Mark A Punke1, Patrick Friederich. 1. Department of Anesthesiology, University Hospital Hamburg-Eppendorf, 52, 20246 Hamburg, Germany. patrick.friederich@zmnh.uni-hamburg.de
Abstract
BACKGROUND: Inhibition of KCNQ2/Q3 channels may cause convulsion in humans. The interaction of bupivacaine with these channels is unknown. The anticonvulsant retigabine activates KCNQ2/Q3 channels and may reverse inhibitory actions of bupivacaine. Potassium channel stimulation may thus constitute a novel approach to treat local anesthetic-induced seizures. The aim of this study was to characterize bupivacaine effects on KCNQ2/Q3 channels and to investigate whether retigabine reverses the effects of the local anesthetic. METHODS: KCNQ2/Q3 channels were transiently expressed in Chinese hamster ovary cells. The effects of bupivacaine and retigabine were studied with the patch-clamp technique. RESULTS: Bupivacaine inhibited KCNQ2/Q3 channels in a concentration-dependent and reversible manner. The concentration-response curve was described by a Hill equation (IC50 = 173 +/- 7 microm, Hill coefficient = 1.4 +/- 0.1, mean +/- SEM, n = 37). The inhibitory effect did not differ between bupivacaine and levobupivacaine (42 +/- 4%, n = 7, versus 42 +/- 5%, n = 10; P > 0.05). Ropivacaine was four times less potent than bupivacaine. The inhibition of KCNQ2/Q3 channels by bupivacaine resulted in a significant and reversible depolarization of the membrane potential. Retigabine (300 nm-10 microm) reversed the inhibitory action of bupivacaine on KCNQ2/Q3 channels as well as the depolarization of the membrane potential. CONCLUSIONS: The anticonvulsant retigabine at nanomolar concentrations reverses the inhibitory effect of micromolar concentrations of bupivacaine. Our results allow the hypothesis that activation of KCNQ2/Q3 channels by retigabine may offer a novel therapeutic approach for the treatment of bupivacaine-induced seizures.
BACKGROUND: Inhibition of KCNQ2/Q3 channels may cause convulsion in humans. The interaction of bupivacaine with these channels is unknown. The anticonvulsant retigabine activates KCNQ2/Q3 channels and may reverse inhibitory actions of bupivacaine. Potassium channel stimulation may thus constitute a novel approach to treat local anesthetic-induced seizures. The aim of this study was to characterize bupivacaine effects on KCNQ2/Q3 channels and to investigate whether retigabine reverses the effects of the local anesthetic. METHODS:KCNQ2/Q3 channels were transiently expressed in Chinese hamster ovary cells. The effects of bupivacaine and retigabine were studied with the patch-clamp technique. RESULTS:Bupivacaine inhibited KCNQ2/Q3 channels in a concentration-dependent and reversible manner. The concentration-response curve was described by a Hill equation (IC50 = 173 +/- 7 microm, Hill coefficient = 1.4 +/- 0.1, mean +/- SEM, n = 37). The inhibitory effect did not differ between bupivacaine and levobupivacaine (42 +/- 4%, n = 7, versus 42 +/- 5%, n = 10; P > 0.05). Ropivacaine was four times less potent than bupivacaine. The inhibition of KCNQ2/Q3 channels by bupivacaine resulted in a significant and reversible depolarization of the membrane potential. Retigabine (300 nm-10 microm) reversed the inhibitory action of bupivacaine on KCNQ2/Q3 channels as well as the depolarization of the membrane potential. CONCLUSIONS: The anticonvulsant retigabine at nanomolar concentrations reverses the inhibitory effect of micromolar concentrations of bupivacaine. Our results allow the hypothesis that activation of KCNQ2/Q3 channels by retigabine may offer a novel therapeutic approach for the treatment of bupivacaine-induced seizures.