IRON HISTOCHEMISTRY OF THE SUBSTANTIA-NIGRA IN PARKINSONS-DISEASE

Raised tissue iron levels in the substantia nigra in Parkinson's disea se (PD) suggests that altered iron homeostasis may underly the disorde r. We have therefore investigated the distribution of non-haem iron in the normal and PD substantia nigra, using a sensitive histochemical p rocedure, to assess the pathogenic potential of this metal. In control cases non-haem iron staining was highest in the substantia nigra iona reticulata (SNr) and associated with the neuropil, oligodendrocytes, astrocytes and non-pigmented neurones. The substantia nigra zona compa cta (SNc) showed lower non-haem iron staining than the SNr, with gener alized impregnation of the neuropil and occasional non-haem iron-posit ive oligodendrocytes and astrocytes. The pigmented dopaminergic neuron es were unstained, often present in areas of neuropil with low iron re activity. In PD the SNc showed increased iron staining of the neuropil with many iron-positive microglial cells associated with extracellula r melanin. The remaining dopaminergic neurones were unstained, though many of the non-pigmented neurones of the SNr were iron-positive.