[Studies of experimental cerebral ischemia with NMR spectroscopy]

In vivo NMR (nuclear magnetic resonance) spectroscopy allows for non-invasive measurement of the intracellular pH and the concentration of different metabolites in defined areas of the brain. Phosphocreatine, ATP and lactic acid are of prime interest in ischaemia research. Moreover, a distinction can be made between glycolysis and the oxidative breakdown of glucose after administering C-13-labelled glucose. Finally, spectroscopy of fluorine-containing inert gases such as Freon-23 allows for measuring cerebral blood flow and for directly relating the metabolic alterations to the changes in cerebral blood flow. Given the non-invasive character of NMR spectroscopy all metabolic process occurring throughout one experiment can for the first time be followed up. Thus metabolic alterations during ischaemia can directly be correlated with post-ischaemic recovery processes. It has been shown with the cerebral ischaemia model in the cat that recovery after circulatory failure rather depends on post-ischaemic changes such as the recirculation rate or the speed of high-energy phosphate formation than on the speed of energy metabolism breakdown or acidosis occurring during ischaemia. The future of nuclear magnetic resonance spectroscopy in experimental ischaemia research certainly lies in the therapeutic range. As the exact extent of ischaemic damage can be determined in each experiment it is possible for the first time to define the effect of a drug substance on metabolic dysfunction in each individual experiment. This method is not only expected to reduce the number of laboratory animals but also to dramatically improve statistical variability compared to group comparisons.