| Popis: |
According to our new hypothesis, based on experimental data, the cerebrospinal fluid (CSF) is not formed at one site (inside brain ventricles) and absorbed at another (dural venous sinuses, perineural sheets of cranial nerves), but it might be formed and absorbed through capillary walls inside brain and spinal tissue, depending on hydrostatic and osmotic forces gradient between blood on one side and CSF and interstitial fluid on the other side. If our hypothesis is correct, the exchange of CSF between CSF system and surrounding tissue would depend on size of the contact area and on difference in blood and CSF osmolarity. This was tested on chloralose (100 mg/kg ; i.p.) anaesthetized cats at normal CSF pressure by collecting outflow sample after ventriculo-aqueductal (smaller contact area) or ventriculo-cisternal (larger contact area) perfusion by isoosmolar or hyperosmolar perfusate. At isoosmolar perfusion, the outflow volume (13.10 ± 2.01 µ L/min) was the same as the infused one in both the ventriculo-aqueductal and ventriculo-cisternal perfusion methods. At hyperosmolar perfusion, significantly higher outflow volume (34.12 ± 3.30 µ L/min) was obtained by ventriculo-cisternal perfusion than by ventriculo-aqueductal perfusion (22.09 ± 2.90 µ L/min) (p). These results clearly show that the CSF volume depends on osmolarity and size of contact area through which osmotic arrival of fluid takes place. Such results strongly support our new hypothesis on CSF hydrodynamics, but don't fit into classical hypothesis of CSF secretion, unidirectional flow and absorption. |
