Interactions of increased pO2 and pCO2 effects in producing convulsions and death in mice

Abstract

In 379 mice subjected to from 1 to 11 atm. of pO₂ and 0 to 304 mm Hg of pCO₂ for 90 minutes, oxygen was convulsigenic at pressures greater than 3 atm. and lethal at greater than 4 atm. Carbon dioxide in 1 atm. of O₂ was not convulsigenic but was lethal at very high tensions. In the presence of O₂ at high pressure (OHP) small elevations of CO₂ tension shortened the preconvulsive latent period, whereas CO₂ tensions greater than 120 mm Hg inhibited convulsions. Survival time in OHP was shortened by the addition of CO₂. An interaction between OHP and CO₂ effects is suggested by both the preconvulsive latent period and survival time data. The effects of CO₂ on OHP and electroshock convulsions are compared and possible reasons for differences are discussed in light of the previously demonstrated general cortical depression and inhibition of convulsions by CO2. The potentiation of OHP convulsions by low CO₂ tensions is probably due to effects on brain blood flow. Although death can occur without convulsions there is a tendency for animals susceptible to convulsions to be also susceptible to the lethal properties of OHP with CO₂. Submitted on July 28, 1960