[Blood-brain barrier and general anesthetics].

The transport of drugs into the brain is prevented in most cases by the presence of the blood brain barrier (BBB). Endothelial cells in the brain of vertebrates are fused together by tight junctions that eliminate the normal pathways of free diffusion existing in the capillary beds of organs other than the brain or spinal cord. Therefore, a molecule that has a molecular weight less than a 500 Dalton can cross the BBB in proportion to lipid solubility. Recent molecular biological studies have contributed to the isolation and functional analysis of transporter proteins at the BBB. There are three types of endogenous transport systems: carrier-mediated transporters, active efflux transporters such as P-glycoprotein, and receptor-mediated transcytosis systems. The structural and functional integrity of the BBB has appeared to be dramatically altered by various diseases of the CNS such as ischemia, anoxia and inflammation, resulting in cerebral edema and damage to the neurons. General anesthetic agents can alter the BBB function. For example, the degree of the BBB disruption was smaller during isoflurane anesthesia than during pentobarbital anesthesia. In this review, we focus on recent progress in the BBB research and functional modulation produced by general anesthetics.