Summary: The effect of somatosensory stimulation on the local CBF (LCBF), CMRglu (LCMRglu), tissue pH, and tissue content of AT P, glucose, and lactate was studied in chloralose-anesthetized rats before and after 30 min of near-complete forebrain ischemia. In nonischemic rats LCBF in primary somatosensory cortex increased by 33%, LCMRglu increased by 55%, tissue glucose content decreased by 21%, and lactate increased by 30%. Local AT P and tissue pH did not change. Functional activation of the intact chloralose-anesthetized rat, in consequence, is associated with the stimulation of "aerobic"glycolysis but does not result in disturbances of energy or acid-base homeostasis. After 30-min ischemia and 3-h recircula-The coupling between neuronal activity, blood flow, and glucose utilization is a well-documented phenomenon that has been extensively studied in the past and that provides the basis for the meta bolic mapping of functional activity of the brain (Sokoloff, 1981). The general concept of metabolic coupling is based on the assumption that the activa tion of neuronal circuits is associated with an in crease of energy and transmitter turnover that has to be fueled by an increased supply of glucose and oxygen. Recently, evidence has been provided that a period of transient cerebral ischemia suppresses the stimulation-evoked increase of glucose utiliza tion for up to several days after the ischemic impact (Dietrich et aI., 1986). The responsiveness of blood flow to changes of Pco2, which is thought to con- tribute to the flow-metabolism couple, is also sup pressed for days, if not months, after ischemia even if spontaneous and evoked electrical activity return to normal (Schmidt-Kastner et aI., 1986).If functional activation of the brain after ischemia requires the same amount of energy as in the intact brain, and if neither blood flow nor glucose con sumption is increased during activation, the brain will have to cover the increased energy demands by utilizing its energy stores. This process should lead to measurable alterations in the regional content of energy metabolites. To test this hypothesis we have studied the effect of functional activation before and after global ischemia of rat brain by combining autoradiographic measurements of local CBF (LCBF) and CMRg\u (LCMRglu) with methods for the pictorial evaluation of energy metabolites and of the acid-base state of the brain ("multiparame tric brain imaging") (Hossmann et aI., 1985).The results obtained demonstrate that following a period of severe forebrain ischemia, activation of blood flow or glucose utilization is completely sup pressed although EEG and evoked potentials re cover. Surprisingly, this dissociation does not cause any disturbances of the regional energy state of the brain, which raises the fundamental question of the