Measurement of Cortical Ph in Spreading Cortical Depression.

RAPOPORT, STANLEY I., AND WADE H. MARSHALL. Measurement of cortical pH in spreading cortical depression. Am. J. Physiol. 206(5) : I 177-1180. 1g64.-The pH of the rabbit cortex was measured during the course of spreading cortical depression. Spreading cortical depression was elicited by chemical (group I) and by electrical (group II) means. Cortical d-c potential changes were recorded separately by a glass membrane pH electrode and by a pore electrode. Records were made of each against an indifferent ground and also of the algebraic addition of the pH electrode and the pore electrode. The maximum cortical d-c potential changes in the initial negative and later positive phase of spreading cortical depression, as recorded by each electrode, were compared statistically. A significant (P < 0.05) pH change of -0.027 4~ .005 (SE of mean) pH units was demonstrated for the positive phase. No pH change was found for the negative phase. Sources of error are discussed. The results do not support the hypothesis that large pH changes are involved in the genesis and mechanism of spreading cortical depression.