The distribution of activated NF-kappaB (p65) was studied in granule cells of the rat fascia dentata using confocal laser scanning microscopy and preembedding immunogold electron microscopy. Activated NF-kappaB, detected with a monoclonal antibody specific for the nuclear localization signal-epitope, was found in proximal dendrites, somata, and nuclei but not in axon terminals of granule cells. Within the nuclei of granule cells, clusters of NF-kappaB immunoreactivity were detected. These data are in line with the proposed function of NF-kappaB as a retrograde signal transducer which transports information from synaptic sites to the nucleus to initiate gene expression.