The overall goal of this project is to advance our understanding of the demyelination process by sequentially and non-invasively evaluating the chemical composition of central nervous system (CNS) tissue using in vivo proton NMR spectroscopy of selected regions (1 X 5 X 5 mm). Demyelination is a process where the myeline sheath undergoes physical and chemical degradation of lipid and protein components and is an integral part of CNS diseases such as multiple sclerosis, encephalomyelitis, and radiation necrosis. This project will use a new in vivo NMR spectroscopic localization technique developed and validated in this grant. In this technique a spin-echo is used with a spatially selective 90 degree rf pulse on the Z axis, a spatially selective 180 degree rf pulse on Y axis, 128 phase-encoding gradients between the 90 and the 180 on the X axis, and no gradient on during acquisition of the echo. After echos are processed with the 2D- Fourier transformed, we obtain 128 spectra along the tissue column defined by the 90 and 180 degree selective pulses. A conventional proton image is used to preselect the tissue column used in spectroscopy. This technique will be developed and validated using phantoms consisting of several different chemically shifted compounds in test-tubes. After the technique has been thoroughly tested, we will use it to study demyelination as a function of time after induction of experimental allergic encephalomyelitis (EAE) (monkey brain), Cs-137 radiation (monkey brain), and helium beam radiation (dog brain). We will evaluate changes in NMR visible lipids, amino acid components and lactate. After the animal is sacrificed, brain tissue will be extracted from the demyelinated plaque for chemical analysis. The results of the proposed experiments will provide new information on demyelination and give evidence for or against the hypothesis that the primary insult is a disturbance in local cellular metabolism before the physical and chemical disruption of myelin.