The Cortical Ischaemic Penumbra Associated with Occlusion of the Middle Cerebral Artery in the Cat: 1. Topography of Changes in Blood Flow, Potassium Ion Activity, and EEG

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Abstract
The gyral topography of the ischemic penumbra associated with middle cerebral artery occlusion was studied in cats; local blood flow (hydrogen clearance, 2-min initial slope analysis), pial surface K activity (Kp), and EEG amplitude were recorded on the ectosylvian, suprasylvian and marginal gyri. Penumbral conditions were defined as a reduction of EEG amplitude in the absence of a major increase in Kp. Whole hemisphere cerebral blood flow prior to occlusion was 35.6 .+-. 11.4 (SD) ml 100 g-1 min-1 (n = 25), and fell significantly (P < 0.001) to 13.0 .+-. 4.7 (SD), 14.1 .+-. 6.6, and 23.8 .+-. 9.3 on ectosylvian, suprasylvian and marginal gyri, respectively. Preocclusion Kp was 3.0 .+-. 0.9 mM (n = 53); sustained, steady-state increases in excess of 11.5 mM occurred in 5 of 7 (71%) experiments on ectosylvian gyrus, in 13 of 22 (59%) experiments on suprasylvian gyrus and in 2 of 24 experiments on marginal gyrus. Transient increases in Kp occurred at occlusion and resolved to baselines significantly higher than control in 5 (23%) experiments in suprasylvian gyrus and in 15 (63%) on marginal gyrus. In 7 experiments on the marginal gyrus (29%), no increase in Kp > 1 mM occurred. In contrast, ECG amplitude on this gyrus was reduced by middle cerebral artery occlusion in 25 of 26 experiments, and apparently, this gyrus is the principal site of ishemic penumbra in the model; in 41% of experiments similar conditionis were also present on the suprasylvian gyrus.