodium nitroprusside injection. A, Representative photomicrographs of in situ hybridization signals showing the expression of TNF-α mRNA (left) and IL-1β mRNA (right) in the brains of mice that received an intraparenchymal injection of the excitotoxin SNP versus vehicle saline (Veh) and killed 6 h, 4 d, 7 d, and 14 d after the injection. The coronal sections (25μm) were taken from x-ray films (exposed for 3 d; Biomax MR; Kodak), whereas the dark-field photomicrographs (insets) were taken from the same brain slices but dipped into NTB emulsion milk (Kodak). The yellow boxes relate to the hybridization signal for the cytokines at the cannula tract and are magnified in the top inset, whereas the red boxes represent parenchymal signals caused by SNP and are magnified in the bottom inset. Please note the transient TNF-α expression that fades completely by 14 d, whereas the IL-1β signal is still present after 14 d. The top right of the figure shows the location of the injection site in the dorsal basal ganglia. Scale bar, 100μm. B, Fluorescent photomicrographs depicting representative examples of FJB staining, which indicates neuronal death (green neurons) in adjacent sections taken from the same mice as in A. The sections were counterstained with DAPI (blue nuclei). Note the rapid onset of neuronal cell death 6 h after SNP injection, which peaked at 4 d and persisted up to time 14 d after SNP injection. Red scale bar, 25 μm; white scale bar, 250 μm.