BRAIN-STEM ENERGY-METABOLISM RESPONSE TO ACUTE-HYPOXIA IN ANESTHETIZED RATS - A P-31 NMR-STUDY

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