Distribution of amyloid beta-protein immunoreactivity in the hippocampus of rats injected with kainate.

The distribution of amyloid beta-protein immunoreactivity was investigated in the hippocampus of rats injected intravenously with kainate. Very light labelling was observed in cell bodies and dendrites of pyramidal neurons and dentate granule cells in the normal hippocampus. At 6,7,9,10,12 and 20 days postinjection, moderately densely labelled astrocytes were present in the stratum oriens and lacunosum moleculare, extending thick processes towards the stratum radiatum which was degenerating. Immunoreactivity was present as floccules in the mitochondria-rich but glial-filament-poor portions of reactive astrocytes, and in fibrillar form in the neuropil. This suggests that amyloid beta-protein might be present in fibrillar (presumably polymerised) form in degenerating profiles and the neuropil, but in floccular (presumably non-polymerised) form in reactive astrocytes.