LACTATE AND PH CHANGE IN CLOSE CORRELATION IN THE EXTRACELLULAR-SPACE OF THE RAT-BRAIN DURING CORTICAL SPREADING DEPRESSION

pH sensitive microelectrodes were used in combination with microdialysis (MD) technique to measure extracellular pH (pH(e)) and extracellular lactate (lac(e)) within the cortex of rat brains during cortical spreading depression (SD). SD was induced by local K+-application and identified by DC recordings. It was accompanied by an extracellular acidification of 0.34 +/- 0.06 pH units and by a 2.8 +/- 0.80 fold increase of lac(e); the recovery of pH(e) took place within three phases, that of lac(e) within 2 phases. The recovery of both parameters was complete about 45 min after the onset of SD. We conclude that the changes of lac(e) and pH(e) are closely related. This indicates both lactate and protons to be transported in parallel.