ICAM-5 is constitutively expressed in hippocampal cells stimulated by proinflammatory cytokines. Fourteen-day-old cultured primary rat hippocampal cells that contain both neurons and astrocytes were treated with 50 ng/mL TNF or IFN-γ for 16 hours. Total RNA from these cells was harvested, and ICAM-1 and ICAM-5 mRNA levels were quantified by real-time PCR (A). ICAM-1 mRNA was significantly increased by TNF or IFN-γ treatment. By contrast, ICAM-5 mRNA was not affected by these 2 cytokines. The protein levels of the 2 ICAMs were also compared (B,C), which showed similar changes as their respective mRNA levels. Data are shown as mean plus or minus SD of triplicates (*P < .05, **P < .01, ***P < .001).