THE PHOSPHOLIPASE-A(2) INHIBITOR BROMOPHENACYL BROMIDE PREVENTS THE DEPOLARIZATION-INDUCED INCREASE IN [H-3] AMPA BINDING IN RAT-BRAIN SYNAPTONEUROSOMES

We previously demonstrated that potassium (KCl)-induced depolarization of synaptoneurosomes prepared from rat telencephalon increased H-3]am ino-3-hydroxy-5-methylisoxazole-4-propionate ([H-3]AMPA) binding to th e AMPA receptor. In the present study, we determined the effects of in hibitors of various calcium-dependent enzymes on this response to depo larization. Treatment of intact synaptoneurosomes with the phospholipa se A2 (PLA2) inhibitor, bromophenacyl bromide (BPB), produced a marked and dose-dependent reduction in KCl-induced enhancement in [H-3]AMPA binding. BPB had no significant effect on [H-3]TPP accumulation in int act synaptoneurosomes, an index of membrane depolarization. In contras t to BPB, inhibitors of calcium-dependent kinases and proteases did no t reduced the KCl-induced increase in [H-3]AMPA binding. The results s trengthen the hypothesis that phospholipase-induced modifications of A MPA receptor properties may be an important component of synaptic plas ticity.