Localization of interleukin-1 receptor messenger RNA in murine hippocampus

The cytokine interleukin-1 (IL-1) has numerous actions in brain, including pronounced neuroendocrine effects. Recent radioligand binding studies have identified high-affinity binding sites for 125I-recombinant human IL-1 alpha in the hippocampus with characteristics similar to those of IL-1 receptors in immune cells. The present study employed in situ hybridization histochemistry with 35S-labeled anti-sense cRNA probes derived from a full-length murine T-cell IL-1 receptor cDNA to identify cells producing IL-1 receptor mRNA in the murine hippocampus. An intense signal was observed over granule cells in the dentate gyrus. A weak to moderate signal was observed over the pyramidal cell layer of the hilus and CA3 region. Other aspects of the hippocampal formation, including the CA2 and CA1 regions, the subiculum, and the entorhinal area, displayed no signal above background. This distribution of IL-1 receptor mRNA was similar to that of 125I-IL-1 alpha binding sites and supports the growing body of evidence implicating IL-1 as a neurotransmitter/neuromodulator in brain.