Functional aspects of the subcommissural organ-Reissner's fiber complex with emphasis in the clearance of brain monoamines

Reissner's fiber (RF) extends along the cerebral aqueduct, fourth ventricle , and the entire length of the central canal of the spinal cord. It grows c ontinuously in the caudal direction by addition of newly released glycoprot eins by the subcommissural organ (SCO) to its proximal end. Several hypothe ses about RF function have been advanced. One of them postulates that RF bi nds biogenic amines present in the CSF and clears them away. In recent year s, this hypothesis has been tested in our laboratory by using several exper imental protocols. Firstly, the CSF concentration of monoamines was investi gated in RF-deprived rats subjected to immunological neutralization of the SCO-RF complex. Secondly, the capacity of RF to bind monoamines in vivo was studied by injecting radiolabeled serotonin or noradrenaline into the rat CSF, and by perfusing them into the CSF, during one week, using an Alzet's osmotic pump. In vitro binding studies were performed using isolated bovine RF. All the findings obtained indicate that RF binds monoamines present in the ventricular CSF and then transports them along the central canal. In t he absence of RF, the CSF concentration of monoamines increases sharply. Mi crosc. Res. Tech. 52:564-572, 2001. (C) 2001 Wiley-Liss. Inc.