Absence of formation of cerebrospinal fluid in the spinal subarachnoid space of the cat.

It is widely believed that formation of cerebrospinal fluid (CSF) takes place within the cerebral ventricles--80 to 85% being produced by the choroid plexus and the remaining 15 to 20% being secreted by the lining ependyma. It has also been suggested that CSF is formed within the subarachnoid space. To investigate this possibility. CSF formation was measured in the isolated subarachnoid space of the cat. In 16 animals that underwent 26 steady-state perfusions, the rate of formation of CSF was found to be only 0.00005 +/- 0.00056 (SE) ml/min. It is therefore concluded that little or no CSF is formed in the spinal subarachnoid space of the cat.