title: Xenon blocks the induction of synaptic long-term potentiation in pain pathways in the rat spinal cord in vivo.
abstract: BACKGROUND
  Xenon's (Xe) mechanisms for producing anesthesia and analgesia are not fully understood. We tested the effect of Xe equilibrated in a lipid formulation or normal saline on spinal C-fiber-evoked potentials and on the induction of synaptic long-term potentiation (LTP).
  
  
  METHODS
  C-fiber-evoked field potentials were recorded in the superficial lumbar spinal cord in response to supramaximal electrical stimulation of the sciatic nerve. Anesthesia was maintained with isoflurane in one-third O2 and two-thirds N2O. Xe equilibrated at a concentration of 600 microL/mL of Lipofundin MCT(R) 20%, (n = 5) or solvent alone (n = 3), and Xe equilibrated at a concentration of 100 microL/mL of normal saline (n = 7) or saline alone (n = 7) was given IV under apnea. High-frequency stimulation of the sciatic nerve was applied 60 min after the injection of Xe-containing formulations or solvents [to induce LTP].
  
  
  RESULTS
  High-frequency stimulation potentiated C-fiber-evoked potentials to 156% +/- 14% (mean +/- sem) of control. Low-dose Xe in saline 0.9% blocked the induction of LTP. High-dose Xe equilibrated in MC(R) 20% showed no additional effect when compared with the solvent, which blocked the induction of LTP.
  
  
  CONCLUSIONS
  Low-dose Xe in saline 0.9% revealed no antinociceptive, but preventive, action in spinal pain pathways.
authors.affiliation: Klinische Abteilung für Anästhesie und Allgemeine Intensivmedizin B, Medizinische Universität Wien, Währinger Gürtel 18-20, AKH, A-1090 Wien, Austria.
authors.forename: Justus
authors.initials: J
authors.lastname: Benrath
authors.forename: Christina
authors.initials: C
authors.lastname: Kempf
authors.forename: Michael
authors.initials: M
authors.lastname: Georgieff
authors.forename: Jürgen
authors.initials: J
authors.lastname: Sandkühler
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D023421:Models, Animal; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000503:physiopathology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D014978:Xenon / Q000494:pharmacology*
chemical_list: D014978:Xenon