Fatty acid amide hydrolase expression in rat choroid plexus: possible rolein regulation of the sleep-inducing action of oleamide

The enzyme fatty acid amide hydrolase (FAAH) catalyses hydrolysis of oleami de, a sleep-inducing lipid whose concentration in the cerebrospinal fluid ( CSF) is elevated in sleep-deprived mammals. Previous studies have reported expression of FAAH by distinct populations of neurons in the rat brain. Her e we demonstrate using immunocytochemical methods that FAAH is also express ed by non-neuronal epithelial cells of the rat choroid plexus. The choroid plexus is formed by invaginations of the pia mater into the ventricle cavit ies of the brain and an important function of the choroidal epithelium is t o regulate production and composition of CSF. Therefore, the role of FAAH i n epithelial cells of the choroid plexus may be to control the concentratio n of oleamide in the CSF and as such FAAH may exert an important regulatory role in shaping the duration and magnitude of the sleep-inducing effect of endogenously or exogenously derived oleamide. (C) 2000 Elsevier Science Ir eland Ltd. All rights reserved.