Pyrogenic treatment with lipopolysaccharide (LPS) or interleukin-6 (IL-6) induces nuclear STAT3 translocation in the vascular organ of the laminae terminalis (OVLT) and the subfornical organ (SFO). STAT3 immunohistochemistry was combined with the detection of marker proteins (glial, neuronal, endothelial) and the nuclear DAPI stain to determine the phenotype of responding cells. At time points with high pyrogen-induced IL-6 plasma levels, nuclear STAT3 signals were co-localized with an astrocytic cell marker. IL-6 might therefore mediate genomic activation of OVLT/SFO astrocytes during LPS-induced fever.