Improved ceramic-based multisite microelectrode for rapid measurements of L-glutamate in the CNS

This paper describes improvements and further characterization of a ceramic-based multisite microelectrode for in vivo measurements of L-glutamate. Improvements include increased recording area, insulation deposition using photolithography for more uniform recording sites and forming the microelectrodes using a diamond saw providing smoother microelectrode edges. The new microelectrodes are triangular in shape, 1 cm in length and taper from 1 mm to a 2-5 μm tip. Details on performing in vivo measurements are given, including microelectrode preparation, pitfalls of the recording method and approaches to enhance reproducibility of the technique. The detection limit for L-glutamate was lowered to ∼0.5 μM and a self-referencing recording technique was utilized to remove interferents as well as decrease noise. Applications of the microelectrodes to study L-glutamate uptake and release in rat prefrontal cortex, cortex, cerebellum and striatum are included.