Margret I. Sellers Ph.D.¹ and John F. Lavender ¹

¹ From the Division of Virology, Department of Infectious Diseases School of Medicine, University of California, Los Angeles

Inhalation of elevated concentrations of CO₂ produces a significant increase in the susceptibility of mice to intravenously inoculated Type II poliovirus. The CO₂ effect is directly proportional to the concentration; 2.5 minutes inhalation of a mixture of 30 per cent CO₂-70 per cent O₂ produces maximal effects, while lower concentrations of CO₂ require correspondingly longer periods. The threshold level is 7 per cent; inhalation of lower concentrations, even for long periods of time, fails to enhance virus infectivity. Placing the animals in the CO₂ atmosphere before injection of virus does not influence susceptibility; virus must be in the circulation at the time CO₂ is inhaled if enhancement of infectivity is to be elicited. The effect is completely reversible, disappearing almost immediately upon withdrawal of the animals from the CO₂ atmosphere. CO₂ mediates an increase in the entry of virus into the CNS from the circulation but does not affect the spread of virus within the CNS; susceptibility of mice to intracerebrally inoculated poliovirus is not influenced by CO₂ inhalation. The mechanism(s) of action of CO₂ can be explained, in part, by the dilatation of cerebral blood vessels and increased rate of blood flow through the CNS produced by the CO₂. However, other factors, which remain unidentified, contribute to the net effect of CO₂.

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This article has been cited by other articles:

• CUTLER, R. W. P., BARLOW, C. F. (1966). The Effect of Hypercapnia on Brain Permeability to Protein. Arch Neurol 14: 54-63 [Abstract]  
• GOLDBERG, M. A., BARLOW, C. F., ROTH, L. J. (1963). Abnormal Brain Permeability in CO2 Narcosis. Arch Neurol 9: 498-507 [Abstract]  

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