SU‐E‐I‐78: Neuromelanin in the Subthalamic Nucleus of Patients with Parkinson's Disease: An Electron Spin Resonance Spectroscopy Study

Purpose: Parkinson disease and related syndromes are associated directly with the concentrations of neuromelanin, iron and other heavy metals, and nowadays it is discussed the possible protective role of neuromelanin by the sequester redox active iron ions, reducing the formation of free hydroxyl radicals and therefore inactivating the iron ions that induce oxidative stress. The aim of this work is to study the concentration ratios between iron ions and neuromelanin in subthalamic nucleus of patients with Parkinson's disease (PD) using Electron Spin Resonance (ESR). Methods: Necropsy samples of subthalamic nucleus from eight human brains were studied: three non‐affected by any neurodegenerative disease and five with Parkinson's disease. The samples were stored in formaldehyde and washed with a solution of 0.01 molar of ethylenediaminetetraacetic acid. ESR experiments were development in a JEOL FA‐200 X‐Band spectrometer at different temperatures between −170° C to room temperature. The relative concentrations of each species were estimated from the double integral values of the fitted spectra. Results: For all samples, ESR spectra showed to be composed of three different signals following the Curie's law. One signal was attributed to high‐spin ferric ions (g∼ 4.3) in rhomboedric symmetry, Cu(II) ions (close to g=2.0) and neuromelanin (g∼ 2.01). The ferric ions concentration ratio between patients and controls was 3.0±0.2. The same ratio for neuromelanine was 0.24±0.06. Conclusions: Our preliminary results indicated a significant increment of iron concentration in PD samples which agrees with previous histochemical and biochemical reports. This finding and the clear reduction of neuromelanin concentration in PD samples suggest the possible role of neuromelanin as iron ions storage.