1. Adrenalin, caffeine and cocaine, in high concentrations in the dextrose substrate, inhibit oxygen uptake, whereas nicotine has no such effect.2. Picrotoxin, prostigmine and tyramine when injected subcutaneously into the rat, tend to increase brain oxygen uptake in plain Ringer's phosphate.3. Dextrose has a protective action against the depressive effect of drugs.4. Electrical convulsions inhibit oxygen uptake; this effect is greater after repeated shocks and is more marked in the dextrose substrate.5. Electrical convulsions and to a greater extent, insulin, interfere with oxygen uptake, in contrast to metrazol and camphor which are metabolic stimulants. The availability or utilizability of dextrose by the brain may account for this difference.Abstract Teaser