Brain tissue sections from 6 and 24 month old Fisher 344 rats were stained for nuclear stain DAPI (blue) and either IL-1β (green) or the endothelial cell specific marker VWF (red). Quantitative comparison of IL-1β expression between vessels derived from 6 month and 24 month old animals is shown in bar graph. Data are mean ± SD (n = 3). ×20. **p < 0.01 vs. 6 months.