Brain stem energy metabolism response to acute hypoxia in anaesthetized rats: A P-31 NMR study

MAMMALS react to acute hypoxia with an initial augmentation and a secondary depression of the respiratory rhythm generated by brain stem neuronal networks. To investigate the cytosolic level of energy rich phosphorus metabolites during these responses, we developed P-31 nuclear magnetic resonance spectroscopy of the brain stem. Moderate hypoxia (p(a)O(2) = 40 mmHg, 2 min) caused a reversible 62 +/- 15% respiratory rhythm depression and decreased cytosolic phosphocreatine levels by 43 +/- 11% (p < 0.01, n = 7) without affecting adenosine triphosphate levels. Cellular metabolic depletion therefore contributes to the brain stem response to hypoxia, and appears to reflect adaptive mechanisms to limited oxygen availability in the brain stem.