ABSTRACT
The blood–retinal barrier controls the flux of fluid and blood-borne elements into the neural parenchyma, helping to establish the unique neural environment necessary for proper neural function. The blood vessels of the retina, like those of the brain, develop a barrier that partitions the neural parenchyma from the circulating blood. The formation of the tight junction complex and the blood–neural barrier depends on the close association of glia with the endothelial cells in the capillaries and arterioles traversing the neural tissue. Tight junctions confer the barrier properties to the endothelial cells within the retinal vasculature creating the blood–retinal barrier. A number of experiments, performed mostly in epithelial cells, demonstrate that occludin contributes to the barrier function of tight junctions. A positive effect of glucocorticoids on barrier properties has also been observed in epithelial cells. The claudins are made of at least 24 separate gene products whose expression helps to determine barrier properties of the tight junctions.
