title: Effect of xenon on excitatory and inhibitory transmission in rat spinal ventral horn neurons.
abstract: BACKGROUND
  The minimum alveolar concentration is determined in the spinal cord rather than in the brain. Xenon inhibits glutamatergic excitatory synaptic transmission in the dorsal horn neurons. However, its actions in the ventral horn neurons have not been investigated.
  
  
  METHODS
  The effects of 50 or 75% xenon on excitatory and inhibitory synaptic transmission were examined in the spinal lamina IX neurons of neonatal rats by using a whole cell patch clamp technique.
  
  
  RESULTS
  Fifty percent xenon inhibited the α-amino-3-hydroxy-5-methyl-4-isoxazole-4-propionic acid-induced currents (amplitudes = 72 ± 9% and integrated area = 73 ± 13% of the control values), and α-amino-3-hydroxy-5-methyl-4-isoxazole-4-propionic acid receptor-mediated electrically evoked excitatory postsynaptic currents (amplitudes = 69 ± 13% of the control values). Seventy-five percent xenon similarly inhibited α-amino-3-hydroxy-5-methyl-4-isoxazole-4-propionic acid-induced currents. However, xenon had no effect on the N-methyl-D-aspartate-induced currents or N-methyl-D-aspartate receptor-mediated electrically evoked excitatory postsynaptic currents. Xenon decreased the amplitude, but not the frequency, of miniature excitatory postsynaptic currents. There were no discernible effects on the currents induced by γ-aminobutyric acid or glycine or on miniature inhibitory postsynaptic currents.
  
  
  CONCLUSIONS
  Xenon inhibits α-amino-3-hydroxy-5-methyl-4-isoxazole-4-propionic acid receptor-mediated glutamatergic excitatory transmission in the spinal lamina IX neurons via a postsynaptic mechanism. In contrast, there are no substantial effects on N-methyl-D-aspartate receptor-mediated or inhibitory synaptic transmission. The suppressive effects on excitatory synaptic transmission in the ventral horn neurons partly account for the mechanism behind xenon's ability to produce immobility in response to noxious stimuli and to determine the minimum alveolar concentration.
authors.affiliation: Division of Anesthesiology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Honda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Baba
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Kohno
mesh_terms: D000465:Algorithms; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D000870:Anterior Horn Cells / Q000187:drug effects*; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D008297:Male; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000187:drug effects; D018079:Receptors, GABA / Q000187:drug effects; D018009:Receptors, Glycine / Q000187:drug effects; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D009435:Synaptic Transmission / Q000187:drug effects*; D014978:Xenon / Q000494:pharmacology*
chemical_list: D018685:Anesthetics, Inhalation; D018091:Receptors, AMPA; D018079:Receptors, GABA; D018009:Receptors, Glycine; D016194:Receptors, N-Methyl-D-Aspartate; D014978:Xenon