MICRODIALYSIS MEASUREMENTS OF PGD2, TXB2 AND 6-KETO-PGF1-ALPHA IN RAT CA1 HIPPOCAMPUS DURING TRANSIENT CEREBRAL-ISCHEMIA

We measured hippocampal CA1 concentrations of PGD2, TxB2 and 6-keto-PGF1alpha in 18 anesthetized rats with stereotaxically implanted microdialysis probes before, during and after 20 min of global cerebral ischemia. The insertion of the microdialysis probe did not appear to cause a continuous major disturbance of arachidonic acid (AA) metabolism because stable eicosanoid concentrations were obtained prior to ischemia. During reperfusion all three eicosanoids increased significantly reaching a peak after 30-60 min and then gradually declined to baseline levels over the next 2-3 h. The ratio of average peak concentrations for PGD2, TxB2 and 6-keto-PGF1alpha were approximately 80:2:1, respectively. The results extend previous work by demonstrating the time course of eicosanoid release in a distinct brain region and confirm the role of PGD2 as the major PG metabolite in brain. We conclude that future studies employing microdialysis may be able to provide a more detailed understanding of the role of AA metabolites in ischemic brain.