Ultrastructural and biochemical studies on ouabain-induced oedematous brain.

Ouabain, a specific inhibitor of active cation transport across cell membrane, was applied topically to brain surface of cats. The cerebral cortex to which 10(3) M ouabain was applied showed a spongy state, which was ultrastructurally revealed to be swelling of the neuronal cell processes, especially of dendrites. Astrocytes did not show swelling even in the most severely affected lesions. There was a marked increase in sodium with a slight increase of water in the cortex treated with 10(3) M ouabain. No evidence of increased vascular permeability was noted in the cortex, morphologically or biochemically. Electron microscopic cytochemistry to detect the sodium ion revealed that the increased sodium in the cortex accumulated in the swollen neuronal cell processes. It is speculated that neuronal rather than astocytic elements might be highly dependent upon active cation transport, and that intracellular oedema in the brain tissue responsible for impairment of active cation transport might be related primarily to neuronal elements.