Cannabinoid CB1 receptor protein expression in the rat choroid plexus: a possible involvement of cannabinoids in the regulation of cerebrospinal fluid.

Cannabinoid CB1 receptors in the brain are expressed on axon terminals presynaptic to neurons that express fatty acid amide hydrolase (FAAH). Postsynaptic FAAH catabolizes endocannabinoids which act as short-range transmitters. It has been previously shown that FAAH is also expressed in the epithelial cells of the choroid plexus. Using immunohistochemisty, we found that CB1 receptor protein is also expressed in choroid plexus epithelia. This is consistent with the hypothesis that FAAH in choroid plexus epithelial cells catabolizes endocannabinoids close to their site of action. Cannabinoids may then act directly on choroid plexus cells, and thereby contribute to the regulation of the composition of the CSF. Copyright 2004 Elsevier Ireland Ltd.