Techniques for Evaluating Efflux Transport of Radiolabeled Drugs and Compounds from the Cerebrospinal Fluid Across the Blood-Cerebrospinal Fluid Barrier

Choroid plexus epithelial cells are known to play a role as the blood-cerebrospinal fluid (CSF) barrier (BCSFB), which separates the compartments of the CSF in the cerebroventricles from the circulating blood. Recent reports have identified the molecular based efflux transport systems at the BCSFB. Because these transport systems participate in the elimination of compounds/drugs from the CSF, these experimental findings about the systems are of great importance to increase our knowledge of the homeostasis of compound concentration in the brain and CSF. There are many reports of in vivo and in vitro methods to examine BCSFB-mediated organic compound efflux transport. In this section, we describe the in vivo intracerebroventricular administration technique to evaluate carrier-mediated elimination of compounds from the CSF in rats. As the in vitro methods, the transport studies using choroid plexus prepared from rat cerebroventricles and a conditionally immortalized rat choroid plexus epithelial cell line, TR-CSFB3 cells, are described in detail. The information obtained from these studies will help us to understand the molecular mechanisms of compound efflux transport across the BCSFB.