Spreading depression: a neurohumoral reaction.

1. The main characteristics of spreading depression are a decrease of spontaneous electrical activity, slow negative potential changes, transmembrane ion translocations, and an increase in tissue lactate. This is a general phenomenon in the central nervous system. 2. Retinal spreading depression, a very useful model for this phenomenon, has been extensively studied in terms of its optical, electrical and mechanical components. Ionic changes in the extracellular microenvironment have also been assessed and chemical substances liberated from tissue have been detected. 3. The velocity of propagation has been measured and some physical and chemical factors underlying the spread of the electrophysiological depression have been identified. Hypotheses about the nature of the reaction are discussed.