The present invention is directed to a method and use of RNA interference (RNAi) for the transient, reversible and controlled opening of the tight junctions of the blood brain barrier and/or the blood retinal barrier. This method may be used in the treatment of many diseases and disorders which require the opening of the blood brain barrier and/or blood retinal barrier. Such methods generally involve the use of an RNAi-inducing agent, such as siRNA, miRNA, shRNA or an RNAi-inducing vector whose presence within a cell results in production of an siRNA or shRNA, targeting tight junction proteins to open the blood brain barrier and/or blood retinal barrier.