Real-time monitoring of extracellular adenosine using enzyme-linked microelectrode arrays

Abstract Throughout the central nervous system extracellular adenosine serves important neuroprotective and neuromodulatory functions. However, current understanding of the in vivo regulation and effects of adenosine is limited by the spatial and temporal resolution of available measurement techniques. Here, we describe an enzyme-linked microelectrode array (MEA) with high spatial (7500 µm 2 ) and temporal (4 Hz) resolution that can selectively measure extracellular adenosine through the use of self-referenced coating scheme that accounts for interfering substances and the enzymatic breakdown products of adenosine. In vitro , the MEAs selectively measured adenosine in a linear fashion ( r 2 =0.98±0.01, concentration range=0–15 µM, limit of detection =0.96±0.5 µM). In vivo the limit of detection was 0.04±0.02 µM, which permitted real-time monitoring of the basal extracellular concentration in rat cerebral cortex (4.3±1.5 µM). Local cortical injection of adenosine through a micropipette produced dose-dependent transient increases in the measured extracellular concentration (200 nL: 6.8±1.8 µM; 400 nL: 19.4±5.3 µM) [ P P