Faculty

2. Functional domains in the GABAA receptor protein: we identified amino acid residues in the protein that are involved in ligand binding using affinity labeling with radio-ligands and microsequencing, and developed a new model of the agonist and modulatory drug sites of interaction in the protein that could convert binding energy into conformational changes regulating ion channel gating. We study this with site-directed mutagenesis and expression of mutant receptors as above.

B. An animal model of drug dependence and epileptogenesis: we gave rats chronic intermittent administration of ethanol to produce multiple withdrawals, resulting in persistent severe withdrawal signs, assessed as an increased seizure susceptibility, using the GABA blocking convulsant, pentylenetetrazol. The animals resemble those made pre-epileptic, or `kindled', by chronic stimulation with subconvulsant levels of electrical activation or convulsant drugs. This seems to be a useful model of human addictive behavior as well as an interesting example of brain plasticity in response to environmental stressors. We are searching for a molecular explanation of the behavioral alterations involving GABAA receptors; we found hypofunction of GABA-mediated inhibition in hippocampus.

C. An animal model of mental retardation and possibly epilepsy: we obtained a mouse mutant deleted in chromosome 7, synthenic with human chromosome 15, an area involved in the human mental retardation mutation, Angelman's Syndrome (AS). We showed that the mouse lacks 3 GABA receptor subunits and that this changes receptor binding characteristics. We are comparing phenotypic characteristics to genotypic in these animals, which are neurologically abnormal, runted and die young. We are also culturing cells from embryonic brains of the mutants to study whether any cellular properties, including GABA responses, are impaired. At the same time, we are looking at human cases of AS and determining whether all patients have epilepsy and are lacking on or more GABA receptor genes.