In cases of cardiac arrest or stroke, the brain is deprived of blood, glucose, and oxygen and ischemic damage to specific neuronal populations occurs. One of the major factors that contributes to the ischemic damage is an increased excitability of neurons. Since neuronal excitation can be inhibited by the neurotransmitter, gamma-aminobutyric acid (GABA), the objective of this research plan is to determine the role of GABA neurotransmission in the neuronal damage following transient global ischemia. The model involves occlusion of 4 vessels (cerebral and carotid arteries) in the rat; changes in GABA neurotransmission are determined at both pre and postsynaptic loci. For presynaptic studies, in vivo microdialysis will be used to measure extracellular GABA levels in brain regions selectively vulnerable to ischemic damage. For postsynaptic studies, MRNA expression of GABA/A receptor subunits, GABA/A receptor binding, and function will be assayed using 1) in situ hybridization histochemistry, 2) receptor autoradiography (using [3H]muscimol to label GABA/A agonist sites and [35S]t- butylbicyclophosphorothionate to label the GABA-gated chloride channel, and 3) ion flux techniques to measure GABA gated 36 chloride uptake in synaptoneurosomes from cerebral cortex, hippocampus, and striatum. The research plan is divided into 3 parts to determine: 1) if changes in extracellular GABA levels promote or prevent ischemia-induced neuronal degeneration, 2) if changes in GABA/A receptor expression, binding, and function in selectively vulnerable regions promote or result from ischemia-induced neuronal death, and 3) if pharmacological agents that enhance GABA/A receptor function protect vulnerable neurons from degeneration and preserve GABA/A receptor characteristics and function in rats with transient global ischemia. These studies should provide new insights into the role of GABA neurotransmission in the initiation, promotion, or prevention of ischemic-induced neuronal injury. In addition, these studies may provide the bases for investigating new treatment strategies for dementias and sensorimotor deficits that occur after cardiac arrest and stroke.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS028791-02
Application #
3415444
Study Section
Neurological Sciences Subcommittee 1 (NLS)
Project Start
1992-03-01
Project End
1995-02-28
Budget Start
1993-03-01
Budget End
1994-02-28
Support Year
2
Fiscal Year
1993
Total Cost
Indirect Cost
Name
Duke University
Department
Type
Schools of Medicine
DUNS #
071723621
City
Durham
State
NC
Country
United States
Zip Code
27705
Zhan, Ren-Zhi; Nadler, J Victor; Schwartz-Bloom, Rochelle D (2007) Impaired firing and sodium channel function in CA1 hippocampal interneurons after transient cerebral ischemia. J Cereb Blood Flow Metab 27:1444-52
Zhan, Ren-Zhi; Nadler, J Victor; Schwartz-Bloom, Rochelle D (2006) Depressed responses to applied and synaptically-released GABA in CA1 pyramidal cells, but not in CA1 interneurons, after transient forebrain ischemia. J Cereb Blood Flow Metab 26:112-24
Pond, Brooks B; Berglund, Ken; Kuner, Thomas et al. (2006) The chloride transporter Na(+)-K(+)-Cl- cotransporter isoform-1 contributes to intracellular chloride increases after in vitro ischemia. J Neurosci 26:1396-406
Galeffi, Francesca; Sah, Renu; Pond, Brooks B et al. (2004) Changes in intracellular chloride after oxygen-glucose deprivation of the adult hippocampal slice: effect of diazepam. J Neurosci 24:4478-88
Pond, Brooks B; Galeffi, Francesca; Ahrens, Rebecca et al. (2004) Chloride transport inhibitors influence recovery from oxygen-glucose deprivation-induced cellular injury in adult hippocampus. Neuropharmacology 47:253-62
Sah, Renu; Galeffi, Francesca; Ahrens, Rebecca et al. (2002) Modulation of the GABA(A)-gated chloride channel by reactive oxygen species. J Neurochem 80:383-91
Schwartz-Bloom, R D; Sah, R (2001) gamma-Aminobutyric acid(A) neurotransmission and cerebral ischemia. J Neurochem 77:353-71
Schwartz-Bloom, R D; Miller, K A; Evenson, D A et al. (2000) Benzodiazepines protect hippocampal neurons from degeneration after transient cerebral ischemia: an ultrastructural study. Neuroscience 98:471-84
Galeffi, F; Sinnar, S; Schwartz-Bloom, R D (2000) Diazepam promotes ATP recovery and prevents cytochrome c release in hippocampal slices after in vitro ischemia. J Neurochem 75:1242-9
Sah, R; Schwartz-Bloom, R D (1999) Optical imaging reveals elevated intracellular chloride in hippocampal pyramidal neurons after oxidative stress. J Neurosci 19:9209-17

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