Blood Brain Barrier

What is the blood-brain barrier?

The blood-brain barrier (BBB) is a set of properties of blood vessels in the central nervous system that regulates movement between the blood and nervous tissue. Endothelial cells and their tight junctions provide a physical barrier; transporters and metabolic processes also control which substances cross. Pericytes, astrocytes, and other surrounding cells help regulate these properties.

What can cross the blood-brain barrier?

Oxygen and carbon dioxide can cross the vessel wall, while glucose uses transport proteins. The barrier regulates exchange; it does not stop everything in the blood from reaching nervous tissue.

Blood-brain barrier function: protection and drug delivery

The BBB helps maintain the chemical environment needed for neural activity, but it is not an absolute shield against infection or toxic substances. Its selectivity also makes delivery of many drugs to the brain difficult. A compound’s ability to act elsewhere in the body does not establish that it reaches the brain in a useful amount.

For the cellular mechanisms and changes in disease, see Daneman and Prat's review, The Blood–Brain Barrier (2015).