ABSTRACT
390This chapter reviews data which suggests that there is no fundamental difference in the way the turtle and rat brain react to inadequate energy supply. This condition is encountered during both anoxia and ischemia in the rat brain and ischemia in the turtle brain. The rat brain fails to survive anoxia and ischemia because of an inherent high metabolic rate combined with relatively low amounts of glycolytic enzymes which cannot adequately maintain energy supply for the cell. However, the turtle brain is able to meet anoxic energy demands through a large glycolytic capacity combined with a low metabolic rate which is further suppressible during anoxia. Our data support that one mechanism which may play a major role in energy savings in the turtle brain during normoxia is reduced ion pumping. However, data do not support reduced leakage conductance as a mechanism for metabolic depression during anoxia in the turtle brain; if ion pumping is reduced during anoxia, it is likely to occur through reduction of other leakage processes such as reduced electrical activity.
