title: Inhibition of human TREK-1 channels by bupivacaine.
abstract: Human TWIK-related K(+) channels (TREK-1) stabilize the membrane potential (mp) of neurons and have a major role in the regulation of membrane excitability. In view of their physiological significance, interaction of bupivacaine with TREK-1 channels may be clinically important. Our aim was to characterize with the patch-clamp technique the properties of human TREK-1 channels and the effects of bupivacaine on these channels expressed in Chinese hamster ovary (CHO) cells. Transfection of CHO cells with TREK-1 channels (CHO(TREK-1) cells) hyperpolarized the mp from -33 +/- 13 to -78 +/- 4 mV. The channels were stimulated by intracellular acidosis. Inhibition of TREK-1 channels by bupivacaine was reversible, concentration-dependent, voltage-independent, and increased with intracellular acidosis. Bupivacaine depolarized the mp of CHO(TREK-1) cells in a reversible and concentration-dependent manner. Concentrations for channel inhibition and membrane depolarization were not linearly related (50% inhibitory concentration value for channel inhibition 370 +/- 20 micro M, Hill coefficient 1.8 +/- 0.1, n = 51; 50% inhibitory concentration value for membrane depolarization 856 +/- 14 micro M, Hill coefficient 2.4 +/- 0.1, mean +/- SEM, n = 27). The results suggest that protonated bupivacaine elicits the observed effects via a site of interaction accessible from the intracellular space. Inhibition of TREK-1 channels and consecutive depolarization of the cell membrane by bupivacaine may contribute to blockade of neuronal signal conduction during regional anesthesia.
  
  
  CONCLUSIONS
  The interaction of bupivacaine with human TREK-1 channels was studied with the patch-clamp technique. Bupivacaine inhibited TREK-1 channels and depolarized the membrane potential of cells expressing TREK-1 channels in a concentration-dependent and reversible manner. Both effects may contribute to conductance block caused by bupivacaine.
authors.affiliation: *Department of Anesthesiology, University Hospital Hamburg-Eppendorf; and †Institute of Neural Signal Transduction, University of Hamburg, Hamburg, Germany.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Punke
authors.forename: Thomas
authors.initials: T
authors.lastname: Licher
authors.forename: Olaf
authors.initials: O
authors.lastname: Pongs
authors.forename: Patrick
authors.initials: P
authors.lastname: Friederich
mesh_terms: D000138:Acidosis / Q000503:physiopathology; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D002021:Buffers; D002045:Bupivacaine / Q000494:pharmacology*; D016466:CHO Cells; D006224:Cricetinae; D004558:Electric Stimulation; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000187:drug effects*; D024683:Potassium Channels, Tandem Pore Domain; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000779:Anesthetics, Local; D001639:Bicarbonates; D002021:Buffers; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; C103742:potassium channel protein TREK-1; D002045:Bupivacaine