Formation of Cerebrospinal Fluid
In 1972, our laboratory developed a method in which the choroid plexus of the sheep could be maintained satisfactorily in an extracorporeal perfusion system for up to seven hours. The experimental system has been presented elsewhere in great detail (1) and will only be briefly described at this time. Arterial inflow to the plexus was controlled by means of a catheter in the internal carotid artery with ligation of all branches except the anterior choroidal artery. Venous outflow from the plexus was collected from a catheter in the internal cerebral vein at the level of the foramen of Monro. In some fifty experiments, we calculated a rate of CSF production of almost 13µ1 min−1 when the perfusion pressure and choroidal artery blood flow was 90–100mmHg and 2.9µl mg−1 min−1, respectively. The virtual concentration of sodium and chloride in the nascent fluid was computed from the net flux of each ion divided by the net flux of water. The concentration for sodium in the nascent CSF was 158 meq/l and 127.9 meq/l of chloride. The ratio of the concentration in CSF/concentration in plasma was found in both cases to be greater than that expected of a simple ultrafiltrate of plasma.
KeywordsAdenosine Triphosphatase Sodium Pump Secretory Epithelium Hypotonic Medium Anterior Choroidal Artery
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