title: Mechanism of Modification, by Lidocaine, of Fast and Slow Recovery from Inactivation of Voltage-Gated Na⁺ Channels.
abstract: The clinically important suppression of high-frequency discharges of excitable cells by local anesthetics (LA) is largely determined by drug-induced prolongation of the time course of repriming (recovery from inactivation) of voltage-gated Na(+) channels. This prolongation may result from periodic drug-binding to a high-affinity binding site during the action potentials and subsequent slow dissociation from the site between action potentials ("dissociation hypothesis"). For many drugs it has been suggested that the fast inactivated state represents the high-affinity binding state. Alternatively, LAs may bind with high affinity to a native slow-inactivated state, thereby accelerating the development of this state during action potentials ("stabilization hypothesis"). In this case, slow recovery between action potentials occurs from enhanced native slow inactivation. To test these two hypotheses we produced serial cysteine mutations of domain IV segment 6 in rNav1.4 that resulted in constructs with varying propensities to enter fast- and slow-inactivated states. We tested the effect of the LA lidocaine on the time course of recovery from short and long depolarizing prepulses, which, under drug-free conditions, recruited mainly fast- and slow-inactivated states, respectively. Among the tested constructs the mutation-induced changes in native slow recovery induced by long depolarizations were not correlated with the respective lidocaine-induced slow recovery after short depolarizations. On the other hand, for long depolarizations the mutation-induced alterations in native slow recovery were significantly correlated with the kinetics of lidocaine-induced slow recovery. These results favor the "dissociation hypothesis" for short depolarizations but the "stabilization hypothesis" for long depolarizations.
authors.affiliation: Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology (V.S.G., P.L., R.C., X.K., L.R., K.H., H.T.) and Center for Physiology and Pharmacology (W.S.), Medical University of Vienna, Vienna, Austria.
authors.forename: Vaibhavkumar S
authors.initials: VS
authors.lastname: Gawali
authors.affiliation: Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology (V.S.G., P.L., R.C., X.K., L.R., K.H., H.T.) and Center for Physiology and Pharmacology (W.S.), Medical University of Vienna, Vienna, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Lukacs
authors.affiliation: Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology (V.S.G., P.L., R.C., X.K., L.R., K.H., H.T.) and Center for Physiology and Pharmacology (W.S.), Medical University of Vienna, Vienna, Austria.
authors.forename: Rene
authors.initials: R
authors.lastname: Cervenka
authors.affiliation: Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology (V.S.G., P.L., R.C., X.K., L.R., K.H., H.T.) and Center for Physiology and Pharmacology (W.S.), Medical University of Vienna, Vienna, Austria.
authors.forename: Xaver
authors.initials: X
authors.lastname: Koenig
authors.affiliation: Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology (V.S.G., P.L., R.C., X.K., L.R., K.H., H.T.) and Center for Physiology and Pharmacology (W.S.), Medical University of Vienna, Vienna, Austria.
authors.forename: Lena
authors.initials: L
authors.lastname: Rubi
authors.affiliation: Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology (V.S.G., P.L., R.C., X.K., L.R., K.H., H.T.) and Center for Physiology and Pharmacology (W.S.), Medical University of Vienna, Vienna, Austria.
authors.forename: Karlheinz
authors.initials: K
authors.lastname: Hilber
authors.affiliation: Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology (V.S.G., P.L., R.C., X.K., L.R., K.H., H.T.) and Center for Physiology and Pharmacology (W.S.), Medical University of Vienna, Vienna, Austria.
authors.forename: Walter
authors.initials: W
authors.lastname: Sandtner
authors.affiliation: Center for Physiology and Pharmacology, Department of Neurophysiology and Neuropharmacology (V.S.G., P.L., R.C., X.K., L.R., K.H., H.T.) and Center for Physiology and Pharmacology (W.S.), Medical University of Vienna, Vienna, Austria hannes.todt@meduniwien.ac.at.
authors.forename: Hannes
authors.initials: H
authors.lastname: Todt
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D008012:Lidocaine / Q000494:pharmacology*; D009124:Muscle Proteins / Q000037:antagonists & inhibitors* / Q000502:physiology; D016296:Mutagenesis; D051381:Rats; D026941:Sodium Channel Blockers / Q000494:pharmacology*; D015222:Sodium Channels / Q000502:physiology; D013329:Structure-Activity Relationship
chemical_list: D000779:Anesthetics, Local; D009124:Muscle Proteins; C466180:Scn4a protein, rat; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D008012:Lidocaine