Sequential cerebral biochemical and physiological events in controlled hypoxemia

Abstract

Effects of controlled hypoxemia on cerebral functional activity were studied in rats using cyclic adenosine monophosphate (cAMP) and aminergic neurotransmitters in the brain tissue as special references. Evidence is presented that: (1) mild hypoxemic stress (Pa 60 to 40 torr) may activate cerebral glycolysis with no evidence of anaerobic metabolism but that further reduction Pa impairs cellular respiration, as evidenced by accumulation of glycolytic products; (2) glycogenolysis in the brain tissue, leakage of potassium ions from the brain cell, increase in brain water, and suppression of neural functional activity occur concomitant with accumulation of cAMP and prior to the fall of adenosine triphosphate; (3) the diminution of cerebral high-energy phosphates during hypoxia is associated with and may be caused by hypoxemia-induced neuroglycopenia and occurs at Pa 15 torr; (4) induced hypoxemia per se does not affect the level of aminergic neurotransmitter substances in brain tissue.