A possible role for phospholipase A2 in the action of general anesthetics.

General anesthetics inhibit Ca(2+)-activated potassium (BK) channels at clinically relevant concentrations. This study examined the possibility that general anesthetics produce their effect on BK channels by disrupting the phospholipase A2 (PLA2)-arachidonic acid signal transduction pathway. Treatment of excised patches with exogenous arachidonic acid (2.5 microM) resulted in a 3.6 +/- 1.3-fold increase in BK channel activity. Subsequent exposure of these patches to concentrations of halothane (0.6 mM), ketamine (100 microM), or etomidate (10 microM) that would normally block the channel by approximately 60-80% in the absence of arachidonic acid did not reduce the channel activity. Arachidonic acid resulted in a significant increase in the 50% effective concentration for the ketamine dose-response curve from 3.4 +/- 0.4 to 693 +/- 379 microM (P < 0.001) as well as a significant decrease in slope from 1.40 +/- 0.21 to 0.59 +/- 0.05 (P < 0.001). The PLA2 inhibitors quinacrine (1 microM), aristolochic acid (250 microM), and octadecylbenzoylacrylic acid (7 microM) inhibited BK channels by 61 +/- 6, 47 +/- 2, and 30 +/- 9%, respectively, and in a manner indistinguishable from general anesthetics inhibition. Aristolochic acid and ketamine significantly inhibit the PLA2-mediated production of arachidonic acid in GH3 cells.