Both activation of phospholipase A 2 causing arachidonic acid release and tyrosine phosphorylation have been proposed to be involved in neuronal functions. Previously, we reported that orthovanadate (Na 3 VO 4 ), an inhibitor of tyrosine phosphatases, stimulated tyrosine phosphorylation in proteins and enhanced Ca 2+ -induced noradrenaline release in rat pheochromocytoma PC12 cells. However, the role of tyrosine phosphorylation on phospholipase A 2 activity and/or arachidonic acid release in neuronal cells has not been well established. The effects of Na 3 VO 4 on arachidonic acid release and prostaglandin F 2α formation were investigated in two types of neuronal cell lines. In PC12 cells, addition of Na 3 VO 4 stimulated [ 3 H]arachidonic acid release and prostaglandin F 2α formation in a concentration-dependent manner. Co-addition of 5 mM Na 3 VO 4 enhanced ionomycin-stimulated [ 3 H]arachidonic acid release. Na 3 VO 4 also enhanced ionomycin-stimulated [ 3 H]arachidonic acid release from GH3 cells, a clonal strain from rat anterior pituitary. These findings suggest that the tyrosine phosphorylation pathway regulates arachidonic acid release by phospholipase A 2 and prostaglandin F 2α formation in neuronal cells.