Selective detection of extracellular glutamate in brain tissue using microelectrode arrays coated with over-oxidized polypyrrole

We describe the selective measurement of extracellular glutamate concentration in rodent brain using ceramic-based platinum microelectrode arrays (MEAs) coated with electropolymerized, over-oxidized polypyrrole (OPP) as a permselective barrier to interference from dopamine and ascorbate. OPP-coated MEAs displayed similar sensitivity (97 +/- 9 nA microM(-1) cm(-2)) and response time (ca. 1 s) to glutamate as previously described Nafion-coated MEAs but, unlike Nafion-coated MEAs, were unresponsive to 5 microM dopamine. Such OPP-coated MEAs afforded selective detection of evoked glutamate release in the dopamine-rich striatum of the mouse brain.