The effects of low level hyperbaric treatment on acute ethanol intoxication

Targets for ethanol action and antagonism in loop 2 of the extracellular domain of glycine receptors

The present studies used increased atmospheric pressure in place of a traditional pharmacological antagonist to probe the molecular sites and mechanisms of ethanol action in glycine receptors (GlyRs). Based on previous studies, we tested the hypothesis that physical-chemical properties at position 52 in extracellular domain Loop 2 of alpha1GlyRs, or the homologous alpha2GlyR position 59, determine sensitivity to ethanol and pressure antagonism of ethanol. Pressure antagonized ethanol in alpha1GlyRs that contain a non-polar residue at position 52, but did not antagonize ethanol in receptors with a polar residue at this position. Ethanol sensitivity in receptors with polar substitutions at position 52 was significantly lower than GlyRs with non-polar residues at this position. The alpha2T59A mutation switched sensitivity to ethanol and pressure antagonism in the WTalpha2GlyR, thereby making it alpha1-like. Collectively, these findings indicate that (i) polarity at position 52 plays a key role in determining sensitivity to ethanol and pressure antagonism of ethanol; (ii) the extracellular domain in alpha1- and alpha2GlyRs is a target for ethanol action and antagonism and (iii) there is structural-functional homology across subunits in Loop 2 of GlyRs with respect to their roles in determining sensitivity to ethanol and pressure antagonism of ethanol. These findings should help in the development of pharmacological agents that antagonize ethanol.

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.