Continuous measurement of cerebrospinal fluid pressure in unrestrained rats

A sensitive method for measuring intracranial pressure in unrestrained, unanesthetized rats has been developed. Two identically calibrated pressure transducers connected to fluid-filled polyethylene catheters were used to simultaneously monitor ventricular cerebrospinal fluid (CSF) pressure and head position. Artifacts due to changing head position were electronically subtracted from ventricular pressure, yielding a continuous dynamic record of “true” CSF pressure. A simple technique for precisely calibrating pressure transducers is also described. The mean CSF pressure obtained in 27 non-stressed freely-behaving adult rats was 64 ± 2 mm H₂O. Handling caused a prompt increase in intracranial pressure of approximately 80–120 mm H₂O. Moment-to-moment fluctuations in intracranial pressure closely reflect changes in central venous pressure. The techniques described are applicable to continuous measurement of CSF pressure in laboratory or clinical settings.