IN-VIVO VOLTAMMETRIC DETECTION OF RAT-BRAIN LACTATE WITH CARBON-FIBERMICROELECTRODES COATED WITH LACTATE OXIDASE

To allow rat brain lactate measurement in vivo, a specific sensor base d on a carbon fiber (phi = 30 mu m) microelectrode coated with lactate oxidase was prepared. Combined with the differential normal pulse vol tammetry measurement method, such a sensor, with a sensitivity of 9.15 +/- 0.91 mA.M-1.cm(-2), provided a lactate linear response in concent rations ranging from 0.1 to 2.0 mM. The measurements performed appeare d to be essentially insensitive to usual interference caused by the el ectroactive compounds present in the brain (ascorbic acid and peptides ), In vivo detection performed in the cortex of the anesthetized rat l ed to the determination of a lactate concentration of 0.41 +/- 0.02 mM , Moreover, to validate the results obtained in vivo, an ex vivo deter mination of the lactate level was also performed in samples of brain t issue, plasma, and cerebrospinal fluid, using both voltammetry and a c linical analyzer with colorimetric-based detection. A good correlation was observed between the sets of data established by both methods.