The central hypothesis for this grant is that interictal hypometabolism seen in epileptic human brain reflects impaired mitochondrial metabolism, on consequence of which is an alteration in glial glutamate metabolism,, especially glutamate uptake. The goal of this subsection is to test specific hypotheses regarding the functional consequences of these changes. using brain slices and cultured astrocytes. Tissue from patients as well as from chronically epileptic kainate-treated rats obtained from human tissue will be correlated with the data obtained in the other subprojects. In the first Specific Aim we will test the hypothesis that extracellular homeostasis is impaired in epileptic tissue. The regulation of [K+]o, the size of the extracellular space and extracellular pH will be assayed using ion-selective microelectrodes in human and rodent tissue. The effect of specific metabolic inhibitors on these variables will be examined. In the second Specific Aim we will examine if glutamate uptake impaired in epileptic tissues. The changes in glutamate and glutamine levels will be measured during synaptic and spontaneous activity and control tissue using HPLC of the extracellular fluid. This links directly with the microdialysis studies in the Core. The effects of glutamate uptake inhibitors on the amino acid concentrations and on seizure activity in both epileptic and control tissue will also be investigated. The third Specific Aim tests the hypothesis that an increase in extracellular glutamate associated with defective glutamate uptake acts to limit glutamate release via presynaptic mechanisms. Finally, confocal microscopy of glutamate- induced Ca2+ transients in cultured glia will be examined to test the hypothesis that elevated extracellular glutamate alters glial plasticity. Cultures from control and epileptic tissue will be used to assess whether epileptic tissue has comparable responses to that chronically exposed to glutamate. We hypothesize that this will be the condition found in tissue from the patients with impaired mitochondrial metabolism. These experiments will complement the other three projects by examining several possible functional consequences of impaired mitochondrial metabolism at the level of single neurons or glial cells.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Program Projects (P01)
Project #
5P01NS039092-03
Application #
6495440
Study Section
Special Emphasis Panel (ZNS1)
Project Start
2001-07-01
Project End
2002-06-30
Budget Start
Budget End
Support Year
3
Fiscal Year
2001
Total Cost
$225,543
Indirect Cost
Name
Yale University
Department
Type
DUNS #
082359691
City
New Haven
State
CT
Country
United States
Zip Code
06520
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Dericioglu, Nese; Garganta, Cheryl L; Petroff, Ognen A et al. (2008) Blockade of GABA synthesis only affects neural excitability under activated conditions in rat hippocampal slices. Neurochem Int 53:22-32
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Malthankar-Phatak, Gauri H; de Lanerolle, Nihal; Eid, Tore et al. (2006) Differential glutamate dehydrogenase (GDH) activity profile in patients with temporal lobe epilepsy. Epilepsia 47:1292-9
Cavus, Idil; Kasoff, Willard S; Cassaday, Michael P et al. (2005) Extracellular metabolites in the cortex and hippocampus of epileptic patients. Ann Neurol 57:226-35
Pan, J W; Kim, J H; Cohen-Gadol, A et al. (2005) Regional energetic dysfunction in hippocampal epilepsy. Acta Neurol Scand 111:218-24
Pan, Jullie W; Takahashi, Kan (2005) Interdependence of N-acetyl aspartate and high-energy phosphates in healthy human brain. Ann Neurol 57:92-7

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