Anesthetics produce subunit-selective actions on glutamate receptors

We assessed the involvement of specific glutamate receptors in the action of anesthetics. In addition to the clinical anesthetics enflurane, isoflurane and halothane, we tested novel halogenated compounds, which are anesthetic or nonanesthetic in vivo, on glutamate receptor (GluR) subunits. these volatile compounds as well as pentobarbital and phenobarbital were tested on kainate-induced currents in Xenopus oocytes expressing GluR1, GluR3, GluR2+3 or GluR6 subunits. The anesthetic 1-chloro-1,2,2-triflurocyclobutane (F3) weakly inhibited kainate responses in oocytes expressing GluR3 receptors but not oocytes expressing GluR1 or GluR2+3 receptors. Surprisingly, F3 potentiated kainate responses in oocytes expressing the kainate-selective receptor GluR6. The nonanesthetics 2,3-chlorooctafluorobutane (F8) and 1,2-dichlorohexafluorocyclobutane (F6) did not affect GluR3 or GluR6 kainate responses. Isoflurane weakly inhibited although enflurane and halothane modestly inhibited kainate responses in oocytes expressing GluR1, GluR3 or GluR2+3 receptors. As with F3, isoflurane, enflurane and halothane potentiated kainate-induced currents of GluR6 receptors. The respective inhibitory and potentiating effects of halothane on GluR3 and GluR6 receptors were enhanced by increasing duration of halothane exposure. In contrast to the opposing action of volatile anesthetics, pentobarbital and phenobarbital inhibited GluR3 and GluR6 kainate responses and had a much greater effect on GluR6 receptors. These results provide novel evidence that anesthetics produce selective actions on glutamate receptors, suggesting that subunit composition may determine the role of glutamate receptors in anesthesia.