GLUTAMATE-GATED CHANNELS IN CENTRAL & PERIPHERAL NEURONS

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The long term objective of my work is to provide a better understanding of synaptic transmission by studying the operation of NMDA, AMPA, and kainate receptors, which form ion channels gated by the neurotransmitter glutamate. Another major goal is to uncover properties of these receptors that may allow for clinical intervention to prevent excitotoxic cell death. The experiments outlined in this proposal focus on the functional properties of kainate receptors. This glutamate receptor subtype is thought to regulate neuronal excitability and may contribute to excitotoxicity under certain conditions; but, currently much less is known about kainate receptors than about NMDA and AMPA receptors. Patch clamp techniques will be used to record the whole-cell add single channel currents evoked by excitatory amino acids in isolated neurons that express native glutamate receptors, and in heterologous cells that express cloned glutamate receptor subunits. Kainate receptors will be characterized with respect to their agonist and antagonist pharmacology, desensitization properties, current-voltage relations, relative permeability to calcium and monovalent ions, and susceptibility to modulation. For experiments on CNS neurons, NMDA and AMRA receptors will be blocked with the non- competitive antagonists MK-801 and GYKI 53655, respectively. A second major aim of this study is to test the hypothesis that kainate receptors regulate synaptic transmission. The action of kainate initially will be studied on synapses formed by hippocampal neurons grown in microcultures. In preliminary experiments, the agonists kainate and domoate have been shown to inhibit both excitatory and inhibitory synapses. The possible mechanisms that may underlie this inhibition will be examined in detail. We will seek to establish whether this action involves pre or postsynaptic kainate receptors and whether they are identical to the receptors that mediate kainate currents in these cells. In addition, we will seek to determine the conditions under which kainate receptors may be activated by the endogenous agonist, glutamate.