LOW-LEVEL HYPERBARIC ANTAGONISM OF ETHANOLS ANTICONVULSANT PROPERTY IN C57BL 6J MICE/

This study investigated the ability of hyperbaric exposure to antagoni ze ethanol's anticonvulsant effect on isoniazid (INH)-induced seizures . Drug naive, male C578L/6 mice were injected intraperitoneally with s aline, 1.5, 2.0, or 2.5 g/kg ethanol followed immediately by an intram uscular injection of 300 mg/kg of INH. The mice were then exposed to e ither 1 atmosphere absolute (1 ATA) air, 1 ATA helium oxygen gas mixtu re (heliox), or 12 ATA heliox at temperatures that offset the hypother mic effects of helium. Ethanol increased the latency to onset of myocl onus in a dose-dependent manner. Exposure to 12 ATA heliox antagonized ethanol's anticonvulsant effect at 2.0 and 2.5 g/kg, but not at 1.5 g /kg. Ethanol also increased the latency to onset of clonus in a dose-d ependent manner beginning at 2.0 g/kg. Exposure to 12 ATA heliox antag onized this anticonvulsant effect. When exposed to 12 ATA heliox, the blood ethanol concentrations at time to onset of myoclonus were signif icantly higher in mice treated with 2.5 g/kg of ethanol as compared wi th blood ethanol concentrations of mice exposed to 1 ATA air. These fi ndings extend the acute behavioral effects of ethanol known to be anta gonized by hyperbaric exposure and support the hypothesis that low-lev el hyperbaric exposure blocks or reverses the initial action(s) of eth anol leading to its acute behavioral effects.