Diffuse cerebral ischemia in the cat: II. Regional metabolites during severe ischemia and recirculation.

Metabolite levels were measured in seven brain regions in cats after 15 or 30 minutes of a severe ischemic insult and after a 90-minute period of recirculation following 15 or 30 minutes of ischemia. Brain levels of phosphocreatine were depleted after a 15- or 30-minute insult, and lactate levels were extremely high at both times. The adenosine triphosphate (ATP) content in many brain areas and the presence of microregions of low reduced nicotinamine-adenine dinucleotide in the brains of the animals that had 15 minutes of ischemia suggested that the ischemia, though severe, was not complete. Recirculation following a 15-minute insult restored brain levels of ATP and phosphocreatine to 70 to 100% of control values in all regions analyzed. In contrast, metabolic recovery from a 30-minute insult was regionally heterogeneous. Thus, there was persistent depression of ATP and phosphocreatine and elevation of lactate, which was localized in discrete cortical foci near the longitudinal midline. The factors governing the localization of metabolic failure must have become manifest during the recirculation period since the ischemic insult itself caused similar metabolic perturbations in all cortical regions.