densities. (A) Comparison of the immunoreactivity of the IL-1β type 1 receptor (IL-1RI) in total membranes (comprising neuronal, glial, and endothelial membranes) and in membranes from purified nerve terminals (synaptosomes) prepared from the hippocampus of adult male Wistar rats. The graph displays the mean ± SEM of four experiments and the blot below illustrates a representative experiments, where we always used three different protein quantities (30, 60, and 90 μg) of both total and synaptic membranes of the same hippocampus in the same electrophoresis gel, and the percentage of IL-1RI immunoreactivity for each amount of protein was calculated relative to the maximum immunoreactivity obtained for each western blotting membrane (that is, that of the band obtained with 90 μg of total membranes). *P < 0.05 and ***P < 0.001 comparing the same quantities of total and synaptosomal membranes. (B) Sub-synaptic distribution of IL-1RI in a comparison of IL-1RI immunoreactivity in synaptosomal membranes (SYN) and in its fractions containing the pre-synaptic, post-synaptic, and extra-synaptic membranes, the purity of which was gauged by the segregation of the active zone marker synaptosomal-associated protein (SNAP)-25, the post-synaptic density (PSD) marker (PSD-95) and the extra-synaptic (vesicular) marker synaptophysin. The percentage of IL-1RI immunoreactivity was calculated relative to the maximum reactivity of each membrane and the data in the bar graph are mean ± SEM of n = 4 experiments.