Energy metabolism in the brain.

Publisher Summary The studies of glucose metabolism in the brain reflect a dichotomy because the complex integrating functions of the brain can only be studied in the intact, functioning brain in the conscious individual (human or animal). On the other hand, the properties of brain cells, cell-cell interactions, and mechanisms are most readily evaluated in vitro under controlled conditions using brain slices, subcellular fractions, or purified, isolated cells of different types. A variety of in vitro methods has been used to assess metabolic activities in different brain cell types and in subcellular structures. Nevertheless, by combining different methodologies and continuously maintaining the in vivo situation as the general standard to which results obtained with different cellular and subcellular techniques must be compared, a picture of cellular interactions in glucose metabolism has emerged, and information has been obtained about the identity of energy-requiring and energy-yielding processes. Perhaps even more importantly, these studies have triggered the development of in vivo methods, primarily utilizing nuclear magnetic resonance imaging and spectroscopy, which have confirmed and further expanded many observations made in vitro . This chapter discusses the pathways and regulation of glucose metabolism in the functioning brain in the conscious human or animal during rest and during stimulation and describes the mechanisms, which increase glucose metabolism in vitro . A combination of these two approaches allows a tentative determination of not only the quantitative contributions to glucose metabolism by some of the major cell types, but also identification of mechanisms creating a demand for metabolically generated energy and their relationships to functional activation and neurotransmission.