GLUTAMATE-GATED CHANNELS IN CENTRAL/PERIPHERAL NEURONS

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Glutamate-gated ion channels play a number of important roles in the nervous system. They are known to mediate the depolarization of postsynaptic neurons at fast excitatory synapses and are thought to regulate transmitter release from presynaptic terminals of some cell types. In addition, they have been implicated in neuronal cell death associated with anoxia and hyperexcitation. Although much has been learned about glutamate receptors in the past 10 years, many aspects of their function remain poorly understood. The long term objective of the proposed research is to provide a better understanding of excitatory synaptic transmission by characterizing the operation of receptors and channels that are activated by glutamate. A second major goal is to uncover properties of the channels that may allow for clinical intervention to prevent excitotoxic cell death. Patch clamp techniques will be used to record the whole-cell and single channel currents evoked by excitatory amino acids in neurons maintained in primary cell culture and in freshly dissociated cells from peripheral sensory ganglia or from the CNS. The work involves two main projects. The first set of experiments will test the hypothesis that negative charges on the external face of the N-methyl-D-aspartate (NMDA) receptor in central neurons contribute to its unique gating and permeation properties, including regulation of the channel by glycine, Zn, polyamines, protons, Mg, and dizocilpine. The second project focuses on the activation and desensitization of non-NMDA receptors in CNS neurons and in dorsal root ganglion neurons, which express a novel form of this receptor. The specific aim is to determine the mechanism or mechanisms that underlie desensitization by studying the action of ions, drugs and proteins that are known to change the gating behavior of non-NMDA receptor channels. Another major focus of this project is to characterize the pharmacology of receptors expressed by DRG neurons with the goal of finding selective agents that can distinguish between the central and peripheral forms of the receptor. Such agents will be critical for establishing the function of the DRG receptor; they also might prove capable of controlling the sensation of pain, because the expression of this receptor in DRGs appears to be restricted to nociceptive neurons.