Glutamate, calcium ion-chelating agents and the sodium and potassium ion contents of tissues from the brain

1. Salts of l-glutamate added to cerebral tissues maintained in glucose–saline–bicarbonate solutions cause the Na+ content of the tissues to increase rapidly and K+ to be lost. Entry of 22Na+ also is accelerated by l-glutamate and this acceleration is inhibited by low concentrations of tetrodotoxin. 2. Tissue Na+ content and its rate of increase after the addition of l-glutamate are affected by the Ca2+ of incubation media. 3. Very rapid and extensive entry of Na+ to the tissue is caused by EDTA, and a moderate entry by citrate and ATP. Calculations of the concentration of free Ca2+ in media after these additions indicate that Na+ entry is sometimes associated with low Ca2+ concentration, but that other substances, especially l-glutamate, act without greatly diminishing Ca2+ concentration. 4. Experiments with 2,4-dinitrophenol and valinomycin are also reported and aspects of the Na+ entry formulated and discussed.