IntroductionParkinson’s disease (PD) is a degenerative neurological disorder caused by the loss of dopaminergic cells within the pars compacta region of the substantia nigra (SN).1Co-incident with the appearance of symptoms of the disease an elevation of iron has been observed within the SN.2–4Iron is suspected to be involved in the formation of reactive oxygen species within the SN, which is hypothesised to lead to the death of dopamine producing cells. It is unclear if the increased oxidative stress caused by Fe in PD is a cause or effect of the disorder.5A common mouse model for study of Parkinsonism is the 6-hydroxydopamine (6-OHDA) lesion method. The lesion is produced by directly injecting the neurotoxin into the region of the SN, where it is taken up by the neurons and kills the cells by the production of active superoxide radicals.6Fe is suspected to play a significant role in the mechanism of cell death and superoxide radical generation.2,3,7–9Development of methods to measure the regional concentration of trace metals in induced Parkinsonism models would be of benefit to probe the mechanism and treatment of PD. Solution nebulisation ICP-MS was employed by Tarohdaet al.10The SN was excised from 6-OHDA lesioned mouse models and analysed for Mn, Fe, Cu and Zn after closed-vessel microwave digestion. The concentration of Mn, Fe, Cu and Zn increased in the SN to a constant maximum at 7–10 days after injection of the neurotoxin. Solution ICP-MS has also been applied to monitoring iron levels in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treated mice, another mouse model for Parkinsonism.11Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) may be utilised forin situanalysis of trace metals in biological tissue. Using a process we termelemental bio-imaging, isotope-specific maps of the spatial distribution of trace elements within thin tissue sections can be constructed. ICP-MS is an element analyser, designed to measure trace levels of the elements unlike other forms of “organic” MS that are used to identify and quantify molecular compounds. Laser ablation is a sample introduction system for ICP-MS that allow for the elemental composition of solid materials, including tissues, to be determined.The biggest limitation of LA-ICP-MS is a lack of reliable validated quantification strategies. Most studies have relied upon certified reference materials or preparation of matrix matched standards. Examples of the former include pig liver paste (LGC 7112) for single point calibration for quantification of trace elements in sheep liver.12Jacksonet al.used pressed pellets of TORT-2 (lobster hepatopancreas), DOLT-2 (dogfish liver) and DORM-2 (dogfish muscle) to build multi-point curves for quantification of Cu, Zn and Fe in rodent brains.13Matrix-matched standards have also been prepared by spiking brain tissue with known amounts of aqueous standards and ablating cut sections.14Elemental bio-imaging has also been applied to imaging of P, S and several transition metals in small sized tumours produced by F98 glioma cell implantation in rat brains.15,16Imaging of trace elements in both healthy and tumourous human brain tissue has also been reported.14,17–19This study presents a method to quantify the spatial and regional distribution of Mn, Fe, Cu and Zn in thin tissue sections taken from a 6-OHDA Parkinsonism mouse model, as well as untreated controls. The regional quantification of the substantia nigra obtained by the imaging method was also compared against that obtained by solution nebulisation ICP-MS.