Perfusion of the cerebral ventricular system in unanesthetized goats

Abstract

Techniques have been devised for repeated perfusion of the ventriculocisternal system in chronically prepared, unanesthetized goats. The methods are designed for investigations of a) functional effects of prolonged changes of cerebrospinal fluid (CSF) composition and b) quantitative aspects of CSF formation and exchange of materials between CSF and blood. The present paper provides a technical background for subsequent papers dealing with specific problems. Goats tolerate perfusion rates of 1–3 ml/min at pressures adjustable between –10 and +30 cm H₂O. Measurements are made of inflow rates, outflow rates, and concentrations of test materials entering and leaving the system. Composition of normal CSF has been determined and directions are given for preparation of sterile synthetic CSF. Brain weight is about 100 g and choroid plexuses 500 mg. CSF volume is 20–25 ml of which 8–12 ml is in the ventricles. Pressure-volume characteristics are described. Steady-state difference between inflow and outflow rates is a linear function of hydrostatic pressure; the slope is related to hydrodynamic resistance to bulk absorption. Preliminary observations are given to show effects of reduced Ca⁺⁺ on nervous control of the cardiovascular system.