Nuclear Spin Attenuates the Anesthetic Potency of Xenon Isotopes in Mice

Abstract

Abstract What We Already Know about This Topic What This Article Tells Us That Is New 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.