Novel, in Vivo Measures of Rat Spinal Cord Glutamate

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DESCRIPTION (provided by applicant): The ability to record the rapid dynamics of in vivo glutamate release and uptake in normal rat spinal cord or after traumatic injury has been limited by the temporal resolution of available methodology. However, this area of research remains of major interest in neuroscience because of the contrasting roles of glutamate as an essential neurotransmitter in normal physiological processes yet as a neurotoxin in pathologies and trauma. This grant is a pilot study to establish a novel, ceramic based, multi-site microelectrode system as an in vivo electrochemical method to measure fast glutamate neurotransmission in normal rat spinal cord. The application of the novel, highly specialized sensors offers the unique capacity for rapid, second by second measures of glutamate release and uptake at platinum electrode sites coated with glutamate oxidase. While this technique has successfully measured glutamate in rat brain tissue, the efficacy in spinal cord has not been established. The first specific aim will validate the ability to record both baseline and evoked levels of glutamate release in spinal cord gray and white matter. These experiments will (i) characterize the extracellular signal and confirm the measure of glutamate, (ii) characterize the signal kinetics in response to KCI evoked release and (iii) compare these parameters in both spinal cord gray and white matter. The second aim will measure the kinetics of glutamate uptake (i) in response to locally applied glutamate and (ii) in response to excitatory amino acid transporter uptake inhibitors. Agents will be delivered through micropipettes attached to the sensors. The ability to rapidly record "real-time", in vivo glutamate events over time in spinal cord tissue represents a valuable alternative to commonly used microdialysis. This significant methodological advance will greatly enhance the ability to elucidate the regulation of normal glutamatergic neurotransmission in normal rat spinal cord and in response to pathology or trauma. It will be essential to validate the technique in rat spinal cord prior to application of the method to spinal cord injury.