Dyes injected into the body's blood supply would stain the tissues of most organs - but not the brain. The walls of the vessels that carry blood into the brain form the barrier. Leaky blood vessels in the body allow many molecules to cross through to tissue, but the tight construction of the vessels in the head guards against brain entry. Blood gases such as oxygen and small nutritional molecules are the main outsiders that can make it in. Accumulating research on animals and humans is helping researchers place important therapeutic agents on the list as well.
Some new techniques latch agents onto molecules that already have brain access.
Some evidence suggests that the transport technique can carry a variety of molecules from the blood to the brain in animal models, which could benefit a number of brain diseases. For example, they combined DHA with proteins that are suspected to protect nerve cells from the damage seen in ailments like stroke and Alzheimer's disease. Nerve cells were protected in rat models of stroke, according to preliminary data. Other researchers found that another molecular combination technique transported therapies, including nerve cell-protecting molecules, to the brains of animals. This version makes use of a vessel site that the molecule insulin uses to get into the brain.