Figure 5.

A, In the hippocampus, aged rats that received a single icm injection of hIL-1RA (112 μg) at the time of surgery continued to express significantly elevated levels of hIL-1RA compared with background (vehicle) and intraperitoneal IL-1RA-administered levels 4 d later. intraperitoneal hIL-1RA levels were no different from background levels at this time point. B, In the liver, regardless of the route of administration, aged rats that received a single injection of hIL-1RA (112 μg) at the time of surgery exhibited levels of hIL-1RA no different from background (vehicle) levels 4 d later. C, In the serum, hIL-1RA was highly and equally expressed 1 h after both routes of administration. At 3 h, hIL-1RA expression levels dropped precipitously (note scale change), with icm-administered levels significantly higher than intraperitoneal-administered levels. At 24 h, hIL-1RA expression levels dropped precipitously again (note scale change). At this time point, icm-administered levels continued to be expressed significantly higher than intraperitoneal-administered levels. At 4 d, hIL-1RA expression levels were no longer different than background (vehicle) levels. **p < 0.01; ****p < 0.0001.