THE RELATIONSHIP BETWEEN SODIUM INFLUX AND VOLUME FLOW INTO THE CEREBRAL VENTRICLES OF CATS

Abstract— The relationship between sodium ion (Na⁺) influx and vol. flow of fluid into the cerebral ventricles was measured during ventriculocisternal perfusion with sucrose solutions of various concentrations. The vol. flow of fluid into the ventricles of cats varied linearly from 0 to 90 μl/min with sucrose solutions of 6 to 780 mOsm/l. In the vol. flow range of 0 to 35 μl/min, Na⁺ influx was essentially constant independent of vol. flow rate with a mean value of 6.95 μEq/min. In the vol. flow range of 25 to 90 μl/min, Na⁺ influx increased linearly with flow rate. Under all conditions, Na⁺ influx was greater than that corresponding to newly formed fluid with a normal spinal fluid Na⁺ concentration. The virtual Na⁺ concentration of nascent fluid was effectively infinite when vol. flow was zero and had an asymptotic minimum value of 109 mEq/l as vol. flow increased above normal. These results demonstrate that Na⁺ influx into the ventricles may occur by diffusion from the surrounding brain and also with vol. flow of nascent fluid.