Physical Activity Determines Survival of Mongolian Gerbils from Forebrain Ischemia

Abstract

The Mongolian gerbil is frequently used in studies on the pathophysiology of cerebral ischemia. Due to the incomplete circle of Willis, simultaneous occlusion of both common carotid arteries reduces blood flow in the forebrain below a critical threshold. The model permits reperfusion of the brain after periods of variable length. With 5 min of forebrain ischemia, most of the animals survive the insult, and brain tissue remains morphologically intact except for the CA1 sector of the hippocampus, where loss of pyramidal cells becomes evident after 2–4 days (Kirino 1982). This phenomenon has been termed “delayed neuronal death” or “maturation phenomenon” (Ito et al. 1975; Kirino 1982). Extensive periods even of unilateral ischemia, e.g., 15–30 min, are followed by tissue damage involving the adjacent CA2/3 sectors of the hippocampus, striatum, and cerebral cortex in addition (Yanagihara et al. 1985). Assessment of survival from ischemia as well as of nerve cell loss has been used to evaluate the effect of pharmacological treatment. Yet, even under tightly controlled conditions, survival and brain tissue damage in individual animals are quite variable. Focal neurological deficits are not induced by this form of global cerebral ischemia. Therefore, behavioral parameters such as locomotor activity were utilized as an additional criterion to evaluate the functional consequences of the ischemic insult on a quantitative basis.