Immunolocalization of the cellular prion protein in normal brain

immunohistochemistry and monclonal antibody 3F4. In the mature hamster and baboon brain, PrPc is localized to the neuropil with a synaptic distributio n and the PrPc immunoreactivity is denser in regions known for ongoing plas ticity. Cell bodies and major fiber tracts have little or no PrPc immunorea ctivity. At the electron microscopic level, PrPc immunoreactivity decorates synaptic profiles, both pre- and postsynaptically. Results obtained with t wo additional antibodies, 3B5 and Pri-304, showed similar patterns of PrPc bands on Western blots, although Pri-304 was less sensitive. On sections th rough the adult hamster hippocampus, 3B5 and Pri-304 both stained the synap tic neuropil while cell bodies in the pyramidal and dentate granule cell la yers were not immunoreactive. Pri-304 differentiated between synaptic layer s in the hippocampus and closely resembled the pattern of staining obtained with 3F4. Preliminary results of developing brain showed that PrPc is init ially localized along fiber tracts in the neonate brain. These results show that PrPc has a synaptic distribution in the adult brain and suggest that there are important changes in its distribution during brain development. T hese results also characterize two additional reagents for studies of PrPc localization. (C) 2000 Wiley-Liss, Inc.