Analysis of water content in rat brain using Raman spectroscopy

: Laser Raman spectroscopy has not been applied to brain tissue. However, this method can possibly analyze the constituent elements of living tissue of cellular and molecular level easily, and this might be essential for further brain research. I attempted to analyze the water content of brain tissues, which was measured by Raman spectrum of CH and OH groups, in normal and edematous rat brain tissues. The experimental results indicated that the peak intensity of CH group originated from protein, 2935 cm-1 in wave number, was constant in normal, dried and edematous brain tissue. Therefore it could be used as internal standard. As the peak intensity of OH group, 3390 cm-1 in wave number, was originated from water, the relative amount of water content in the brain tissues could be evaluated by OH/CH value. The OH/CH value was not significantly different between the cortex and the thalamus, but it was significantly higher in the gray matter (thalamus) than in the white matter (pons). The OH/CH value was decreased in dried specimens. In experimental edematous brain tissues, which was produced by intraperitoneal injection of organic tin, the OH/CH value was evidently increased in the thalamus but not much changed in the pons. This results were well compatible with cytotoxic edema, which was reported to be produced by organic tin. It is suggested that laser Raman spectroscopy can be used for brain edema research as one of the strong weapon, in analyzing water content of brain tissues on a cellular level.