MODEL EXPERIMENTS WITH GADDUM'S PUSH-PULL CANNULAS

Abstract

Push–pull cannulas of various sizes were placed in an agar gel containing 10 μg/ml of quinine sulfate and were perfused at various rates. The quinine content of the outflow was determined fluorometrically. The amount of solute extracted by the cannula depended on the size of the contact area between the perfusion fluid and the gel but not on the rate of perfusion. From data obtained in these model experiments, the diffusible fraction of some of the suspected transmitters in the central nervous system was calculated.