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Basic Mechanisms of Epilepsy and the Actions of Antiepileptic Drugs

Robert L. Macdonald
Professor and Chair of Neurology
A-1124A MCN
6140 MRB III
615-936-2287 (office)

My laboratory is focused on understanding the structure and function of recombinant and native gamma aminobutyric acid (GABA) type A (GABAA) receptor channels, and the basic mechanisms of epilepsy and anticonvulsant drugs. GABAA receptor channels are the major inhibitory neurotransmitter receptors in the brain. Reduction of GABAA receptor function produces seizures and epilepsy in animals and man, and enhancement of GABAA receptor function has been used to treat seizures. At least four forms of human epilepsy have been linked to mutations in the alpha1 and gamma2 GABAA receptor subunits. The mechanisms for neurotransmitter activation, regulation of the opening and closing (gating), desensitization and intracellular trafficking of these channels are unknown.

We study recombinant and native GABAA receptor channels using single channel and whole cell patch clamp recording and ultra rapid drug application techniques. Single channel and whole cell recordings of native neurotransmitter receptor channels are made from acute hippocampal slices to study their physiological and biophysical properties and regulation by drugs and phosphorylation. Recombinant receptors and channels are studied using acute transfection of mammalian cells with expression vectors containing receptor subunit cDNAs followed by whole cell or single channel recording. Site-directed mutagenesis and construction of receptor chimeric cDNAs are used to determine binding and kinase phosphorylation sites, and to characterize receptor channel gating and desensitization. Human mutations are made in relevant receptor channel subunits to determine the basic mechanism underlying these genetic human epilepsies. Receptor trafficking is studied using flow cytometry, confocal microscopy and biotinylation and Western blotting of receptors.