Effects of anesthetic agents on focal adhesion kinase (pp125 FAK) tyrosine phosphorylation in rat hippocampal slices

Background: Tyrosine protein kinase proteins exert a prominent control on signaling pathways and may couple rapid events, such as action potential and neurotransmitter release, to long-lasting changes in synaptic strength and survival. Whether anesthetics modulate tyrosine kinase activity remains unknown. The aim of the current study was therefore to examine the effects of intravenous and volatile anesthetics on the phosphorylation of focal adhesion kinase (pp(125)FAK), a functionally important nonreceptor tyrosine kinase, in the rat hippocampus. Methods: Phosphorylation of pp(125)FAK was examined in hippocampal slices by immunoblotting with both antiphosphotyrosine and specific anti-pp(125)FAK antibodies. Experiments were performed in the absence (control) or presence of various concentrations of pharmacologic or anesthetic agents or both. Results: Clinically relevant concentrations of thiopental, propofol, etomidate, isoflurane, sevoflurane, and desflurane induced a concentration-related increase in tyrosine phosphorylation. In contrast, ketamine (up to 100 mum) and the nonimmobilizer F6 (1,2-dichlorohexafluorocyclobutane, 25 mum) did not significantly affect pp(125)FAK phosphorylation. The anesthetic-induced increase in pp125FAK phosphorylation was blocked by GF 109203x, RO 318220, and chelerythrin (100 mum), three structurally distinct inhibitors of protein kinase C and U 73122 (50 mum), an inhibitor of phospholipase C. The propofol- and isoflurane-induced increase in pp(125)FAK phosphorylation was reversible and showed nonadditivity of effects with phorbol 12-myristate 13-acetate (an activator of protein kinase C, 0.1 mum). In contrast, ketamine (up to 100 mum), MK801 (10 mum, an N-methyl-D-aspartate receptor antagonist), bicuculline (10 mum, a gamma-aminobutyric acid type A receptor antagonist), and dantrolene (30 mum, an inhibitor of the ryanodine receptor) were ineffective in blocking anesthetic-induced activation of tyrosine phosphorylation. Conclusion: Except for ketamine, anesthetic agents markedly increase tyrosine phosphorylation of pp(125)FAK in the rat hippocampus, most likely via the phospholipase C-protein kinase C pathway, whereas the nonimmobilizer F6 does not. These results suggest that pp(125)FAK represents a target for anesthetic action in the brain.