Potassium and Water Distribution in Depression

Abstract

The ionic theory of cell excitability shows how impulses are generated, conducted and propagated by movements of ions between the cells and the extracellular fluid. It is known that changes in the concentration of sodium and potassium in either the extracellular water (E.C.W.) or the intracellular water (I.C.W.) may have a marked effect on the resting and action potentials of excitable cells. If affective disorders are manifestations of complex but reversible changes in brain excitability, hen these in turn might be caused by alterations in the concentration of electrolytes within the cells of the central nervous system (C.N.S.). Although it is not possible to measure the distribution of electrolytes specifically in the C.N.S. in man, it is possible to measure their distribution in the body as a whole. In previous papers we have shown that residual sodium (intracellular plus a small quantity of bone sodium) is increased by 50 per cent. in depression (Coppen and Shaw, 1963) and by nearly 200 per cent. in mania (Coppen, Shaw, Malleson and Costain, 1965). The present paper shows that there are also abnormalities in the distribution of potassium, the other main cation determining cell excitability, in patients suffering from severe depression.