title: Bupivacaine inhibits endothelin-1-evoked increases in intracellular calcium in model sensory neurons.
abstract: BACKGROUND
  Endothelin-1 (ET-1) induces pain-like behavior in animals and man by activating the Gq protein-coupled receptor endothelin-A (ETA ). Activation of ETA receptors on nociceptor membranes evokes intracellular calcium transients and alters membrane Na(+) and K(+) channel and TRPV1 currents, leading to neuronal hyper-excitability manifested by spontaneous and evoked pain behaviors in vivo. In addition to blocking sodium channels, local anesthetics inhibit the Gq protein-coupled signaling of several inflammatory and pro-algesic mediators. In this study, we aimed to investigate the actions of local anesthetics on ETA -mediated increases in intracellular calcium in ND7/104 model sensory neurons.
  
  
  METHODS
  Increases in intracellular calcium were measured by the fluorescent indicator fura-2 in a sensory neuron-derived cell line (ND7/104), which endogenously expresses ETA receptors. Effects of lidocaine and bupivacaine, along with their respective membrane-impermeant derivatives QX-314, LEA-123 and LEA-124, on peak calcium responses to ET-1 were measured.
  
  
  RESULTS
  Bupivacaine suppressed ET-1 responses in a concentration-dependent and non-competitive manner with an IC50 of 3.79 ± 1.63 mM. Bupivacaine (6 mM) reduced the Emax for ET-1 from 50.07 ± 1.91 mM to 27.30 ± 2.92 mM. The actions of bupivacaine occurred quickly and were rapidly reversible. Membrane-impermeant analogs of bupivacaine (LEA-123 and LEA-124, 6 mM) were without effect, as was lidocaine (10 mM) and its quaternary derivative QX-314 (10 mM).
  
  
  CONCLUSIONS
  Bupivacaine inhibits ETA -mediated calcium transients at clinically relevant concentrations through an intracellular target. The anti-inflammatory and analgesic actions of bupivacaine may be at least partially due to its inhibitory action on Gq -coupled receptors, including ETA.
authors: Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.|Department of Pharmaceutical Biosciences, Division of Biological Research on Drug Dependence, Uppsala University, Uppsala, Sweden.
authors: M J
authors: MJ
authors: Makdessi
authors: Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
authors: T P
authors: TP
authors: Barr
authors: Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.|Boston Latin School, Boston, MA, USA.
authors: W
authors: W
authors: Xue
authors: Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
authors: G R
authors: GR
authors: Strichartz
mesh_terms: D000704:Analysis of Variance; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D002045:Bupivacaine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D018929:Cell Culture Techniques; D019332:Endothelin-1 / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D051381:Rats; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000779:Anesthetics, Local; D019332:Endothelin-1; D002118:Calcium; D002045:Bupivacaine