Shock-induced cytoplasmic NADH fluorescence changes in the living cat brain cortex: effect of dexamethasone.

The effect of dexamethasone administration on cerebrocortical NADH fluorescence, blood flow and blood volume, intracellular oxygen tension and electrocorticogram (ECoG) was studied in anaesthetized cats in two sets of experiments. Haemorrhagic shock was induced by stepwise decrease of mean arterial blood pressure from the control level a to 80, 60 and 40 mmHg. The bleeding was followed by reinfusion of the shed blood. The method of producing shock was identical in the untreated and dexamethasone treated groups. Dexamethasone was administered in the control period. The results are summarized as follows: (a) Dexamethasone, given in pharmacological doses failed to alter blood flow or blood volume, NADH fluorescence and the intracellular oxygen tension in the cerebral cortex of the cat; (b) Haemorrhagic shock resulted in a marked increase of cytoplasmic NADH fluorescence in the untreated group, while these changes were much smaller in the dexamethasone pretreated animals; (c) Dexamethasone pretreatment significantly reduced the extent of shock-induced cortical vasodilatation. In some experiments the brain cortex became ischaemic at 40 mmHg MABP; (d) Dexamethasone pretreatment failed to eliminate the shock-induced decrease in cortical intracellular oxygen tension and the irreversible deterioration of ECoG. It is suggested that the decrease in cortical cytoplasmic NAD reduction and the concomitant lactate acidosis might be involved in the ability of dexamethasone to control oedema during shock and other pathological conditions.