Measurement of brain tissue oxygen at a carbon paste electrode can serve as an index of increases in regional cerebral blood flow

Simultaneous monitoring of tissue O-2 and regional cerebral blood flow (rCBF) was performed in the striatum of freely-moving rats. Differential pulse amperometry and constant potential amperometry were used to monitor O-2 levels at a carbon paste electrode (CPE), while rCBF values were obtained using the H-2 clearance technique. Two forms of behavioural activation were studied and the resultant changes in tissue O-2 and blood flow compared. Both tail pinch and induced grooming produced immediate and parallel increases in O-2 and blood flow which returned to baseline on cessation of activity. These findings indicate that under conditions of physiological stimulation the direct voltammetric measurement of O-2 in brain tissue with a CPE can be used as a reliable index of increases in rCBF, resulting in an improvement in time resolution from 5 min (H-2 clearance) to < 1 s (amperometry). Because tissue O-2 is a balance between supply by the blood stream and utilisation by the cells, increases in O-2 current are an index of increased blood flow only when supply significantly exceeds utilisation. (C) 1997 Elsevier Science B.V.