Changes in Enzyme Activities of the Choroid Plexus and Brain Tissue following Bilateral Carotid Ligation in Correlation with the Formation of Cerebrospinal Fluid

The activity of four enzymes which are thought to be correlated to the production of CSF, such as acid and alkaline phosphatase, carbonic anhydrase, and Na-K ATPase, were determined biochemically in the choroid plexus and the frontal lobe brain tissue in adult rabbits. The activities of these enzymes, except Na-K ATPase, were transiently enhanced in the choroid plexus after bilateral ligation of the common carotid arteries, although considerable decrease was found in the brain tissue. Since the above results had suggested that enhancement of secretory activity of the choroid plexus followed bilateral carotid ligation, the rate of CSF formation was measured by means of the ventriculocisternal perfusion method in the same species of animals before and after bilateral carotid ligation. However, no significant changes were observed in the rate of CSF formation until 2 hours after carotid ligation. After bilateral occlusion of the common carotid arteries, vertebral blood flow, measured electromagnetically, immediately increased to twice its normal rate. Also, resin casts made of the choroid plexus after bilateral carotid ligation, confirmed that there was an adequate blood supply to the entire choroid plexus through the vertebral-posterior choroidal artery system. Considering the dual source of CSF production, it is likely that the secretory activity of the choroid plexus not only is unaffected by a sudden change of cerebral blood flow but also may compensate for the reduced production of CSF in the brain for at least a temporary period. Therefore, in face of ischemic-anoxic changes in the brain this could lead to the maintenance of a normal rate of CSF production by a homeostatic control mechanism.