BLOOD BRAIN BARRIER  [ back to Glossary Index ]
Blood Brain Barrier or BBB refers to the extremely small, narrow and densely packed blood vessels which stand between the major arteries supplying the inside of the head and the arteries which penetrate and directly supply the brain tissue. The purpose of the BBB is to screen out and exclude large molecules from the intra-cerebral circulation which could be toxic to the brain. The BBB is highly effective in protecting the brain. However, it also limits therapeutic options by blocking healing drugs from getting inside the brain. One well known example is dopamine. Parkinson's patients must receive L-dopa (which gets converted to dopamine in the brain) because dopamine molecules are too big to get through the BBB in pill form. The same goes for for administration of "trophic factors" following a TBI to increase survival of traumatized brain cells and stimulate axonal sprouting and development of new synapses. Such trophic factors need to be injected through the skull into selected portions of the brain.