Glucose metabolites in the striatum of freely behaving rats following infusion of elevated potassium.

The outcome of patients with traumatic brain injury (TBI) can be predicted by the extracellular potassium concentration and the change in energy homeostasis. In this study, the authors investigated the effects of high potassium concentrations on extracellular levels of glucose, pyruvate and lactate in the rat striatum. Applying artificial cerebrospinal fluid (ACSF) enriched with 120 mM potassium by reverse microdialysis leads to an increase in lactate and reduction in glucose and pyruvate. Consequently, the lactate to pyruvate ratio was also increased. These data are discussed in the context of recent studies on lactate/pyruvate conversion and the potential mechanisms whereby high potassium could affect this equilibrium. We conclude that ischemic-like events are unlikely to explain these K(+)-induced changes.

Metabolic changes in rat striatum following convulsive seizures.

Generalized convulsive seizures increase glucose utilization within the brain but their impact on metabolism is not well known. The striatum receives excitatory input from widespread sources in the brain and could potentially reflect energy depletion in the brain resulting from generalized seizures. We utilized multiprobe microdialysis in freely moving rats subjected to maximal electroshock to simultaneously measure glucose, lactate, and pyruvate levels in the interstitial space within striatum and in peripheral subcutaneous tissue. A brief convulsive seizure was associated with marked changes in striatal and peripheral metabolism during the post-ictal state that lasted up to 1 h. There were significant central and peripheral elevations of glucose, pyruvate, and lactate, reflecting increased glucose metabolism. Interestingly, the lactate-to-pyruvate ratio increased significantly in the periphery but remained unchanged in the striatum. Thus, there appears to be brain mechanisms that maintain adequate energy sources and prevent anaerobic shift during the post-ictal state.