Transport properties of vertebrate blood-nerve barrier : comparison with blood-brain barrier

In the central nervous system, the blood-brain barrier (BBB) separates the brain and cerebrospinal fluid (CSF) from the blood and regulates exchange of various substances between blood and brain. In the peripheral nervous system, the microenvironmental of nerve fibers and their supporting cells, the endoneurial space, is also enclosed and separated from the blood by the blood-nerve barrier (BNB). The BNB consists of endoneurial blood vessels and the epi-perineurial sheath. In this review, we discuss recent studies, in part from our laboratory, regarding the transport characteristics of the BNB, and try to provide insights into the role of the BNB in peripheral nerve function and metabolism. A good part of this treatise is devoted to a critical discussion of analytical techniques needed to quantify and interpret BNB permeability and transport, as limitations in methodology can lead to misinterpretations of critical factors regarding the BNB.