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U konzervativnom liječenju povišenog intrakranijskog tlaka već dugo se koriste hiperosmolarne otopine (najviše manitol) koje se daju intravenski, ali točan mehanizam njihovog djelovanja na snižavanja intrakranijskog tlaka nije u potpunosti razjašnjen. Stoga je u ovom radu eksperimentalno, na mačkama proučavan utjecaj promjene osmolarnosti krvi i cerebrospinalnog likvora na volumen cerebrospinalnog likvora, te povezanost tih promjena volumena likvora s intrakranijskim tlakom. U tu svrhu korišteni su modeli direktne ventrikulo-akveduktalne i ventrikulo-cisternalne perfuzije s izoosmolarnom i hiperosmolarnom otopinom umjetnog likvora, spontanog istjecanja likvora iz cisterne magne i mjerenja tlaka likvora u lateralnoj moždanoj komori. Promjene osmolarnosti krvi vršene su intravenskim davanjem 20% manitola, te intraperitonealnim davanjem destilirane vode. Dobiveni rezultati pokazali su da promjene osmotskih sila u likvorskom sustavu dovode do promjena ukupnog volumena cerebrospinalnog likvora i da su promjene tlaka likvora (intrakranijskog tlaka) direktno povezane s tim promjenama volumena likvora. Veličina promjene volumena likvora ovisi o površini likvorskog sustava koja je izložena promjenama osmotskih sila. Također je pokazano da pri fiziološkom tlaku likvora, bez promjena osmotskih sila nema „čistog“ stvaranja niti apsorpcije likvora. Svi dobiveni rezultati nisu u skladu s klasičnom hipotezom o sekreciji, cirkulaciji i apsorpciji likvora, ali su u skladu s predloženom novom hipotezom o dinamici cerebrospinalnog likvora., Hyperosmolar solutions (mostly mannitol) have long been used in clinical practice to reduce intracranial pressure, but the exact mechanism by which this effect occurs is still unclear. So, in this study we wanted to investigate experimentally, on cats, the effect of changes in serum and CSF osmolarity on CSF volume and how this changes of CSF volume influence on intracranial pressure. For this purpose we used experimental models of direct ventriculo-aqueductal and ventriculo-cisternal perfusion with both isoosmolar and hyperosmolar aCSF, the free drainage of CSF from a cannula put into the cisterna magna and the measuring of CSF pressure by the cannula put into the lateral ventricle of the brain. Serum osmolarity was changed by intravenous application of 20% mannitol or intraperitoneal administration of distilled water. Obtained result showed that the changes of osmotic forces in CSF compartments leads to changes of total CSF volume and that changes of CSF pressure are directly connected with this changes of CSF volume. The extent of CSF volume changes depends on the size of contact area of CSF system that was exposed to the changes of osmotic forces. It was also shown that with physiological intracranial pressure, without changes of osmotic forces, there was no “net” CSF formation or absorption. All obtained results contradict the classic hypothesis of secretion, circulation and absorption of CSF, but support proposed new hypothesis of CSF hydrodynamics.