Members of my laboratory are studying excitatory amino acid (EAA) or "glutamate" activated receptor-channels in the vertebrate central nervous system. The principal approach to these investigations involves recordings of EAA activated receptor-channels in mammalian brain neurons in primary culture and recombinant receptor-channels expressed in mammalian cell lines. Single channel recordings are employed to analyze basic biophysical parameters of receptor channel function. Whole cell voltage-clamp recordings are also combined with single cell molecular biology methods in an effort to ascertain the likely subunit compositions of pharmacologically and biophysically distinct receptor-channel subtypes observed in cerebellar granule neurons.
Recent studies have focused on pharmacological and biophysical properties of members of the nonNMDA family of EAA receptor-channel found in isolated cortical and cerebellar neurons. Patch clamp recordings of single channel currents activated by application of selective EAA receptor agonists provide evidence for at least six different non-selective cation permeable channels. Molecular cloning has demonstrated at least 14 cDNAs coding for different proteins that are capable of forming functional EAA receptor-channels in homomeric or heteromeric combinations. However, comparatively little is known about what factors regulate the cell specific expression of the diverse group of EAA receptor-channels that form in different brain neurons and glial cells. The molecular technique of expression profiling the relative abundance of messenger RNAs for 9 of the nonNMDA receptor subunits is being used to provide a picture of the ratios of messages within individual cells that are functionally and pharmacologically distinct from one another in order to propose models of subunit composition for the particular receptor-channel subtypes expressed in individual neurons. Single cell RT-PCR is used to determine which of several molecular variants of the individual subunits is present. This information is being applied to studies of channels formed by transfection of mammalian cell lines with different subunits.