MECHANISM OF SPREADING CORTICAL DEPRESSION

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Abstract
In neurologically isolated cerebral cortex the onset of spreading depression causes a slow negative shift in cortical DC potential, preceded by a brief burst of intense neuronal activity. The amplitude of the negative potential shift may be increased by applying KC1 to the cortex or by polarizing the cortex positive-to-negative in the direction of spread of the depression. Polarization in the reverse direction and local strong repetitive stimulation decrease the amplitude of the potential shift. Clamping the cortical blood supply and asphyxiation by N2 both cause an increase in amplitude and duration of the cortical negativity. These facts are discussed in relation to the hypothesis that the spread of depression depends on the liberation of K+ from the cortical neurones.