Postischemic Hyperperfusion and Outcome: An Experimental Study

The selective vulnerability of discrete brain regions after short episodes of cerebral ischemia is a phenomenon still unexplained. In the hippocampus in particular, nerve cell loss may become prominent after only 5 min of ischemia. Neurons appear intact during the initial 1–2 days of reperfusion, after which they succumb. In order to investigate the mechanisms involved in this “delayed neuronal death,” and postischemic nerve cell damage in general, in a previous study we demonstrated that preischemic physical activity may protect experimental animals from damage in the gerbil forebrain ischemia model (in preparation; Weber et al. 1989). With 15 min of ischemia there was a dramatic enhancement of survival from 44% in controls to 85% in animals which had access to a “running wheel” before experiencing ischemia. Although the phenomenon is of much scientific interest in itself, it may serve as a tool to study the significance of pathophysiological parameters for outcome from an ischemic episode: With animals from conventional cages and those from cages with access to a running wheel, two groups of gerbils with a known and significantly different prognosis are available. Hence, it is possible to use these animals for short-term experiments where the final outcome of individual experiments cannot be assessed. The present investigation served to compare postischemic regional blood flow for the two groups.