Perioperative Medicine  |   August 2018
Nuclear Spin Attenuates the Anesthetic Potency of Xenon Isotopes in Mice: Implications for the Mechanisms of Anesthesia and Consciousness
Author Notes
  • From the Department of Anesthesiology, Union Hospital (N.L., D.L., L.Y., H.T., Y.X., C.W., L.F., Y.C., S.Z.); and Department of Pharmacology, School of Basic Medicine (H.L.), Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
  • Corresponding article on page 228.
    Corresponding article on page 228.×
  • N.L., D.L., L.Y., and H.T. contributed equally to this article.
    N.L., D.L., L.Y., and H.T. contributed equally to this article.×
  • Submitted for publication September 3, 2017. Accepted for publication March 7, 2018.
    Submitted for publication September 3, 2017. Accepted for publication March 7, 2018.×
  • Address correspondence to Dr. Zhang: Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 1277 Jiefang Street, Wuhan 430022, Hubei Province, China. zhangshihai@vip.163.com. Information on purchasing reprints may be found at www.anesthesiology.org or on the masthead page at the beginning of this issue. Anesthesiology’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue.
Article Information
Perioperative Medicine / Basic Science / Central and Peripheral Nervous Systems / Pharmacology
Perioperative Medicine   |   August 2018
Nuclear Spin Attenuates the Anesthetic Potency of Xenon Isotopes in Mice: Implications for the Mechanisms of Anesthesia and Consciousness
Anesthesiology 8 2018, Vol.129, 271-277. doi:10.1097/ALN.0000000000002226
Anesthesiology 8 2018, Vol.129, 271-277. doi:10.1097/ALN.0000000000002226
Abstract

What We Already Know about This Topic:

  • Xenon is a noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist. The interaction of xenon with the NMDA receptor is determined by quantum-level van der Waals London forces between the electron shells of xenon and the electron clouds of nonpolar regions of the NMDA receptor.

  • In addition to the van der Waals forces, several xenon isotopes have nuclear spin. Whether the quantum property of nuclear spin affects the potency of xenon is not known.

What This Article Tells Us That Is New:

  • The potency of two xenon isotopes with nuclear spin, xenon 129 and xenon 131, is less than the potency of two xenon isotopes, xenon 132 and xenon 134, that do not have nuclear spin. This difference in potency cannot be explained, either by differences in outer electron shells (there are none) or the variations in atomic mass.

  • The results suggest that some of the effects of xenon on consciousness may be mediated by quantum mechanisms.

Background: Xenon is an elemental anesthetic with nine stable isotopes. Nuclear spin is a quantum property which may differ among isotopes. Xenon 131 (131Xe) has nuclear spin of 3/2, xenon 129 (129Xe) a nuclear spin of 1/2, and the other seven isotopes have no nuclear spin. This study was aimed to explore the effect of nuclear spin on xenon anesthetic potency.

Methods: Eighty C57BL/6 male mice (7 weeks old) were randomly divided into four groups, xenon 132 (132Xe), xenon 134 (134Xe), 131Xe, and 129Xe groups. Due to xenon’s low potency, loss of righting reflex ED50 for mice to xenon was determined with 0.50% isoflurane. Loss of righting reflex ED50 of isoflurane was also measured, and the loss of righting reflex ED50 values of the four xenon isotopes were then calculated. The exact polarizabilities of the isotopes were calculated.

Results: Combined with 0.50% isoflurane, the loss of righting reflex ED50 values were 15 ± 4%, 16 ± 5%, 22 ± 5%, and 23 ± 7% for 132Xe, 134Xe, 131Xe, and 129Xe, respectively. For xenon alone, the loss of righting reflex ED50 values of 132Xe, 134Xe, 131Xe, and 129Xe were 70 ± 4%, 72 ± 5%, 99 ± 5%, and 105 ± 7%, respectively. Four isotopes had a same exact polarizability of 3.60 Å3.

Conclusions: Xenon isotopes with nuclear spin are less potent than those without, and polarizability cannot account for the difference. The lower anesthetic potency of 129Xe may be the result of it participating in conscious processing and therefore partially antagonizing its own anesthetic potency. Nuclear spin is a quantum property, and our results are consistent with theories that implicate quantum mechanisms in consciousness.