cultured neurons. Rat hippocampal neuronal cultures at 7 days in vitro (DIV) were exposed to 100 ng/ml IL-1β for 15 minutes in the absence or in the presence of the antagonist of the IL-1β type I receptor, IL-1Ra (5 μg/ml), added 30 minutes before addition of IL-1β. Cells were then lysed on ice in a minimum volume of radio-immunoprecipitation assay (RIPA) buffer for western blotting analysis to quantify the immunoreactivity of the activated (phosphorylated) form of (A) p38 (p-p38) and (B) JNK (p-JNK). In both panels, the bar graphs display the mean ± SEM of three to four experiments, and the blots below illustrate a representative experiment showing that IL-1Ra (A) prevented the IL-1β-induced phosphorylation of p38 and (B) attenuated the phosphorylation of JNK. In each experiment, membranes were first used to detect each phosphorylated MAPK, and then reprobed for the total amount of MAPK, so that the activation of each MAPK was calculated as a ratio between the phosphorylated and total immunoreactivities, which were expressed as a percentage of control (CTR) values (that is, in the absence of any added drug). *P < 0.05 and **P < 0.01 compared with control; #P < 0.05 compared with the effect of IL-1β in the absence of IL-1Ra.