The work of Quastel and associates1 has shown that narcotics even in low concentrations inhibit specifically the oxidation in vitro by brain cells of d-glucose, lactic acid and pyruvic acid. This inhibitory action takes place, not by preventing the access of oxygen to brain cells nor by interfering with the activation of oxygen by brain catalysts, but by impairing the hydrogen-liberating mechanisms (dehydrogenase activity) which normally result in activation of lactic or pyruvic acid.
Narcotics inhibit this dehydrogenase activity, presumably by forming surface films or adsorption compounds which prevent the access of hydrogen donators to their activating enzymes.2 Thus, the effect of the narcotic is to diminish the ability of the brain cells to oxidize lactic or pyruvic acid or d-glucose. The access of oxygen to the cell is quite unimpaired, but the diminished oxidizing ability of the cells results in a lowering of the amount of energy
BRAZIER MAB, FINESINGER JE. ACTION OF BARBITURATES ON THE CEREBRAL CORTEXELECTROENCEPHALOGRAPHIC STUDIES. Arch NeurPsych. 1945;53(1):51-58. doi:10.1001/archneurpsyc.1945.02300010061005