EFFLUX OF GLUTAMATE INTO THE PERILYMPH OF THE COCHLEA FOLLOWING TRANSIENT ISCHEMIA IN THE GERBIL

Using a microdialysis technique followed by an enzyme cycling analysis , we measured changes in the glutamate levels in the perilymph of gerb il cochleae before, during and after transient ischemic insult. The ba sal glutamate level in perilymph was 0.35 +/- 0.22 pmol/mu l. An almos t immediate and continuous rise in the level of glutamate occurred aft er the ischemic insult, which advanced even further after recirculatio n; the average concentration was higher than 40 pmol/mu l 55 min after recirculation. The compound action potentials (CAP) monitoring the au ditory function totally disappeared after ischemic insult. However, CA P reappeared after recirculation; the threshold for acoustic stimulati on was higher than that observed at the pre-ischemic state. (C) 1997 E lsevier Science Ireland Ltd.