Hyperbaric ethanol antagonism in mice: studies on oxygen, nitrogen, strain and sex

Male and female C57BL/6J and male BALBc/J mice were injected with 3.6 g/kg ethanol or saline and exposed to 1-10 atmospheres absolute (ATA) air, to 1 ATA 80% helium-20% oxygen, or to 12 ATA helium-oxygen having oxygen partial pressures between 0.5 and 18 times normal. Hyperbaric helium-oxygen significantly reduced sleep-time and increased wake-up brain ethanol concentrations in all mice tested. The degree of antagonism was not enhanced by increasing the oxygen partial pressure. Hyperbaric air increased sleep-time and decreased wake-up brain ethanol concentration in C57 mice. Hyperbaric air induced a pressure-related lethal effect beginning at 6 ATA in intoxicated BALBs. These findings demonstrate that hyperbaric ethanol antagonism extends across strains and sexes, that the degree of antagonism cannot be enhanced by increasing the oxygen partial pressure, and that air is not suitable as an antagonistic hyperbaric gas. The findings are consistent with membrane theories of anesthesia.