The thiosulphate (35S) space in the CNS of rats after ventriculo-cisternal perfusion.

Abstract

1. The determination of the extracellular space in the central nervous system with measurement of the distribution of extracellular labels is complicated by the particular properties of the cerebrospinal fluid system. Though, the disturbing “sink-action” of the CSF-system can be circumvented, if the indicator is applied to the brain-tissue not only via the general circulation, but also by ventriculocisternal brain-perfusion. 2. After ventriculo-cisternal perfusion the35S thiosulphate space in the CNS of rats is 15.4% of the total brain water space once a steady state of distribution has been established. The Na- and K-concentration in the brain-tissue does not vary greatly during perfusion, although a decrease in brain water content can be observed after 120 and 180 minutes. 3. The calculated intracellular sodium and potassium concentration in brain tissue (mixed grey and white matter) is 38 and 123 meq/l cellwater respectively. 4. Our results agree with the ECS-values obtained by the “fast-compartment” analysis by the indicator elution methods; therefore we believe, that the35S thiosulphate space in the CNS is in close correlation with the true extracellular space. In our opinion the ventriculo-cisternal perfusion is well adapted for determining the extracellular space in the CNS in various forms of experimental brain edema.