Presence of NF-kappa B-like and I kappa B-like immunoreactivities in postsynaptic densities

THE distributions of I kappa B and NF-kappa B immunoreactivities were examined immunohistochemically in the rat brain by the electron microscopy. Antibodies were raised against synthetic peptides with the sequences specific to the human MAD-3 type I kappa B or NF-kappa B. Both I kappa B alpha and NF-kappa B immunoreactivities were localized in the dendrites including the spines and, particularly, the post-synaptic densities (PSDs) of the hippocampus and the cerebral cortex. The PSD fraction prepared from the rat brain contained an activity that inhibited the binding of NF-kappa B to the kappa B DNA elements. These results suggest that the NF-kappa B/I kappa B system or a similar mechanism may play a role in signal transmission from synapses to the nucleus.