Use of the Isolated Canine Brain in Studies of Cerebral Metabolism, Metabolite Transport, and Cerebrovascular Physiology

Abstract

Traditionally, investigators have used in vitro and in vivo techniques to study metabolism in the brain. Although a great deal of useful information has been derived from studies with in vivo and in vitro systems, a number of difficulties are inherent in such preparations. For example, the preparation of in vitro systems results in disruption of the usual membrane barriers, thus enzymes are placed in an abnormal environment that may contain unusual concentrations of activators, inhibitors, or substrates. Another drawback is that short periods of anoxia are encountered during preparation of brain slices, homogenates, and various cell organelles. Such anoxic conditions are known to produce adverse effects and irreversible changes in the higher centers of the brain. Consequently, one is faced with the monumental task of relating data obtained from the in vitro system, after having made appropriate corrections for artifacts resulting from preparation, to metabolism in the intact organ. This difficulty could be avoided by using in vivo preparations were it not for physiologic and metabolic interference from other tissues. A way to circumvent most of the disadvantages of both the in vitro and in vivo systems in the study of cerebral metabolism is to use an isolated organ preparation.