The choroid plexus (CP) epithelium forms the blood-cerebrospinal fluid (CSF) barrier and, along with the blood-brain barrier, maintains the fluid environment of the brain. The CP not only secretes CSF, but also transports potentially toxic xenobiotics and waste products of neural metabolism to the blood for eventual clearance in kidney and liver. However, studying CP is difficult, due to complex morphology, ana-tomical location and small size of the tissue and little is known about the molecular mechanisms, functional complexity and hormonal regu-lation of organic anion secretion. To further...