Abstract
Exposurre to 25% carbons dioxide increased the concentration of phenobarbital, salicylic acid, acetazolamide and urea in all anatomical regions of the cat brain. Conversely, brain levels of all of thsese substances were reduced by hyperventilation.
High concentrations of carbon dioxide produced a greater relative increase in the entry and accumulation of salicylic acid, phenobarbital and acetazolamide in predominantly myelinated areas than in gray matter. Hyperventilation produced the opposite effects. These findings are discussed in relation to the anatomical structure of myelin and changes in the dissociation of organic electrolytes.
Urea, a non-electrolyte, did not exhibit any correlation between blood pH and concentration in different brain regions. The change in urea penetration suggests that carbon dioxide has a significant and perhaps unique effect on the entry of materials into the brain.
The effect of changes in blood flow and tissue binding on these results is also discussed.
Footnotes
- Received August 24, 1960.
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