THE ROLE OF MULLER CELLS IN THE FORMATION OF THE BLOOD-RETINAL BARRIER

We have compared the ability of Muller cells and astrocytes to induce the formation of barrier properties in blood vessels. Muller cells cul tured from the rabbit retina, and astrocytes and meningeal cells cultu red from the rat cerebral cortex, were injected into the anterior cham ber of the rat eye, where they formed aggregates on the iris. We have examined the barrier properties of the vessels in those aggregates and , for comparison, the barrier properties of vessels in the retina, cil iary processes and iris. Two tracers were perfused intravascularly to test barrier properties. The movement of Evans Blue was assessed by li ght microscopy, and the movement of horseradish peroxidase by light an d electron microscopy. Our results indicate that Muller cells share th e ability of astrocytes to induce the formation of barrier properties by vascular endothelial cells, and we suggest that Muller cells play a major role in the formation of barrier properties in retinal vessels.