High-resolution 1H nuclear magnetic resonance study of cerebral hypoxia in vivo

1H NMR spectra at 360.13 MHz were obtained of the rat brain in vivo by using a surface coil placed over the skull. Resonances of numerous metabolites were identified by comparison with the 1H NMR spectra of excised rat brain tissue and acid extracts of the tissue. Changes in cerebral lactate levels resulting from the administration of gas mixtures low in oxygen were monitored in the in vivo brain spectra with a time resolution of 2.3 min. The electroencephalogram and electrocardiogram were recorded simultaneously during the NMR experiment. Reversibility of the hypoxic response was documented when, upon oxygen administration, cerebral lactate returned to its prehypoxic level. These experiments demonstrate the applicability of high-resolution 1H NMR to monitor pathophysiology of brain metabolism in real time.