Visualization of brain interstitial fluid movement during osmotic disequilibrium

Abstract

The movement of brain interstitial fluid was visualized in cats with the use of dextran blue 2000. The dextran blue was injected intracerebrally, and the cats were subsequently infused or perfused with anisotonic sucrose solutions. Increasing the serum osmolality by intravenous infusion of a hypertonic sucrose solution or decreasing the ventricular fluid osmolality by perfusion with a hypotonic sucrose solution effectively shuts off CSF flow. Conversely, volume flow is increased by either infusing hypotonic sucrose or perfusing with hypertonic sucrose solutions. Cats which were neither infused nor perfused demonstrated a relatively well-defined dye pattern in cerebral white matter. In the brains of cats infused with hypotonic sucrose the dye was more diffuse and asymmetrical. In the brains of cats infused with hypertonic sucrose the dye pattern was discrete and symmetrical. There was no apparent difference in the dye pattern, as compared to controls, in the brains of those cats whose ventricles were perfused with either hypertonic or hypotonic sucrose solutions. Injection of dye into the brains of dead cats produced dye patterns which were more discrete than those seen in controls. It is concluded from observations made on the various dye patterns that there is a movement of interstitial fluid within the brain when serum osmolality is altered. This fluid may contribute to the increase in CSF volume flow which results when serum osmolality is decreased.