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 mu M-1 cm(-2)) and response time ( ca. 1 s) to glutamate as previously described Nafion- coated MEAs but, unlike Nafioncoated MEAs, were unresponsive to 5 mu M dopamine. Such OPP- coated MEAs afforded selective detection of evoked glutamate release in the dopamine- rich striatum of the mouse brain.