The blood-brain barrier.
D000818:Animals; D001253:Astrocytes / Q000502:physiology; D001692:Biological Transport; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism; D002196:Capillaries / Q000033:anatomy & histology / Q000502:physiology / Q000648:ultrastructure; D002478:Cells, Cultured; D002560:Cerebrovascular Circulation; D004727:Endothelium / Q000166:cytology