Quantitative microanalysis of perineuronal nets in brain tissue

The relevance of the perineuronal nets (specialised extracellular matrix surrounding a part of the neurons in brain tissue) as a possible protection of neurons against oxidative stress induced by metal ions (e.g. Al, Fe, Cu and Zn) is an actually discussed hypothesis. It is assumed that the perineuronal nets are able to bind metal ions and thus reduce the oxidative stress to neurons. Therefore, we used nuclear microscopy (μPIXE) in order to investigate the concentration and distribution of iron in rat brain loaded with colloidal iron with special emphasis to the perineuronal nets in the extracellular matrix. The elemental microanalysis was performed on 6 μm thin resin embedded sections. The perineuronal nets accumulated more Fe than other extracelullar matrix components leading to well defined, neuron-related structures in the Fe maps. In order to quantify the affinity, the iron accumulations in the perineuronal nets were analysed for different Fe loadings. We present first results that support the hypothesis that perineuronal nets act as chemical protection mechanism against oxidative stress due to their ability to bind metal ions