NONHEME IRON HISTOCHEMISTRY OF THE NORMAL AND ALZHEIMERS-DISEASE HIPPOCAMPUS

Increased free radical production may occur in Alzheimer's disease (AD ). In view of the central role of iron in free radical reactions we ha ve investigated the distribution of non-haem iron in the hippocampal f ormation in normal control individuals and in patients with AD. In con trols, non-haem iron was principally associated with glial elements an d the neuropil, with highest levels in the stratum radiatum/lacunosum, fimbria, alveus and oriens layers. Except for the subiculum, the pyra midal cell layers and the granule cell layer showed little or no non-h aem iron staining. Intensity of staining was in the order of subiculum much greater than CA2 and adjacent regions of CA3 > CA4 > the remaind er of CA3 > CA1. In the hippocampus in AD, iron was associated with ce lls containing neurofibrillary tangles (NET) and was present in glial cells and neurites of senile plaques (SP). These findings were most pr onounced in CA1 pyramidal cell layer and subicular complex although no t all NET or SP were stained. Since the NFT and SP staining for non-ha em iron appears to be associated with glial cells, the association of non-haem iron with the pathological stigmata of AD may be a secondary response of glial cells, in particular microglia, to neuronal damage.