Special Focu S: Blood-Brain Barrier editorial

Diseases and disorders of the CNS remain extremely difficult to treat because most cur rent therapeutics do not readily cross from the blood into the brain and spinal cord. This is due to a series of cellular interfaces within the CNS that have collectively come to be known as the ‘blood–brain barriers’ (BBB). These barriers permit and even enhance the entry of certain compounds whilst severely restricting the entry of many others. Understanding the nature of these barriers and how they restrict the entry of different compounds is key to finding new approaches for delivering therapeutics into the CNS. In the injured brain, physical damage to blood vessels at the site of injury temporarily disrupts normal BBB function and allows compounds present in the blood to gain direct access to brain tissue in and around the injury site. This period of compromised barrier function could provide a ‘window of opportunity’ through which therapeutics could be administered to ameliorate secondary brain damage. Blood–brain barriers