Blood-brain barrier

Blood-brain barrier (BBB) is a highly selective semipermeable border of endothelial cells that prevents solutes in the circulating blood from non-selectively crossing into the central nervous system. The blood-brain barrier is composed of high-density cells restricting passage of substances from the bloodstream much more than endothelial cells in capillaries elsewhere in the body.

Structure

The blood-brain barrier is composed of endothelial cells of the capillary walls. These cells are connected by tight junctions, which are composed of smaller subunits, frequently biochemical dimers, that are transmembrane proteins. The blood-brain barrier is further reinforced by the basement membrane and astrocytic endfeet.

Function

The primary function of the blood-brain barrier is to protect the brain from changes in levels of ions, amino acids, peptides, and other substances in the blood. It also prevents many substances from entering the brain and damaging brain tissue. This includes many drugs, which can make treatment of brain diseases more difficult.

Clinical significance

The blood-brain barrier becomes more permeable during inflammation. This can occur due to brain injuries or infections, allowing antibiotics and phagocytes to move across the BBB. However, this can also allow bacteria and viruses to enter the brain. Some diseases, such as meningitis and encephalitis, are a direct result of pathogens crossing the BBB.

Research

Research into the blood-brain barrier and its components is a significant focus in the development of drugs for the treatment of neurological disorders, including Alzheimer's disease, Parkinson's disease, and multiple sclerosis.

See also

• Neuroscience
• Neurology
• Pharmacology