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.

Hyperbaric ethanol antagonism in mice: time course

C57BL/6J mice were injected intraperitoneally with 3.6 g/kg ethanol and exposed to 1 ATA air or to 1 or 12 ATA helium-oxygen immediately, 5, 10 or 20 minutes after injection. Immediate and delayed hyperbaric exposure produced similar significant reductions in sleep-times and increases in wake-up brain ethanol concentrations. These findings demonstrate the effectiveness of delayed hyperbaric treatment in reducing ethanol sleep-time and eliminate decreased absorption and altered distribution as critical factors mediating the antagonism. The results are consistent with current theories of anesthesia and support a direct mechanism involving brain cellular membranes.

Temperature dependence of ethanol depression in mice

The relationship between environmental temperature, body temperature and ethanol depression was investigated in male C57BL/6J mice. Animals were injected with ethanol (3.6 g/kg) or saline and placed in an experimental or normal room temperature (control) environment. Environmental temperatures from 12-37 degrees C significantly influenced rectal temperature, sleep-time and wake-up brain ethanol concentrations. The rectal temperatures of ethanol-treated animals ranged from 1.5 degrees C greater to 11.3 degrees C lower than their matched saline controls, supporting indications that ethanol impairs normal thermoregulation. Sleep-time decreased up to 43% and wake-up brain ethanol concentrations increased as rectal temperature decreased from approximately 38-32 degrees C. More severe hypothermia after ethanol (rectal temperature less than 29 degrees C) increased sleep-time and decreased wake-up brain ethanol concentrations. These results indicate that sleep-time and brain sensitivity to ethanol vary with rectal temperature in accordance with predictions based on membrane expansion and partition theories of anesthesia and the anticipated anesthetic-like actions of severe hypothermia.

Low-level hyperbaric ethanol antagonism in mice. Dose and pressure response

Dose- and pressure-related interactions between ethanol anesthesia and low-level hyperbaric helium-oxygen environments were studied in mice using conditions which eliminated the possibility of hypoxia during compression and hyperbaric helium-induced hypothermia. Hyperbaric helium-oxygen (1-12 atmospheres absolute) reduced sleep time in a pressure-related manner. The degree of maximum ethanol antagonism decreased as the ethanol dose increased (3.2, 3.6, and 4.0g/kg). The results are consistent with membrane theories of general anesthesia and suggest a possible common mechanism between ethanol antagonism at low hyperbaric pressure and high-pressure reversal of anesthesia.

Antagonism of ethanol narcosis in mice by hyperbaric pressures of 4-8 atmospheres

Hyperbaric treatment with 100% oxygen or oxygen-helium mixtures at 4-8 atmospheres absolute significantly reduced ethanol sleep-time and increased wake-up blood ethanol concentrations in C57 mice. The results indicate that the antagonism does not result from direct effects of oxygen nor from enhanced ethanol elimination, but appears to involve a direct effect of hyper-baric treatment.

Memory facilitation by post-training injection of ethanol

Immediate post-training IP injection of ethanol (0.75--4.5 g/kg) significantly enhanced retention of a one-trial passive avoidance task in mice compared to saline controls. Ethanol (4.5 g/kg) in the absence of footshock did not affect test performance. The memory facilitation may reflect ethanol's effects on neurotransmitter, macromolecular, or hormonal systems, or a reduction in interference.

Reversal of ethanol intoxication in humans: an assessment of the efficacy of L-dopa, aminophylline, and ephedrine

The effect of postethanol treatment with L-Dopa, aminophylline and/or ephedrine was investigated. In one experiment, healthy, male, moderate drinkers ingested ethanol (0.8 g/kg) and then either L-Dopa (1.5 g), or placebo. In a second experiment, subjects ingested ethanol followed by aminophylline (200 mg), ephedrine (50 mg), aminophylline (200 mg) plus ephedrine (50 mg), or placebo. Double-blind, within-subjects, crossover designs were employed. Treatment with L-Dopa significantly reduced ethanol's effect on the electroencephalogram, motor coordination, and divided attention performance (t-test for paired data). Treatment with aminophylline and/or ephedrine also significantly reduced ethanol's effects on the electroencephalogram and motor coordination. The ethanol-antagonism may result from central noradrenergic stimulation.

Reversal of ethanol intoxications in humans: an assessment of the efficacy of propranolol

The effect of post-ethanol ingestion of a single dose of propranolol on acute intoxication was studied in 13 healthy male volunteers. A within subjects, double-blind, crossover design was employed. Each subject participated in two experimental sessions. In each session, subjects took a battery of tests under three conditions: Sober, Alcohol (0.8 g/kg) and Alcohol (1.1 g/kg) + Pill, in that order. The pill contained propranolol (40 mg) in one session and placebo in the other. Ethanol significantly reduced motor coordination, memory and divided attention performance and altered mood scores. Propranolol significantly increased ethanol's effects on divided attention, inebriation ratings and the electroencephalogram without significantly altering blood alcohol concentrations. There was no indication that propranolol antagonized any of ethanol's effects. These results agree with studies indicating that ethanol's effects are increased by a reduction in the functional capacity of central catecholamine systems. It is suggested that central catecholamine-stimulating drugs may reverse some of ethanol's effects.