## 4 Discussion  
In this study the bio-chemical composition of seven different brain regions from healthy rats were investigated, using FTIR and LAICPMS spectroscopies. Application of these techniques to  
Figure 6: Distribution of the elements: (**A**) Cu, Fe, Zn, Mg, C, Ca, P, and S in the rostral, and (**B**) the caudal part of rat brain sections. The color bar represents a high-concentration, in red, and a low-concentration, in blue. mammalian tissue, is not new, but in comparison with standard histopathological techniques, these approaches offer much more biochemical detail that may be important and pertinent to advance the understanding of pathologies. In combination with the PCA data, other brain regions that may prove to be susceptible to diseases, may be identified. The study revealed that FTIR spectroscopy allows for the investigation of molecular structures from biological samples, with minimal sample preparation; providing a unique information that cannot be gained by alternate methods. Importantly, the technique is a non-destructive, sensitive, and fast, bio-diagnostic tool [26]. FTIR results were in alignment with published work that the gray matter is made up of neural cell bodies, astro-glials, and capillaries, and contains very little lipid [27]. This data also revealed that the WM consists mostly of myelinated axons, with a high lipid-content, which showed strong absorption bands in the lipid region (3000-2750 cm\({}^{-1}\)) and the ester band (1740 cm\({}^{-1}\)). In order to get a more detailed understanding of the lipid-structure configuration in the brain, the ratio between certain lipid spectral bands to the total lipid contents, were measured. This may be a good indicator and platform for detecting tissue alterations associated with pathologies. The lipid/protein ratios reveals information about the cell membrane function, since the changes in the lipid-protein content can affect the membrane symmetry and thickness, and leads to the confirmation of changes in the membrane receptors and ion-exchange channels [28]. For example, the ratio between the CH\({}_{2}\) spectral bands to the C-H stretching of the total lipid band revealed information about the lipids chain length. The ratio between the olefinic=CH band at 3000-3027 cm\({}^{-1}\) to the total lipid content at 2994-2800 cm\({}^{-1}\), provided information on the degree of unsaturation in the lipid biological system [29]. The changes of the band ratios of certain bio-chemical component can be used for characterization purposes, as well as to monitor tissue alterations. The high CH\({}_{2}\)/lipid and low CH\({}_{3}\)/lipid ratios in the WM, CC, and CE indicated that these regions are characterized by long fatty-acid chains. These results are in a good agreement with a previous report [30], which stated that brain WM contains long-chained fatty acids. In another study, the authors showed that the sphingolipids from gray matter contained predominantly medium-chained fatty acids, while those from myelin or from white matter, contained predominantly long-chained fatty acids [31]. These regions also showed a high ratio of (C=O) carbonyl ester/lipid, indicating a high content of esterified-fatty acids. In contrast, the regions of SSMC, CP, TH, and the CA and DG of the hippocampus, exhibited low CH\({}_{2}\)/lipid and high CH\({}_{3}\)/lipid ratios, indicating short fatty-acid chains. These differences may reflect the functions of these regions. The low Olefinic=CH/lipid ratio in the WM, CC, and CE, in comparison to the GM regions of SSMC, CP, TH, and the CA and DG of the hippocampus, indicated that these WM, CC, and CE, were characterized by saturated and/or mono-saturated fatty acids, while the SSMC, CP, TH, and HP were predominantly characterized by polyunsaturated fatty acids. These results are in good agreement with the published data from [PERSON] et al. [30]. The FTIR results revealed that in the HP, the CA and DG showed a lower lipid-content than in the AV region.